## Ecological Risk Assessment of the Proposed Use of the Herbicide Imazapyr to Control Invasive Cordgrass ( Spartina spp. ) in Estuarine Habitat Of Washington State

Prepared For:



## Washington State Department of Agriculture

Olympia,WA 98504

Prepared By:

ENTRIX, INC



# . Olympia, Washington

98502

PROJECT NO. 3000901

October 30, 2003

### Ecological Risk Assessment of the Proposed Use of the Herbicide Imazapyr to Control Invasive Cordgrass ( Spartina spp. )

in Estuarine Habitat of Washington State

Prepared For:

Washington State Depart ment of Agriculture 1111 Washington Street

Olympia, WA 98504

Contract Manager :

Mr. Kyle Murphy

(360) 902-1923

Prepared By:

ENTRIX, INC. 148 Rogers St NW Olympia, WA 98502 (360) 352-3225 Project No. 300901

Project Manager:

Jeffrey P. Fi sher, Ph.D.

Contributing Authors :

J.P. Fisher, B. Mavros , D. Waller, M. Heller,

B. Suedel, B. Gillespie, J. Slocomb

October 30, 2003TABLE OF C O N TENTS

Page

1.0 Introduction

............................................................................................................... .........1

2.0 Problem Formulation

........................................................................................................ 3

2.1 Overview of Spartina Inf e station in Washington State ...........................................3

2.1.1 Distribution ..................................................................................................4

2.1.2 Biology .........................................................................................................7

2.2 Ecological Receptors, Community Descri ptions, and Threatened and En dangered Species In P r im ary Areas W h ere Spartina is Distributed ......................................7 2.3 Conceptual Model ..................................................................................................20

3.0 Haz a rd Assessment

.......................................................................................................... 23

3.1 Mechanism of Action and Efficacy .......................................................................24

3.1.1 Mechanism of Action .................................................................................24

3.1.2 Efficacy on Target Vegetation ...................................................................25

3.2 Environm ental Fate and Che m istry .......................................................................31 3.2.1 Physical Chem istry ....................................................................................31

3.2.2 Environm ental Degradation .......................................................................32

3.3 Toxicity to Terrestrial R ecepto rs ...........................................................................40

3.3.1 Mamm als ....................................................................................................41

3.3.2 Birds ...........................................................................................................44

3.3.3 Insects ........................................................................................................45

3.3.4 Reptiles and Am phibians ...........................................................................46

3.4 Toxicity to Aquatic Receptors ...............................................................................46

3.4.1 Fish .............................................................................................................47

3.4.2 Aquatic Invertebrates .................................................................................50

3.4.3 Non-target Aquatic Vegetation ..................................................................50

3.5 Adjuvant and Inert Ingredient Toxi city to Terrestrial and Aquatic Ecological Receptors .........................................................................................51

3.5.1 Inert Ingredients .........................................................................................52

3.5.2 Surfactants..................................................................................................52

4.0 Exposure Assessment .......................................................................................................5 7

4.1 Estim ated Environm ental Exposure Concentrations (EEC) ..................................57 4.1.1 Application Rate ........................................................................................57

4.1.2 Water Concentrations.................................................................................58

4.1.3 Expected Plant and Anim al Residues ........................................................60

4.1.4 Sedim e nt Concentrations ...........................................................................61

FINAL

O c tob e r 200 3 Pag e i4.2 Ecological Receptor Ex posures .............................................................................62

4.2.1 Mam a lian Exposure ...................................................................................68

4.2.2 Avian Exposure ..........................................................................................71

4.2.3 Insect Exposure ..........................................................................................71

4.2.4 Reptiles and Am phibian Exposure.............................................................71

4.2.5 Aquatic Anim al Exposure ..........................................................................72

4.3 Adjuvant and Inert Ingred ient Exposure Assessm ent ............................................73

5.0 Risk Chara c teriz a tion to Ecological Recepto rs from the Use of Imazapyr to Control Spartina .............................................................................................................................74

5.0.1 Mamm al Ri sk .............................................................................................74

5.0.2 Avian Risk .................................................................................................77

5.0.3 Insects ........................................................................................................78

5.0.4 Reptiles and Am phibians ...........................................................................78

5.0.5 Fish .............................................................................................................78

5.0.6 Aquatic Invertebrates .................................................................................79

5.0.7 Non-target Aquatic Vegetation Risk ..........................................................80

5.1 Relativ e Hazard and Risk Characterizati on of Im azapyr, Gly phosate, Surfactants, Inert Ingredients, And The Use of No Che m ical Control Or Other Agents For Spartina Eradication ............................................................................................81

5.2 Uncertainties and Data Gaps ..................................................................................83

5.3 Conclusions and Recomm endations ......................................................................85

6.0 References

................................................................................................................. ........87

List of Appendices

Appendix A: No Action Alternative
Appendix B: Exposure Ca lculation Wo rksheets
Appendix C: Avian Species in W illapa Bay
Appendix D: Terrestrial a nd Amphi bious W ildlif e in the W a lla pa Bay Wate rshed
Appendix E: Threatene d a nd Enda nger e d Species a nd Species of Concern within Washi n gton State, a nd t h e Pote ntial for I m azapyr Exposure fr om Spartina Treat m ent

List of Tabl es

Table 2-1: Spartina Distr i bution a nd Treat ment in Washington Stat e, 1997- 2002.

.......................... 6

Table 3-1: Product for m

ulations of i m aza pyr.

.................................................................................. 23

Table 3-2: Effica cy of Wipe- on App lications of I m azapyr and Gl yphosat e.

................................... 25

FINAL

O c tob e r 200 3 Pag e iiTable 3-3: Exa m ples of Aquatic Spe c ie s Effectively Controll ed by I m aza pyr.

.............................. 26

Table 3-4: Plants known to be re si sta n t to the use of i m a zapyr

. ....................................................... 26

Table 3-5: Effe ct of rat e , ti m i ng a n d spra y vol ume i n 2000 on the e f fica cy of i m aza p yr and gl yphosate for smooth cordgrass control in Willapa Ba y, WA.

........................ 30

Table 3-6: Effects of her b icide rate a nd application spra y vol ume i n Augus t 1999 on

sm ooth c o rdgrass control in Willapa Bay, WA.

........................................................ 31

Table 3-7: Persistence a n d Bi oconc entrati on of I m azapyr in Mi ssouri a nd Fl orida Pond Water, Se di ment and Re si dent Aquatic Biota

. .......................................................... 40

Table 3-8: Hazard Cla s sifica tions to Address W i ldlife Ri sk fr om Her b icide Use

. .......................... 41

Table 3-9: Acute and Subchronic M a mmalian Toxicicity to I m aza pyr.

.......................................... 42

Table 3-10: Lethal a nd Sublethal Toxi city of Arsenal in Controlled Avian Experi ments

. ............................................................................................................... 44

Table 3-11: Toxicity Cla ssifi cations t o Address Acute Ri sk to A q uatic O r ganism s f r om Che m ical Us e.

............................................................................................................ 47

Table 3-12: 96-hour LC 50 Values wit h 0.3 g juve nile rainbow t r out exposed to

i m azapyr ( A rsenal) or gl yphos ate ( R odeo) ta nk mixes

. ........................................... 48

Table 3-13: Toxicity of Technical Grade I m azapyr and Ar senal* (with sur f actant) to Algae and Aquatic Plants , as Esta blis hed Through Controlled Product Registrant St udies.

...................................................................................................... 51

Table 3-14: Acetic Acid Toxic ity to Ecologic a l Receptors.

............................................................. 52

Table 3-15: Effe ct of sur f actant appli e d in Septe m ber 1999 a nd 2000 on t h e efficacy of

i m azapyr for smooth cor dgrass c ont r o l in Willapa Bay, WA.

.................................. 53

Table 3-16: Che m istry a nd Fate of Surfact ants Potentially Used With I m a z apyr a nd Glyphosate

. ................................................................................................................. 54

Table 3-17: Toxicity of Sur f actants With and Wi thout Herbic ide.

................................................... 55

Table 3-18: Acute toxicit y of nonylphenol to a quat i c biota.

............................................................ 56

Table 4-1: Summary of Maxi mum and Average I m azapyr De tections in Relevant

Environmental Media wi th Applicat i on Rates of 1.5 l b s a.i

. /a cre.

........................... 61

Table 4-2: Exposure Pa ra m e ters for A ddre ssing Risks from WSDA’s I m azapyr Applicati ons for Spartina Control.

............................................................................ 63

Table 4-3: Esti m a te d Exposur es to Terre strial Wildli fe Rec e ptors from I m aza pyr Applicati ons ( m g/ kg-body wt) *

................................................................................. 69

FINAL

Octob e r 200 3 Pag e iiiTable 4-4: Esti m a te d s u rfactant conc entra tions i n estuary wate rs where Spa r tina could

be treated wi th i m a zapyr , assuming c onstant sur f a c tant rate of 1% in spray volume, complete solubility on incoming tide, and the “worst

case” sce n ar io of no a d sorption on se di m e nt or Spartina canopy.

........................... 73

Table 5-1: Hazard quotient calculati ons from esti mated exposure doses of i m azapyr to
terrestrial wi ldlife.*

.................................................................................................... 75

Table 5-2. Hazard Quot ient Calc ulat ions fr om Es ti m a ted Aquatic Biota Exposures *

.................... 80

List of Figures

Figure 2- 1: Typical mul t i -clonal distr i buti o n of Spartina alterniflora i n Wil l a pa Bay.

................. 5

Figure 2- 2: Typical Spartina alterniflora mea d ow in Willa pa Ba y.

............................................... 5

Figure 3- 1: Che m ical str u ctur es of the t w o for m s of i m a z a pyr

. .................................................... 24

Figure 3- 2: Box whis ker gra p h of Spartina control as a function of rate of im azapyr and

glyphosate use in ex periments conducted in W illapa Bay, W A

f

r om 1997 to 2000 .28

Figure 3- 3: Box whis ker gra p h of Spartina control as a function of dr y tim e f o r im azapyr (1.68

kg/ ha) and gl yphos ate (8.4 kg/ h a) use in experi me nts conducte d in W i lla p a B a y , WA for m

1997 to 2000 .

............................................................................................... 29

Figure 3- 4: I m a zapyr Di ssoci a tion Under Di ffer e n t pH .

............................................................... 32

Figure 3- 5: De gra d ation Pa t h

way of I m a zapyr .

............................................................................. 33

Figure 3- 6: De gra d ation Rate of I m a z a pyr in Sandy-Loa m Soil

. ................................................. 34

Figure 3- 7: De gra d ation of I m a z a pyr’ s Ini tia l Phot ode gra d ati o n Pr oduc ts CL 119060 and CL

9140 in a controll ed aer ob ic aquatic s y ste m using Miss ouri pond water

. ................ 36

Figure 3- 8: Res i dues of i m a zapyr in wat e r a n d se di ment fr om a Loui sia n a pond treat ed wit h

1.5 b a

. i. / acr e ...............................................................................................................

. 37

Figure 3- 9: Persi s te nce of i m az apyr i n e s tu a r ine wat e rs of Wi llapa Bay fol l owing direc t
appli cati o n t o a n

unve get a ted tida l mu d flat . Dat a r e pres ent e d a r e mea n

val u es of

triplicat e sa mple s +/- SE .

............................................................................................. 38

Figure 3- 10: Persi s te nce of i m az apyr i n e s tua r ine s e di me nt i n Will apa B a y, W A

af ter direct

appli cati o n t o a n

unve get a ted tida l mu d flat . Dat a r e pres ent e d a r e mea n

val u es of

triplicat e sa mple s +/- SE .

............................................................................................. 39

Figure 3- 11: Penetrati o n dista n ce in a r tifi c ial be ak test s .

................................................................ 45

Figure 3- 12: Plasma sodi um and gil l ATPase acti v ity of chinook sal m on expose d t o i m azapyr . 50

Figure 4- 1: Mud- boat applicat or use d to apply herbicide in W i l l apa Bay to c ontr o l Sparti na.

... 59

Figure 4- 2: Esti ma ted water concentrations of ima zapyr i n ti dal waters wit h

no ca nopy

interc epti on and a n

a

ppli cation r a te of 1.5 lbs/ acre (0 .68 kg/acr e )

. ............................ 60

FINAL

O c tob e r 200 3 Pag e i vFigure 4-3: Esti mated plant residue c oncentrations over ti me, with an initial ap plication rate of

1.5 l b s/ac re.

.................................................................................................................. . 65

Figure 4- 4: Esti ma ted c o nce n trati o n of undil u te d i m a zapyr in various spra y vol ume appli cations.66

Figure 5- 1: Haz a rd quoti e nt ( H Q) esti mati on based on rainbow trout LC 50 values of these

sur f a c tant s a s devel o ped by Smit h et al . (2003), where H Q = estimated water

concentr atio n/LC50.

..................................................................................................... 83

FINAL

Oct o ber 2 0 0 3 Page v

### 1.0 INTRODUCTION

The Washi n gton State Depart ment of Agriculture (W SDA) has legislative m a ndate to control

noxious a n d invasive weeds in the State of Wa sh ington. Noxi ous we eds are plants that whe n established are highly destructive, competitive, or diff icult to control by cultural or chemical practices (RCW 17.10.010). Cor d grass ( Sparti na spp. ) a dom i nant invasive we ed spreading throughout many of Washington’s most produc tive estuarine tide flats, is consi d ere d a noxi ous weed under state code ( W AC 16-750-011) . W i t h in th e estuari n e environments of Was h ington Stat e only one he rbicide, glyphosate (i.e . Rode o tm ), i s currently authorized for Spartina spp . control (NPDS Per m it # WAG- 993000). Gl yphos ate is relatively non-toxic to ani m als and is effective on a wide range of pla n t species. Howe ver, its use t o control cordgrass is hi ndered by drying ti m e s that lim it its eff i cacy under the tidal conditions i nherent to estuaries. It also requires higher application rates than an alte rnati v e herbici d e potentiall y available for use

, i m aza pyr (i.e.

Arsenal tm ). The goals of thi s ecol o gi cal risk assessment ar e therefore t o 1) summarize current knowledge c oncerning the toxicity of of i m aza pyr to target and non-target organis m s, 2) esti m a te potential exposure to ec ological rec e ptors relevant to the aquatic (estuar i ne) environments where

the herbicide m a y be appl ied, and 3) c h aracterize r i sks from that expos ure t o the individual species

and ec osyste ms where Spartina s pp. i s distribute d

.

This ecological risk assess ment should be co nsidered supple m ental to the original 1993

Environmental I m pact Statem ent th at evaluated the potential benefits and r i sks from t h e use of the herbicide gl yphos ate (i.e. Rodeo tm ) and other mechanical mana ge ment alternatives to control Spartina ( W SDA 1993). Speci fically, this assessment eval uat e s the risks to fish, wildli fe and nontarget vegeta tion from the propose d use of i m azapyr (i.e. Arse nal tm ) to control s m oot h cordgrass in

estuarine waters of W a shington St ate. Under the EP A Se ction 3 for Section 24( c ) pesticide registration s ought for i m azapyr use i n an est u ary, applications would be made directly to the pla n t during l o w ti de, a nd it is t h is scenari o for which ris k s were cons idered.

Appendix A to this supplem e nt re ferences the “no-action” alternative, which, in contrast to the earlier 1993 EIS, conside r s the “no-action” scena r io to be a continua nce of the curre nt integrate d
pest mana ge ment sche me for Spartina contr o l tha t involves the use of c h e m ical ( g lyphosate) an d

mechanical control means. That is, “no action” in the curre nt conte x t a nd in the ve rnacular of SEPA guidance, woul d constitute the enviro nmental base line upon which i m az apyr use is compared; t h e potential inclusion of i m azapyr int o WSDA’s i n tegrated pest m a nagement scheme

for Spartina control would there f ore r e presen t the “pref e rred alternative”.

The outline and methods of the m a i n body of this report refle c t standa rd ec ological risk assessment guidelines ( E PA 1996). Thus , the report be gi ns with the “pr oble m for m

ulati on”, which summarizes the scope of the proble m, the need to consid er alternative contro l mechanisms, and the

approac h to the assess ment . The proble m for m

ulation is f o llowed by the “hazard assessment ”

which r e late s the current understa ndi ng of i m aza pyr’s environm e n tal fate , and its t o xicity to the range of target and non-target organis m s whe r e testing has been conducted. The hazard

assess ment i s followed by the “e xpos ure assess me nt,” where the pathways and doses possible for

i m azapyr exposur e to the representative biolog ical receptors are evaluated. The exposur e assessment considers the threatened and enda ngered (T&E) avian and aquatic species where

i m azapyr could be applied where data per m it . If no toxicit y data we re available for species typical

of the estuar ine environments wher e i m paza pyr use is proposed, the n toxicity data fr om surr ogate species were used. The use of su rr ogate species with si milar diet ary and/or beha vior patterns ha s

FINAL

Oct o ber 2 0 0 3 Page 1been shown to provide a relatively reliable predicto r of aquatic toxicity when toxicity data are lacking for s p ecies of gre a ter relevanc e to specific areas (Sa ppi ngton et al. 2000).

Standar d EPA and other test species were also us ed as surr ogates to model potential expos ure to terrestrial omnivores, herbivores and carnivores . It can be reasonabl y assumed tha t a sim ila r relationship as found wit h aquatic species sensiti vity exists for other wil d life. Howe ver, only sit e

speci fic risk assessments would be a b le to fully quanti f y risks to resident and m i gratory wildli fe receptors from c h e m ical expos ure. Not w ithstanding, this a s sess ment us ed surr ogate species suc h as the rat, ra bbit, quail a nd mallard duck to gauge expos ure to other wil d life that would be likely t o use estuarine habitat within W a shington State. The rat provides a reas onable surrogate of an omnivore, t h e rabbit an e x clusive her b ivore, a nd t h e quail and duck provide surrogates of upland and wetland bird specie s , respectively.

The effects of speci fic contam i n ants at the broa der ecosyste m le vel m a y also vary signi ficantly

a m ong ec os yste ms bas e d on the physical and che m i cal proper ties of the ch em ic als th em s e lv es , an d the unique combination of physica l , che m ical, a nd biol ogical proces ses occurring in eac h
ecosyste m . Such ecosys t e m di ffere n ces can dire ctly bring a b out di fferenc e s in ani m al populati ons or indirectly affect habit a t. For exa m ple

, wildli fe populations resident t o environme n ts naturally enriched with metals may tolera te a much higher concentr ation of metal exposure than naïve populations. That is, populations of expose d organis m s m a y di ffer in their response to

conta m inant s dependi ng on their natural tolerance to the che m ical, their behavioral and life histor y characteristics (e.g., pre

- expos ure), the dose to which they are expose d, and the duration o f

expos ure. Further m ore , responses may be tra n sient (and therefore r e versible) or per m a n ent (irreversible).

With the preceding disc ussion in mi nd, t h e obje ctiv es of t h i s EIS suppl e m ent can be succinctl y summarized as f o llows:

• To d e s c ribe th e tox i city hazard s of im azapy r to m a rin e and es tu arine aq uatic organis m s, as known.

• To de scr i be the t o xicit y

ha za rds of i m a z a p yr to terrestrial and am phibi ous w i ld lif e, as known.

• To describe the toxicity ha za rds of i m a z a p yr to non-t ar get ve get a ti on, a s known.

• To identify sensitive species th at m a y be im pacted in different re gi ons where i m a z a p yr could be applied.

• To esti mat e ( m odel) ecol ogi ca l receptor exposure (dose) by identify ing complete and

in com p le te e xpo su re p a th

ways , tak i n g in to ac cou n

t env i ronm en ta l f a

te an d tra n sp o r t th ro ug h both phys ical a n d bi ol ogic al me a n s

.

• To characterize the risk or threat to other environm ental com ponents po tentially affected by

im azapy r.

• To com p are risk s f r om th e po ten t ia l u s e of im azap yr rela tive to th e ex is ting use of gl yphos a te and other existing control m e thodologies, such that the ex isting control m e thods can be

con s idered the “no act ion alternatives”.

• To i d e n ti fy the me t h od or i n te gr ati on of t r eat me n t me t h od s , fro m r e v i ew of new literature

and W S DA’s existing program , t h a t be st cont rols Spartina spp . with the m i nim u

m

a m ount of

risk to th e en viro nm ent.

FINAL

Oct o ber 2 0 0 3 Page 2

### 2.0 PROBLEM FORMULATION

To frame the scope of t h e Spartina proble m in the State of Was h ington, the potential m e ans to control it, a nd the probable risks a nd be ne fits of t h e use of Arse nal tm as a component in the integrated manage ment of t h e invasive wee d , a th orough unde rstanding of th e scope of the proble m is needed. This chapter define s the scope of the proble m , the assess ment endpoi nts that best represent the m a na ge ment goals of the WSDA for Spartina control, the concep tual models we will

use to c onsi d er exposure to releva nt ecological re ceptors, and the methodology by which risks t o ecological receptors are quantified and characterized.

Toxicol ogy i s the study of poisons . It exa m i n es a nd atte mpts t o de fine the range in responses of a n organis m or organi s m s t o variable doses of a ch e m ical or c h e m icals

. Thus, the mo st i m portant factors regulating chemi cal toxicity are the ex posure dose, the duration of exposur e , and t h e potency of t h e che m ical. The genotype, and nutr itional and physiol ogica l, state of a n ecological
receptor at the ti me of e xposur e can also a f fe ct che m ic al toxicity. The introduction of che m ical s into an ecosystem can cause direct har m

to organi s m s, or may indirect ly aff e ct their f itness—the ability of an ani m al to survive and produce viable offspring. The re sults of c h e m ical e xposur e may be i mmediately apparent or m a y become noticeabl e only after c onsiderable delay. Recognizing th e effects of exposure on ani m als may require anal yses through a suite of meas ure m ent endpoints

. Measure m ent endpoints may include physiologic a l, neur ologi cal, be havioral, endocrine- m e diate d, or a variety of other indicators that could be c onstrued to play a role in the survival of the organis m

.

Ecologic a l r i sk asses s m ent represe n ts a branch of toxic o logy wherein the e f fects of putati v e poisons are exam ined not only at th e individual organismal level as outlined above, but also at the broader population a nd ecosyste m le ve l. Thus, t h e pur pose of t h is ecol ogical risk ass e ss m e nt is t o deter m ine the nature, ma gnitude , and transience or pe rm an en ce o f ob s e rv ed o r ex p e c t ed e f f e c t s to
anim als and their habitat f r om exposure to im az apyr, based on WSDA’s pr ojected appli c ation rates and integrat ed pest manage ment pra c tices. The assess ment relies heavil y on ecological hazard

studies that have been c onducte d over the past se veral years, product regi stration study results, and

conservative deter m inisti c exposure modeling at the organis m al level. Effe cts at the organis m a l level are pr esumed to be reflecti v e of poten ti al effects a t the popul ation level, though no quantitative measures of effect at the population l e vel are calc u lated

2.1 Over view of Spartina Infestati on in W a shingt on St ate

Spartina is an invasi ve weed tha t inhabits ti deflats

, salt m a rs hes a nd estuaries throughout Washington State’s coast a l areas. There are now fo ur species of Sparti na found in Wa shington’s

waters, Spar tina alternifl ora, Spartina patens

, Spartina angli c a and a ne wly disc ove red specie s found in the fall of 2001 in Gr ays Harbor a nd Island County, Spartina densiflora. So meti me s referred to as cordgrass, Spartina alterniflora and Sparti na patens are native to the Eastern and

Gul f coast s of the United States and are integrated into these regions’ nat u

ral ecosyste m proc esses

. Spartina anglica is an intentionally cr eated hybrid. Spartina densiflora is native to South America

which has a l so invade d Hu mboldt Bay in Cali fornia. In its native envir o nments, t h e spread o f Spartina is controlled by natural bi ological age n ts, and by natural disturbance factors such a s hurricanes and tidal action.

FINAL

Oct o ber 2 0 0 3 Page 3The potential of exotic species to c h a nge the phys i cal structure and in so doing alter the ecological functioning of the e n tire habitat unit has been well docume n ted (Zippere r 1996). In several of Washington State’s coast a l habitats, Spartina spp. outcompetes and displac e s native ve getation and results in changes to local eco system s by converting littoral m udf lats to salt marshes. These changes t h reaten to i m pact native fisheries, shell f i s h beds , wat e rfow l migr ations and ot her wildli fe by reducing the habitats carrying capacity for these ani m als.

2.1.1 Dis t ribu tio n
Spartina alterniflora typifies an i nvasive spe c ies by ha ving a wide tolerance to habitat require ment s, fast disper sal rate, clonal reproducti on and fe w t o no nat u

ral pr edators in its invaded range ( Z ippe rer 1996). Spartina alterniflora was most likely i n troduce d to the Was h ington c o ast when it was used in the packing of East Coast oysters for shi ppi ng during the lat e 1800s. In

addition to the accidenta l introduction, S. alterniflora was also intentionally planted by a gun club

betwee n 1941 and 1946 t o stabilize bank eros i on on their pr operty in Pa dill a Bay. Spart i na anglica was also intentionally introduced, to stabilize dikes and provide forge f o r cattle in Port Susan Bay. The pathwa ys of introduction for bot h Spartina patens a n d the ne wly disc overed S. densiflora are not known a t this ti me.

Spartina spe c ies have spread through out Washington State’s coastal counties. Infest ations range from only a fe w square f eet to more t h an 6,800 solid acres. Currently ther e are an esti mated 7,500

solid acres i n terspersed a m ongst 20,000 total invaded acres i n Washington’s coastal habitat. Tabl e 2-1 summarizes the locations, size and recent treat m e nts of Spartina sp. found in Washington Stat e ( W SDA Le gislative Re port 2002). Figures 2- 1 and 2-2 de monstr ate typical clone and fiel d colonies ( m e a dows) of Spartina , as occurring toda y in W illapa Bay.

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Oct o ber 2 0 0 3 Page 4Figu re 2-1: T y pi cal m u lt i-clo n al distrib u tio n of Spartina alterniflora in Willapa Bay

. (So u rce: WS DA 2003. )

Figu re 2-2: T y pi cal Sparti na alterniflo ra meadow in Willapa Bay

. (ph o to credited to K. Pa tten, b y

perm is sion. )

FINAL

Oct o ber 2 0 0 3 Page 5Table 2-1: Spa r t i na Di stribu tio n a nd T r ea tme n t i n Wa shi ngto n Sta t e , 199 7-2 002.

C ount y Sparti na P r es ent in 20 02 Sparti na Tr ea t e d, 19 97 - 2 0 0 2 200 2 Tr ea t m e n t Me th o d s

Pacific (Will ap a B a y) Ov er 6, 80 0 s o lid acr e s

sp re ad o v er > 15 ,0 0 0

acr e s 199 7 –a pp ro x. 74 2 soli d acr e s

199 8 –a pp ro x. 45 0 soli d acr e s

199 9 –a pp ro x. 60 0 soli d acr e s

200 0 –a pp ro x. 80 0 soli d acr e s

200 1 –a pp ro x. 90 0 soli d acr e s

200 2 –a pp ro x. 18 04 s o lid ac res M o w / her b i cide , he rb icide

, se ed ling

re mov a l, v a ri ous mech anic a l c ont r o l.

Gra y s H a r b o r Scatt e re d clo nes and

seedli ngs 0

. 2 5 ac res e a ch 199 7 th ro ug h 20 0 2 - all t r e a t ed He rbici d e

, se edli ng r e mov a l, mo w

S n oh om ish A p pr ox. 3 5 0 so lid a c r e s

spr e a d ove r > 4

, 5 00 ac res 199 7 –a pp ro x. 89 solid ac res

199 8 –a pp ro x. 12 6 soli d acr e s

199 9 –a pp ro x. 90 solid ac res

200 0 –a pp ro x. 15 8 soli d acr e s

200 1 –a pp ro x. 75 solid ac res

200 2 –a pp ro x. 23 8 soli d acr e s M o w / her b i cide , he rb icide

, se ed ling

re mov a l, dig

, m e chanic a ll y c r us h, mo w.

I s la nd A p pr ox. 3 5 0 so lid a c r e s

spr e a d ove r > 1

, 0 00 ac res 199 7 –a pp ro x. 25 0 soli d acr e s

199 8 –a pp ro x. 16 0 soli d acr e s

199 9 –a pp ro x. 15 5 soli d acr e s

200 0 –a pp ro x. 13 0 soli d acr e s

200 1 –a pp ro x. 72 solid ac res

200 2 –a pp ro x. 18 0 soli d acr e s M o w / her b i cide , he rb icide

, se ed ling

re mov a l, mec h a n i call y crush

, mo w.

Skagi t App r o x . 40 solid acr e s

spr e a d ove r > 2

, 0 00 ac res 199 7 –a pp ro x. 91 solid ac res

199 8 –a pp ro x. 57 solid ac res

199 9 - all tr ea te d

200 0 –a pp ro x. 60 solid ac res

200 1 –a pp ro x. 33 solid ac res

200 2 –a pp ro x. 37 solid ac res M o w / her b i cide , he rb icide

, se ed ling

re mov a l

, di g

, m o w.

Clalla m 1 in fes t ati o n < 0. 001 ac r e s

in size 199 7 – tr ea te d t w ice

199 8 – tr ea te d t h r ee tim e s

199 9 – tr ea te d t w ice

200 0 – tr ea te d t h r ee tim e s

2 0 01- 02 – tr ea ted fo ur t i me s Dig

Jeff ers on 14 i n f e sta t io ns - a p p r o x

. 0.01 s o lid ac r e s total 199 7 - all tr ea te d

1 9 98- 20 00 - a ll tr ea t e d tw ice

2 0 01- 02 – a l l tr eat e d th re e t i me s Mo w, mo w/ he rbic ide, di g, s e e d lin g

re mov a l

Kitsa p 8 in fes t ati ons - a p p r o x. 1

solid acre total 199 7 - all bu t 2 t r i bal si tes

199 8 - all tr ea te d once

199 9 - all tr ea te d t w ice

200 0

- 0 1 - all t r e a t ed onc e

200 2 - all tr ea te d t w ice Mo w, mo w/ he rbic ide, di g, s e e d lin g

re mov a l

King 2 in fes t ati ons - si ngle

clones a n d a fe w seedli ng 199 7 – mo nito r e d

199 8

- 9 9 - all t r e a t ed onc e

200 0

- 0 2 - all t r e a t ed t w ic e Dig

San Ju an Re -g r o wth fo un d at on e

site. 2 ot he r si tes clean f o r

f o ur co n s e c ut ive y ear s 97 - all tr ea te d

98 - all tr ea te d

99 – mo nito r ed

200 0

- 0 2 - all t r e a t ed onc e Surv e y

, di g

F r om Was h in gt o n St at e De pa rt me nt of Ag ricul t u r e’s Re po r t t o the L e g islat u r e

, P r o g r e s s of th e 20 02 S par t i n a Er adic a ti on Pro g r a m

, Dec e mb e r 15, 2 0 02

FINAL

Oct o ber 2 0 0 3 Page 62.1.2 Bio l ogy

Spartina is a rhizom at ous perennial grass that can prolifer ate from eithe r sexual reproduction or vegetative pr opagation. Shoots sprout from below ground rhizomes in the spring and re ach a height

of thr ee to s i x feet by mid-summer

. Spartina f l owers f r om late June to October; however, not all populations within Wa shington St ate flower. Sexual re production may require a sufficient undergr ound biomass to trigger. Populations that do not flower depend on vegetative propagation and/or lateral growth to spread. Te mperature, photoperiod soil temperatur e, and soil salinity ha ve been shown to influe nce occurrence a nd ti m i ng for the populat ions that do flower. Salinity has also

been s h own to a f fect gr owth rate , see d ling developm e n t and s p atial zonati on (Feist 1999).

Dispersal of Spartina is accom p lished when water currents, ani m als or humans transport seed, rhizome pieces or entire plants to new locati ons. Humans are the m o st prevalent cause of Spartina dispersal, eit h er through i n tenti onally plantings or accidental spre ad. Water f owl and other birds are

known t o ingest seeds a nd rhiz om e s , sprea d ing ma terial thr ough their feces. Water spread se eds

and rhizome s fragme nts via natural c u rrents and tid al actions. These me chanisms of dispersa l create great diff iculties in cont rolling the spread of the weed.

When new plants are es tablished t h rough either seeds or vegetative propagation, sur v ival appear s to be linked to competition with ot her plants. Low light levels cause d f r om other plants m a y inhibit

survival. See d and vegeta tive propa ga tion see m s t o be i m porta nt in the c o l onization of disturbed or bare areas. In contrast, growth of established co lonies out- competes native plant species resultin g in a nearly complete m o noculture of Spartina pla n ts in invade d habitats. These colonie s or clones reproduce by the lateral spread of undergrou nd r h izom es and above gr ound tillers.

Spartina alt e rniflora, S. patens, and S. anglica become dor mant during th e winter and die ba c k.

Ho wever , Spartina densiflora does not become dor m a nt and pr oduc es new pla n t m a terial throughout t h e year . In a ddition, the seed via b ility of S. densi flora appear s to be muc h higher than

the other s p e c ies of Spart i na . These traits m a y potentially allow S. densiflora to invade new areas

more rapidly than t h e ot her Spartina species in Washington State.

In its native habitats S. alterniflora f u nctions as essential f e edi ng grounds and nurs ery areas for numerous species of invertebrate s, fi sh, shorebir ds, migrator y wa terf owl, and sma ll mammals. In

contrast S. alterniflora alteration of mud f l ats co uld elim inate critical f o raging habitat of juvenile

sal m onids, flatfish, shor ebirds , and migrator y waterfowl. In addition, c o mposition a nd abundanc e of benthic invertebrates may be s ubs tantially alte red by cordgrass coloniza tion of mudflats because these spe c ies are strongly infl uence d by the physic al environment (Zippere r 1996).

2.2 Ecological Receptor s, Comm uni t y Descript ions, and Thr eat ened and Endangered Species In P r imar y

A r eas Where Spar tina is D i s t ribute d

As de monstr ated in Tabl e 2-1, Spartina is found in multiple locations withi n Puget Sound, a nd o n the Pacif i c Coast within W illapa Bay. Most areas of Spar tina distribution in Puge t Sound are

localized and can be contro lled by mechanical means ( see Table 2-1). The t w o are a s of varying

size and dist ribution, W i llapa Ba y and Pa ddila Bay, require t h e use of che m ical c ontr o l m e ans to achieve the goal of eradi cation, and c h e m ical cont ro l m u st re main a viable alternative for all areas where Spart i na is found if me chanical m e ans prove i n effectiv e in the f u ture . W ith this understanding, an overvi e w of t h e ec ological comm unities and ecological r e ceptors in Willapa and Padilla bays is provided belo w. The W illapa Bay and Padilla Bay ecosystems share many

FINAL

Oct o ber 2 0 0 3 Page 7sim ilarities with the other areas Spartina has col onized i n Washington St ate, although due t o thei r size, the ecosystems support a greater diversity of species. These habitats, as well as other coastal

habitats of Was h ington where s m a ller colonies of Spartina have esta blished, s u pport several priority spec ies, some of which are lis ted as threatened or enda ngered (T& E ) under the Enda ngered Species Act (ESA). Thus, this se ction also provides a s u mmation of the T&E species i n Washington State, and the potential for these spec ies to occur in areas where im azapyr treatments
of Spartina c ould occur.

Willa pa Ba y

W illapa Bay is located in the southw estern corner of the W a shington coast. It is approximately 38

km l ong a n d 8 km wide (Gringas et al. 2000). At high tide, the aquatic environme n t of W illa pa Bay is appr oxi m ately 88,000 acre s , howe ver al most ha l f of t h e Bay is drai ned at low tide (Cohen et al. 2001). W illapa Bay in almost fully enclosed by the Long Beach Peninsul a, a 30 km-long barrier spit that was f o rmed by the deposition of Columbia River sediments. The W illapa Basin has received an average of 85 i n ches of rain per year over the past 75 years of recor d ( http://www.tidepool.org/ w isc w eb/ w isc98nw2.ht ml) . W illapa Bay has a drainage basin of approxi mate ly 2,550 s q uare m iles

, and the mai n tr ibutaries that drain into the bay include the North, W illapa, and Naselle rivers. The Palix Ri ver is on of the m i nor c ontributors to the m e an daily runoff. Mean daily runoff to W i llapa Bay re presents approxi m a tel y < 0.05 percent of the bays

total volume.

Willapa Bay is W a shington’s largest outer coast estuary (Cohen et al. 2001). W illa pa Bay is a largely unalt ered environment

, howe ver it has be en signi fica ntly i m pacte d by the c o l onization of

non-indi genous/exotic species. Of t h e 892 vasc ular plants i n the Willapa Basin ( w hich include s headwater habitat outs i de of the brackish e s tuary) approxi m a tel y 250 specie s have been

introduce d. Si m ilarly, 30 of t h e 473 species of vertebrates identifie d in the basin have been

introduce d ( www.tidepool.org/ wisc web/wisc 98nw2.ht m l) . Approxi matel y 34 e xotic aquatic plant

and ani m al species were recently identified withi n the W illapa Bay estuar y during a 2000 research expedition sponsor ed by the Wa shington State Depart ment of Natura l Resourc e s ( W DNR) Nearshore Habitat Progr a m ( C ohen et al. 2001) . W i t h in the estuar y habi tat of the ba sin, the t w o most signi fi cant plant species introduced are the Japanese eelgrass ( Zostera japonica) a nd the

s m ooth c o rdgrass ( Spartina alterniflora)

.

The most problematic exotic speci es f o und within W illipa Bay is the smooth cord grass. This

invasive s p e c ies is outc o mpeting native aquati c vegetation for s p ace and nutrient resources. Spartina also degrades habitat f o r aquatic, terrestrial and aviana nimal species utilizing W illapa Bay. Betwe e n 1994 a n d 1997, Spart i na populations expa nde d at a rate of 485 percent within the southern por tion of Willa pa Bay ( W ill apa Bay Est u ary 2001)

.

In addition to the m a jor issues created by the introduct i on of Spar tina , numer ous aquati c invertebrate ani m al spe c ies have bee n introduce d intentionall y or inadver t ently into Willapa Bay during the past century. The degre e to whic h th e s e introducti ons have dis p laced native species is

less underst ood tha n the displace ment cause d by Spartina . Some of the known non-native

introductions are tabulated in Table 2-2.

FINAL

Oct o ber 2 0 0 3 Page 8Table 2-2: Com m on Non-n a ti ve I n verteb r a t es in Wi lla pa Ba y

.

Ge nera l Ta xon Spe c ies First Pug e t
Sou n d

Rec o r d

Hobson ia florida 1940

Polydora cornut a 1932

Pseud opo lydora bassar g inen sis 2000

Pseud opo lydora kem p i japo nica 1951 Annelida ( polyc haeta)

Streblosp i o ben e dicti 1932
Crepid u l a forn ica t a 1905

Illyana ssa ob so le ta 1907

Ocinebrellus inornatus 1924 Molluska (pr o so branchia)

Uro s al pi

nx

i

n o r na t u s 1890

Cra s sos t re a gi g a s 1875

Mya aren aria 1874

Neotrap e zium lir atum 1924

Petricolaria pholadiformis 1927 Molluska (b ivalv e )

Vener up is ph ilipp i nar um 1924

Eusar iel

l a zoste r icol a 1953

B a la nu s i m p r ov

isu s 1853

Nippoleucon hinumensis 1979

Limnoria tripunctata 1871 or 187 5

Ampithoe valid a 1941

Corophium ach erusicum 1905

Corophium insidiosum 1915
Grandidierella japonica 1966

Jass a ma rmora t a 1938 Anthropoda (cru stacea)

M e li

ta ni ti da 1938
Entoprocta (bry ozoa) Bowerbanki g r a c ili s 1923

Botrylloide s v

i o l

aceu s 1973

Botryllus schlo sser i 1944- 47 Urochordata (as c idiacea)

Molgula manhat t ensis 1949

Porifera Clathria prolifera 1945- 49

Cnid aria (h ydro zoa) Cordylophora caspia 1920

Cniidar ia (ant ho zoa) Diadumene lin eata 1906

Sour ce: Coh en e t a l

. 200 1

Several of the resident shellf is h species in W illapa Bay suppor t substantial commercial harvest

and/or far m i ng industrie s (Table 2- 3). The mos t signific a nt

species incl ude the Pac i fic Oyster ( Crass o strea gigas ) and t h e native Dungenes s crab (PNCERS 1998)

.

FINAL

Oct o ber 2 0 0 3 Page 9Table 2-3: Com m e r ci a l Sh ell f is h Specie s w i thi n Wil l ap a Ba y

.

Common Name Scient ific Na me T y pe of Species

Pa ci fi c oy st er Cra s sos t re a gi g a s O yst er Dunge ne ss cr ab Cancer ma gist er Crab

Red ro ck crab P l ag usi a c h a b r us Crab

Geodu ck Pano pe a a b rupt a Clam
Quahog (hard s h e ll) A r c t

ic a is landic a Clam

Softshel l cl am Mya aren aria Clam

Native lit t lene ck Proto t ha ca stam inea Clam
Cherrysto ne Merce nar ia m e rcenar ia Clam

Sour ce: PNC E RS 19 98

Anadromous salm onids use W illapa Bay’s major tributaries f o r migration, spawning, incubation and early-re aring (Table 2-4). Habit a t within W i llapa Bay is also i m porta nt habitat for larval and juvenile mar i ne and ana d rom o us fi s h rearing. It i s , “arguably th e most i m portant nurs e ry estuar y on the coast f o r juvenile Englis h sole ” (B. Dumba u ld, WDF W , pe rsonal c o mmunic a tion to We ndy

Sue Wheeler , WSDA, 11/14/2000). Paci fic herring spa w n on the eelgrass beds in the early spring,

and the estuary also supports lesse r- known s m elt and sand la nce runs ; all three of these species are

i m porta nt forage fish for Paci fic sal m on. Anchovy, sal m on and st urgeon have supporte d

commercial fisheries in t h e outer bay in the past.

W illapa Bay is also a major m i gration stopover lo cation f o r shorebirds in the spring and winter ( W illapa Nat i onal Wildlife 2001) . An esti m a ted 100,000 to 1,000,000 shore b irds stop t o feed i n the

m

u df lats of W illapa Bay and other coastal re gions of W a shington State during the spring.

However

, spring and wi nter peak shorebird numbe rs ha ve been declini n g by 54 a n d 67 percent, respectively since 1991 due to i n festat ion of Spartina

.

The distribution of ducks within W illapa Bay was m odeled by W illa pa National W ildlif e (2001). The hierarchy of distribut ion within W illapa Bay according t o m i d- winter aerial waterfowl surveys

is: South Ba y (47.1%) > East Ba y (28.6%) > Nor t h Ba y (18.8%) > West Bay (4.2%) > Pe ninsula (1.2%). The most si gni fi cant region for duc ks, the South Ba y, is als o harbors the great e st density

of Spartina . A summ ation of som e of the comm on av ian species found with in W illapa Bay is provide d in Appendix C. (USFWS 1991).

W illapa Bay, its surrounding wildlif e ref uge, and the extensive contigous lowland f o rests also support a di verse asse mblage of terr estrial and a m ph ibious wildli fe. Some 53 speci es of ma mmals and 19 herptiles (reptiles and amphibians) have been reported, as summarized in Appendix D (USFWS 1991).

FINAL

O c tob e r 200 3 Pag e 10Table 2-4: Ana d romo u s Sa lmo n id Dis t ribu tio n and Utiliz ation w i thi n Willa pa Ba y Tri butari es.

River Speci es Run Prima r y Use River Mi les Use d % of Stream

Used

Migra t i o n 0

. 0

- 7

. 3 20 % Chin oo k sa lmo n Fal l Spawn i n g / R ear ing 7.3-3 1 .2 63 %

Migra t i o n 0

. 0

- 7

. 2 19 % Coho sa lm on N/A Spawn i n g / R ear ing 7.2-2 6 .8 52 %

Migra t i o n 0

. 0

- 7

. 4 20 % Stee lhea d W i n t e r Spawn i n g / R ear ing 7.4-3 0 .2 61 %

Migra t i o n 0

. 0

- 9

. 9 26 %

Rearin g/ Migrat io n 9.9-1 5 .2 14 %

Spawn i n g / R ear ing 15.2- 25. 2 27 % Nase l l e R i ver

Chum sa lmo n N/A

Migra t i o n 2 5

. 2

- 25. 6 1 %

Migra t i o n 0

. 0

- 0

. 3 1 % Chin oo k sa lmo n Fal l Spawn i n g / R ear ing 0.3-5 9 .3 98 %

Migra t i o n 0

. 0

- 0

. 3 1 % Coho sa lm on N/A Spawn i n g / R ear ing 0.3-6 0 .0 99 %

Migra t i o n 0

. 0

- 0

. 6 1 %

Rearin g/ Migrat io n 0.6-2 2 .0 36 % Stee lhea d W i n t e r Spawn i n g / R ear ing 22.0- 60. 0 63 % North River

Chum sa lmo n N/A Migra t ion 0.0-5

. 8 10 %

Chin oo k sa lmo n Fall Migra t ion 0.8-4

. 0 34 %

Coho sa lm on N/A Migra t ion 0.8-4

. 0 34 %

Stee lhea d W i n t e r Migra t i o n 0.8-4

. 0 34 % P a lix Riv e r

Chum sa lmo n N/A Migra t ion 0.8-4

. 0 34 %

Migra t i o n 0

. 0

- 7

. 5 16 % Chin oo k sa lmo n Fal l Spawn i n g / R ear ing 7.5-4 1 .3 72 %

Migra t i o n 0

. 0

- 5

. 5 12 %

Rearin g/ Migrat io n 5.5-5

. 8 1 %

Spawn i n g / R ear ing 5.8-4 1 .8 76 % Coho sa lm on N/A

Migra t i o n 4 1

. 8

- 44. 1 5 %

Migra t i o n 0

. 0

- 5

. 5 12 %

Rearin g/ Migrat io n 5.5-2 8 .2 48 % Stee lhea d W i n t e r Spawn i n g / R ear ing 28.2- 41. 3 28 %

Migra t i o n 0

. 0

- 2 8

. 3 60 %

Spawn i n g / R ear ing 28.3- 31. 8 8 % Willapa River

Chum sa lmo n N/A

Migra t i o n 3 1

. 8

- 36. 0 9 %

Willapa Bay Green sturg eon N/A Spawn i n g / R ear ing N/A N/A

Source: S t reamNet 2003

FINAL

O c tob e r 200 3 Pag e 11Padi lla Bay

Padilla Ba y is an 11,000 acre shallow-water bay in north Puget Sound, i n corporating the deltas of the Skagit a nd Sa mish Rivers. Padi lla Bay is delineated by the salt wate r edge of the North For k Skagit River delta in Puget Soun d. Padilla Bay is approximately 8 miles long an d 3 m iles wide (Padilla Bay NERR 2002). The Skagit River provides the majority of the f r eshwater and sediment resources to the bay. The bottom of Padilla Bay is very shallow due to sedim e nt transport f r om the Skagit River, which creates a broa d tidal f l at during low tide and f l ooded during high tide (Padilla Bay NERR 2002)

.

Eelgrass me adows occ u py nearly 8,000 acres of t h e ba y, and are m a de up pri m arily of two species: native eelgr ass ( Zostera marina ) and a non-native specie s ( Zostera japonica ). The eelgrass

meadows stabilize the mud- flat subs t r ate that dominates the bay, and provide food and shelter for

various f i sh and wildlif e . Eelgrass and algae ar e the m a in prim ary producers within Padilla Bay (Thom 1988). The salt marsh associated with Pa dilla Bay was diked and drained bef o re 1900 f o r f a

rm land, leaving a small f r in ge of the salt marsh that incl udes spe c ies suc h a s salt gra s s ( Distichlis spicata ), salt brush ( Ari p lex patula ), p i c k le we ed ( Salicorni a virginica ), and seaside arrowgrass ( Triglochin maritimum ).

The salt marsh and mudflat of Pad illa Bay has problems with two n on-nat i ve inva sive species of cordgrass ( Spartina alterniflora and Spartina anglica ) that are competi ng fo r resources held by

native s p eci es ( W SDA 2000)

. S. alterniflora (smooth cordgrass) was f i rs t introduced into Padilla Bay in the early 1940s and by 1979 approximately 3 .5 acres were reported in Padilla Bay; S. alterniflora was re porte d to have increased to 17 acres by 19 97 ( W SDA 2000). S. anglic a (common c o rdgrass) for m ed from al lopolypl oidy of the steril e hybri d S. X townse ndi i in England. S. anglica has strong hybrid vigor a nd has take n over approxi m a tely 25,000 acres of i n tertidal salt

marsh on the British coast within the past 100 yea r s ( W SDA 2000). S. anglica was reported in the Puget Sound by 1979 i n an esti mated covera ge of 15 acres ; by Septe m ber 1997, a pproxi matel y 1,000 solid acres was re ported wit h in North Puge t Sound (over 8,000 a c res of this region was

i m pacted).

Aquatic organisms f o und within Padilla Bay include crabs, sh rimp, mud snail, and various organis m s t h at are s upported in salt m a rs h/ mud fl at habitat. Extensive eelgrass me adows in t h e bay provide excellent habitat for fi nfis h suc h as sal m on, perch, a nd herring, but also m a ny invertebrate species (e .g. wor m s , s h rimp, cla m s). Thes e spe c ies in tur n

support gr eat blue her o n, eagle, otter, and seal populations. The eelgra ss m e a d ows of the Padilla Bay est u ary provi de

suitable habitat f o r m a ny dif f erent lif e stages of aquatic organism s. F o r exam ple, young Dungeness crabs, one of the most econom i cally important aquatic or ganisms in Padilla Bay, utilize

intertidal cobble found within t h e ee lgrass meadows (Dinne l et al. 1986)

.

FINAL

O c tob e r 200 3 Pag e 12Table 2-4: Ma ri ne I nve rte b rate Sp ecies w i thin Pad ill a Ba y.

Ph y l u m Common Name Scient ific Na me Exotic

Nem e r t e a S a n d nem e rtea n Cerebrat ulus californ i en sis no

Nemerte a G r e e n n e mert ea n Emp l e c to nem a g r acile no

Nemertea Restless worm Paran e mert es pe regrin a no

Anne lid a Lu gw orm A b a r en ic ol a p a ci fi ca no

Anne lid a R o u g h

- skinne d l u g w o r m A b a r en ic ol a cl apa re di i no

Anne lid a T h r e a d w o r m Notoma stu s t enu is no

Cnid a r i a S e a p e n A b ie ti na ri a sp

. no

Cnid a r i a O r a n g e

- s t r i p e d j e l l y f i s h Gonio nem us vert ens no

Cnid a r i a A g g r e gat e a nem o n e Anth op le ura e l e g ant issima no

Cnid a r i a B r o o d in g a nem o n e E p iac t i s prol ifera no

Cnid a r i a T e a l i a Tealia sp. no

Cni d a r i a S t alk e d jelly fi s h Hal i c l

ys tu s a u r i c u la no

Cteno p h o r a S e a goo seberr y Ple u robra c hia b a c he i no Brachiopo d a L a m p she l l Terebrata l ia tran sversa no

Echinod ermat a Blo o d star Henri c ia le v i u s c u la no

Echinod ermat a Six-ra yed sea st ar Lept aster i a s

h e xact is no

Echinod ermat a Purp le st ar P i s a s t e r oc h r ac eu s no

Echinod ermat a Sunf lower star P y

c n o p o d i a he li an t h oi de s no

Echinod ermat a Green sea urchin S t ro ng yl

oc en t r otu s d

r o e b a c h i e nsis no

Echinod ermat a Red sea cucumb er Cu c u m a ria mi ni

at

a no

Echinod ermat a White se a cu cum ber Eupe nta c ta qu in que sem i t a no

Chaet ogn ath a A r r o w w o r m Sag i t t

a elega ns no

Chordat a H a i r y sea squ i r t B o ltenia v ill

os a no

Chordat a Broad ba se sea squ i rt Cnem ido c arp a f i nmarkie n sis no

Chordat a W a r t y sea squ i rt Pyura h a u s tor no

Mollu s c a M o s s y ch ito n Mopa lia m u sco s a no

Mollu s ca Large varie gat ed limp et Notoa c m ea persona no

M o ll usc a P l at e li m p e t Notoa c m ea scut um no

Mollu s c a F i n g e r lim p e t Coll is ell a digitali s no

Moll usc a S h iel d li m p e t Coll is ell a pel t a no

Mollu s c a L i m p e t Unid ent if ie d sp. no

M o ll usc a S p in dl e wh elk Sear le sia d i ra no

Mollu s c a C h i n e s e h a t Calyptr aea fa st ig iat a no

Mollu s c a H o o k e d slipper s h e l l Crepid u l a adu nca no

Mol l u s c a S l ip per she l l Crepid u l a sp

. no

M o ll usc a S c re w sn ai l B i tti

u m s p

. no

Mol l u s c a H a i r y she l l Tri c ho t r op is s

p

. no

Moll usc a A m phis s a Amph i s sa sp. no

M o ll usc a K e y h ol e li m p e t Diod ora a s pera no

Mol l u s c a C h i n k sh el l Lacuna variega ta no

M o ll usc a S i tka pe ri wi nk le Lit t or

ina sit k

a na no

FINAL

O c tob e r 200 3 Pag e 13Ph y l u m Common Name Scient ific Na me Exotic

Mollu s c a C h e c k e r e d periw in k l e Lit t or

ina scu t u l at

a no

M o l l u s c a C o w r y ? Cyprae o l ina pyr i f o rmis no

Mollu s c a J a p ane se hor nm o u t h Ocene bra in orna ta (= jap o n i ca) ye s

Moll usc a A t lantic oys t e r dril l Urosa l p i

n x

ciner ea ye s

Mol l u s c a B a sk e t sh el l Nassar iu s fra t er

culu s ye s

Mollu s ca Lean ba sket she l l Nassar iu s me nd icu s no

Mollu s c a L e w i s ' mo o n sn a i l P o linic es l

e wis i i no

Mol l u s c a T u r r e t she l l Bat i llaria at trame n tar i a ye s

Mol l u s c a J a p ane se fa l s e c e r i t h Bat i llaria zona lis ye s

Mollu s c a W r i n kled th a i s Thais lam e llo s a no

M o ll usc a B l ue t o p sh el l Calliostom a ligat um no

Mollu s c a P u p p e t marg arit e Margar ite s pup illus no

Mol l u s ca Tay l or ' s se a sl ug Phy l l a plys ia tayl ori no

Moll usc a B u b b l e s h ell A c te oci n a sp

. no

Moll usc a B a r r e l bubbl e Act e o c ina harp a (Retusa h a rpa) no

Moll usc a B u b b l e s h ell Haminoe a sp. no

M o ll usc a B lis t e r p a p e r bu bb l e Hami noe a ve si cu la no

Moll usc a B a r r e l bubbl e Cylichn a sp. no

Mollu s c a O d o s t o m e Odost o m i a sp

. no

M o ll usc a O p a l esc e nt nu dib r a n c h Hermissend a cra s sicorn is no

Mollu s c a S c u l p t u r e d n u t c l a m Ac i l a ca str a en si s no

Mol l u s c a H e a r t co c k l e Clino c ard i um nu t t allii no

Mol l u s c a J a p ane se o y s t er Cra s sos t re a gi g a s ye s

Mollu s c a D i p p e r c l a m Lyo n sia striata no

Moll usc a P o l l u t e d mac o m a Macoma in qu ina t a no

M o ll usc a B e n t -n os e d cl a m Macoma na sut a no

Mollu s c a S a n d c l a m Macoma se ct a no

Mol l u s c a E a ster n s o ft- sh el l cl a m Mya aren aria ye s

M o ll usc a B l un t so f t

- s h ell c l a m Mya trun ca ta no

M o ll usc a B l ue mu ss el M y

til u s ed ul is no

Mollu s ca purp l e varn ish clam Nuttall ia obsc urata ye s

M o ll usc a R o ck oys t e r Podo de smu s ma cro s chisma no

Mol l u s c a N a t i ve l i t t l ene c k cl a m Proto t ha ca stam inea no

Mollu s c a W a s h i n g t o n clam Sa xidomu s gigan teu s no

Mol l u s c a B u t t er cl a m Sa xidomu s nut ta lli no

Mollu s c a H o r s e c l a m Schizo tha e rus n u tta llii no

Mol l u s c a J a ck kn if e cl a m Sol e n si cari us no

Mol l u s ca Jap ane se l i t t l ene ck c l a m Vener up is ph illip a rum ye s

Mollu s c a W h i t e te l l e n Tellina m ode st a no

Mollu s c a H o r s e c l a m Tre s us c a pa x no

M o ll usc a D e n t ali u m De n t ali

u m re ct uis no Arthrop o d a H o r s e barn a c l e B a la nu s ca ri os us no Arthrop oda Smoo th acorn ba rnacle B a la nu s c r en a t us no Arthrop o d a A c o r n b a rna c l e B a la nu s gl a n d u l a no

FINAL

O c tob e r 200 3 Pag e 14Ph y l u m Common Name Scient ific Na me Exotic

Arthrop o d a E e l g r a s s iso p o d Idot ea r e secata no Arthrop o d a O l i v e

- g r e e n isop o d Idot ea w o sne s en skii no Arthrop o d a O r e g o n p i l l b u g Gnorimo s p haer o m a ore gon en se no Arthrop o d a B e a c h ho p p e r Orche s t i a traskia na no Arthrop o d a S k e l e t o n shrimp Caprel l a lae v is cu la no Arthrop o d a C o o n

- s t r i p e d s h r i m p P a n dal us da n ae no Arthrop o d a G r a y s h r i m p Crangon n i gr

icau da no Arthrop o d a S h o r t

- sp in e d shr i m p Hepta c arp u s bre v ir

ostrus no Arthrop o d a G h o s t shrim p Call ianass a c a li forniens is no Arthrop o d a M u d shr i m p Upoge bia p uge tt ensis no Arthrop o d a P o r c e l a i n c r a b Petro l isthe s erio merus no Arthrop o d a H e r m i t cr a b Pagur us gra n o s imanu s no Arthrop o d a H a i r y h e r m i t crab Pagur us h i rsut iu sculus no Arthrop o d a D e c o r a t o r c r a b Oregon ia gracilis no Arthrop o d a S p i d e r cra b Puge tt ia gra c ilis no Arthrop o d a K e l p c r a b Puge tt ia prod uct a no Arthrop o d a D u n g e ne s s cr ab Cancer ma gist er no Arthrop o d a R e d ro c k c r a b Cancer pro d u c tu s no Arthrop o d a G r a c e f u l can c e r Cancer gra c ilis no Arthrop oda Purp le sh ore cra b Hemigrap su s n u dus no Arthrop o d a G r e e n shore cr a b Hemigrap su s or e gone nsis no Arthrop o d a P e a cra b P i nni xa occ i d

e n ta li s no Arthrop o d a P e a cra b P i nni xa s c h m it ti no Arthrop o d a B u r r o w c r a b P i nni xa tu bi co la no Arthrop o d a H e l m e t c r a b Telme s su s che i r agon us no Arthrop oda Sea s p ider Ha l o s o m a vi ri

di

nte s ti na le no

Sou r ce: S. Rigg s, Person al C o mm u n i catio n , Pad illa Bay Natio n a l Est u ari n e Research Reserv e, 2 003

The complex of aquatic and inte rtidal habitats supported in Padilla Bay and its conjoined

freshwater deltaic environm e n ts support the early rea r ing and t h e salt wate r/freshwate r physiol ogica l transitions of substantia l anadromous sal m onid stocks (Table 2-5). In addition, over

50 other resi dent fish s p e c ies have be en reporte d i n the ba y (Table 2-5). Both herring and s m elt use the eelgrass meadows of Pad illa Bay for spawning, and both sp ecies are signif icant salmonid

fora ge s p eci es.

FINAL

O c tob e r 200 3 Pag e 15Table 2-5. Ana d romo u s and Resi d ent Fish Sp ecies Fo un d w i thin Pa dilla Ba y an d

Ass ocia t ed Tri butari es.

Common na me Scient ific Na me Anadromous /

Resident

Pin k salm on O n cor h yn ch us g o r b u s c ha Anadr omo u s

Chum sa lmo n O n cor h yn ch us k

e ta Anadr omo u s

Coho sa lm on O n cor h yn ch us k

i sut c h Anadr omo u s

So ckeye sa lmon O n cor h yn ch us n e r k

a Anadr omo u s

Chin oo k sa lmo n O n cor h yn ch us t

s hawy t s c h a Anadr omo u s

Coasta l cut t hro a t trou t Salmo clar ki clar ki Anadr omo u s

Stee lhea d O n cor h yn ch us m y k i ss Anadr omo u s
Dolly varde n / bu ll trou t Salvelin us ma lm a Anadr omo u s
Spin y d ogf ish Squa lus a c an th ia s Resident

Big skate Raja b i no cu la ta Resident

Ratfish Hy d

r ol

ag us c o l l i e i Reside nt

Pa cific herring Clup ea hare ngu s pa llasi Reside nt

Northern an ch ovy E n g r au lis mo rd ax

mo rd ax Reside nt

Surf sm el t Hypo me su s pr e t

i o su s pr et

io su s Reside nt

Long fin sme l t Spir in ch us th aleicht h ys Reside nt

Northern lampf i sh S t e n o b r ac hi us

l

e u c op sa rus Reside nt

P l ain f i n mi ds hi pm a n Por i ch th ys no tat u s Reside nt

Northern cling f ish Go b i es ox m a ea nd ric u s Reside nt

Pa ci fi c tom c od Microga du s pr oximus Reside nt

Red bro t u l a Brosmop h ycis m a rginat a Reside nt

B l ack b e lly ee lp ou t L y c o do ps is p a ci fic a Reside nt

Tube-snou t A u lo rhy n c h us f

l av

id us Reside nt

Three-spined stickleba ck Gaster osteu s acule a tu s Reside nt

B a y pi pe fi sh Syngn ath u s griseolin eat us Reside nt

Shiner per ch Cy m a t o ga st e r

agg re g a t a Reside nt

Pile per ch Rhacochilu s va cca Reside nt

Striped seap erch Emb i ot

oca lat e ra lis Reside nt

Pa ci fi c sa ndf i s h Trich odo n tr icho don Reside nt

Northern ronq uil Ronqu ilu s jord an i Reside nt

(P a c i f ic ) s n ak e pri ckl e b a c k Lump enu s sa gitt a Reside nt

Blu e b a rred prickleba ck P l ect o b r an ch us e v i d

es Reside nt

B l ack p r ic kl eb ack X i phi st

e r

at

ro

pu rp u r e u s Reside nt

Penp o i nt gu nne l Apod ict

h ys flavid us Reside nt

Crescen t g unn el Pho l is laet a Reside nt

Sadd leba ck g u n nel Pho l is orna ta Reside nt

Pa cific sa nd la nce Ammo dyte s h e xapter us Reside nt

Y e llowtail roc k fish S e b a st es

fl

avi d us Reside nt

S h a r pc hi n roc k f i sh Seba s t e s

za cen t r u s Reside nt

Rock gr een ling Hexa gramm o s la goceph alus Reside nt

FINAL

O c tob e r 200 3 Pag e 16Common na me Scient ific Na me Anadromous /

Resident

White s po tte d gr e enlin g Hexa gramm o s st eller i Reside nt

Lin g cod Ophio don e l on ga tus Reside nt

Padd ed scu l p i n A r t e di us

f

e ne st ral

i s Reside nt

Silverspot ted scu l p i n B l eps ia s ci rrh os us Reside nt

S h a r pn os e sc ul pin Cl in oc o t t u s ac ut ic e p s Reside nt

B u f f al o sc ul pi n Enop hrys biso n Reside nt

Soft sculpin Gilb ert i d

i a siga lu t e s Reside nt

Pa ci fi c st agh orn sculpin Lept ocott u s arm a tu s Reside nt

Great sculpin Myo x o c e pha lu s polya ca nth o ceph alu s Reside nt

Sailfin sculpin Na u t i c h t hys oc ulo f as ci at us Reside nt

Tadpo le scu l p i n Pyschro l ut es par ado xu s Reside nt

Grunt sculpin Rhamph o c ot tu s r i chard s o n i Reside nt

Ribb ed scu l p i n Tri g lo ps

pi

ng el i Reside nt

Cabe zon Scorpae nich tyhys m a rmorat us Reside nt

Sturg eon po ache r A g o nus aci p en se ri nu s Reside nt

Tuben ose p o a c h e r P a lla si na ba rb a t a ai x Reside nt

Smoo th alliga tor fish Anop lago nu s ine r mis Reside nt

Pa ci fi c sp in y lu m p su c k er E u mi c r

o t

re mu s orb i s Reside nt

S p o t t e d s n ail f i s h L i pa ris c a ll yo d on Reside nt

Ribb on sn ailf ish L i pa ris cy cl

op us Reside nt

Marbled sn ailf ish Lip a ris den nyi Reside nt

Tide poo l sn ailf ish Lip a ris florae Reside nt

Show y sna i lf ish Lip a ris pu lche llus Reside nt

Spe c kled sa ndd ab Cith arich t h y

s stig maeu s Reside nt

Arrowtoo th floun der Ather esthe s st

o m ia s Reside nt
Starry f l o und er P l ati

c h t hys s t

ell

a t u s Reside nt

Butt er so le Iso p sett a isolep is Reside nt

Rock sole Lep ido p sett a b i lineat a Reside nt

S l en de r so le Lyo p sett a e x ilis Reside nt

Dover sole Mic r ostomus paci fi cus Reside nt

Eng l is h so le Par o p h r y

s ve tu lu s Reside nt

Sand so le P s e t tic h th ys me la n o s t i c t u s Reside nt

Sour ce: S. Rigg s, Per s o n a l Co m m un icat ion

, Pad i ll a Ba y Na t i on al Estu arine R e search Re ser v e, 20 03

Padilla Bay is a reserve for mi grator y avian sp ec ies in the winter (approxi m ately 50,000 ducks, covering 26 species), as well as resident spec ie s (Padilla Bay NERR 2002). Resi dent specie s include great blue heron, dunlin (a shorebird), bal d eagle, pere grine falcon, m e rlin, a nd snowy owl

. There are approxi mately 240 species of birds that utilize Padill a Bay as eit h er a foraging resource

, nesting are a , or migrator y route

.

FINAL

O c tob e r 200 3 Pag e 17Terrestrial ma mmals in the Padilla Bay reserve include blac k-tailed deer , raccoon, skunks, c oyote

, muskrat, and long-tailed weasel; ma rine m a mma l s th at use Padilla Bay i n clude har b or seals, and

occasionall y Cali fornia sea li ons and porpoises (Table 2-6)

.

Table 2-6: Terre strial and Aq uati c Mam m ali a n Speci es i n th e Padi ll a Ba y Reg i on.

O r d e r C o mmon na m e Scientific name E x o t ic

Mars u p i a l a V i rgi n i a oposs u m Dide lp his virg in ia na ye s Vagra n t shr e w Sore x vagr an s no Insectiv or a Mole Unid ent if ie d sp. no Chirop t e r a B a t Myo t is sp p. no Lago morph a E a stern cott ont a i l S y

lv

il ag us fl

o r

i d

an u s ye s Doug la s' squ i rrel Tamia s ciuru s d

o uglasii ( i or ii) no

Northern f l yin g squirre l Glau com y s sabr inus no

Bea v er Cast or can ade nsis no

Townsend's vole Microtu s town se ndii ( i or ii) no

Muskrat Ondatra zib e th icus ( z ibe t h i

ca?) no Roden tia

Deer (wh i te-f oot e d ) mou s e Per o m y sc us ma ni cu lat u s no Coyote Canis la tran s no

Red f o x Vulpe s vu lp es (fu l va?) no

Raccoo n Procyo n lot o r no Striped sku n k Meph it is me ph it is no

River otter Lutra cand en sis no Carnivora

Long ta iled w e a s el Muste l a frena ta no

Artioda ct yla Mule (b la ck- ta ile d ) de er Odoco i leu s hem ionu s co lum b ianu s no

Ceta c e a P o r p o i s e Unid ent if ie d sp. no

Harbor sea l P h oc a vi tu li

na no Pin n i pe dia Sea lio n Unid ent if ie d sp. no

Sou r ce: S. Rigg s, Person al C o mm u n i catio n , Pad illa Bay Natio n a l Est u ari n e Research Reserv e, 2 003

Spe c ifi c Re ceptors Exa m ine d fo r Expos ure
Plants typical to the envi r o nments where i m azapyr c ould be used to contr o l Spartina i n clude such species as eelgrass ( Zost era marina and Zostera japonic a ), a nd a variety of algal spe c ies such a s sea lettuce ( U l va sp.)

. Ani m als could include ungulates s u c h as deer, el k and rabbit, omnivore s such as racc oons, terre strial carnivor es such as bobcat and c oyote, a v ian species suc h as ospre y, eagles and gulls; reptiles such as tu rtles; amphibians such as f r ogs; an d insects such as mosquitoes

. Obligate aquatic ani m al species include the arra y of Pacifi c sal m oni ds native to Was h ington’ s waters, s u ch as coho sal m on, but al s o other fish species suc h as j uvenile flat fish ( P le uronectidae)

, juvenile sturgeon (Ascipenserid ae), and bullhead (Cottidae). Add itional aquatic species potentially

expose d to i m azapyr include the vast list of be nthic and mobile inve rt ebrates common to the

intertidal zone of W a shington’s estuarie s such as dungeness and rock crab ( Cance r spp ). As

oppos ed to modeling exposure to all of the s e (and other) pos sible plants and ani m als that could be potentially expose d to i m az apyr from Spartina treatment, we evaluated exposure in select surrogate “guilds”.

FINAL

O c tob e r 200 3 Pag e 18Recept o r “guilds,” speci es with si mi lar life historie s or niches in the environment, are used to

esti m a te exposure rather than esti m a ting expos ur e for each i ndividual species where a che m ical

could be a p plied. The as sumption of this approach is that the gene ral characteristics of each guild will provide risk estim ates that are r e presentative of the entire guild. As such, each guild can be extrapolated m o re br oa dly than single species esti m a tes. The underlying concept is that each receptor fall s into a gr oup of potential receptor s that functi on in si mila r ecological niches or "guilds." For exa m ple, many specie s of heron a nd egret fee d on s m all fish and inve rtebrates and require trees for roosts. As such, herons a nd e g rets displa y si m ilar life histories a nd woul d b e anticipated t o have si mil a r expos ures to i m aza pyr . A single s u rrogate, s u c h as the grea t blue heron,

for whic h re liable life-hi story info r m ation is avai lable, may be used for c a lculating ri sk and t h e results m a y t h en be extrapolated to the guild as a whole

. This approach all o ws the risk assess ment to directly e v aluate spec ies for whic h the best e xposur e infor m ation is a v ailable. This approa ch also allows results to be extrapolated to a broa der range of pot ential recept ors, thereby maxi mizing

data usa g e a nd applicabil ity of res u lts

.

Surrogate species wer e selected in each identi fi e d receptor guild. The s e lected surr ogates have

been studied suff iciently to enab le risk calculations to be made even though a surrogat e itself may

not nece ssar ily be pre s e n t withi n the study area (e.g., mallard). All of the other re ceptors are present in Washington State and are represent a tiv e of fee d ing guilds present. The funda ment al assumption that was m a de in this stu dy was that if negligible risk is deter m ined f o r the surrogate species, t h en the entire guild is pr otected.

Speci fic wildlife receptor guilds wer e selected based on t h e evaluation of exposur e pathwa ys and the possibili ty that a given receptor could come into contact with i m azapyr applied for Spartina control. The receptor selections wer e li m ited mainly to those rece ptors (species) that are found i n the areas where Sparti na is distributed, and to s u rrogate spe c ies f o r which suff icient lif e history

and/or toxic o logical infor m ation existed so that reasonable exposur e factors could be used t o estim a te exposure and risk. The f o llowing bullets briefly s u mmarize the e c ological rec e ptor guilds

for whic h exposure calc u lations wer e evaluated. Life history char acteristics of these r eceptors are
described ful l y in Cha p ter 4.

• Mallard Duck (Anas p l atyrhy nchus)

. This avi a n species was considered a representative (pri m a rily herbivorous) waterfow l species bird t h at is common to t h e ar eas of interest. This species was evaluated due to its direct and indirect expos ure through the consumption of aquatic pla n t s

.

• Sca up ( Ayt h

ya sp. [ marila = greater; affines = l e sser]). The s e species ar e more omni vorous than the m a l l ard, cons uming a high pr oportion of t h eir diet as ani m al protei n, especially duri ng spring a nd fall m i gration periods . Ani m al s ource s in the diet include mu s s els, s m all fi sh, and

other benthi c and pelagi c invertebrat e s. The lesser scaup is considerabl y m o re common in

Was h ington, but both are coastal s p ec ies.

• Red Fo x ( Vul p es vul p es ). This mammalian species is a medi um

- s ized pri m arily ca rnivorous

ma mmal of t h e cani n e fa mily t h at is r e sident to much of weste r n Washi ngt on, and whose range is expandi ng. It is a surrogate for other carni vorous s p e c ies such as the wol f , c oyote, a n d

mustellids.

• Norway Rat (R a ttu s nor veg icus ). A mamma l i a n speci es of near ubiquitous distribution in

low l and areas throughout W a shington State and the U.S .. It is particulalry com m on around

FINAL

O c tob e r 200 3 Pag e 19coastal areas where it has been introduced through tr ade vectors of shipping. Rats are

c o mmonl y us e d for t o xic i t y

te sti n g.

• Deer Mouse ( Peromysc us manis c ul atus). A common herbi vorous ma mmal spe c ies found in a variety of ecosystems, including coastal grassla nds. Mice a r e also commonly used i n toxicity testing.

• Bobwhite Quail ( Co linus virgi n i

a nus) A common avian test species. This species is not

found in Wa shington Sta t e, but serve s as a good s u rrogate for th e introduced Calif orni a (valley) quail, Lophortyx californica, whic h is relatively common in we stern W a s h i ngton. This species is prim arily herbivorous, eating mostly seed s. Quail are commonly used to test avian sensitivity to toxicants.

• Marsh Wren (Cistothorus pal u stri s). A common native avian species to coastal grasslands

and salt m a r s h habitats in W a s h ington State. Thi s species consumes a high proportion of it s diet in a n i m a l protein.

• Cotto ntail Ra bbit (Sylvilagus sp). A strictly herbivor ous species c o mmon to muc h of

western Was h ington, but introduce d originally from the east c o ast. It is al so a typical EPA tes t species used particularly t o evaluate der m al sensiti vity.

Thre atene d and Endangered Sp ecies and Species of Concern

Threaten ed and end a n g e red species are thos e speci es that have been gi ven speci al l e gal and

pr ote c ti ve des i gna t i o ns by fe der a l or state governm e nt r e source agencies. A federally endangered species is one that is in danger of extincti on throughout all or a signif icant portion of its range. A

federall y t h

reat ened speci es i s o n e likely to b e co m e an end a ngered s p ecies w i th in th e fores e eab l e f u

tu

re th ro ug hou t a l l or a sign if ica n

t p o r t ion of its range. A speci es of concer n is one for which status

inform ation suggests the species is not abundant, and for which additional inform atin is sought.

Addre ssing expos ure and risk to t h reatened a nd e ndangered species ge ne rally require s the use o f
surrogate re ceptor guilds because they are rarely used ( f or obvious reas ons) to esta blish toxicit y infor m ati on on ne w che m icals (Sa p pington et al. 2000) . A summary of a ll federal T&E species in Washington State, their Washington State status, and their potential for ex istence in areas wher e i m azapyr treat m e nts of Spartina coul d occur base d on their habitat prefer ences is incl uded in this report as Appendix E. Fr om this information, the potentia l e xposure of T& E spe c ies is t r uncated t o only a f e w select species. In brie f

, utilization of W a shington’s co astal areas by threatened and endangered (T&E) speci es is pri m ari l y li m ited to the listed salm onid species f r om the Columbia and Puget Sound basi ns. In addition, several coastal avian species listed as sensitive, candidate, or

state-m o nitor species ar e common to W illa pa Bay and other areas where Spartina is di stributed.

2.3 Concept u al Model

A conceptua l m o del wa s developed for i m aza pyr (F igures 2- 3 and 2-4). This conce p tual model

accounte d for the sourc e s, pathways, and route s of exposur e to the different trophi c levels and ecological re ceptors. Exposure of ec ological rece ptors to i m a zapyr used t o control Spartina spp

. could occur directly or inadvertantly ( i ndirectly) through i ngest ion of conta m inate d food, water, or

sedi m e nt, t h r ough inhalat i on of aerosol, or thr ough direct contac t (e.g., insect s).

FINAL

O c tob e r 200 3 Pag e 20Figu re 2.3: Co ncept u al site m o del for im azap yr stressor imp a cts to t e rr estrial recept ors.

FINAL

O c tob e r 200 3 Pag e 21Figu re 2.4: Co ncept u al site m o del fo r Im azap yr stressor imp a ct to aqu a t i c recept ors.

FINAL

O c tob e r 200 3 Pag e 22

### 3.0 HAZARD ASSESSMENT

The hazard assessment portion of a risk assessmen t summarizes environmental fat e and toxicity data developed on the com p ound(s) of inter e st . To understand c h e m ical haz a rds, some

funda mental aspects of t oxicology should be clarified. A central tenet of toxicology is that there is

som e expos u re dose at which no e ffect is m eas urab le in the response te sted, and t h is paradigm is

considere d a valid mode l for this as sess ment. T h is dose or concentration is known as the no

observa ble e f fect le vel or conce n tration ( N OEL or NO EC ). The low e st obse rvable eff e ct level or

LOEL corre sponds to the lowest dos e at which a st atistically signi ficant difference is meas urable

relative to a n une xpose d control gr oup. Beyond these typic a l m e as ures, standard t o xicological

term s include the LC 50 , the exposure concentration that k ills 50% of the anim als tested; the EC 50 , the concentration that elicits a non-lethal eff e ct in 50% of t h e orga nis m s teste d with the

meas ure m ent endpoint . Measures s u ch as the LC 90 or EC 90 sim p ly ref e rence variations in the proportion of the populat ion tested that responds to the test (in this case, 90%). Other ter m s suc h as the IC50 or IC10, refe rence a conc entration tha t results in inhibition of an endpoi nt—in this case 50% and 10% inhibition respectively. These terms ar e of ten used to gauge th e eff e ct of a chemical on endpoi nts such as gr owth, or in- v i t ro end point s such as t h e inhibition of an enzyme.

In consideri ng the hazar ds of i m az a pyr, it is i m portant to re cognize how the che m i c al can first

enter into commercial us e. I m aza pyr has been pr oduce d unde r differe n t c o mmercial for m

ulati ons with technic a l i m aza pyr and i m azapyr isopropyla m ine salt (49 percent water so lution) (Table 3- 1).

The for m

ula tions have the sa m e mec h anis m of ac tion on targe t plants, but differe n t environm e n tal factors control the efficacy of each for m

ulati on and where t h ey mi ght be applied. Most testing related to the toxicity of im azapyr is related to th e technical compound instead of the commercial

for m

ulati on. The Arsenal ® formulation listed below is the fo r m

ulati on projected for use in the estuary setting for Sparti na control. Mechanism of action, environmental f a te, and toxicity studies

described in detail below ref e re nce the s e general for m

ulations.

Table 3-1: Produ ct fo rmula t ion s o f im azap y r

.

Commercial Product % Imazapyr

Technical % Imazapyr Isopropylam i ne salt % In ert Ingredient Source

Arse na l ® N/A 25 75 oth e r inert ingred ie nt s Cyan am id 199 7
Chopp er ® N/A 1 99 oth e r inert ingred ie nt s Cyan am id 199 7

Arse na l ® Herb icide 28.7 N/A 71.3 o t her inert ingred ie nt s BPA 20 00

Arse na l ® Ra ilr oa d
Herbicide 27.6 N/A 72.4 o t her inert ingred ie nt s BPA 20 00,
USDA 199 5

Arse na l ® Ap pl ic at o r s Concentra te Her b icide 53.1 N/A 46.9 o t her inert ingred ie nt s BPA 20 00

Chopp er ® Herb icide 27.6 N/A 72.4 o t her inert ingred ie nt s BPA 20 00
Chopp er ® 22.6 5.4 72 oth e r inert ingred ie nt s USDA 199 5
Chopp er ® RTU N/A 3.6 30 prop ylen e glycol

5.0 isopr opa no l

61.4 o t her inert ingred ie nt s USDA 199 5

FINAL

O c tob e r 200 3 Pag e 233.1 Mechanism of Ac tion and Efficac y

3

. 1

. 1 M ech an i s m o f A c t i on

The mechanism of action of an herbicide is the biochemical and/or phys ical m e thod by which it has been engineered to kill or suppr ess the grow th of speci fi c plants. I m azapyr (2- [ 4,5-dihydr o-4- methyl-4-(1- m ethylethyl)

- 5-oxo-1H- im i d azol- 2-yl]- 3pyridi n ecarboxylic acid) is the active ingredient in the commercially availa ble for m

ulations Arsenal ® , Chopper ® , Stalker ® , Assault ® , and

Contai n ® . The herbicide is commonly produc ed in either a we a k acid fo r m

or as an is opropyla m ine salt (Figure 3-1). The is opropyla m ine salt for m

is generally dis s olved in a s o lution cont aining 49%

water, a nd most c o mme rcial product s sold are in this salt form. I m aza pyr was first registered under

the commer cial for m

ulat ion of the isopropylam i n e salt Arsenal ® in 1984 and a g ain with the weak

acid for m

ula tion Choppe r ® in 1993 ( C yana m i d Ltd. 1997).

Figu re 3-1: Ch emical stru ctur es of the tw o forms of imazap y r

.

The specif i city of an herbicide f o r target vegeta ti on varies by herbicide fa mily. I m aza pyr belongs

to the che mical fa mily i m idaz olinone. The i m i d azolinones are non-sele ctive herbici d es used t o control wee d s, broadlea ved herbs, a nd woody s p ecies. I m a z a pyr is pri m arily adsorbed through plant tissue

, but can also be ads o rbe d through root s in the s o il . The comp ound is translocated in the xyle m a nd phloe m to the m e rist e m atic tissues . The mec h anism of a c tion is through inhibition

of bra n ched- c hain a m i n o acid synthe sis. Speci fic a lly, i m aza pyr inhibits the enzym e ac etohydr oxy acid synthase (AHAS) or acetolact ate synthase (ALS) whi c h catalyzes the product i on of t h ree branched-chain aliphatic am ino acids (valine, le ucine, and isoleucine) that controls protein synthesis and cell gr owt h (Cox 1996).

I m azapyr is slow-acting and is gener a lly m o st e f fective during post e m ergence axilla ry buddi ng (Hanlon and Langeland 2000) . Pla n t s stop growt h in itially in the root s and continue i n the a bove ground port i ons, with complete death occurri ng approxi mately one m o nth a f t e r treat m ent

, depending on environmenta l conditions (Cox 1996).

Ani m als do not synthesi ze their own three bra n c h ed -chain al iphatic a m ino acids, but obtain the m by eating pl ants and other ani m als; t h erefore the engineered mechanism for plant toxicity is not generally rel e vant to bir d s, ma mmal s, fis h or in vertebrates. Toxicity a s sociated with excessive

doses administered to ani m als o ccurs by di ffere n t mechanisms.

FINAL

O c tob e r 200 3 Pag e 243.1.2 Effica cy o n Target Ve g e tation

No n- Spartina Studies
Kay (1995) exa m ine d the efficac y of wipe-on applications of i m az apyr on the common ree d ( Phragmites australis ) in aquatic systems. Similar to Spartina in the Pacif i c Northwest, the common reed is considered highl y invasive in the m i dwest and Atlantic states, as well as

W a shington, serving little habitat value for f i sh and wildlif e . In this f i el d-based experim e nt, both

i m azapyr (Arsenal tm ) and glyphosate (Rode o tm ) were tested at 0.5 and 0. 25-strength dil u tions with 1% surfactant (X-77 tm ) added t o the application m i xtures. Control and cut pl ots received n o herbicide treat m ent

. When examined at the end of the growing season, Ka y observe d s i gnifica ntly

im p r ov e d Phragmites s uppressi on with Arse nal tm relative to Rodeo tm , at bot h treat m ent concentrations (Ta b le 3-2). Howe ve r, the overal l control for either treat m ent chemi c al using the wipe-on a p plication met hod was not considere d a cceptable. Short pl a n ts were s h rouded from wipe

treat m e nt by larger plants, rendering com p lete c ontrol i m possible. In addition, e f fe cts on nontarget e m ergent plants were doc umented.

Table 3-2: Effica c y o f Wipe -on Ap plica t io ns o f Im azap y r and Gl y p h o sate

. (sour ce: Kay 1995 ) 1

Treatment Rate % Dead in 19 91 % Surfac e Covered with L i ve

Reeds in 19 92 % Surfac e Covered with L i ve

Reeds in 19 93

Control—No Herbicide or Mechanical C ontrol 0 3 a 8 0 a 7 8 a

Cut Trea tmen t— No Herb icid e 0 1 0 0 e 2 d 4 c Arse na l 25 % 5 7 c 5 5 b 6 4 a Arse na l 50 % 7 5 d 1 6 c 5 5 a Rodeo 25 % 3 8 b 6 5 a b 7 0 a Rodeo 50 % 3 3 b 4 7 b 7 0 a Rodeo (spr ay) 1.25 % 1 0 0 e < 1 d 1 5 b

1: Da ta in colum n s r epre s en t t he mean of thre e re plicate s

. W i t h in co lum n comp arisons are no t sign if icant if t he le tter f

o llow i ng the va lu e list ed in a ce ll is fo und in an oth e r ce ll wit h in th e sa me c o lu m n

. Es ti m a t e s o f k ill an d s u rvi v al we re v i s u a lly bas e d

. In a study looking at the re sponse of torpedo grass ( Pani cum r e pe ns ) t o di ffe re nt a

ppl ic ati on rat e s of

im azapy r an d im azapy r with flu r id o n e, th e lev e l of control observed in the diff eren t plo t s v a ried spatially and substantia lly depending on condition s where it was applied (Hanlon and Langeland 2000). In this stud y, im azapyr (Arsenal TM ) was applied in thre e canal sys t em s of Lak e Okeech ob ee at a rate of 0.28, 0 .56, 0.84 or 1.12 kg acid equi val e nts ( ae) /ha in a total tank m i x volu m e of 187 L / ha ( 20 gal/ acr e) t h at cont ai ne d 0.5% noni onic sur f a c ta nt

( K e n et ic tm ). Som e tr e a tm en t p l o t s also ha d the

im azapyr com b ined w i th 0.43 kg fluridone/ha. In one canal syst em where applied, highly effective

c o ntr o l was obtai ne d wi th i m a z a p yr on one si de of t h e ca na l, ye t lit tle or no c o ntr o l was obtai ne d on the opposite side of th e ca na l, de sp ite s i m ila r tre a tm en t volum e s and condit ions. The authors

s p ec ula t e d that fl oa ti ng per i phy ton m a ts in abundance on one side of the canal reduced the stem density of torpedo grass there a nd also m a y have boun d u p th e app l ie d he rb ic id e su ch th a t th e

to rp edo g r as s along that si de of the canal re c e i v ed a l o wer dos e . Ot her ke y fa ct ors t h a t ma y ha ve affected the resu lts of this study included: (1) s o il m o is tu re af f e c t ed by hydroperiod fluctuations (from dry to 1.7 m inundation dept h between areas), and (2) canopy of em ergent thatch reducing the

r e growth of t h e speci es is enhan ced. Unfort unatel y, t h e author s did not attem p t to anal yze tissu e

concentrat ions in eit h er ta rget or non-t a r g e t ve geta ti on, or in the wa te r s u c h th a t di fferent iati ng t h e

cau s e s of th e treatm ent di fferences could be resolv e d wi th les s unce rtai nty. Not w it hst a ndi n g, the

FINAL

O c tob e r 200 3 Pag e 25study d e m onstrated clear con t ro l w i th im azapy r, particu l arly wh en the thatch overbu r d e n was bu rn ed

before herbicide treat me nt , as was done in one of t h e ot her ca nals whe r e tr ea t m e n t s we re a p pli e d.

W h en th e th atch was no t rem oved or burned, as was done in the third canal, no effecti v e plan t suppression was obtained. T h e addition of fluridon e to the m i xture did not appear to influence efficacy at any of the treatm ent con cen tratio ns . Al though the result s of these studies show that

env i ronm en tal con d itio n s can high ly affect the efficacy of im azap yr treatm e nts in the a q u a tic

env i ronm en t, it co uld be concluded that predic ti ng effi cacy i s far from a stochastic (random ) proces s provided a basic understandi ng of the application c onditions is considered p r ior to tr ea tm e n t.

Table 3- 3 summarizes some of t h e target aquatic and terrestri al nuisance plant specie s for which

i m azapyr has had reported effi cacy ( U SACE 2003).

Table 3-3: Exa m ple s o f Aqua tic Specie s Effe ctiv el y Co ntrol l ed b y Im azap y r

. (So u rce ACO E

2003 )

Common Name Scientif ic N a me

Giant Ree d Arund o d ona x L.

Butt onb u s h C e p h a la nth u s o c ciden ta l i s Purp le Loo se str i f e Lyt h rum sa licaria L.

Melaleu c a Melaleu c a qu inq uener via (Ca v .) Bla k e Torpedo Grass Pan i cum r epe ns L.

Common Reed P h ra g m it es

au st ra li s (Ca v .) Trin. e x Ste ud.

Brazilian Pe ppert r ee Schinu s t e reb i nt hif o liu s R add i

Giant Fo xta i l Setar i a ma gna Griseb.

Tamarisk or Sa lt Cedar Tamarix sp p.

Catta ils Typha spp

. Para Gra s s Uro c hl oa m u t i c a (Forsk.) T.Q. Ng uye n

There are a number of weeds that have devel oped resista n ce to i m az apyr (Table 3-4). It is suspected that these plants have de veloped cro ss-resistance to im azapyr f o llowing the use of

herbicides with the same mode of action (i.e., acetolactate synt hase inhibition), pri m arily t h e sulfonyl urea herbicides (Cox 1996) . Resistance is afforded plants by developing a structurally

si m ilar for m

of the enzyme acetolact ase synt hase that is not blocked by i m azapyr to the sa me degree. The resistant enzyme for m

is thought to have deve loped pri m a r ily from a single point mutation (Sa t hasivan et a l . 1991).

Table 3-4: Plan ts kno w n to be re sistant to th e use of im azap y r

. (sour ce Cox 1996 )

Common Name Scientif ic N a me
Rigid r y e g r a ss Loli u m r i gi du m

Kochi a K o c h i a scopari a

Com m o n c h ic kwe ed St ell a ri a me di a

Russi an this tle Salsola iberica

P e re nn ia l ryeg ra ss L o l iu m pe ren n e

A nnu a l sowt histle S o n c h u s o l er aceus

Br as sic a ce ae s p p

. Ar a b id op sis th ali a na

Al gae s p p. Chlorella emers o nii

FINAL

O c tob e r 200 3 Pag e 26Spa rtina Co ntrol Studie s Comparison studies of t h e efficacy of i m azapyr re lative to glyphosate on S. alterniflora control

have bee n re cently conducted by Patte n and Stenva ll (2002) and Patten 2002. In these st udies each

herbicide was tested at di fferent appli cation rates and/or dr ying ti m e s be fore tidal submerge nce or rain. Compa r isons were made in trea ted Spartina m e a d ows at application rates of 0.84 and 1.68 kg

ae/ha for i m azapyr and 4.2, 8.4, and 18 kg-a e /ha for glyphosa t e. I m az apyrwas dissolved in a cropoil sur f actant while gl yphosate was dissolved in a non- ionic s u rfacta nt at 1% v/v. The herbicides were applie d using a backpack spr a yer equi pped with a 1.5 or 3m boom e quippe d with Teej et
11001 or 11002 nozzles that disper se d the herbici d e mixtures at a rate of 94 to 940 L/ ha. Efficac y

was e v aluate d base d on a visual rating of percent control in a treated plot assessed approxi m a tel y one year following treatment compared to an untreat ed plot. The results of this study, representin g

numerous trials bet w een 1997 and 2000, are re fle c ted in t h e box pl ot in Fi gure 3- 2 on t h e following

page.

As de monstr ated in Fi gur e 3-2, a treat ment c once n tr ation of 0.84 kg-ae/ha of imazapyr was slightly

more e f fective than 8.4 kg/ha glyphosate for c o ntrol of Spar tina , but both treatments at these rate s had high variability and produced inco mplete control. At the higher rates of application of each

herbicide ne arly complet e control wa s obtaine d ( g enerally gr eater than 90%), and i m azapyr ha d less variability around the m e dia n and slightly greater effectiveness a t Spartina control than glyphosate. As depicte d, more tha n 10-ti m e s th e a m ount of glyphosate was require d to achieve

si m ilar c ontr o l as was obtained with i m aza pyr, bu t i m aza pyr tr eat m e nts pr oduced a grea ter number of outliers at the higher treatm e nt rate. The variability in treatm ent response for either herbicide was not discussed by the authors. Treatment vari ability may have been due to f a ctors such as overlying thatch (Hanlon and La ngeland 2000) , di fference s in pl ot si ze bet w een years, or surfa c tant di fferenc e s.

FINAL

O c tob e r 200 3 Pag e 27Figu re 3-2: Bo x a nd w h isker gr ap h of Spartina cont r o l as a function of rat e of imazap y r and gl y p hosate use in experime nts conducted in Willa pa Bay

, WA from

1997 t o 2000. (So u rce: Pa tten and Stenvall 2002. )

Note: Boxe s in box- plot s depict the data bet w ee n the 25 th and 75 th percentiles, with the cross bar in the box represe n ting the medi an of the dat a , and the hinges ( w hi skers) representing the highest a nd l o west data values for the m a in body of data (5 th a nd 95 th percentiles); dots beyond the whiskers are considered outliers by standard statistical convention.

Effe cts of drying ti me were e x a m i n ed in a se pa rate exper i m e nt using the 1.68 kg/ha i m az apyr

treat m e nt and 8.4 kg ae/ha glyphosate treat m e nt only (Patte n a nd Stenvall 2002) . Dryi ng ti mes for this experi ment were segregated by 4-7 hours and greater than 7 hours. Pat t en and Stenvall’s study

found that imaza pyr provided more control with less variabili ty and short e r dry ti m e r e quire ments
whe n compared to glyphosate (F i gure 3-3). Glyphosate at 8.4 kg/ ha was not as effective at Spartina control when pr ovided a drying ti m e of only 4-7 hours. E v en when allowed at least seven hours of dry ti m e , the gl yphosate treat m e nt e xhi b ited greater variability around t h e media n than

either of t h e i m azapyr dry-ti m e treat ments. In c ontrast, i m a zapyr e f fica cy was not signi ficantly

differe n t between the 4-7 and > 7 hour dry times inve stigated. W h ile the resu lts of this experim e nt demonstrate the sensitivity of glyphosate to drying ti m e , the results would have been more usef ul if the glyphos a te treatment concentration that provid ed nearly complete control (18 kg ae/ha) was compared against the i m azapyr treat m ent that provi ded s i m ilar Figur e 3-3). The comparison depicted i n Figure 3-3 lea v es in questi on what fa ctor dos e may have played in this e f fica cy trial.

FINAL

O c tob e r 200 3 Pag e 28Figu re 3-3: Bo x a nd w h isker gr ap h of Spartina cont r o l as a function of dr y

tim e for imazap y r (1.68 kg/ha) and gl y phosate (8. 4 kg/h a) u s e in experiment s con d u c ted in Willapa Bay

, WA fo rm 1997 to 2000. (So u rce: Pa tten and Stenvall 2002. )

Additional studies by Patten (2002) exa m ined th e efficac y of i m azapyr and glyphosate wit h

various s eas onal ti m i ngs, spra y vol um es and with several sur f actants. Fo rmulations of these surfactants are proprietary and therefore a full anal ysis of the i r com p onents is not possible (their toxicity is discussed i n Section 3.5) . Seasonal a pplication ti mings corre sponded to t h e stage of plant developm ent f r om preanthesis (late June to mid-July), anthesis ( m id-July to August), or see d filling ( S ept e m b er)

. Application volumes ranged fr om 23 to 374 L/ ha at active ingredient

concentrations of 0.84 a nd 1.68 kg-a e /ha for i m a zapyr, and 7.2 and 8.4 kg/ha for gl yphos ate and application volumes from 94 to 748 L/ha at c o ncentrations of 3.63 to 8.4 kg/ha for glyphosate

. Sur f actants evaluated included R11 tm , A g ri-D ex tm , Haste n tm , LI100 tm , Syl-Tac tm , Ki netic tm , and Dyn e -Amic tm

.

The efficacy of i m azapyr and glyphosate relative to application date were inconsistent, and shown

to be m o re influenced by spray volume than by application t i m ing, provi ded applicati on occurred during the growing seas on. Hi gher spray volumes tended to result in more consiste nt Spartina control; however, this trend was not consistent across all dates and sites (Table 3-5). This

inconsiste nc y was considered due more to cha nge s in est u arine co nditions (e.g., storms, tides, mudcovered lea v es) tha n to physiologic a l changes i n Spartina during di fferent seasons. The least

effective dat e s for i m azapyr efficacy were earl y July and October.

FINAL

O c tob e r 200 3 Pag e 29Table 3

- 5: Effect o f ra te, timi ng an d spra y vol ume in 20 0 0 on the efficac y o f im azap y r and gl y p h osa te for sm ooth cordg rass c ontrol in Wi llapa Ba y , WA. (So u rce: Pa tten, 20 02. )

Applicat ion Spra y Treatment Ef ficac y % Contro l

Herbicide Rate kg/ha Applicat ion Date in
Year 2000 Volu me L/ha Site 1 Site 2

Ima z ap y r 0

. 8 4 Ju l y 6 9 4 4 0 3 5
Augu s t 2 9 4 8 1
Augu s t 3 1 9 4 4 7 8 9
Sept emb e r 1 4 9 4 6 3

Octob e r 7 9 4 1 9 9 0

Ju l y 6 4 6 8 4 4
Augu s t 2 4 6 8 4 9
Augu s t 3 1 4 6 8 9 2
Sept emb e r 1 4 4 6 8 8 4

Octob e r 7 4 6 8 2 3 4 6

Ima z ap y r 1

. 6 8 Ju l y 6 9 4 8 3
Augu s t 2 9 4 9 4 9 9
Augu s t 3 1 9 4 3 6
Sept emb e r 1 4 9 4 9 4 9 6

Octob e r 7 9 4 4 4

Ju l y 6 4 6 8 7 7
Augu s t 2 4 6 8 9 7
Augu s t 3 1 4 6 8 9 2
Sept emb e r 1 4 4 6 8 9 3

Octob e r 7 4 6 8 5 9
Glyp ho sat e 8

. 4 Ju l y 6 9 4 2 0 0
Augu s t 2 9 4 3 0
Augu s t 3 1 9 4 0 6 9
Sept emb e r 1 4 9 4 3 2

Octob e r 7 9 4 6 2 4 6

Untreat e d 0 0

I m azapyr at 1.68 kg/ha provi ded excellent control of Spar tina when a pplied atultra-low application vol um es (23 and 47 L/ha) (Table 3-6). Th e study showe d that as long as drying ti m e wa s sufficie nt, good control could be ac hieved with low vol ume applications. Acr o ss all sites and experi ments described i n Patten’s 2002 paper, 58 and 88% cordgrass c ontrol was obtained with

i m azapyr applications at 0.84 and 1.68 kg ae/ha , respecti v ely. Glyphosate, by comparison, provide d 45 and 81% c ontrol, whic h was obtai n ed at the 7.2 and 8.4 kg/ha appli c ation rates, respectively. All sur f acta n ts use d in the study pr ov ided delivery of the herbic ides to yield eff e ctive control of the target or ga nis m

.

FINAL

O c tob e r 200 3 Pag e 30Table 3-6 : Effects of herbici de rate a nd ap plica t io n s p ra y vol um e in Augu st 199 9 on

smoo th cordgrass con trol in Wil l ap a Ba y , WA. (So u rce: Pa tten, 20 02, )

R a t e Spray

Volume Treatment effi c acy % control

Herbic ide kg/ha L/ha Site 1 Site 2 Site 3 Site 4 Site 5 Site 6

Ima z ap y r 1

. 6 8 2 3 9 3 9 3

Ima z ap y r 1

. 6 8 4 7 9 6 9 9 9 3 8 4 9 6 9 5 Glyp ho sat e 8

. 4 9 4 8 5 5 2 8 9 4 8

Untreat e d 0 0 0 0 0 0

3.2 En viro nm ental F a te and Ch emistr y

3.2.1 Phy s ica l Ch emis try

Solubility

I m azapyr is ionized under typical environme n tal c onditions of pH 5-9, and is therefore highly soluble in water. The solubility of i m aza pyr va r i es some what with th e product for m

ulation. The solubility of i m azapyr increases w ith temperature. For exampl e, th e solubi lity of the compound is reported as 9,740, 11,272, and 13,470 mg/L ( p pm ) at 15 o C, 25 o C, and 35 o C, respectively (Mangels a nd Ritter 2000). Typi cal te mperat ur es of a p plication in Washington State would bracket the solubility meas ures recorded between 15 o C and 25 o C. Generally, solubility will bracket the range of 1 t o 1.5% (i.e

., 10,000 to 15,000 mg/L ) in water at 25 o C. A sat u

rated 1%

solution of i m azapyr in freshwater at 25 o C will exhibit a pH of appr oxi m ately 3 to 3.5 (Toxnet 2003) . Because of the high solubili ty of the compound, it has inherentl y low sorpti on potential, and relatively high potential f o r mobility through soils.

The octanol: w ater partition coe f ficie n t (LogP) of im az apyr is reported as 1.3, re flecti ng its high solubility in water, low solubility in lipid (octanol ), and hence low propensity to bioconcentrate or

bioaccumula te (ToxNet 2003).

I m azapyr has a melting poin t range of 169 to 173 o C.

Dissociati o n constants reported for i m azapyr re flect its ionization potential under typical

environme n tal conditions. For rea d er clarific a tion, the pH at whic h an acid is 50 percent

dissociated betwee n its non-ioniz e d and ionized for m s is call e d its pK a . Thus, whe n the pH of a solution is equal to its pK a the chem ical wil l be disperse d equally betwee n an ionized and

unionized st ate. I m azapyr dissociates at two di ffer ent pH le ve ls, with diss ocation cons tants (pKa)

of 1.9 and 3.6. I n ge nera l, ioni zed for m s of chemi cals represent lo wer ecol ogical risk because they are unable to penetrate cell me mbrane s due to low lip id solubili ty. For acids such as i m pazapyr , a s the pH is elevated above the pK a the proportion of the compound in an ionized state will increase

. In the marine intertidal mudf lats where the i m az apyr woul d be applie d t o contr o l Spartina , the pH

of sedi ment surfa ces a n d sedi ment pore water shou ld be elevat ed above ne utral, and the compound

will be entir ely in an ionized state (Figure 3-4). However

, surfactants a p plied with the product are designe d to facilitate upta k e for product efficac y, a nd there f ore reduce this e l e m ent of pr otection.

FINAL

O c tob e r 200 3 Pag e 31Figu re 3-4: Imazap yr Disso c iati on Under Differ e nt pH Conditions.

(So u rce: Ma ngels and Ritter 20 00. )

3.2.2 Envi ro nme n tal Deg r ad atio n

Synopsis

The rate and for m

of degradation of i m azapyr va ries somewhat with the environment where it i s applied. M ove ment wit h in the envi ronment (e.g., through soils, water, plan ts, se di ments) of the

weak a c id i s pri m arily deter m ined t h rough by t h e pH of the host system . The primary for m

of degradation in water is via phot odegr adation. Photol ysis hal f-lives in wat e r have been reported at 2 days; however degradation decrea ses with inc r easing pH. Ozone may also degrade i m azapyr whe n applie d in a water treat m e nt set ting (Ras hi n and Graber 1993) . I m az apyr has bee n detected

in sur f ace and gr ound wa ter sampl e s taken by the Washingt on State Depart m e nt of Ecology following ae rial application on fo rest lands, although regular monito ring of the herbicide is lacking (Cox 1996). In soils, degradation i s pri m arily driven by m i crobial metabolism. Microbial

metabolis m i n sedi ment s has not bee n thoroughly i nvestigated.

S

o il A d sorption an d Degradation

I m azapyr wi ll adsorb to soils a nd sedi m e nt weakly. It has a reported organic carbon partition

coefficie n t ( K oc) in soil of 142 cc/g (Mangels a nd Ritter 2000). Thus, i m azapyr is considere d relatively mobile in soils. Adsorption is pH dependent, again, re fle c ting its propensity for

ionization at pH levels a bove its pK a (Figure 3- 4). For exa m ple

, a pH below 5.0 i n soil li mits movement due to an increased adsorption capacity within the soil; whereas above a pH of 5.0

concentrations of i m a z a pyr be come negatively c h ar ged (i.e., ionized) and do not bind well wit h soils, which increases its m obility. Th e adsorption coeff i cient f o r Arsenal tm , an isopropyla m ine

salt for m

ula tion, varies for di fferent types of soil. The adsorption coe f ficient repor ted for cl a y loa m s o ils is 1.7 verse s 4.9 for silt loa m soils with 4.0 per cent organic m a tter (PM E P 1985). Leaching has been obser ved up to 50 cm in soil. Anot her study related to imazapyr mobility in soil

observe d significa n t residues to a de pth of 1.5 to 3 m (4.9 to 9.9 feet), de pending on application rate (Cox 1996). Leaching has bee n observed up to 50 c m in s o il. Anot her study related t o

FINAL

O c tob e r 200 3 Pag e 32i m azapyr mobility in soil observed si gni ficant r e sidues t o a depth of 1.5 to 3 m ( 4.9 to 9.9 feet), depending on applicati o n rate (Cox 1996).

The pri m ary degradation pathwa y for i m azapyr i n soils is through microbial m e tabol i s m , wit h photolysis a nd other de gradation pa thways providing a li m i ted source of degr adation. Durin g aerobic m i c r obial m e ta bolism, the i m idaz olinon e ring is opened and a hydroxy metabolite i s for m e d as a result of the convers ion of the carboxi lic acid gr oup on the pyri d ine ring (Fi gure 3- 5). Reporte d half-lives of i m azapyr (t ec hnical grade) in soil ra nge fr om 25-141 da ys ( C ya na m i d Lt d. 1997, Cox 1996). Most of the reported variation in soil hal f -li f e is related to detecti on m e t hod applied i n the study: plant injury vers us laborat or y analysis.

Figure 3-5: Degradati on Pat h w a y of Imazapy r

. (So u rce: Ma ngels and Ritter 20 00. )

Recent studi es by t h e manufacturer exam i n ed the aerobic metabolism of i m azapyr in sandy loam soils (Mangels and Ritt er 2000). They pr opos e d a hal f -li f e of 117 da ys based on degradation through the first 28 days of t h e study. Howe ver, after 4 mont hs, when the study c oncl uded, only

26% of the dose a pplied had degra d ed, a nd only 5.6% of t h e dose ha d completely mineralize d (degraded) t o CO 2 . The authors considered the r a pid early degradation to ref l ect the m o re active microbial community in the soil initi ally availabl e, as the soi l s us ed i n the testing we re derived from an agri cultural fiel d (Figure 3- 4). In a second, 12- m onth study al so using sandy loa m soil with an application rate of 1.0 to 1.5 ppm, 66% of the applied dose still rem a in ed at the end of the study. No volatilization of the pare nt compound occurred. When usin g the data fr om 0 to 9 months

FINAL

O c tob e r 200 3 Pag e 33only, the hal f -li f e was est i m ated at 12.8 m ont hs, bu t the final three m onths of the study revealed no signi ficant a dditional de gradation, extending the ha lf

- l if e e s tim a t e to 1 7 m o nths. A replicate 12

month st udy showe d 88% of t h e applied i m a zapyr was r ecoverable after 365 days. These

collective results reveal that degradati on rates can vary s ubstantially even within an expe ri m e nt.

Figure 3-6: Degrad ation Rate of Imazap y r in Sandy -Loam Soil. (So u rce: Ma ngels and Ritter 20 00. )

The key par a m e ters that appear to effect the soil degradation rate of i m az apyr in the field include

te m p erat ure, organic carbon, and particle size. In a study by McDowell e t al. (1996), the half-li f e for i m azapyr (from Arsenal tm ) was addressed using a bioassa y appr oac h tha t gauged t h e ti m e ta ke n for the a m o unt of herbi c ide in the “ p lant-available” pool to e qual hal f of that whic h was applied. Using the lentil growth bioassay in New Zealand Templeton silt loam soils, the half -lives varied by approxi mate ly 87 da ys depending on te mperatur e, soil orga nic m a tter, and microbi al biom a s s carbon ( μ g- C/g s o il), with a range of 68.6 to 155.4 days . Degra d ation of the te chnical grade

i m azapyr in soils through m i crobial activity report e dly increased with the following environmental conditions (1) warmer temperatures (15 ° C vs. 30 ° C), (2) prese n ce of sa ndi er soils (i.e., sandy loa m vs. clay loa m ), (3) aerobic soil conditions, (4) increasing soil moisture, (5) increasing pH, (6) lowe r organic matter soil. However

, the effect of orga ni c m a tter c ould not be i s olated fr om the effect of pH under t h eir experi me ntal design, so the i m pa ct of t h ese variables on degradation rate was not entirely conc lusive.

In another s t udy by the m a nufactur ers of i m az apyr, Cya n a m id Ltd. ( 1 997), re port e d that the

i m azapyr isopropyla m ine salt degrade d 6 mont hs faster (3 vers es 9 months) at 45 ° C tha n at 37 ° C.

The related i m azapyr acid for m

ul ation also degrad ed faster with the sam e condit i ons as the technical grade i m azapyr

.

Anear obic s o il m e tabolis m of i m pa zapyr appea r s to be ins i gnifica nt from the e x is ting studies

conducted to date. In one study, s o il was treate d with i m pa za pyr at 1.0 ae/ acre.

There are al so reports of i m azapyr “leaking” out of the roots of treated plants and i m pacting surrounding native vege tation. A st udy by Lee et al. (1991) reporte d an increas e of i m azapyr

FINAL

O c tob e r 200 3 Pag e 34residues 231 days a f ter t r eat m e nt due to runoff of residues from plant surf aces af ter rainf a ll and release from decayi ng pl ant matter. Rainfall afte r application of i m azapyr has shown t o increase the ability of the chem ical to be adsorbed, howeve r im pacts due to increase d mobility in the soil column may out weigh efficacy i m provem ent.

Degradation in Aquatic Environments

Conditions i n aquatic e n vironments differ s ubsta ntia lly f r om those of terres trial soils, both in terms

of the re gula r exchange of waters wit h in the sedi ment (porewater) and over it, and in the range of

oxyge nation experienc e d in typical s e di m e nts tha t can a f fect microbial metabolis m (i.e., aerobic

verses a n aer obic ratios) . Early studie s in fres hwat er, pri m arily by t h e pr oduct registrant, exa m ine d the pathways and mechanis ms of degradation i n water and underlying sedi m e nt (Mangels an d Ritter 2000). Typical controlled degradation studies examine th e rate of degradation by the

accumulation of radiolabled CO 2 , which repr ese n ts the final br eakdown product of a radiolable d parent compound and its inter m edia te degradati on products. These studies are done either in water, moist sedi m e nt, or in slurries of water and s e di m e nt.

The degra d a tion of i m az apyr when a pplied direct ly to water largely m i mi cs the pathway by which the herbicide would be solubilized at high tide af ter application to Spartina during low tide. Residual imazapyr on the plants that may not have completely dried or adso rbed will be inundated by the incoming tide a nd pre s uma b ly sol ubili ze. Aquatic degra d ation studie s with i m a z apyr applied to a freshwater surface direct ly have s hown that i m a zapyr initially photodegr a des rapidly to two pri m ary products, “ C L 119060”, a n d “CL9140” (Figure 3-5). Accor d ing to t h e manufacture r s, CL119060 is biologically oxidiz e d to CL 9140, a nd eventually mi neralizes to carbon dioxide (CO 2 ) following the cleavage of the pyri d in e ring structure. Hydrolysis of the parent compound was found t o be negligible , with c ontr o lled experiments in di stilled water

, documenti ng onl y 3% of hydrolysi s product ( C L252974—see Figur e 3-5) accumulate d a f te r 12 days of inc ubation in pH 9 water. This hydr olysis produc t gradually i n creased over a 30 da y incubation period to 6.9% of the rec overed product, but the pH 9 value as tested would rarely be

seen in the estuarine environm ent and hydrolytic m echa n i s m s of degradation in situ woul d probabl y be less than obs er ved in this study.

In a controlled aerobic a quatic study with both phot odegra d ati on products a pplied at 0.083 ppm in Missouri and Florida pond water, le s s than 22% of t h e applie d radi oactive dose dissipa ted fr om the water pha se into the sedi ment phase. The quantit y of CL 119060 decre a se d from 77 to 0.5% of the

adm i nistered dose in this replicated laboratory experim e nt while the concentration of CL 9140 initially increased (Figure 3-7—Missouri data only). However, both imazapyr degradation products rapidly de grade d, with half l i ves less t h a n or e qual t o 3 da ys (Ma ngels a nd Ri tter 2000)

.

FINAL

O c tob e r 200 3 Pag e 35Figure 3-7: Degradati on of Im az ap y r ’s I n itial Photodegradati on Products CL

119060 an d CL 9140 in a contr o lled aer obi c aquatic sy st em usi ng Missouri pond

wa t e r

. (So u rce: Ma ngels and Ritter 20 00. )

Unlike lab degradation e xperi ments where more va riables ca n be c ontrol l ed and mea s ured, fiel d experiments are generally termed “dissipation” studies, as the multiple variables inherent to such
syste m s li mit the ra nge of ana l yses that can be conducted. With this understanding, comple ment ary field dis s ipation e xperi m e nts we re conducted by the product registrant in shallow

Florida and Louisiana fr eshwater pond syste m s where the parent produc t i m azapyr ( a s Arsenal tm )

was a pplied to the sur f ac e of the wat e r at 1.5 l b a e /acre (883 ppb). Dissi pation ( f ield degradation)

was followe d in water a nd se di m e nt over 180 days . Figure 3-8 re flects study re sults fr om water
and sedi ment analyses fr om the Louisiana pond study through the first 30 days of study, over which period the vast majority of di s s ipation ha d occurred. Similar results were obtained with the Florida pond syste m ( not shown) although de gradati on was slightly faster a

nd there di d not appear to be the i n itial spike in t h e sedi me nt concentratio n that was observed in t h e Louisiana pond syste m (Figure 3- 8) . The first

- order hal f -l ives in the water and s e di m e nt we re 1.9 and 12.8 days, respectively. No dete cta b le residues of i m aza pyr were f o und in the water and sediment af ter 14

and 59 da ys, respectively.

FINAL

O c tob e r 200 3 Pag e 36Figu re 3-8: Resid u es of imaz ap yr in w a ter and sedi ment fr om a Louisi ana pond

treat ed w i th 1.5 l b ae/ acr e. (So u rce: Ma ngels and Ritter 20 00. )

Tidal flux i n estuarine environments also provi de s a consiste nt and predict a ble rinsing effect that will solubilize applied herbicide and contribute to its rem oval f r om an area where recently applied. Freshwater degradation studies in slurries pr obably repr esent the most si mila r laborator y conditions for degradation comparis ons to tidal environments. Ho wever, to our knowledge these

tests have been done i n freshwater only. These conditions c h allenge the researcher a tte m p ting to isolate the variety of me chanis ms that could be responsi b le for degradation of i m az apyr in a n estuarine set ting. Rece nt studies have addressed som e of the uncertaint y. Patten and Stenvall (2002) exa mined the fate of i m azapyr applied dir ec tly to se di ment to gauge its per s is tence over
ti m e . In thi s study, i m a zapyr conc e n trations we re m easure d in intertidal waters and sedi m e nts adjacent to a Spartina meadow. Ana l yses were c onducte d 3, >24 and > 48 hours a f ter application

at the standa rd treat m e nt concentration of 1.68 kg ae/ha used i n the efficac y trials discussed earlier

. Sediment samples collected three hours af ter appli cation were retrieved immediately af ter the f i rst tidal wash over the treated area. The study design was conservative in that there was no intercepting algal or e m e r gent vegeta tion overlying the sediment where the herbicide was applied. In this study, the m a xi mum ge omet ric m ean concentration of imazapyr det e cted in sedi ments fro m four replicat ed trials detected 3-hours appli cati on was 5.4 m g / kg-se diment . Twe n ty-four t o seventy-si x hours a f ter application t h e geomet ri c m e a n ma xi m u m dete ction was 2.26 mg/ kgsedi m e nt, roughly hal f of that detect ed a f ter th re e hours

. In the water

, 0.119 mg/ L i m aza pyr wa s detected a f te r 3-hours

, and less th an 0.00006 mg/ L (the method detection li m it) was detected a f ter
24 to 48 hours. The i n tent of this study, howe ver, wa s pri m arily gea r ed towards addressing ecological ri sk under a c onservative application s cenario, as oppose d to the in situ degradation. No

“ti m e zer o” data were re ported in the study result s, nor were other environm e n tal conditions that may have e f fected the r e sults reported suc h as t e m p erat ure, organic carb on, etc

. Wi thout s u ch data, the in situ degra d ation ca n onl y be esti mated.

Some of the experi ment al design iss u es with th e preceding e xperi ment were addres se d in a mor e intensive fat e study conducted by Patten subsequen tly (2003). In this study, i m azapyr was again applied to ba re m u d flat a t 1.68 kg/ha with 1% ( v/ v ) Agridex s u rfac ta nt to a plot size of 30 x 33 m in the upper intertidal zone. The ti dal front at this site could cover the application area in 13

FINAL

O c tob e r 200 3 Pag e 37minute s . A standar d backpack spr a yer with a 3 m boom was use d t o apply the herbicide /

surfa c tant mixture at a ra te of 97L/ h a in the early m o r n ing. Th e pH 7.9 se di m e nt cont ained 49% water, and 51% dry matt er. The soli d constituent s of t h e se di ment contai ned 5.4% or ganic matter

, and 18.3, 65.5, 16.2 perce n t sand, silt and clay, re spectively. Water was c o llected in 1L jars burie d

within 1 c m of their lips in the se di ment t o capt u

re the inc o ming tidal fr ont a f ter application, and the jars were spaced in tri p licate at 10 m interval s a l ong the tida l front “gri d”. W a ter sa mples were

collected aft e r the 1 st , 2 nd , 3 rd , and 7 th tides, correspondi ng to 3.5, 14, 28 and 77 hours a f ter

treat m e nt. Square se diment cores 8-c m dee p were obtaine d in si m ilar positions along the grid a s the water sa mples

, but unlike the previous experi m e nt, sa mples were taken i m mediately a f te r application ( t i m e 0), as well as the 1 st , 2 nd , 6 th , 14 th , 28 th and 56 th tidal exchange af ter treatm ent.
These exc h a nges corresponded with 1, 14, 27, 77, 184, 366 a nd 703 hour s after the initial sedi m e nt application. Finally, sedi ment sub-sa mples were obtained f r om triplicate Spartina plots (3x4 m )

treated with the sa me application regi m e as th e bare sedi ment to gauge c a nopy i n terce p tion under typical treat ment regi me s. In this trial, the treated Spartina was 1.7 m tall, and was concentrated i n

an area appr oxi mately 2 m above Mean Lower Low W a ter (MLLW ) MLLW . All of these areas of

treat m e nt were then compared a g ains t sa mples ta ken from untr eated bare se di m e nts.

Figures 3-9 and 3-10 reflect Patten’s (2003) re su lts on the water and sedi m e nt pe rsistence o f

i m azapyr. As depicted, measurable concentrations of i m azapyr declined exponential l y in both the

water and se di m e nt. Fol l owing appli cations to t h e bare interti d al mud fl at, the maxi mu m av erage

water conc entration detected was 3.4 μg/ L (ppb) a n d the maxi mum a v era g e sedi ment concentration detected was 5.4 mg/kg (ppm ). The “zero asymptote” was a pproached at 40 and 40 0

hours for the water and s e di m e nt, res p ectively ( F i gures 3-9 a n d 3-10).

Figure 3-9: Persistence of imazap y r in estuarine w a t e rs of Willapa Bay follo w i ng direct appl icatio n to an u n vegetated ti da l mud flat. Data re presented are mean

val ues of t r iplicat e sampl es +/- SE. (So u rce: Pa tten 2003

. )

FINAL

O c tob e r 200 3 Pag e 38Figure 3-10: Persistence of imazapy r in estuarine sedi ment in Willapa Bay

, WA
after direct appli cati o n to an u n v eget ated tidal mu d f l at. Dat a r e pr esent e d ar e mean valu es of tripli cat e sampl es +/- SE. (So u rce: Pa tten 2003

. )

Persiste n ce i n Biologic a l Tissues
Biological t i ssues may act as an additional r e servoir for che m icals applied i n te ntionally or

inadvertentl y to the environmen t. When a n organis m ac cumu lates chem icals in its tissues

f o llowing direct exposure it is known as bioconc e ntration . I f the organis m is consumed (predated upon) by another or gani sm re sulting in a higher conc entration of t h e c h e m ical i n the predator, the

chem ical is considered to bioaccumulate in t h e “food web”. In si mple ter m s, the che m ic al

accum u lates at a rate f a ster than norm a l m e tabolic processes elim inate it. A l though

bioconcentration and bioaccu mulation m a y have toxicity i m pl ica tions, toxi city varies by chem ical and dose, t hus these mechanis ms should be c onsidere d independently whe n e v aluating the biological fa te of a pplied herbicides. As indic a te d in the discussion of physical chem istry (Section 3.1) the octa nol:water pa rtition coeffi cient and its hi gh solubil ity indicate the compound is not apt

to concentra t e in tissue. Notwithsta nding, to address i m az a pyr and its degradation products in biological ti ssues, sever a l treat m e nt studies of relevance have bee n conducted in Florida a nd Missouri pond systems that contai ned bluegill, tilapia, catf i sh an d crayfish (Mangels and Ritter 2000) . The ponds contained 75, 2 8, 213 or 261 ppb i m azapyr following tre a t m ents of Arsenal tm to the banks and outer edge s of the ponds at a rate of 1.6 lb ae/acre in spray solutions of 21 to 23 gal.

Ulti m a te concentrations in the ponds varied due to dilutiona l profiles i n herent to the ponds ( e .g., volumes). Table 3-7 summarizes the principal fi nd ings from t h is study in each of the pond syste m s evaluated.

FINAL

O c tob e r 200 3 Pag e 39Table 3-7: Pe rsi s te nc e and Bioc once ntratio n of Imaz a p y r in Miss ouri an d Fl ori da Pon d

Wate r, Se di ment an d Reside nt Aq uati c Biota.

(So u rce: Ma ngels and Ritter 20 00. )

Metric
Measured Untreated
Control

Pond Pond 1 (MO Pond #11) Pond 2 (Fl pond # 11) Pond 3 (MO Pond #21) Pond 4 (FL Pon d #21)

Initial Water
Concentra t i on

μg/L (ppb) < 0. 207 28 7 5 2 1 3 2 6 1

Initial Sedi ment
Concentra t i on

μg/ k g ( ppb) < 0

. 4 7 5

~ 1

. 5 1

~ 2

. 5 1

~ 1 0

. 2 1

~ 10.2 1

Half- l ife i n P ond

Water ( d a ys) N o t app licab l e 1 4

. 1 8

. 4 1 4

. 5 3

. 9

Half- l ife i n P ond

Sed i me nt s No t ap pl ic ab le No t c a l c u l a t ed 2 Not ca lculate d

, (too few d a ta) Not ca lculate d 2 9.2

Residu e in

b l ue gi ll Al l sam p l e s <5.3 5 p pb < 50 pp b (MDL 3 ) < 50 pp b (MDL 3 ) 3 hr s p o st trt

. = 0.63 6 p p m, there a ft er < 50

ppb (MD L 3 ), < 50 pp b (MDL 3 )

Residu e in

cat f i s h Al l sam p l e s <5.3 5 (e xcept 1

s a mp le at 14

. 1 ) < 50 pp b (MDL 3 ) < 50 pp b (MDL 3 ) 3 hr s p o st trt

. = 0.23 3 p p m, there a ft er < 50

ppb (MD L 3 ) < 50 pp b (MDL 3 )

Residu e in tila pia All sam p les < 5.35 < 50 pp b (MDL 3 ) < 50 pp b (MDL 3 ) 3 hr s p o st trt

. = 0.06 8 p p m, there a ft er < 50

ppb (MD L 3 ) < 50 pp b (MDL 3 )

Residu e in

cr a y f i s h All < 5. 35 (excep t 1 @ 10.6) < 50 pp b (MDL 3 ) < 50 pp b (MDL 3 ) 3 hr s p o st trt

. = 0.05 9 p p m, there a ft er < 50

ppb (MD L 3 ) < 50 pp b (MDL 3 )

1: Ba sed on interpr e tat i o n o f gr aph ical dat a pr epare d by the re sear che r s 2: Sed i me nt le ve ls persiste d in the s e po nd s; the au t hors at trib ute d t h is to an un usua l inver s ion th at re sult ed in pond tur b idity prior to po nd treat m ent and red u ced the r a te of ph oto degra dat io n

3: MDL = m e th od d e te ct ion lim i t

A separate s t udy exa m ined the pote n tial for bioc oncentration and persiste nce in a mol l usc species

, the freshwat er clam ( Corbicula fluminea ). In t h is study, cla m s were exposed t o the Arsenal tm for m

ulati o n of i m azapyr in a mesocosm cont aining wate r and se diment , and the water was inoculated with 0.091 mg ae/L. Si m ilar to the study results reported above , no i m aza pyr wa s detected in t h e cla m tis s u e at or above the 50 μg/ kg (ppb) de tection li m it. Over the 28-day study,

the concentr ation of i m a zapyr in the water dec lined only m i ni mally, from 81 to 75.1 ppb, while the

sedi m e nt concentration i n creased from non-detec t able to 29.2 ppb at the end of the experi ment.

No t oxicity was re ported.

3.3 To xicit y t o Terr estri al Receptor s

In this section we examine data f r om acute, su b-chronic

, and chronic i m aza pyr exposure studi es with terrestrial wildlif e and invertebrates. The toxicity of imaz apyr to these ecological receptors is

FINAL

O c tob e r 200 3 Pag e 40discusse d, a s known, a nd data ga ps are identi fie d. The de scriptions of toxicity in Table 3-8 established by the Environmental Protection Agency (EPA) are used as a tem p late to qualitatively gauge study results discussed. As de picted, these descriptions vary slightl y depe nding on the cla ss of a n i m al be ing tested (a vian or ma mmalian) a n d the study being perfor m ed (a cute oral LD 50 or dietary LC 50 ). The LD 50 is the statistical derivation of a dieta r y or drinking water dose , whic h is predicted to cause 50% m o rtality in th e gi ven populati on being teste d . The LC 50 is a similar number, bas e d on the concentration of a compound in air or water. The criteria for these descriptions are presented below in Table 3-8. The specifi c toxicity data discusse d below are separated i n to si mple ani m al classi fi cations (e.g ., ma mmal s , birds, insect s, etc.) a nd the studies conducted generally re fl ect EPA pr otocols with standard te st spec ies. In using t h is toxicit y classif i cation scheme it becomes possible to qualitatively compare toxicity values of the active ingredient a nd pr oduct for m

ulati ons a m ongst spe c ies.

Table 3-8: Haza rd Cla ssifi cation s to Ad dress Wild life Ris k from Herb icide Use. (EPA 1995 )

M a m m a l s M a m m a l s A v i a n A v i a n

Hazard Catego ry Acute Oral or D e rmal LD 50 (mg/kg) Acute Inhalatio n LC50 (ppm) Acute Oral LD 50 (mg/kg) Acute Inhalatio n LC50 (ppm)

Very h i gh ly t o xic <10 <50 <10 <50
High ly t o xic 10-50 51-50 0 10-50 50-50 0

Modera t e l y to xic 51-50 0 501-1 000 51-50 0 501-1

, 00 0
Slig ht ly to xic 501-2

, 00 0 1001- 500 0 501-2

, 00 0 1,00 1-5, 000

Practica lly no n-to xic >2,0 00 >5,0 00 >2,0 00 >5,0 00

It m u st be r ecognize d that species di fferenc e s in terrestrial ecological rece ptors ( m a m mals, birds, etc.) may exist that are not predic table f r om the classif i cation sche me re presented in Table 3-9.

Some wil d life recept o rs that m a y be at risk of e xposur e to imaza pyr are rarely used in toxicity testing for la ck of a c onsi s tent supply and approve d protoc ols. For exa m ple

, we found few data on

omnivorous and carni vor ous s p ecies such as the r accoon and coyote

, large ung ulates such as the

black-tailed deer that commonl y fora ge along estuary margin s, and m i grator y shorebirds

, passerines, and reptiles and amphibians.

The use of surrogate test species wit h si m ilar diet ary and/or behavior pat t erns has be en shown t o provide a relatively reliable predictor of toxicity for the most sensitive spec ies of f

i sh (Sappington et al. 2000). A si m ilar relationship l i kely exists for other wil d life recept ors that are not routinely used for toxicity testing when compared agai ns t surrogat e s. Howe ver, only site -specific ris k

assess ments woul d be able to fully quantify risks to resident and m i grator y wildli fe rece ptors fr om che m ic al exposure in ea ch location where Spart i na control with i m aza p yr is envisioned. This

assess ment t h erefore must use surrogate species s u ch as the ra t and rabbit t o gauge t oxi city to other

wildli fe that m a y be more likely t o be found using the habitat found al ong the stat e- m a na ged roadways of W a shington State. The rat provides a reasonable surrogate of an omnivore

, the rabbit

an exclusive herbivore, and the qua il and duck provide sur r ogates of upland and wetland bir d species, r e spectively.

3.3.1 M a m m a l s

Based on EP A criteria specified in T a ble 3-9, im azapyr w o uld be cons id er e d p r a c t ic ally non

- t ox ic to

m a mm als based on acute and chroni c studies conducted with a vari ety of m a mm alian species. Fo r

FINAL

O c tob e r 200 3 Pag e 41exam ple, th e rep o rted acu t e oral L D

50 concentration for ra ts is >5,000 m g / kg. N o signif icant

bioaccum u lation has been reported in ma mma l s

. Ra ts were obs er ve d t o ra pi dl y e x cr et e ima z a p yr i n urine and f e ces w i th no resi dues det ected i n their l i ver, kidney, m u scle, fat, or blood. R e sults f r om a series of tests loo k ing at th e mamma l i a n res p onse to a c u te ora l , der m a l , and i n hal a ti on

a d mi ni str a ti ons of i m a z a pyr is opropyl a mi ne t e ch nical, im azapy r tech n i cal, an d im azapy r isopropylam i ne w a s com p iled by Cyan am id L t d. (1997) ( T a b l e 3- 9)

.

Table 3-9: Acu t e and Sub c h r oni c Mamm alia n Tox ici c it y to I m aza p yr.

Test
Substance Animal Speci es Administration
Route Gender LD 50 or ED 50 body

wt., (or) ppm diet* Effect Testing Faci lity

, (reporting year)

M a l e > 10 ,00 0 * D A Oral F e m a l e > 1 0

, 0 0 0 * D A

M a l e DA, B, A, S, CY, C, DBW Intra periton ea l

F e m a l e 3

, 7 0 0 DA, B, A, S, CY, C, DBW

M a l e > 5, 0 0 0 D A Sub c u t an eou s F e m a l e > 5, 0 0 0 D A

M a l e > 2, 0 0 0 N O E L Rat

Dermal F e m a l e > 2, 0 0 0 N O E L

M a l e > 10 ,00 0 D A Oral F e m a l e > 1 0

, 0 0 0 D A

M a l e 3

, 4 5 0 DA, B, A, S, CY, C, DBW Intra periton ea l

F e m a l e 3

, 0 0 0 DA, B, A, S, CY, C, DBW

Male > 5, 000 DA, B, S Ima z ap yr isopro p ylam in e techni cal (49.3 % )

Mou s e

Sub c u t an eou s Female > 5, 000 DA, B, S Medi cal Sc ienti f ic Research,
Labor ator y (1 983 )

M a l e > 5, 0 0 0 N O E L R a t O r a l F e m a l e > 5, 0 0 0 N O E L

M a l e > 2, 0 0 0 N O E L Rabb i t D e r m a l F e m a l e > 2, 0 0 0 N O E L American C y a n a m id Compan y (198 3)

M a l e > 1

. N D Ima z ap yr techni cal

R a t I n h a la t i o n Female > 1. (ana ly ti ca l) ND Food and Drug

Research
Labor ator ie s (1 9 83)

M a l e > 5, 0 0 0 D A R a t O r a l F e m a l e > 5, 0 0 0 D A American C y a n a m id Compan y (198 3)

M a l e > 5, 0 0 0 D A Mou s e O r a l F e m a l e > 5, 0 0 0 D A American C y a n a m id Compan y (198 6)

M a l e > 2, 1 4 8 N O E L Rabb i t D e r m a l F e m a l e > 2, 1 4 8 N O E L American C y a n a m id Compan y (198 3)

Male > 0. 2 NOEL Ima z ap yr isopro p lyam in e 25 % AS

R a t I n h a la t i o n Female > 0. 2 (ana ly ti ca l) NOEL Food and Drug

Research
Labor ator ie s (1 9 83)

NOEL = no to xic sign s, D A = de cr eased ac tivit y , N D = na sa l d i sch a r ge, B = blep har opto s is, A = ata x ia, S = se dat io n, CY =

cyano sis, C = co nvu l sion, DBW = de crea se d b o d y weig ht

Sour ce: Cyana mid Lt d. ( 199 7) 4

, 2 0 0

FINAL

O c tob e r 200 3 Pag e 42Signi ficant sub-lethal effects were reported for each for m

ulat ion of i m azapyr tested at doses that exceeded the “practically non-toxic ” acute lethal criteria for adm i nistr a tion routes, except the

inhalation r o ute, where s ublethal e f fe cts occurre d at lower dos es (Table 3- 9). The mos t signi ficant

effect was found wit h t echnical gra d e i m azapyr isopropyla m ine ad mini stered via intraperitoneal injection, although because the othe r for m s of i m azapyr did not test reacti ons using thi s method, i t
is hard to draw conclusi ons on the r e lative toxic ity of i m a z a pyr isopr opyla m i ne tec h nical grade

. Further m ore , this met h od of toxic a nt administ ration is not environme n tally relevant beca us e

ma mmals would not be dosed i n this m a nner in a natural setti ng. No over a ll observa ble effect was

noted for a n y for m

ulation of i m azapyr adm i niste r ed der m ally, and e f fects in m a mmal s expos ed to

i m azapyr via inhalation were only obser ved with i m azapyr technical grade.

Technical grade i m azapyr is repor ted as moderately irritating to rabbit eyes, with complete recovery wit h in 7 days of exposure ( B PA 2000, Cyana m i d Ltd. 1997). The sa me result was found

with i m azapyr isopropylam ine 25% AS. I m azapyr tec hnical is also reported as m ildl y irritating t o rabbit skin (BPA 2000, Cyana m id Ltd. 1997). Studies reviewed by the EPA conc luded tha t
i m azapyr technical is corrosive t o t h e eyes and can cause i rreversible eye damage ( C ox 1996).

Commercial for m

ulati ons of i m azap yr appear to be less toxic by this r oute of exposure.

Der m al exposure st udie s have shown i m azapyr t o yield statis tically inconsistent suble t hal e f fects.

Where an effect was obser ved, it was usually obs erved as er ythe m a , a loc a lized increa se in blood flow observed as a ‘reddening’ or r a sh-like symp tom. A 21-day sub-acute rabbit dermal toxicity study at dos es of 0, 100, 200, or 400 m g /kg/day r e v ealed no c onsistent pat t ern of toxic ity, and the NOEL was concluded to be the highest dose te s t ed (HDT) ( 400 mg/kg/ day) (Fed Re g, 62, 1997)

even t hough a hi gher dose would most likely be more accurate. Anothe r study with i m az apyr isopropyla mine (25% AS) was reported to cause slight erythe m a at 24 and 72 hours post-der m al

expos ure in rabbits; however, the sa me for m

ulat i on was obs e rved to for m

no der m a l reaction in guinea pi gs (Cyana m i d Ltd. 1997) . Other der m a l e xposure s t udies in bot h rats and ra bbits repor t

LD

50 c once n trations at > 2,000 mg/kg, and > 2,148 mg/kg, res p ectively ( T able 3-9)

.

The product registrant conducted s u bchronic diet ar y toxicity t e sts where i m aza pyr isopropyla m ine

was adminis t ered orally at conce n tra tions of 0, 1000, 5000 a nd 10,000 ppm for 13 c onsecutive

weeks (Cya na m i d Ltd. 1997). The st udy re ported the maxi mum NOEL for rat diets as 5,000 pp m (325 mg/ kg/ day in male s and 370 mg/kg/day i n fe males). Anothe r 90-day rat fee d ing st udy a t doses of 0, 15,000, and 20,000 mg/ k g-diet yielde d a NOEL values of 1,695 mg/kg/da y the HDT,

and a n esti mated ( F ed Reg 1997).

C

h ro n i c T e

stin g

Chronic toxi city studies have been c onducte d wi th m i ce, rats , dogs and r a bbits to address effects

on survival , carcinoge ne sis, teratoge necity and i n tergenerati onal effect s. Dogs fed doses of 0, 25,

125 a nd 250 mg/kg/da y i m azapyr s h ow e d no sta tistically significa n t e f fe cts on survi v al or other endpoi nts monitored. The product re gistrant conc luded t h e NOEL at 250 mg/kg/day, t h e HDT.

Rats a nd mi ce fed i m aza pyr for 2 a n d 1.5 ye ars ( r es pectively) exhibite d a n increase d i n cidence of congestion of the brai n in fe males ( m i ce), flui d acc um ulation in the air sacs of the l ungs in fe males ( m ice), i n cre a sed inci dence of ki dney cysts in ma l e s ( m ice) , increase in abnor mal blood for m ation in the spleen (rats), increase of blood pooling in the liver (rats), incr ease i n t hyroid cysts (rats), and

a decrease i n food e f fici ency (rats). The diets contained 0, 1,000, 5,000, or 10,000 ppm i m aza pyr. However

, the results from these chronic diet ar y exposur e studies revealed no significa nt

FINAL

O c tob e r 200 3 Pag e 43differe n ces a m ongst the treat m e nt conce n tr ations, a n d the EPA has concl uded NOEL concentrations at the highest dose tested—i n this case, 1,301 mg/kg/ day in m i ce, and 503 mg/kg/day in male rats (Fed Reg 62, 1997). Tumors were iden ti fied i n both the high-dose and control groups at insigni ficantly di fferent rates a nd the EPA therefore concluded the herbicide i s not consi d er ed to be car cinogenic

. In vitro gene m u tation studies using the Ames Sal m onell a

assay, c h romos o me aberration ass a y, poi nt muta tion assa y, uns cheduled DNA s ynthesis

, and

dom i nant-let hal assay yi elded no si gnific a nt re sults, and the herbicide was concluded to lack

muta genic a c tivity (Fe d Reg 62, 1997).

Chronic concentrations of i m a zapyr a t dose leve ls up to 1,000 mg/kg per day in rats and up to 400 mg/kg per day in ra bbits resulted in no signi f i cant di fferences amongst the doses tested for

mutations or birth de fect s (Cya na mid Ltd. 1997). Once agai n, the NOEL for Arsenal tm in th e s e developme n t a l toxicity studies was re ported at the HDT for ra bbits (400 mg/kg/da y), but lowered to 300 mg/kg/day for the rats, as the highest dos e tested (1,000 m g /kg/day) increased salivation in the gravid fe males, even though no specific devel opm e n tal toxi city endpoint was altered in the rats. No intergenerational e f fects were observed in a s ubsequent t w o-ge nerati on rat study conducted at dietary conc entrations up to 10, 000 ppm (738 mg/kg/da y) and the HDT was a g ain accepted as the

NOEL.

3.3.2 Bi rds

The repo rted acu te oral LD 50 concentration for bobwhi te quail and m a llards is >5,000 m g /kg-diet.

The r e ported s u ba cute ora l LD 50 concentration for bobwhite quai l and m a llards reproduction is >1,890 m g /kg-diet. These values represent the hi ghest doses tested to date. No signif icant

bioaccum u lation has been r e por t ed i n avian speci es

. Resu lts f r o m past av ia n studies cond ucted by th e

pr oduc t re gistr a nt wit h

Ars e nal tm a

nd/ or t e c h nica l gra d e i m a z a pyr a

r e s u mma r i ze d in Ta bl e 3-10.

Table 3-10: Lethal and Sub l eth a l T oxici ty of Arse nal in Control l ed Avian Ex pe ri ments.

Species /Test L D 50 or LC 50 NOEL (of test substance)

Northern Bo bwh i te Qua i l LD 50 / 18- week d i et ary
exp o sure eff e cts on e gg prod uctio n

, h a t c ha bilit y

, & ha t c h l ing sur v iva l ) > 1, 890 mg/ k g (~200 mg/ k g-q u a il) 1,89 0 m g / k g (~200 mg/ k g-q u a i l = the HDT)

Mallard Du ck LD 50 / 1 8

- we ek di et a r y ex po su re effe ct s on egg pr odu ct ion

, h a t c ha bility, &

hat ch ling sur v ival >1,8 90 m g / k g-d i et (~200 mg/ k g-d u ck) 1,89 0 m g / k g-d i et (~200 mg/ k g-d u ck)

Northern Bo bwh i te LD 50 /5 da y a c ute dietar y
exp o sure eff e cts on sur v iva l ) >5,0 00 m g / k g-d i et (~674m g/ kg-qu a il) 5,00 0 m g / k g-d i et (~674m g/ kg-qu a il)

Mallard Du ck LD 50 /te st 8 50. 220 0 ( 5 da y acute
die t ar y e x p o sure effe ct s on sur v ival) >5,0 00 m g / k g-d i et (~1149 mg /kg-du ck) 5,00 0 m g / k g-d i et (~1149 mg /kg-du ck)

W illapa Bay, Padilla Bay, and other locations in the state where Spartina has c o loni zed provide

substantial a nd signi fica nt water f owl habitat (see Ap pendix B for revie w of ecology in t h ese areas).

As suc h, test ing with the mallard duc k provides a good surrogate for other waterfowl species that use these areas and could potenti ally be exposed to i m azapyr after a Spartina treatment. Shorebirds also use these estuarine habitats, and W illapa Bay supports the m o st significant stopover point a l ong the we st coast for migrating shorebirds. Shorebirds ar e greatly affected by the

colonization of Spartina , as it reduces available foraging ha bitat f o r these species. Indeed, monitoring s t udies ha ve shown that s horebirds wi ll not us e Spartina mea d ows to fe ed in (Patten

FINAL

O c tob e r 200 3 Pag e 44and Stenvall 2002). Notwithstandin g, the toxic o logical risks to shor ebi r ds m u st be considered.

Unfort unatel y, we found no data to address the pote ntial toxicity of i m az apyr to shor ebirds. One study, howe ver, exa m ined the penet r ation force re quired to penetrate mudflat sedi ment colonize d

with Spartina relative to an uncolonized mudf lat, and a colonized mudf lat treated with tilling or herbicide. In that study, an artif icial Dunlin be a k penetrated a si m ilar (i nsigni ficantl y di fferent )

distance in the tilled Spartina meadow as in the ba re mudf lat. Herbicid e treated m eadows killed

the Spartina , but did not softe n the se di m e nt, like the tilling. These result s suggest tha t the habitat

risks from Spartina inf e station are not necessarily allevi ated by herbicide treat m ent alone.



### unt r ea t e d

sp r a y e d spr a y + m o w

t ille d m udf l a t b eak

pr o b i n g de n s i t y /0 .2 5 m 2 100

80

60

40

20

0

-2 0

Figure 3-11: Penetration di stan ce in artifi cial b e ak t est s. (So u rce: Pa tten and Stenvall 2002. )

In addition t o the toxic o logical data gap on s horebird and rapt or species, no data were i d entified on preening exposure or inha lation expos ure pot entials associated with i m aza p yr.

3.3.3 Insec ts

The reported acute conta c t LD50 toxicity concent r ation for the hone y bee is approxi m ately > 0. 1 mg i m aza pyr/bee (Ga g ne et al. 1991 ). SERA (1999) esti mat e d this dose to be greater than 1,000 mg/kg-bw, a ssum i ng 100% absorption of the applied dose

, and an average body w e ight of 0.093 g/bee [0.1 mg/0.000093 kg = 1075 m g / kg-bee

, or ~ 1,000 mg/kg-bw]

. Sim ilar to the avian and

ma mmalian studies previ ously addre s sed, there was no dose te sted that resulted in acute or chronic mortality, and the NOEL f o r the b ee was taken to be the highest dose tested, or 100 ug/bee (1075 mg/kg). Usi ng the ma mmalian t oxic ity criteria adopted by the EPA ( T abl e 3-9), i m az apyr woul d

be considere d practically non-toxic to the bee

.

FINAL

O c tob e r 200 3 Pag e 45In terrestrial environments, herbicide treat m e nt ha s been shown to increase the local abundance o f arthropods—likely as a response to the increase d food suppl y for these detr itivores fr om the dead

and deca ying vegetation. Arthropods serve as a s ubstantial, hi gh-energy food source for m a ny bird species, a n d this relationship holds true both fo r terrestri al birds, as well as waterfowl an d shorebirds during periods of migrati on (Cohen e t al. 2000). A care f ul exa m ination of the use of dead and decaying (post

- treated) Spartina has not been conducted; however, it is conc eivable that a

si m ilar relati onship woul d be obser ved during the decay process.

3.3.4 Rep t il es a n d Amph ibia ns
Toxicity i n for m ation of i m azapyr wi th regards to reptiles and a m phibian s was not found through standard literature search engines.

3.4 To xicit y t o Aq uati c Recept ors

A wi de range of freshwa t er and m a ri ne fis h and a quatic invert ebrates occur in the surfa c e waters o f

Was h ington. The type of species found depends upon suc h factors as wa ter temperat ure, salinity, pH, a nd flow conditions . Beca use of the diversit y of aquatic habitats throughout the st ate no single species is r e presentative of all habitat s where fish and invertebrates could be exposed t o i m aza pyr. Although Washington St ate suppor ts several Enda ngered Speci es Ac t (ESA)-listed aquatic species, these specie s are ofte n not those that are use d for toxicity t e sting. Inde e d, most tes ting that has

been conduc ted has foc u sed on fres hwater specie s, or marine species that are not gene rally found

in Washi ngt on State’s estuaries . Thus, although the central focus of this r i sk asse ssm en t co nsid ers the potential use and risks from i m az apyr when a pplied in a n estu arine environment, the following

discussion on i m aza pyr’ s aquatic toxicity consi d ers the total weight of evidence ac quired fro m aquatic s p eci es from vari ous s y ste m s.

In this secti on we examine the acut e and chroni c toxicity st udies conducted on i m a z apyr in the aquatic envi ronment. Specifically, the acute and chronic toxicity and accumulation potential of

i m azapyr to fish, aquatic invertebra tes, and non-tar g et aquatic plants are discussed. Acut e data are generated by the conduct of 2 to 4 day-long studies unde r controlled conditions . Table 3-11 provides ge neral risk a ssess ment st andards for fis h and a quatic invertebrates bas e d on acute toxicity LC 50 concentrat ions. This guide was used as a prelim inary tem p late to gauge risks associated with project actions that are broad in scope, suc h as the use of i m azapyr by W S DA for agricultural mana ge ment . Chronic effects in aquatic organis m s are usua lly based upon adverse reproductive or growth e f fects, such as decrease d hatching success, de cre a sed sur v iva l of lar v ae, decreased growth of larvae or j uveniles, and decreased reproduc tive capability. Chronic eff ects may occur from either acute or ch ronic exposur es. In the majority of studies re vie w ed in t h i s section, little or no chronic toxicity data were a v ailable bec a use earlier tier acute testing did not

indicate the need for furt her data development.

FINAL

O c tob e r 200 3 Pag e 46Table 3

- 11 : Toxicity Cla ssi fica ti ons to Add r es s Acu t e Risk to Aquatic Org anism s fro m Che m ic al Use.

Fish or Aquati c Inverteb r ate s Hazard Catego ry Acute Concentration LC 50 (mg/L)

Very hi ghly toxic <0.1
High ly t o xic 0.1-1

Modera t e l y to xic >1-10
Slig ht ly to xic >10-10 0

Practica lly no n-to xic >100

3.4.1 Fish

The reported acute toxicity LC 50 concentration f o r rainbow trout , bluegill sunf ish, and channel

catfish is > 100 mg/ L based on product registra nt studies with technical grade i m az apyr using

standard 96- h r exposure studies (Ma ngels and R itter 2000). Tests were also conduct e d with the Atlantic silverside to address the potential toxicity of i m azapyr to marine fis h. I n those tests the highest concentration tested was 184 m g /L, which yielded no signif i cant toxicity (mortality). As

with studie s with terrestri al ani m als

, the NOEC was taken as t h e HDT, or 100 mg/ L for freshwater

fish a nd 184 m g /L for marine fish. On this basi s, i m azapyr wa s considere d practically non-toxic to

f r eshwater f i sh based on toxicity criteria outlined in Table 3-11.

I m azapyr has not been thoroughly te sted for chr onic or sub- lethal effect s with a wide variety of aquatic or ga nis m s , but those fe w te sts conducted are worth summarizin g. Early li fe sta g e sur v ival

tests with r a inbow trout and fathe a d m i nnow e m bryos a nd sac- fry continuously expose d to
i m azapyr revealed no effects on hat c hing or sur v ival at concentrati ons as high as 92.4 a.i

. mg/L and 118 mg a.i/L, re spe c tively. Ag ain, these were the highest concentrations tested. A full life cycle test wi th fathead mi nnow with concentrations up to 120 mg a.i./ L als o did not elicit toxicity.

It is unclear why the product regis t rant did not pursue testing with hi gher conce n trations to

establish the true maximum tolerated dose. Su ch testing has applications whe n addressing potential spill scenarios with the hi ghly soluble herbicide. Howeve r , re cent results by Universit y of Washingt on researc h e r s help t o el i m inate t h is uncertaint y (C. Gr ue personal c o mmunication, 2003) . Grue and others e x a m i n ed t h e toxicity of i m aza pyr in 96-hr ta nk te sts wit h juve nile rainbow trout (Ta b le 3-12) . As de monstrate d in these te sts, the concentrations required t o a c hieve 50% mortality are exceedingly high. Indee d, the conce n tr ation of t h e for m

ulati ons required exceed the total salt concentration of full strength sea- wa te r (typically 30,000 to 38 ,000 mg/L). The NOEC

concentrations have not been calculated fr om th is work as of the publication date of this

assess ment. As one pur pose of the s t udies wa s to compare t h e toxicity of i m azapyr with Rode o tm (glyphosate)

, data are summarized for this herbici d e as well. As further de m o nstrated in Table 3- 12, the LC50 of glyphosate establi s hed in the sa m e trials was approxi m ately t w o orders of magnitude more toxic t h an the Ar se nal tm her b ici d e.

FINAL

O c tob e r 200 3 Pag e 47Table 3

- 12 : 96-hou r L C 50 Value s w i th 0.3 g juveni le rai n bow trout expose d to imazap y r (Arse nal ) o r gl y p hos ate (Rode o) ta nk mi xes

. (So u rce: C. Grue 2003, p e rsonal com m unica tion. )

Product Test ed LC 50 of Concent r ate LC 50 Exp r es sed as Acti ve Ingre d ient

Arse na l Herb icid e 77,7 16 ppm Ar se nal (72,1 83-72 ,24 3 )* 22,3 05 mg/ L ima z ap yr (20,7 18-20 ,89 1 )*

Arse na l Co ncent rate 43,9 47 mg/ L (41

, 446-4 6 ,4 08)* 23,3 36 ( 22, 024-2 2 ,64 3 )*

Rodeo 782 mg/ L (71 9 -8 45)* 782 ( 719-8 45)*

* 95 % conf id en ce inter v a l of four replicat ed tria ls with ge ome t rica lly arra nge d con c entra tion s a nd a nega tive contr o l.

Sub-lethal e ndpoi nts other than the e a rly-life-stage and li fe c y cle tests conducted with the standar d test species have not be e n full y explored with i m a z apyr. One recent study exa m i n ed the potential

for i m aza pyr (Arsenal) and glyphos a te (Rodeo) to elicit m i cronuclei in the Africa n cichlid fish ( Tilapia rendalli ) abdominally injected with the herbicides ( G risolia 2002) . Micronucle i have been

propos ed as a reliable indicator of environme n tal m u tage ne sis in aquatic and terrestrial ani m als,

and have be en evaluated in a variety of m o ll usc, fish and a m phibians as an indicator of pote n tial

muta genicit y (Al-Sabti and Metcalfe 1995, Ver n ie r et al. 1997). Micronuclei are reflected as

chromosoma l abnor malit ies in blood s m ear s. Howe ver, the signi ficance of elevated micronuclei frequency at the populat ion level ha s not been fully deter m i n ed. In the Grisolia (2002) study

, signi ficantly elevated numbers of mi cronuceil were observe d following i m azapyr exposure , but only at 80 mg/kg-bw, t h e m a ximum tolerated dose (MTD). Eviden ce of sub-lethal effects at the

MTD are not considere d valid indi cators of sub-lethal toxi city, as the fish are exhibiting overt cytotoxicity (cell death) signs. Chr o mos o mal ab errations suc h as m i cronuclei are common during cell death; t h eir signi fic a nce to mut a genicity st udi es is rele vant when occurring a s a sub-lethal toxicologic a l response to che m ic al exposur e dose s below those whic h ca use cell death.

Thre atene d and Endangered Fish Species Hazards

Res i de nt fi s h populati ons manage d by the USF W S under t h e Endanger ed Species Act (ESA) are delineated as “distinct popula tion segm ents” (DPS), while th e NOAA-Fisheries, which m a nages mari ne a nd ana d romous ESA-li ste d stocks, deli n eate s popul a tions as “ e vol utionaril y signi fi cant
units ” (ESUs ) . Addre ssi ng the uncerta inty posed by using surrogate te st s p e c ies that ma y or may not
be as sensiti ve as the t h

r eatened and endangered (T &E) populations unique to an area is al ways problematic in ecologi ca l risk asse ssme nts. For exa m ple, Mayer and Ell e rsieck (1986), in thei r compil ation of an ac ute t oxicit y

dat a base for 410 c h e m ical s test ed on a q uati c orga nis m s , found that

toxici ty a m ongst specie s could r a nge by as m u ch as f i ve orders of ma gnit ude , a n d for a gi ven speci es , toxi city c oul d ra nge by as much as 9 or ders of ma gni t ude . Thi s data ba se , howe v er , lac k e d

critical revie w t o t hor oughl y filt er te st c o mpa r ison s t h at were appropriat e (e .g., standardized test conditions). In W ill apa Bay, where the Sparti na inf e station is the greatest , no f i sh populations are

considered “threat ened” or “endanger e d” unde r the ESA. In Pu g e t Sound l o cati ons where Sparti na has c o loniz e d, t h e native chinook sa lmon and coastal bull trout are bo th considered th reatened, wit h

the for m er managed by t h e NOAA- fish eries, and latter by the USF W S.

No im azapyr toxicity tests have be en conducted w i th DPS or ESUs’ of fi sh li sted as t h

r eat ened or

e n da nger ed in the Stat e of Wa s h i n gt on. Alt h ough testing has not been conduc te d with th es e s p e c if ic native populations that m a y utilize Spartina infested habitats in W a sh ington, the sta ndard testing

conducted w i th the closely relate d rainbow trout discussed in the preceding section provides a good

su

rrog ate fo r pred icti ng sur v ival effect s i n t

h ese closely relat e d native stocks. Toxi city testing under FIFRA requires data to be co llected o n su rrog ate s p ecies th at addre sse s ac ute t oxi city, em bryo-larval

FINAL

O c tob e r 200 3 Pag e 48su rv iv al, an d life

- cy cle tests. As ind i c a ted b y th os e tes t s , im az apy r would be consid er ed practi cal ly

non-toxic on the basis of re sults in rainbow trout, blue gill and f a

thead m i nnow.

Studies con ducted in th e early 1970 s exam ined the se nsitiv ity of four fish fa m ilies to 65 different

chem icals (Macek and McAllis ter 1970); salmonids were the m o st sensitiv e of the four fam ilies (12 species) represen ted. A more recent stu dy by Sappington et al. (2000) evaluated the

com p arative sensitivity of eight ESA-listed fish species to standa rd test organism s exposed to five different pesticides or m e tals in order to validate the use of surrogate species as a predictive tool in toxcilogical assessm ents. Acute 96-hr exposure trials were co nducted, but none of the

chem icals tested by these author s were herbicides, and all bu t nonylphenol had had significant previous testing. The sensitivity of listed cold -water species tested (Apache trout, Lahontan cutthroat trout, greenback cutthroat trout) did no t differ signif i cantly after 96-hr exposures from rainbow trout for copper, nonylphenol, or carbaryl . However, they were significantly m o re sensitive to the organophosphate perm ethrin a nd pentachlorophenol than the rainbow trout. Toxicities exhibited throughout th e testing varied with chem i cal, with som e listed species exhibiting greater or lesser sensit ivity than the standard test speci es at som e ti m e points (e.g., 12 hours). Although differences were docum ented whic h were som e ti m e s statistically significant depending on the tim e point, the listed species we re not always the m o st sensitive. Most

im portantly, the m a ximum degree of difference reco rd ed was less than two-fold, exce pt pentachlorphenol and perm ethrin for which th e listed spe c ie s exhibited LC 50 concentrations less than half of the surrogate rainbow trout. The aut hors concluded that a safety factor of two woul d provide a conservative estim ate in risk asse ssm ents for lis ted co ld -water, warm

- w ater an d euryhaline fish species ba sed on these findings.

Another comm on criticism of eco lo gica l r i sk a s se ssm en ts re ly ing on surrogate sp ecies to ad dres s poten tial T&E sp ecies ef fects is th e lack of data on subl ethal endpoints of site -specif i c relevance.

The co as tal estuaries wh ere im azap yr could b e applied to control Spartina s e rve as a p r imary s t ag ing

area for salm on s m olts that are m i grating to the sea to m a ture. The brackish salinties found in th e

es tu aries p r o v id e a rang e of s a liniti e s sa lm on sm olts u s e to a d ap t to ful l strengt h

sea-water. The

osm o regulatory capaci ty has b e e n u s e d a s one te s t to es ta b lish whet her a chemi c al mi ght affect t h i s

sen s itive life stag e. P a tten (2 003 ) exam ined th is ca pacit y, measur ed as pl asma sodium level and gill

ATPas e activity in a 2 4

- h r seawater ch allen g e, in chinook salm on sm olts exposed to im azap yr concentrations up to 1.6 mg / L ( F i g u

r e 3- 12 ). T h is ma x i mu m t e st c o nc entra t i o n wa s over 470-fold

g r e a te r th an t

h e ma x i mum w a t e r con cen tratio n recov e red in the com p an io n s t u dy wh ere im azap yr

was app lied to bare-m u d an d m eas ured in waters f r o m the f i r s t tida l wash (P a t te n 20 03 ). A s dem onstrated in F i gure 3-12, th ere was no consistent dose-response effect recorded on these

e n dpoi nt s of s u ble t hal physi o l o gic a l re le va nc e.

FINAL

O c tob e r 200 3 Pag e 49Figure 3-12: Plasma sodium and gill ATPase activity of ch inook salmon exposed

to imaz ap yr. (sour ce: Pa tten 2003

. )

3.4.2 Aqu a ti c In v e rteb rates

One study where Arsenal was applied with a su rf

a c tan t ( n o t de f i ne d) w i th the f r e shw a te r wa te r f l e a ( Daphnia m agna ) yielded a 48-hr LC50 of 350 m g -Arsenal/L (79.1 m g ae im azapy r /L) and an

NOEC of 180 m g -Arsenal/L (40 .7 mg a e / L )

. Ot her pr oduc t regis t ra

nt

s t udie s wher e Daphnia wa s

exp o s e d to an im azapy r form ulatio n (~5 0 % ) lac k i n g the sur f act ant produc e d a 48- h our EC 50 concentration of 373 m g a. e. /L (Cy a nam i d 1 997). The results of thes e two studies hi ghli ght t h e poten tial effect of su rfac tant on aquatic toxicity, and the author s con c lud e d th at th e, “components of

t h e Ar se nal for m

ula t i o n, ot her t

h a n

a s u r f

a c ta nt , do not influence the toxicity of im azapyr to aquatic

or ga nis m s

. ” Ki nt ner and For b is ( 1 98 3) also reported 24 and 48-hour LC 50 concentrations of greater

than 100 m g /L (the HDT ), in static tes t s c o nduct ed wit h

ne wly- ha tc he d Daphnia (les s than 2 4 hou rs old). Chronic studies have also been conducted with the water fl ea (Manning 1989). In that study,

no adv e rs e effects o n su rviv al, reproduction or growth of 1 st generation Daphia we re re c o rd ed af te r 7, 14 and 21-days of exposu re at concentrations up to 97.1 m g /L, the HDT. Per FIFRA registration

requ irem ents , the NOEC was co ns id ered to b e th e H D T ( 9 7

. 1 mg / L )

, a n d th e ma xi mu m a l lo w a ble

tox i cant con cen tratio n (MATC) was considered to be > 97.1 m g /L.

Testing wit h other invertebrate species that exhi bit alternative lif e cycles has been lim ited to
growt h studies with t h e Eastern oyster ( Crassostrea virgi n ica ), and sur v ival of pi nk shri mp. Although these species a r e not native to coastal Wa s h ington, they do provide reasona b le surrogate s for the Paci fic oyster ( Cr assostre a gi gas ) a nd bur rowing shri mp ( Ne otryp a ea s p .) that are common

to areas where Spartina has become established. In these product regist rant tests, the EC 50 fo r growt h inhi bition was e s tablished at a concentr a tion greater than 132 mg-i m a za pyr/ L , with t h e NOEC set at this conc entration—t he HDT. The pink shri m p sur v ival LC 50 was > 189 mgi m azapyr/L, and the NOEC was agai n set at t h is HDT (Mangels and Ritter 2000).

3.4.3 Non -ta rg et Aqu a ti c Ve geta t io n
Native salt marsh plants and algae re sident to the estuarine environments where i m azapyr coul d be applied have the potential to be negatively affecte d by the broad spectrum herbicide, and a range of studies by both the product registrant and others document this possibility. Table 3-13 summarizes

FINAL

O c tob e r 200 3 Pag e 50product re gi strant studie s with a vari ety of freshw ater and marine algae a nd aquatic pl ants exposed to either technical grade i m azapyr, or to Arsenal with sur f actant. As indicated in Table 3-13, toxicity to the vascular plant duckweed was nea r ly three-orders of magnitude greater than the toxicity associated with t h e alga l species tested. Notably, the toxi city of the Arsenal form ulation

did not di ffe r fr om that of t h e tec hnic a l grade i m a zapyr for duckwee d, a lthough it was fo und to be approxi mate ly 5- fold more toxic to gr een algae

.

Table 3

- 13 : Toxici ty of Techni cal Grade I m az ap y r and Arse nal * (w ith surfac t an t) to Alga e and Aq uati c Pl ants, as Es tabl ish e d Th ro ugh Con t roll ed Produ c t Re gistra nt Stu d ies. (So u rce: Ma ngells an d Ritter 2000

. )

Species /Test E C 50 E C 25 Green Alg ae Gro w th ( Selena stru m capricor nut um ) 7 1 m g / L

14.1 mg /L* 48 m g /L

8.36 mg /L*

Fre s h w at e r di at om ( Na vic u l a p e l lic ul os a ) > 59 mg/ L > 59 mg/ L

S a lt wa te r di at o m ( Skeleto nem a cost atu m ) 85.5 mg/L 42.2 mg /L

Blu e -gree n algae ( Ana bae na flos- aqua e) 11.7 mg /L 7.3 mg/ L Duckweed ( Le m na g i b b a ) 0

. 0 2 4 m g / L

0.02 16 mg/ L * 0.01 3 m g /L

0.01 32 mg/ L *

Recent studi es conducte d by Patten (2003) also document the potential for i m azapyr to im pa c t non-target vegetation in those areas where Sparti na control is envisione d. In this study, the e f fects

of i m aza pyr were exa m ined on th e non-native Japanese eelgrass ( Zoster a japonic a ) and compared against gl yphosate. This species of e e lgrass dom i n at es the intertidal zone unlike the native eelgrass ( Z. marin a ) which is primarily f o und s ub-tidal. For both herbicides the eelgrass canopy was killed

if

herbicide was applied on dry eelgrass at low t i de, although the i m a z a pyr was more toxic. I f applied with a fil m of water overlyi ng the bed, t h en no e f fec t was recorded. Within 12 mont hs
post-treat me nt, all i m pa c t ed eelgras s beds had r e c overe d. There wa s no difference in t oxicity over the range of doses teste d , (0.84 kg ae /ha and 1.68 kg ae/ha). Persistence was not recorded in the

sedi m e nt underlying thes e eelgrass be ds, hence res i stance to the establishm ent of native salt marsh plants such as Salicornia was not c ons idered a ris k

.

3.5 Adj u vant and Inert Ingredient Toxi ci t y to Terr est rial an d Aqu a ti c Ecol ogi c a l

Re ce pto r s

Adjuvants a r e carriers mixe d with herbicides that increase the binding and/or uptake of th e herbicide i n t o target plants. Typic a l a d juvants incl ude sur f actants and crop o ils that are mixed with the herbicide prior to application. Inert ingredie nts are components withi n the patent ed herbicide product for m

ulations that are report e d to ha ve no herbicidal activity. Cur r ent FIFRA regulations do not require manufacturers to reveal the sur f act an t for m

ulat ions, as FI FRA regulate s the active ingredients only. Si mil a rly, m a ny of the inert i ngredients i n the commercial for m

ulations of the

various i m a zapyr products on the market are not known. Herbicide toxicity studie s conducte d

under FIFRA are re quir e d to eval uat e the active i ngr edient of the product fo r m

ulati on only, and not the toxicity of the “inert ingredients” or the surf actants that m a y be used to f a cilitate plant adsorption a nd uptake of the herbi c ide. For so m e e c ological recept o rs, particul arly aquatic receptors, the choice of which sur f actant is used to adm i nist er the herbicide can have substantial ecological re levance, as t h e fe w tests conducted w ith surfacta n ts have shown higher toxicity than

the herbicide. Sim ilarly, in environments where a variety of herbicides and/or pestici d es m a y be used, the potential for che m ic al interactions of inert ingredients shoul d also be understood to

FINAL

O c tob e r 200 3 Pag e 51mini mize risks. This sect ion of the hazard assessment therefore a ttempts to summarize the existing

infor m ati on on the toxici ty inherent t o the inert ingr edients and surfactants that could be used in the application of i m aza pyr t o contr o l Spartina

.

3.5.1 Ine r t I

n g r ed ients

Two of the inert ingredients in Arsenal ® are listed as glacial acetic acid (CAS #64-19- 7 ) and water (CAS #7732-18-5) ( N CAP 2003). Wa ter is non-toxic and re quired for li fe. The toxic ity of aceti c acid is tabul a ted below (Table 3- 14) , as s u mma r i zed by Mer c k (1989) a nd Verchuer en (1983).

Acetic aci d i s also a component of LI 700, a common non-ionic sur f actant with pote n ti al use with

i m azapyr.

Table 3-14: Ac eti c Aci d Tox ici t y to Ec olo g ic a l Recep to rs

.

Test spec ie s Class of organism Toxicity t est Toxicity end point Value Unit

Whea t P l a n t E C 5 0 Visib l e in jur y 2 3

. 3 mg/m 3

Alf

a lfa Pla n t EC 50 Visib l e in jur y 7.8 mg/ m 3

Corn Pla n t EC 50 Visib l e in jur y 50.1 mg/ m 3

Pseud omon as put ida Ba cter ia Toxicit y thre sho l d Multiplicat io n inh i bit i o n 2850 mg/ l

Mic r ocys ti s

aerug in osa Alg ae Toxicit y thre sho l d Multiplicat io n inh i bit i o n 90 mg/ l

Scene de smu s quadr icau da Green a l g ae Toxicit y thre sho l d Multiplicat io n inh i bit i o n 4000 mg/ l

Ento sip hon sulca t um Proto z o a Toxicit y thre sho l d Multiplicat io n inh i bit i o n 78 mg/ l

Uronema pard u c zi Proto z o a Toxicit y thre sho l d Multiplicat io n inh i bit i o n 1350 mg/ l

Vort icella camp a nula Proto z o a Toxicit y thre sho l d Perturb a t i on le ve l 12 mg/ l

Brin e shr i m p A r t h r o p o d a T L m * 3 2

- 4 7 m g / l
Grammarus pu le x Arthrop o d a T L m * 6 mg/ l

Lim nea o v at

a Mollu s c a Perturb a t i on le ve l 1 5 mg/ l

Blu e g i l l F i s h T L m * (2 4

, 96-hr--

r e sp ec ti ve l y ) 1 0 0

- 1 000

, 75 mg/ l

Mosqu i to f i sh Fish TLm (24-9 6 hr) 251 mg/ l

Fathe ad m i n now Fish LC 50 (1 , 2 4

, 48, 7 2

, 96-hr--res pec tively ) D e a t h 1 7 5

, 10 6

, 106, 79 , 7 9 ) mg/ l

Cule x sp

. lar v ae Insects TLm (24-4 8 hr) 1500 mg/ l

Mice Mamma ls LC50 ( l hr) Inha la tion 5000 ppm
*med ia n t o leran c e lim i t

3.5.2 Su rfa c ta nts

Sur f actants are used to reduce the surface tension of water, enabling a “bridge” to for m

bet w een

two c h e m ic als or medi a that woul d not nor mally m i x (e.g., oil and water). When use d with herbicides, they are intended to ma xi m i ze the a m ount of s p ray s o lution that sticks to the leaf surface, and hence increase uptake. Surfactan ts commonl y used to promote i m azapyr a nd glyphosate a d sorption and upta k e ar e generally of two class e s: non-i oni c nonylphe nol alcohols and/or fatty acids, and cr op-oil based concentrates . Studies evaluating the efficacy of i m azapyr and glyphosate with various sur f actants have re veale d fe w di ffer ences in the efficacy of t h e her b icides

FINAL

O c tob e r 200 3 Pag e 52based on the surfa c tant (Patten 2002). All sur f act ants tested with imaza pyr provi d ed e f fective control, but R-11, the a p proved sur f a c tant for use w ith glyphosate, w a s not tested with im azapyr, maki ng a di rect compari s on di fficul t (Table 3-15). However

, the author states that “application

made with s hort dry ti me m i ght bett er distinguis h surfacta n t effects than did these trials, all of

which had a m ple dry ti me”.

Table 3

- 15 : Effec t o f surfac t an t appli ed in Sep t em ber 1999 and 2 000 on the effica c y of imazap y r fo r s m oo th c o rd grass c ontrol in Wi llapa Ba y , WA. (So u rce: Pa tten, 20 02. )

Per cent control 13 months afte r treatment

Herbic ide Rate (kg/ha) Surfactant Per cent (v/v) Site 1 Site 2 Site 3

Ima z ap y r 1

. 6 8 Agri-De x 1

. 0 9 9 8 5 9 6

1

. 6 8 Agri-De x 2

. 0 9 6

1

. 6 8 Hast e n 1

. 0 1 0 0 8 3 9 4

1

. 6 8 Kin e t i c 0

. 5 8 9

1

. 6 8 Dyn-Am i c 1

. 0 9 6

1

. 6 8 Syl-Ta c 1

. 0 9 2
Glyp ho sat e 8

. 4 R 1 1 1

. 0 6 9 8 5

Untreat e d n a n a N a 0 0 0

Although there appears t o be little differenc e a m ongs t sur f a c tants in their potentiation of herbicide efficacy, their inherent chem ical properties can ha ve a range of envir o nmental issues that are independent of the herbic ide for m

ulati on they m a y be applied with. For this reason, it is prudent to

exa m i n e the i r properties and toxicity independe n tly. Table 3-16 summarizes des c riptions of

surfa c tant environmental fate, che m ist r y and t oxici ty as pr ovided in the ori g inal EI S and obtaine d

from the m a nufacturer’s material sa fe ty data sh eet s ( W SDA 1993E, cha p t e r 11.0 0). I n brie f, the

acute toxicit y of alkylphenol ethoxylate surfact ants like R- 11 tm and X- 77 tm to fis h and other aquatic speci es has been r e ported in the range of 4 to 12 mg/L. Acidi f ying agents like LI-700, and crop-oil based surfactants like Hasten tm a nd Agr i -Dex tm exhibit lower toxicity. On the basis of

EPA a quatic toxicity criteria, all the surfa c tant s used woul d be consi d ered practically non-toxic (LI700 tm , Hasten tm a nd Agri- D ex tm ) to m o derat e ly toxic ( R -11, X- 77) . All of the s u rfactants can

cause irritation to skin a n d ocular tiss u e at high do ses, and rec e ive ratings of moderate (scores of 4

to 6 on a n 8 pt sc ale) i rrita tion in mammals (Table 3-17). By oral a d m i ni stra tion, the lim ited testing done with the surfactants in ma mmals indi cates they would class i fy as “pract ically nontoxic”.

FINAL

O c tob e r 200 3 Pag e 53Table 3-16: Ch emi s try and Fa te of Su rfa c tants Po ten t iall y Use d With Im az ap y r an d
Gl y p ho sate

.

Surfactant Known Ingredients* &
Surfactant C l as s Chemical Prope rties Degradation Rate and Pathway General Toxicity Rating*

R-11 tm (sur fa ce acti va to r) , Wil b u r

- E lli s Co. I s op ro pyl ( b u t yl) alcoh o l
20 %, no nio n ic s u rf act a n t s 80% (octyl phenoxy pol yet h oxy )

, sili co ne

. Class : N oni on ic alkyl ph e nol e t h o x y lat e So lu ble i n li pi d & wat e r

, F l am ma ble, Sp ec

. Gr avit y = 1

. 0 Sl owly bi od eg ra d e d by

pr og re ssiv e s h or t eni ng of et ho xyl at e c h a i n; int e r m e d ia te b r ea kdow n

pr od uct s of p o lyt h eyl e n e glyc ol (a nt i- fr eez e ) an d

sho r t

- c hai n et ho x y lat e s

. Ma mm als: p r a c ti c a lly

no n- tox i c or all y , m ild ski n irri ta ti on p o ssi bl e

Fis h an d ot he r aq ua tic
b i ot a: m o d e r a t e ly t o xic

LI -7 00 tm (p en et ra tin g

su rf acta nt ), Lo ve la nd

In dus tri e s

, Inc

. Ph os ph ati d yl ch oli n e ( l ecith i n) a t 80 0 g/L

, pr opi on ic aci d

, a n d alkyl phenyl

h y dr oxyp o l yo xyeth y le ne
Class : Ac idi f yi ng ag en t So lu ble i n li pi d & wat e r

, Not Fl am ma bl e Sp ec

. Gr avit y = 1

. 03 Bi od eg ra da ti on

pr esu m e d r api d d u e to

n a t u r a l l e c i th in

in gr ed ie nt s. Ma mm als: p r a c ti c a lly

no n- tox i c or all y , b u t

cau s es sk in ir rit a t i on

Fis h an d ot he r aq ua tic
b i ot a: m o d e r a t e ly t o xic

X- 7 7 tm (spr ea de r acti va to r) , Vale nt Corp. Alk y la ryl p o l y (ox y e t hy le ne ), gl y c ols

, fr ee f a tt y a c i d s, is op rop y l

alc o h o l.

Class : N oni on ic alkyl ph e nol e t h o x y lat e So lu ble i n li pi d &w at er, F l am ma ble Sl owly bi od eg ra d e d by

pr og re ssiv e s h or t eni ng of et ho xyl at e c h a i n; int e r m e d ia te b r ea kdow n

pr od uct s of p o lyt h eyl e n e glyc ol (a nt i- fr eez e ) an d

sho r t

- c hai n et ho x y lat e s

. Ma mm als: p r a c ti c a lly

no n- tox i c or all y

Fis h an d ot he r aq ua tic
b i ot a: m o d e r a t e ly t o xic

HASTE N tm Pr o p ri et ar y: fa tt y aci d s fr om se ed oi ls es t e ri fie d

with al co hol

Class : oil b a se d s u r f ac ta nt No n- i o n i c, d i sp er si b l e in

wat e r as mi cel l es

, b u t
unk now n sol u bility.
Sp . Gr avi t y = 0.9 Bi od eg ra da ti on
pr esu m e d r api d, b u t no
fo rm al s t u d i e s co nd uct e d
of w h ic h w e ar e a w ar e. Ma mm als: p r a c ti c a lly

no n- tox i c th ro ug h or al

ro ut es

Fis h an d ot he r aq ua tic
b i ot a: sligh t ly t o xic

AGR I -D E X tm P r o p ri et ar y: h eav y r a n g e
pa ra ffi n- ba se d pe t r ol eu m oil w i th p o ly ol f a tt y aci d

est e r s an d pol yethoxyl yated
d e r i va t i ve s

Class : oil b a se d s u r f ac ta nt Disp ers i bl e i n w a t e r (f

or ms mic e ll es)

, moderate fl am mability, Bi od eg ra da ti on
pr esu m e d r api d, b u t no
fo rm al s t u d i e s co nd uct e d
of w h ic h w e ar e a w ar e Ma mm als: p r a c ti c a lly

no n- tox i c th ro ug h or al ing e st io n, mil d ski n an d

eye ir ri ta nt

, Fis h an d ot he r aq ua tic

b i ot a: p r a c tically no ntoxi c
*Se e t a b l e s 3- 9 a nd 3- 12 for t o xicit y classif i cat i o n sche me s

Past studies with glyphosate have shown t h at the toxicity of surf actants is generally greater than the toxicity of the herbi c ide for m

ul ation or active ingredient alone. For exa m ple

, st udies wit h

Rode o for m erly discusse d in the origi n al EIS rela t e how t h e toxicity of the Rode o for m

ulation was 1,100 mg/ L without surfactant

, a n d 680 mg/ L with the mixtur e containing 0.4 percent X-77 (Mitchel et al 1987). A si milar re lationship has been obs erved with aquatic inve rtebrates wit h Rodeo ( H enry 1992). Recent studies with both i m azapyr ( A rsenal) and glyphosat e (Rodeo)

exam ined the inherent toxicity of the surf actants a l so, both wit h and withou t the herbicides (Smith et al. 2002, unpublished data). As de monstrated i n Ta ble 3-17, the t oxicity of the seed and crop-oil

based sur f ac tants Hasten and Agri- D ex to rainbo w trout was two to thre e orders of magnitude lower (respectively) than R-11 in this study. W h en sur f a c tant was mixe d with herbicide, the toxicity of the surfactant was reduced and the toxicity of the herbicide was increased. These studies reveal that the toxicity associated with he rbicide/surf actant m i xtures is not additive, and is generally associated wit h the su rfactant. Of the sur f actant s ex amined in detail, the order o f toxicity, from lowest to highest , would appear t o be as foll ow s: Agri- D ex, Hasten, LI700, X- 77

and R-11. I t is note w ort hy, that only R-11, the s u rfacta nt tha t a

ppears most toxic from the re cent

FINAL

O c tob e r 200 3 Pag e 54tests, is appr oved for use with glyphosate in th e estuarine envi ronment where herbicide treat m ent
of Spartina is conducted.

Table 3-17 Toxic i ty of Su rfa c ta nts With an d With out Herbicid e. (So u rces: Sm ith et a l . 20 0 2, Henry 199 2, Mitch e ll et al. 1987, WS DA 1993E. )

Chemical Teste d Mammali an Tox icity LD 50 (ppm) Aquatic Toxicit y (ppm)

R-11 surfa c t ant 5,84 0 or al, 1 300 0 derm a l (rabb it) 6.0, ra inb o w tro u t 96- hr LC 50 * 4.2, b l ue gill sun f ish 96-hr LC 50
LI-70 0 surfa c t ant >5,0 00 oral, 5

, 00 0 derm a l (rat) 17, r a inbow trou t 96-hr LC 50* 22, r a inbow trou t 24-hr LC 50* 210, b l ue gill sun f ish 96-hr LC 50 190, da phn ia 48- hr LC 50
Hast en sur f a c ta n t No Dat a 74, r a inbow trou t 96-hr LC 50* 98, r a inbow trou t 24-hr LC 50* Agri-De x sur f a c t ant >5,0 10 oral (rat), > 2, 020 derm a l (rabb it) 271, ra inb o w tro u t 9 6 -hr LC 50* 386, ra inb o w tro u t 2 4 -hr LC 50*

X-77 surf a c ta nt > 5, 000 ora l (rat)

, > 5

, 00 0 d e rma l ( r abb it) 4.2, ra inb o w tro u t 96- hr LC 50 4.3, b l ue gill sun f ish 96-hr LC 50 2, wa ter f l e a (d a phn ia) 48-hr LC 50
Rodeo (as g l yph o sa te) 3,80 0 or al, 5

, 00 0 derma l (ra bb it) 580, ra inb o w tro u t 9 6 -hr LC 50 545, wat e r f l e a ( daph nia) 4 8 -hr L C 50
Rodeo + X-77 No Dat a 130, ra inb o w tro u t 9 6 -hr LC 50 130, wat e r f l e a ( daph nia) 4 8 -hr L C 50
Rodeo + R-1 1 No Dat a 5.4, mg /L ra in bo w trout 96- hr LC 50*
Rodeo + L I 70 0 No Dat a 23, mg/ L ra in bo w trout 96- hr LC 50*
Arse na l + Ha ste n No Dat a 113, mg /L ra in bo w trout 96- hr LC 50
Arse na l + Agr i -d ex No Dat a 479, mg /L rainb o w trou t 9 6 -hr L C 50 *
*Unpu blish ed dat a from Sm it h e t a l . ( s u b mitte d t o Bull. En v. Of Co nt am. And To x.). Data re pre s en ts mean of 4 tria ls, upper 95 %

con f iden ce lim i t with in 5 to 20 % o f me an over a l l h e rbicide trials ( n o t shown)

The non-ionic alkylphenol derived surfacta n ts ma y pose additional hazar d s beyond t h e evidence provide d in acute toxicit y tests. The alkylphe nols and octyl phenol ethoxylates belong to a broader

class of che m icals known as t h e “ nonyl phenol s ”. It has been esti mate d that appr oxi m ately 80 percent of the alkyl phenol ethoxylat es are nonyl phenol ethoxylates a nd t h e other 20 percent are octyl phe nol ethoxylate s (Cox 1998) . Bec a use t h ese compounds are not part of the herbicide

for m

ulati on, their exact for m

ulat i ons are patent protected and ar e not re portable under FIFRA.

Ho wever , t h e E P A c onsiders th e nonylphe nols as an “inert of toxicol ogi cal conc ern.” Nonylphe nol ethoxylate s degrade to nonyl phenol a nd related compounds that can be somewhat persistent in the envir o nment

. Subl ethal effect s at exposure concentrati ons bel o w a c utely toxic level were previously de scribed ( W SDA 1993E) and include d impaired swi mming acti vity, altered breathing rat e , and reduc ed heart rate in fish at 0.5 m g / L , and inhibited si phon retracti on, byssal

thread for m ation and reduced burrowi ng activity in sessile shellf ish at conc entrations gr eater than 1 mg/ L . Lethal effects a s reported in t h e literature are summa rized in Table 3-18. The i n ter m e d iate breakdown products of t h ese sur f act ants can incl ude both linear and branched chain a l kylphe nols,

which ma y also have inherent toxi ci ty. Some of these products have bee n shown to elicit wea k estrogenic effects when adm i ni stered at high doses to laboratory animals (r eference). Deter m inin g the actual quantity of alkylphenols in each surfa c tant for m

ulati on, and their potential

FINAL

O c tob e r 200 3 Pag e 55environme n tal concentra tions and ris k s is not entirely possible because the proportions in eac h

surfa c tant for m

ulation ar e not known.

Table 3-18: Ac ute to xic i ty of n o n y l p hen o l to a quatic b i ota

.

Test spec ie s Class of organism Toxicity t est Toxicity end point Value Units

M

y

til u s ed ul is 1 M u ss el B i oco n c e nt ra ti o n Factor N A 1 0 W e t w e i g h t

Caenorh abd itis
ele gon s 2 Nemato de LC50 (2 4 hr) Death 7.2 mg/ l

Mysidop sis ba hia 2 Mysid LC50 (9 6 HR) Death 43 mg/ l

Fathe ad m i n now 2 Fish LC50 (9 6 HR) Death 135 mg/ l

Gadus m o rhu a 2 Fish LC50 (9 6 HR) Death 3000 mg/ l

FINAL

O c tob e r 200 3 Pag e 56

### 4.0 EXPO SURE ASSESSM E NT

In this chapter we characterize the potential exposu re to f i sh and wildlife re ceptors from the use of

i m azapyr to control Spar tina ba sed on exposure para m e ter s gene rated fr om c u rrent and proje c ted application practices. Wildlife s p eci es are pre dom inantly e xpose d to he rbicides by consumi n g treated vege tation and/or water, and/ or by trans f er

of the che m ical through natural food chains. Contact (der mal) and inhalation exposure can pr ovide addit i onal, although m a r g inal , expos ure

. Inhalation e xposur e of drift is gener a lly extre m e l y li m ited because appli cation equipment create s noise that ca uses mobile birds and ma mmals to a void the i m mediate area . Noctur nal ani m als s u c h as the rat would largely avoid inhalation exposu r e because WSDA applie s herbicides only duri n g daylight hours. For this assess m e nt drinking water expos u re woul d also be li m i ted because

treat m e nts will occur in estuarine waters wher e fr eshwater is lim ited, although rain is generally abundant, a nd consumption of fres hwater acc umulate d on the plants is possi ble. Our a b ility t o characterize i m azapyr exposur e for som e sector s of wildli fe such as a m phibians a n d reptiles is

li m ited beca use of a lack of ba sic biological (l ife histor y) and toxicol o gical infor m ation. Sit e specif i c studies would be required to address qu antitative risk assessment in each area where Spartina has infeste d, so exposure mode ling was conducted in lieu of s ite speci f ic wor k

to gauge

expos ure doses based on application rates and de livery mechanis ms of releva nce to wildli fe receptors. Exposure doses were th en compared to reference doses fr om t h e toxicity l iterature to gauge the potential toxici ty to relevant ecological r eceptors.

4.1 Estimated Environmental Ex posure C o ncentr ations (EEC)

The exposure concentrations or do se experienced by biot a will diff er by m e di a (i.e., air, water, food, and se di m e nt), the habitat th ey use, how frequent they use the habi tat, and the application

rates of i m pazapyr. Esti mates of environmental expos ure concentrations (EEC) of imaza pyr can be derived fr om e m pirica l studies, and also from modeling, al though the for m er is pre f erred. This section summarizes the expos ure concentrations th at have been m e a s ure d e m piricall y, and those

from the lite rature that have been de veloped th r o ugh modeli ng exercises. Table 4-1 summarize s

em pirical results where i m azapyr wa s detected in environmental m e di a

. The derivation of many of these values was summarized in Chapter 3 of th is doc ume n t. The dis c ussion below provide s assumptions applicable t o EEC a nd exposure mode ling.

4.1.1 App lica t io n Ra te

For Spartina control, onl y the Arsenal tm i m az apyr for m

ulati o n is projecte d for use

, howe ver, no product endorse m ent is assumed. To model th e esti ma ted environmental c onc entrations of

i m azapyr in Arsenal tm , the differe n t m e thods used for ap plication mus t be unders tood. This

includes a p plication rates

, fre quenc y, application volumes, and interception rates. The f o llowing assumptions were used re garding appl ication rates.

• Although l o wer rates may be used in certain areas, for e c ological e x posure a nd risk interpretations we assume that Arsenal w ill be applied at the m a ximum concentration

recomme nde d on the ma nuf acturers label for a q uatic use—6 pi nts Arsena l/acre. Six pint s per acre is equivalent to 1.5 lbs active ingred ient (acid equiva lents)/acre = 0.68 kg/acr e = 1.68 kg/ ha.

• Applications will occur a maxi mum of one time per year until eradication is complete.

FINAL

O c tob e r 200 3 Pag e 57• The neat herbicide f o rmulation will be d iluted with water and surfactant prior to application. Surf actant will be added to th e herbicide/water m i xture to yield 1% of the

spray s o lution applie d.

• Three methods of her b ici d e adm i nistration are pos sible for Spartina control : (1) hand-held sprayer unit, (2) boom- mounted spr a yer, and (3) aerial sprayer. Spray volumes by these

methods can vary from a m i ni mum of approxi m at ely 2.5 gallo ns/acre to a maxi mum of 80 gallons/acre.

• Herbicide quantity ( m a s s) per unit area will not vary by spray volume (i.e., 1.5 lb/acre) but

surf actant rates will, as these are norm alized to spray volume. U ltra-low to low spray volumes of 2.5 to 20 gallons/acre are the most likely a pplication r a tes, but ris k s of

surf actant toxicity are also considered with high volume appl ications up t o 80 gallons per

acre.

4.1.2 Wate r Co nc entration s
Concentrations that reach the water will be affected by Spart i na canopy interception, adsorptio n onto the Spartina , uptake into the root zone, and aerial dr if t. However, the “w orst c a s e ” i m aza p yr

water conce n trations are assumed by consideri n g no adsorpti on to se di ment and/or vegetation, no

foliar interce p tion, and c o mplete sol ubility on a n incom i ng tide. Under th ese highly conservative conditions, water concentrations will change w ith depth, as represented in Figure 4-2. As

demonstrated in this f i gure, th e modeled water concentration at the l o west depths e v aluated are consistent with an incoming tidal prism and are al so reflecti v e of the empi rical results of Patten (2003) disc ussed earlier and summar ized in Tabl e 4-1. Unde r the worst case scenari o, where the herbicide was applied to bare- m ud, Patten (2003) projected extre m ely r a pid dissipat i on from the equation f = 0.0015 e xp((319/x+ 38))

. The s e field experi ments sugge sted that applied i m azapyr woul d not be m e asurabl e af ter appr oxi m ately 40 hours.

Under typical treatm e nt conditions the Sparti na canopy wil l intercept herbicide, and will thus

eff ectively titrate the herbicide into the incomi ng waters as t h ey rise over t h e Spartina canopy. The highest c onc entration of applied herbicide will be deposited in the upper ca nopy and he nce will not

be solubilize d until the water depth re aches this portion of the c a nopy, allowing for great e r dilution than would be expecte d if the her b i c ide was dis t ributed uni for m ly on the plants. Although t h e herbicide is highly soluble, adso rption and uptake into plant matter is facilitated by surf actant and

will also reduce the available herbicide for so lubilization under typi cal applications.

FINAL

O c tob e r 200 3 Pag e 58Figu re 4-1: Mud-b o at ap pli cat or used to ap pl y h e r b ici d e in Willapa Ba y to control Sp artin a

.

Linders at al. (2000) proposed a folia r interceptio n rate of 40% in grasses based on a r e cent revie w of r e tention values from pestic ide and herbicide applications th roughout t h e world. Pa tten (2003) has propose d a foliar interception rate of 75% for Spartina treated with i m azapyr based on

e m pirical re sults, and t h is sa m e va lue has be e n proposed by the manufact urers of Ar senal tm (Mangels et al. 2000). High interc eption rates will m a xi mize potential exposure for terrestrial herbivores, and mini mize potential exposure to aquatic recept o rs whereas t h e reverse is true when interception rates are lower.

FINAL

O c tob e r 200 3 Pag e 590 1 2 3 4 5 6 7 8

0 0 .2 0

. 4 0 .6 0

. 8 1

Wat er D e p t h ( m )Est. Water ConcentrationImazapyr (mg/L)

Figu re 4-2: Estim a ted w a ter co ncentr atio ns of imazap y r in tidal w a ters with no

cano p y int e rcepti on an d an ap plicati on r a te of 1.5 l b s/ acr e (0. 68 kg/ acr e )

.

4.1.3 Exp ecte d Pl ant and An i m al Res i du es

As disc usse d above , int e rception rat e s will a f fec t both plant residues as well as pot ential water

concentrations. For Spartina clones, the Linder et al. intercepti on value of 40% is more realistic with field applications be cause of the greater a m ount of edge around the clones and potential for greater drift off the application site. For Sparti na m e a d ows , higher inte rception rate s are m o re likely, a nd t h e 75% inter ception value of Patten (2003) will be consi d ered valid. Whe r e the foliar interception rate is 40%, it is assum e d that 10% of the non-i n tercepted i m aza pyr wil l drift off-sit e (or on non-target vegetat i on) and the re m a ining 50% will m a ke contact with underlying sedi ment
and be solubilized upon the firs t ti dal wa sh. These latter values wer e derived fr om studies conducted in grasslands i n the Netherl a nds during t h e growing pha se ( U SES 2.0, 1998).

Pesticide res i dues following applicati ons of 1 lb/ acre were e s ti m a ted in a variety of plants and insects by Hoerger & Ke naga (1972) and more re cen tly recor d ed from e m pirical dat a by Fletche r et al. (1984). In the Hoerger and Kena ga s t udy, tall grass had est i m ated average residue concentrations of 73 mg/ kg and e s ti mated m a xi mu m concentrat ions of 87 mg/kg. In t h e 1984 st udy by Fletc h er and ot hers, tall grass ha d average e m pirical res i dues of 29 m g / kg, and esti m a te d

maxi mum c oncentrations of 87 mg/kg. At the 1.5 lb/acre rate propose d for Spartina control wit h

i m azapyr, the esti m a ted average resi due concent r ation detect able s hortl y after spraying would be approxi mate ly 110 m g / k g based on the m o del of Hoerger and Kenaga , and 43 m g /kg based on the

e m pirical re sults of Fle t cher et al. (1984) (ext r a

polated to the higher application rate). The

esti m a ted maxi mum resi due woul d be 131 mg/kg unde r bot h studies ( T able 4- 1). No field data on

i m azapyr residues i n treated Spartina meadows or clones were ava ilable for review to compare against these residue estimates.

The residue of i m azapyr in plant tissues will cha nge over ti me, and this degradation has not been

exam i n ed empirically in treated Spar tina . For t h e chronic di etary exposure assess me nts describe d in Section 4.2, the concentration in plant tissues over ti me was there f ore modeled f o r this portion

FINAL

O c tob e r 200 3 Pag e 60of the assessm ent using the methods of SERA ( 2001). Empirical residue conc entrations i n Spartina ove r ti m e following treat ment re m a in a s o urce of unce r tainty.

Table 4

- 1 : Summ ar y of Ma xi mum an d Ave r ag e Imazap y r Detection s in Rel e v ant

Envi ro nme n tal Medi a w i th Ap plic atio n Rates of 1

. 5 l bs a

. i./ac r e

.

Environmenta l Media Maximum

Measur e d Averag e Ma xim u m Measur e d,

or Est i mated Maximum* Averag e of a ll s a mples

Measur e d, o r Ty pical

Estimated *

Surfa c e Wa ter 5.77 mg /L [ 1a] 3

. 4 0 mg /L [ 1b] 0

. 1 mg/ L [1c ]
Pore Water 3.29 mg/L [ 2a] 2

. 9 4 mg /L [ 2b] 0

. 0 4 2 m g /L [2 c ]
Treated Se d i men t with no Ov e r lyi n g Ca no py 5.7 mg/ k g [3 a ] 5

. 4 mg/ k g [3 b ] 3

. 2 mg/ k g [3 c ]

Sed i me nt U nder Treated Canop y 2.27 mg /kg [4a ] 1

. 4 2 mg /kg [4b ] 1

. 4 mg/ k g [4 c ]

Pla n t Tissue ( l o n g gra s s) No da ta 131 mg/ k g [5 a ] 4 3 mg /k g [ 5b] , 1 10 mg/ k g [5 c ]
Anima l T i ssu e No da ta No da ta < 50 ug /kg-wet w t.

[ 1 ] a

. F i rs t t i d a l f l us h, 0. 6m ou t s ide imme diat e sp ray zone a t op b a re mud w i t h no f o lia r in t e rcep tion

, 3. 5 h r s post trt m n t; b—a vera ge o f 3 sa mp les t a ke n a t fir s t
f l u s h 0. 6 m o u t s ide s p ray zone ; c—g eome t ric me an of a l l sa mples co llec t ed 3

. 5 t o 4 hours pos t trea tmen t at 0

. 6

, 6

. 0 and 60 m out s i de sp ray z one (P att e n 2003 )
[ 2 ] a

— H i ghes t va lue of t h ree rep lic at es t a k en 1 h r post trea t m en t ; b

— ave r age o f thre e samp les ; c—av era g e o f t h ree sa mples t a ken in sedimen t unde r c a nopy 15 days a f t e r trea t m en t. (Pa t t e n 2 003 )
[ 3 ] a

— 1

- h r pos t trea tment w i t h in trea t m e n t zone o f bare mud ; b

— 1- hr pos t t r e a tmen t, average of 3 sa mple s; c—ge ome t ric me a n o f a ll samp les co lle ct ed 3

. 5 t o 4

hours pos t trea tmen t at 0

. 6

, 6

. 0 and 60 m out s i de sp ray z one (P att e n 2003 )
[ 4 ] a

— 1

- h r pos t trea tment w i t h in trea t m e n t zone unde r canopy ; b—1

- hr p o st t r eatme nt, av era ge of 3 sa mp les (75 % int e rcep tion ra t e); c

— geom etric m ean o f a l l samples co llected 3. 5 to 4 hou rs pos t trea tment (Pa t t e n 2003 )
[ 5 ] a

— E m p i rica l mea s urem ent s from Hoe r ger and Ken ag (19 7 2 ) and Fl e t ch er e t al. (1984); b

— fro m e m p i rical measu r emen t s o f Flet ch e r e t al. (1984 ); c

— from

modeled resu lt s of H oerge r and Ken aga (1972)

4.1.4 Sedi men t Conce ntratio ns

Li m ite d test ing of mari ne sedi ment concentr ati ons followi ng i m azapyr treat m e nt has bee n conducted by Patte n (2003), as des c ribed in se c tion 3.0. The worst ca se value in sedi m e nt i s represented by the maxi mum sedi me nt concentrat ion detected in trea ted ba re mud (5.7 mg/kg), t h e upper li mit woul d be re presented by the avera g e of the ma xi mum values from Patten’s trials, and the typical e nvironmenta l concentrati on pres umes canopy inte rception, or 1.42 mg/ kg (Table 4-1)

. All of these values are conservativ e i n that the measurements were taken af ter the f i rst tidal wash,

and hence re present “acute” sedi m e nt conditions a s oppose d to more chroni c sedi m e nt c onditions

. The half -lif e in estuarine sedim e nt s will be substantially less than th e 12.2-day half -life determined

in freshwate r pond sedi ments by Mangels and R itter (2000) because of the tidal exchange of

waters. However

, due t o the non-st atic nature of t h e est u ari n e environment, true sedi m e nt hal f

lives cannot be deter m ined from emp i rical m easu r em en ts and “d is s i pation” rates more accurately describe what is actually occurring in the estuarine environment— capturing the multiple

mechanis ms that reduc e sedi ment concentrations over ti me. Patten (2002) proje c ts that the

sedi m e nt c o ncentration of i m azapyr after bare- m ud treatment followed an exponential decline and could be pre d icted from the equation f = 0.0013 e ( ( 137 /( x + 23 ) ) . In those studies, approxi m a tely one

fourth of the m a xi mum detected c o ncentration of i m az apyr in sedi ment one hour a f te r treat m e n t (5.7 mg/kg) was detect able after r oughl y 4 days post tre a t m ent (Fi g ure 3-9), and the decay equation pre d icted the complete dissi pation of th e herbicide fr om sedi ment in 400 hour s.

FINAL

O c tob e r 200 3 Pag e 614.2 Ecological Receptor Exposur es

In this section, speci fic doses are es ti m a ted for im azpyr to terrestrial and aquatic receptors, by a variety of e x posure pathways of relevance to the habitats where Spartina treat m e n ts could occur.

Lif e history data f o r terrestrial wildlif e we re a c quired from the W ildlife Expos ure Handbook (USEPA 1993) and from anonym ous (2003) for the bobwhite quail, marsh wre n , deer mouse

, cottontail rabbit, m a llar d duck, Nor w ay rat and lesser scaup. These s p ecies, or closely relate d species, util ize habits where Spart i na is distri buted, and/ or they are test spe c ie s for which toxicologic a l data have been developed. The ma rsh wren is prim arily a wetland and salt m a rsh species that consumes a diet al m o st exclusively of ani m als and insects, and is particularly commo n in coastal ar eas. The deer mouse co nsum e s a diet of seeds and nuts pr i m aril y and is found in a wide variety of ha bitats throughout t h e stat e. The mallard is a “puddl e” duck t h at consume s pri m arily vegetation, but also some invertebrates. The sc a u

p is a “diving” duck a n d is m o re omnivorous in its dietary habits than the m a llard. Both duck species will consume more high protein/f a t anim al foods prior t o periods of m i gra tion a nd bree ding (Cohe n et al . 2000) . The cottontail rabbit is an obligate herbivore and a test sp ecies used commonly to address dermal sensitivity. The Norway rat is a representative omnivore common to coastal areas, and the rat is also a commonly used test species. Average weights, sur f ace areas, and daily consumption rates were used to represent

expos ure to wildli fe spec ies. The s e numbers can exhibit a gre a t deal varia tion a m ong populations, but populati on-speci fic data fr om eac h of the area s where Spartina is distributed was not available

.

Acute Diet ary Expos ure Modeli ng Method
The acute dietary expos ure was det e r m ine d from the mode led e m pirica l plant residue studie s discusse d in section 4.1, taking the average plant re sidue detected from grassland applications o f

herbicide at 1.5 lb ae/acr e. Dose was m odele d by the m e thod of SERA (1999) use d to address the ecological ri sks of i m azapyr use in forestry appl i c ations for t h e USDA. Brie fly, dos e (D) = A x C(Prop)/ W, where A = food consumption per da y ( kg), C = c oncentration in food ( m g/kg), Prop = proportion of diet as treated vegetation (percent), and W = average body weight (in kg). Typica l and upper food concent r ation li m its were obtained from resi due studies outlined in Table 4-1, as previousl y discussed. Body we i ght and food consumption para m e ters were obtained fr om the

Wildli fe Exposure Handbook or an onymous ( 2002) and are pr esented i n Table 4-2. No dissipation

or de gradati on is assume d, a nd t h e ac ute exposure is pre s umed to e quate to a “bolus” (s ingle dose ) dietary exposure of t h e herbicid e. The following para m e ter s we re as sume d for this modeling:

• Conc entration in food: = 131 mg /kg (upper) , 43 mg/kg (typic al)

• Proporti on of Diet Conta m inate d (Pr o p):

= 0.75 (obligate herbivor e in treated Spartina mea dow, based on 75% inter ception rate of Patten 2003) = upper li m it exposure

= 0.4 (base d on 40% inter c eption rate from Linders et al.2000) = typical proportion

of diet as sumed for omn i vore and car nivore e xpos ure.

FINAL

O c tob e r 200 3 Pag e 62Table4-2: Exposure Parametersfor Addressing RisksfromWSDA’sImazapyrApplicationsforSpartinaControl.SpeciesAdult BodyWeight(grams)Daily FoodIntake(g)DailyWaterIntake(ml)InhalationRate(m3/day)SurfaceArea(cm2)DietPreferenceRelevant Life HistoryCharacteristicsRelevanttoExposureConceptual ExposurePathwaysBobwhiteQuailB:1901520F:0.10M: 0.11F:298M: 320Plantsandinsects.Maxinsects20% insummerBreedinginApril-July; hatchingMay toAugust;Non-migratory;annualmortalityrateofapprox. 80%UnlikelyforSpartinaapplication,but consideredsurrogatefornonwater dependentbirdspeciesMarshWrenB:11.2583NodataF:45M: 48Insects, spiders,mollusks, andcrustaceansBreed inApril; hatchinMay;Migration infall andspring; likely tobefoundwithincoastalmarshhabitatwhereSpartinais abundantPrimary:DietarySecondary:InhalationofdriftTertiary: Water IntakeDeerMouseB:219(lactating)7F:.025M: 023F:86M: 91Mixtureofnuts,seeds,andinsectsBreedseveraltimesduringtheyearPrimary:ingestionofgrain,habitatuselimited,however.Secondary;inhalationofdriftCottontailRabbitB:1,2861801250.631,254Grasses,shrubs,woodyplantsBreedseveraltimesduringtheyearPrimary:ingestionoftreatedplantmatterNorwayRatB:3001533Nodata500OmnivorousBreedseveraltimesduringtheyearPrimary:dietaryingestionofmarineinvertebratesSecondary:water intakeTertiary:skincontactInhalation exposureunlikely due tonocturnalbehaviorMallardDuckF:1,043M: 1,225250F:0.042M: 0.055F;0.42M: 0.48F:1,030M: 1,148Asurfacefeeding “puddle”duck,feedsonanomnivorousdiet.Dietary patternsvarywithseason. Inwinter, mallardsfeedmostlyonseedsmast, and toalesserextentinvertebrates.Inthemigratory and breedingseasons,highproteinandfatdiets are consumed,withmoreinvertebratebiomass.Primary:dietaryexposurethroughanimal,plantandsedimentingestion,and featherpreening.Secondary:inhalationofdriftTertiary:water intakeRedFoxF:4,130M: 5,250F:285M: 362F:355M: 441F:1.7M: 2.0F:2760M:3220Omnivorous: mostly smallmammals, birds, insects,andfruit.Plantmaterialis commoninsummerand falldiet.BreedinginDecember-FebruaryPrimary:dietaryingestionofmarineinvertebratesSecondary:water intakeTertiary:skincontactFINALOctober 2003Page 63SpeciesAdult BodyWeight(grams)Daily FoodIntake(g)DailyWaterIntake(ml)InhalationRate(m3/day)SurfaceArea(cm2)DietPreferenceRelevant Life HistoryCharacteristicsRelevanttoExposureConceptual ExposurePathwaysScaupF:770M: 86050F:0.064M: 0.062F:0.34M: 0.36F:842M: 906Juvenilesateentirelyanimalmatterin NW territoriesstudy;61% animal matterinLouisianastudy,PacificFlywayspringmigrationfromMarch—April;fallmigrationfromSeptember-mid-October.FINALOctober 2003Page 64C h ro n i c D i eta r y E x

po s u re Method—On Site

Chronic diet ary expos ur e was eval uated using t h e sa me m e thod adopte d by the USFS in their

evaluation of i m a z pyr use for fores t ry appli cations (SERA 1999), with several modific a tions

relevant to t h e proposed application r a tes to contr o l Spartina . In the chronic dietary assessment, it is assumed that consumption of treated vegeta tion will occur for a 90-day period beginning

i mmediately after che m i cal application. Food c onsumption para m e ter s are based on the W ildli fe Exposure Handbook reference as cit e d in Ta ble 4-2. The res i due of i m az apyr in Spar tina grai n a t
ti m e zer o (C o ) is bas e d on the ac ute dietary exposure s cenario described above . The residue ove r ti m e was based on t h e foliar decay coefficient ( k ) = ln(2)/t 50 , where t 50 = the foliar half -lif e. The

concentration on t h e ve getation a f te r ti m e ( C t ) is calculated as C t = C o e -k t , and is r e flected i n Figure 4-3 below.

0 20 40 60 80 100 120 140 160 180 200181522293643505764717885

Da ys Po s t Tr eat mentEstimated Plant Residue(mg/Kg)

Figure 4-3: Estim a ted plan t residue concentr ations ov er time, with an initial

ap plicati o n rat e of 1. 5 lbs/ acre.

The integral of the concentration af ter tim e t (C t) is divide d by the duratio n of dietary expos ure t o calculate the ti m e

- w eight ed average concentration on ve getation. Daily dos e is calculated f r om the proportion of the diet conta m inate d, divided by body weight ( w hich va ries by ani m al). The specifi c

param e ters used are as f o llows:

• Duration of expos ure (T) = 90 da ys

• Body weight ( W) —avera ge varies by ani m al , from Table 4-2, units in kg

• Food consumption per day—varies by an i m al, fr om Table 4-2, units in kg

• Foliar half time (t 50 ) = 37 days (upper li m it), 26 da ys (typical e xposur e)

• Foliar residue (rr): = 131 mg/kg (upper li m it), 43 mg/kg (typical exposure)

• Dri f t = 1.0

• Decay coeffi cient (k) = ln(2)/t 50 = 0.0462/day (upper li m it); 0.0267/ day (typical exposure)

• Initial Concentration on Vegetation (C o) = Appli c ation Rate x (rr) x Dri f t
= 196.5 ( upper); = 64.5 (t ypical)

FINAL

O c tob e r 200 3 Pag e 65• Conc entration on Vegetat i on at ti me T (C t) = Co e -kT

• Ti m e

- w eight e d avera g e c oncentration on Ve getation ( C tw a ) = Co(1-e -k t )/(kT)

= 46.5 mg/ k g (upper); 24.4 mg/kg (typical)

• Proporti on of Diet Conta m inate d (Pr o p):

= 0.75 (obligate herbivor e in treated Spartina mea dow)

= 0.4 (omnivore on meadow fri nge, or transient wil d life)

• Chronic Diet ary Dose Absorbed (CD) = (C tw a )(food intake/ d ay)(Prop)/ W

Drinking Water Consumption Modeling
Exposure to imazapyr t h rough drinking water i s unlikely due to the brackish water conditions

where Spart i na is found. It is possible, however, that small animals a nd insects will collect drinking wa ter from the Spartina c a nopy a f ter a rain. Thus, th e drinking water pathway is considered complete f o r the terrestrial wild li fe c o nsidered in thi s assess me nt

.

Spill Scenario
For this exposure scenario, the upper lim it of e x posure was taken to be drinking wat e r obtained

f r om the applied (undiluted) solutio n that could accumulate on the plant s and be c ons um e d (e.g., via licking). The concentration of i m azapyr i n the undiluted solution will vary by the spray volume, as depicted in Figure 4- 4. As demonstrated in this f i gure, the ultra-low spray volumes result in the highest “neat” concentration of i m azapyr, whe r eas high s p ray volumes dilute the

i m azapyr in solution. Most app lication techniques envisi oned would appl y the herbici d e in the 10 gal/acre to 40 gal/acre ra nge. Exposure via this met hod woul d be consiste nt with an acc i dental spill scenario. Dose (D)

, in units of mg/kg- bw, is calc u l a ted as t h e product of (C x A)/ W , whe r e C =

0 10 00 0 20 00 0 30 00 0 40 00 0 50 00 0 60 00 0 70 00 0 80 00 0

0 2 0 4 0 6 0 8 0 1 0

A p p lic a t io n V o lu me ( g a l/a c r e )Imazpyr Concentration inApplied Solution

0

Figure 4-4: Estim a ted con centr ation of undiluted im azapy r in v a rio u s spr a y volu me

ap plicati o ns.

Not e : Higher spray volumes coul d be us ed and would result in lo wer exposures, as predi cted.

FINAL

O c tob e r 200 3 Pag e 66concentration in ambient water (mg/L), A = water consumed pe r day (in liters), and W = body weight (i n kg). This dose calculation was adop t e d fr om SERA (2001), with modif i cations to

reflect the e s ti m a ted e x posure c onc entration. Bo dy weight data for e a ch of the ani m als are represented in Table 4- 2. For the e xposur e calc u lations, the upper li mit expos ure concentration (C) f o r the drinking water (spill) scenario presumed a spill (and in gestion) of concentrated spray solution that was to be applied at a r a te of presumed to 10 ga l/acre (17,966 mg-i maz a pyr/L), and the typical exposur e was presum e d to occur from a spill at the standard application rate of 20 gal/acre (8,983 mg-i maz a pyr/L).

Runoff scenario
Ingestion of conta m inat ed water fr om an acute expos ure sc enario for r unoff repre s ents a more
realistic case for what m i ght actually occur in the treated envir o nment. Again, however

, due to the

brackish conditions wher e Spartina is found, it is unlikely that si gnifica nt drinking would occur by

any s m all ma mmal. Sal t glands in ducks e n abl e their inges tion of brac kish water a nd for this reason, an esti m a tion of uptake fr om a runoff concentration is leg iti m a te . The c a lculat ion of dos e is consistent with the equation used to predict uptake f r om a spill scenario (D = CxA/W ) , and the

estim a ted environmental concentr ations used for modeling are ta ken f r om the emp i rical results

summarize d in Table 4-2 (Patten 2003). Thus

, the upper li mi t expos ure wa s based on an EEC of 3.4 mg-i maz a pyr/L, and t h e typical exposure wa s based on a n EEC of 0.1 mg/ L

.

Dermal ( Contact) Expos u re M odeling Method
The ‘worst case’ (upper li m it) scenari o for cont act exposure was based on the presumption of an

ani m al being exposed di rectly to the spray, wi t h 100% a b sor p tion oc urri ng over the first 24-hour period. Thi s is a highl y conser vative exposure mo del, in that it assumes 100% abs o rption of the dose, whic h would over esti m a te fur bearing a n i m al and bir d exposures due to fur and feather

interf erence, respectively. Also, the derm is is largely i m per m eable t o water soluble substance s , thus, although adjuvants delivered with the herbicide will f acilitate uptake, absorbtion of herbicide

that reaches the skin will not be complete. The assump tions for the der m al absorbti on model were

as f o llows:

• Period of exposure (T) = 24 hrs

• Body weight ( W ) = aver age weight i n kg, as indicated from Wildli fe Exposure Handbook,

or other liter a ture i f no data were ava ilable withi n th e exposure handbook.

• Exposed sur f ace area ( S A): cm 2 = 1110( W) 0. 6 5

• Applicati on Rate ( A R) = (1.5 lbs/acre )( 0.01121—a conversion fa ct or) = 0.0168 mg/ c m 2

• Amount deposited on the ani m al (Amnt) = 0.5 x SA x AR ( n ote: typical der m al e xpos ur e assumes 50% of a n i m al is covered by direct s p r a y, upper li mit exposur e presumes 75% of

ani m al is covered a nd the product of SA x AR is multiplied by 0.75.

• Estim a ted Absorbed Dose = D abs = Amnt/ W

O t h e r E x

po su re P a thw a ys Additional routes of exposure are acknowledged both in the conc eptual model (Figure 2-1) and

also in Tabl e 4-2. However, we consider the ab ove exposur e scenarios t o represent t h e pathways where expos ure could be m a xi mal. Pathwa ys suc h as chronic expos ure to conta m inate d water a r e incomplete for the proposed use of Spartina i n a n estuarine s e tting. The acute run- off sce n ario to

FINAL

O c tob e r 200 3 Pag e 67contaminated water—where an ani m al m i ght drink water that has been in contact with treated vegetation is also unlikely to be completed in the estuarine setti ng bec a use the bra c kish waters

where Spartina is distributed are not potable to most wil d life ( a lthough wa terf owl with salt glands are capable of drinking a lim ite d a m ount of salt water). W e did not m o del this type of exposure

, as the m o re severe exposure scenario, the acu te spill based on the drinking of neat solution,

addresse d a more signi fi cant exposur e.

Acute inhala tion expos ure is possible

, but consi d e r ed insigni f i cant bec a use the disturba nce create d during treatment will cause most an imals to avoid the ar ea being immediately treated. Aerial drif t will vary by nozzle type and app lication volume, and has been esti m a ted at 10% in grasslands in

the Netherla nds (Linder et al. 2000). Such dri f t can be both a com p one nt of inhalati on exposur e off-site , and/ or oral or der m al e xposure off-site . The proba bility of this occurrence representing substantive expos ure is considere d i n signi ficant

, and the exposure model i ng conducte d for on-site exposures will yield substantially higher doses th an potenti al exposures off-site. Since these results indicated insignificant risk (as describe d below), off-site exposu re from dri f t was not
modeled.

4.2.1 M a m a li an Expos ure

Mammalian wildlif e can be expose d to i m a zapyr thr o ugh der m al , or al (inge stion) or inhalati on

route s , although the dieta r y r oute is c onsi d er ed most lik e ly in p r a c t ic a l s e tt ings ( U SDA 1996a). We

model e d expos ure to the rabbit

, ra t, m o use a nd fox as re pre s enta tive mammalian herbivores and

omni vore s for t hos e ar ea s whe r e i m a zapyr c oul d be a p plied to control Spartina . As de monst r ate d i n Tabl e 4- 3, t h e acute der m al and diet ary exposur e s yiel ded t h e highest mo dele d doses to all of t h e mammalian wildlif e exam i n ed for this study for t hose pa t h ways that are most realisti c in-situ (i.e., not involving a spill scenario) Ba sed on life histor y characteristics of f o od intake, body weight, and

sur f ace area, t h e deer mous e woul d have the highest esti m a ted exposure of the m a mm alian

ecol ogical r ecept o rs consider ed, for all of the e xposur e pat h

ways consi d er ed. This finding is relatively intuitive in that the species has the smallest home range, and highest f o od and water

intake and sur f ace area r e lative to body wei ght . Esti mates of dos e within each ex posure pathway

varie d by sli ghtl y more t h an one or der of ma gnit ude a m ongst the ma mma lian spe c ies exa m i n ed (Ta b le 4- 3). The red fox had t h e lowe st mode led exposure from contact exposur e , wherea s the Norway rat had the lowest modele d exposure for the ac ute and ch r oni c dietar y scenari o s. The

smaller sur f ace area/body wei ght ra tio of the fox, a nd t h e omni vor ous ha bit s of bot h the fox a nd rat, were largely responsible for the lowe r esti mate d e xposur e s by these species, relative to the mouse

and ra bbit

.

Estimates of im azapyr ex posure ingested f r om an acute spill scenario were high f o r all mammalian speci es, yiel ding acute dose esti mates in the high mg/kg-bw to low g/ kg- bw range

, for the upper an d typical spill concentration esti mate s. These acute “dri nking water/spill” scenar io values exceeded

the e s ti mate d exposur e for ot her pat h

ways by t w o to t h

re e order s of magnit u de. Howeve r, it is likely t h at all of t h e mammali a n s p eci es modele d would vol untarily a voi d drinking wat e r containi ng im azapyr f r om a spilled, und iluted spray solution; thus , the practical use of these modeled exposures requi res fi el d val i dati on. Dri nki ng wat e r c ons um ption under the run-off sce n ari o s yields more

realistic estimates of exposure, and reduced the exposure doses t o t h e model e d ma mmal s by ove r three or der s of magnitude, wit h

a ma xi mum est i m at ed exposure in the deer mous e of 1.133 mg/kg,

and a mini mum in t h e male fox of 0.008 mg/ k g—the l o west dos e esti ma ted by all e x pos ure r out e s considered.

FINAL

O c tob e r 200 3 Pag e 68Table4-3: Estimated ExposurestoTerrestrialWildlife ReceptorsfromImazapyrApplications (mg/kg-bodywt)*ReceptorAcute DietaryExposureChronic DietaryExposureAcute DrinkingWaterExposure (Runoff)Acute DrinkingWater(Spill) ExposureDermal(DirectContact)ExposureDeer MouseUpper:42.11Typical:13.82Upper:14.95Typical:7.84Upper: 1.133Typical:0.033Upper:5 989Typical:2 994Upper:54.07Typical:36.04ScaupUpper:3.05 M, 3.40FTypical: 1.00M,1.12FUpper:1.08 M, 1.21FTypical: 0.57M,0.63FUpper:0.210M,0.216 FTypical: 0.006 M,0.006 FUpper: 1107M,1143FTypical: 554 M,572 FUpper:14.74M,15.33 FTypical:9.83M,10.22FMallardDuckUpper:20.05M,6.58FTypical: 6.58M,7.73FUpper:7.12 M, 8.36FTypical: 3.73M,4.39FUpper:0.186M,0.143 FTypical: 0.004 M,0.005 FUpper:983M,758 FTypical: 491 M,379 FUpper: 13.03 M, 13.78FTypical: 8.68M,9.19FNorway RatUpper:2.62Typical:0.86Upper:0.49Typical:0.93Upper: 0.374Typical:0.011Upper:1 976Typical:988Upper:21.32Typical:14.21MarshWrenUpper:37.26Typical:12.23Upper:13.23Typical:6.94Upper: 0.903Typical:0.027Upper:4 7910Typical:2 395Upper:67.27Typical:44.84BobwhiteQuailUpper:7.757Typical:2.546Upper:2.75Typical:1.44Upper: 0.358Typical:0.011Upper:1 891Typical:946Upper:25.01Typical:16.67Cottontail RabbitUpper:13.75Typical:4.51Upper:4.88Typical:2.56Upper: 0.330Typical:0.010Upper:1 746Typical:873Upper:12.81Typical:8.54Red FoxUpper:3.61Typical:1.19Upper:1.28Typical:0.67Upper: 0.286 M, 0.292FTypical: 0.008 M,0.009 FUpper: 1509M,1544FTypical: 755 M,772 FUpper:7.83M,8.51FTypical:5.22M,5.68F*SeeAppendix B for full calculationsofdosebyexposurepathwayfor eachreceptorspecies modeled.FINALOctober 2003Page 69The lowest dietary dose was modeled in the rat at 0.049 mg/ k g, for a “t ypi cal ” chronic dietar y dose (see Ta ble 4.2). The hi ghest die t ary dos e wa s c a l c ul ated for t

h e acut e diet ary exposure in the deer

mous e c o ns uming a di et wi th the “ u pper ” li mit EEC, t o yiel d a dose of 42. 11 m g /kg. The highest non-spill dose was esti mated in the deer mouse via direct contact to s p ra y, yielding a dos e esti mat e of 54.07 mg/ kg- bw.

4.2.2 Avi an Exp o sure
Exposure for birds m a y occur via the sa m e pathwa ys as m a mmal s : ingestion, contact and

inhalation. The broa d array of life history beha vior s prevents an assess ment of all bird species.

We modele d potential doses to the bobwhite quail, m a rsh wre n, m a llard duck and grea ter scaup, to provide for a range of dietary habi t s and life hi story beha vi ors. All of these spec ies, with the exception of the bobwhit e quail, coul d be foun d i n the re gions of Was h ingt on State whe r e Spartina is currently distributed (western Was h ington’ s lowlands s upport Cali forni a quail, a cl osely relate d species). A s dem onstrated in T a ble 4-3, the marsh w r en ha d the highest projected dose am ong the species via the non- drinking exposure pathways consider ed (i.e., 67 mg/kg via direct contact application). The highes t acute and c h ronic dietar y doses wer e also projec ted for the marsh wren

of all the bir d species, pr i m arily due t o its high fo od intake rel a tive to its body weight. Si m ilarly,

the mallard duck wa s est i m ated to c o nsume r oughly six- fold more i m aza pyr than the greater scaup because of the assumed dietary di fferences co nsidered bet w een these species (i.e., pri m ary herbivore vs. omnivore)

.

4.2.3 Insec t Exp o sure
Exposure for insects was modeled in the bee for t h e direct contact exposure scenario due to spray from an acute exposure only (Meade 1983). Dos e was esti mated as described in Sec tion 4.1 for

direct conta c t exposure, using t h e be e as a surrogate for all t e rrestrial insects. The di rect contact

expos ure for the bee yielded an esti mated dose of 0.0223 mg/ kg for a typi cal exposure (assum i ng 50% of the i n sect wa s covered) , and 0.0335 mg/kg for th e upper li m it esti mate (ass uming 75% of

the ani m al was covere d). Dietary and drinki ng water consumption were not c onsidered, a s previousl y discussed.

4.2.4 Rep t il es a n d Amph ibia n Ex pos ure
Reptiles and am phibians (herptiles) can be exposed to herbicides through the same pathways as mammals, birds and terrestrial invertebrates—vi a dietary consumption, inhalation and direct contact. Amphibians may be par ticularly sus cep tible to contact exposu re from direct spray applications whereas contact expos ur e to reptiles is unlikely to yield si gni ficant dose s due to t h e relative imperm eability of th eir skin. Exposure param e ters have not been developed to accurately gauge reptile or amphibian exposure s and no toxicity inf o rmation was identif i ed f

r om the literature

from whic h t o qua ntify or esti m a te expos ure to the s e groups of ani m als

.

Although a form al dose cannot be es tim a t ed f o r h e rp tiles

, the po te ntial f o r e xpo s u r e c a n b e

c o nsi d ere d by e v al ua ti ng t h e pote ntia l her p til e inhabitants of the es tuarine areas wh ere Spar ti na

treatm ents could occur. The USGS (2003b) reports a tota l of 19 herptiles potenti ally resident in the

broader W i llapa Bay area (http://w ww.npwrc.usgs.go v/resource/othrdata/chek bird/r1/willrept.htm )

. These sp ecies are also po ssible in other areas of P uget S ound and co as ta l W a shing t on. Twelve of

th es e 19 s p ecies are am phib i an s and are therefo r e in tolerant of the saline conditions inherent to

es tu aries wh ere Spartina is d i s t r i bu te d. Expo su r e to th es e 1 2 sp ec ie s is the r ef o r e c ons id e r ed an

in com p le te p a thway

.

FINAL

O c tob e r 200 3 Pag e 71Three of t h e 19 her p tile species re cognize d to W illapa Bay are sea turtles, and include the leatherback ( Caretta caretta ), logger head ( Dermochleys cori acea ) and gr een sea t u

rtle ( Chel onia myd a s ). All of these species are listed as either threatened or endangered. W illapa Bay is not designate d a s critical habitat for a ny of these sp e c ies (50 CFR Part 226), a nd we could not veri fy

that indivi duals of t h ese species’ have been sp ecifically si ghted i n the area. Doc u m e ntation

reviewe d suggests very infre quent si ghtings of t h ese sea t u

rtles are possible in the outer bay and

marine areas due to their relatively cosmopolitan o ceanic dist ributions. However, the green turtl e is considered pri m arily a tropical species wherea s the logge rhead a nd le atherback t u rtles have a greater toler a nce for colder waters and woul d be more likely to be observed off of coastal

W a shington. W h ere Spartina is distributed, the probability of turtle occurrences is suff iciently low

to consi d er e xposur e an incomplete pathwa y for t h ese threate n ed a nd e n dangered spec ies.

Only two snake species are recogn ized as typical inhab itants of the W illapa Bay area, the common gartersnake ( Thamnophi s sirtalis ) and the northwester n

gartersnake ( Thamnophis ordinoi des )

. These speci es may be also found elsewhere in c o astal regions of wester n Was h ingto n environments near wher e Spartina occurs. Thes e species ca n be found occasionall y in or nea r water, although the y woul d be c onsidered ve ry uncommon in sal t m a rsh ha bitats. The

northwester n garter snake is pri m ar ily a terrestri al species and the common garter is commonly found near freshwater which it may use to esc a pe pr edation or other dist urbance ( S te bbins 1985)

. The potentia l for expos ur e to these ani m als is extre m ely low due to their life history be havior that

woul d largel y preclude t h eir us e of salt m a rsh habitat where Spartina is distributed. No dose s ar e esti m a ted for these receptors.

4.2.5 Aqu a ti c Ani m al Exp osu re
Exposure to fish and aquatic invertebrates could o ccur f r om drif t entering wa ter during application

, from r unoff from plants following a p plication from rai n and ti da l inundati on, a nd/or from leaching

from treate d vegetati on and sedi ment under lying treat ment areas. The estimated water concentrations to which aquatic animals could be exposed will va ry with depth f o llowing initial application, as depicte d in Figure 4-2. For the expos ure cal culations, the worst cas e exposur e concentration (C) for water was as s u med t o be 5.77 mg/L, the m a xi mum c oncentration detected on the edge of the treat m e nt zone on an incom i ng tide after appl ication to bare mud (Patt e n 2003)

. The upper limit was ass u m e d to be 3.40 mg/ L , and the typi cal concentr ation was 0.1 m g / L , as summarized in Table 4-1. Benthic infauna and epif auna atop mudf la t sediments will be exposed to the highest concentrations. Se di me nt detritivor es, be nthic epifa una an d be nthic infauna wer e assumed to be expose d to concentrations of 2.27, 1.42 and 1.4 mg-i ma za pyr/kg- sedi m e nt to represent the worst case, upper li mit and typical conce n trations found in se di me nt by Patte n (2003) . Benthic infauna were a ssume d to be e xposed to the pore wate r leve ls detected i n the Patten study (2003), 3.29, 2.9 4 and 0.042 m g / L to re present the worst ca se, upper li mit and typic a l

expos ure sce n arios.

As previously discussed, the bioconcentratio n and bi oaccumulation of i m azapyr i n aquatic organisms is extrem ely low due to the compound s high water solubility and low lipid solubility. Empirical results detaile d in Table 4-1 of t h is do cum e nt highlight how meas urable concentrations in fish and aquatic inve rtebrate tiss u es were de tected only in sa mples collected 3 hours a f ter

treat m e nt, but subseque nt m easure m ents were not detectabl e . There f ore the potential of expos ur e through inge stion of exposed a quatic invertebrate s or ot her food s ources i s substantial l y reduce d.

No bioaccumulated doses are therefore esti mated.

FINAL

O c tob e r 200 3 Pag e 724.3 Adj u vant and Inert Ingred ient Exposure Assessment

The mass of sur f actant applied per unit sur f ace area can change w ith the application volume used to dilute the herbicide. As a result, it is esse ntial to consider the potential exposure to aquatic

ani m als at the range of potential application vol um es . A va riety of sur f actants coul d be used, on the basis of past practice s , but all are assumed t o be m i xed with herbicide at a rate of 1% (w/v).

We e v aluat e d the pote n tial concentration of s u rf

actant over a range of potential application

volumes use d, ranging fr om the ultra

- low range ( 2.5 gal/acre) as applied in som e treat m ent trials by Patte n (2002) to 80 gal/acre, whic h is consi s te nt with the r a tes used t o apply gl yphosate under

the current che m ic al control progra m ( W SDA 1993) . As de monstrate d in Table 4-2, initial

concentrations of sur f act ant coul d be projected t o be quite high under the most c ons ervative of assumptions and highest application r a tes. At a water depth of 0.0125 m (a pprox. 1⁄2 in)

, as would

be consistent with an incom i ng tidal lens, the spray volume of 80 gal/ac r e could be projected to yield nearl y 60 mg/ L surfactant, whereas lo w a nd ult r a-low rate s of applic ation yiel d correspondi ngly lower c oncentrations.

Table 4-4 : Estima ted s u rfactant c once ntratio ns in estua ry w a te rs w here Spa r ti na co uld be

tre a te d w i th imaza p y r , assu ming c onstant su rfactant ra te of 1 % in s p ra y vo lum e , co mple te
solub ili ty o n inc o min g tide , and th e “w orst c a se” sc ena ri o of n o ad s o rp tio n on sedim e nt o r Spa r t i na ca nop y

. Su rfacta n t c onc entration s a r e i n m g /L

Depth (m) 2.5 gal/ac r e 5 gal/acre 10 gal/acre 20 gal/acre 40 gal/acre 80 gal/acre

0.01 2 5 1.87 2 3

. 7 4 4 7

. 4 8 14.9 6 2 9

. 9 2 5 9

. 8 4

0.02 5 0

. 9 3 6 1

. 8 7 2 3

. 7 4 7

. 4 8 14.9 6 2 9

. 9 2

0

. 0 5 0.46 8 0.93 6 1

. 8 7 3

. 7 4 7

. 4 8 14.9 6

0

. 1 0.23 4 0.46 8 0.93 5 1

. 8 7 3

. 7 4 7

. 4 8

0

. 2 0.11 7 0

. 2 3 4 0.46 8 0

. 9 3 5 1

. 8 7 3

. 7 4

0

. 4 0.05 8 0

. 1 1 7 0.23 4 0

. 4 6 7 0

. 9 3 5 1

. 8 7

0

. 8 0.02 9 0

. 0 5 8 0.11 7 0

. 2 3 4 0

. 4 6 8 0

. 9 3 5

FINAL

O c tob e r 200 3 Pag e 73

### 5.0 RISK CHARACTERIZATION TO ECOLOGICAL RECEPTORS
FROM THE USE OF IM AZAPYR TO CONTROL SPARTINA

To character ize risks from the pote n tial practice of applying i m azapyr in an estuary setting, the potential i m azapyr exposure and effects to ecological receptors are integrated in a tot a l ‘weight of evidence analysis’. The analysis exa m ines the e s ti m a ted dos e and c h e m i c al propertie s (toxicity, metabolism, environmental f a te and transport) that infl uence t h e i m pact that i m az apyr could have

on bi ota. Characterization of risk was made by calculating t h e haza rd quotient f r om the estimated

environme n tal concentrat ions or exposure doses c a lc ulated in section 4.0 of this report. The hazard quotient is derived by dividing the esti m a te d expos ure concentration or dose by the toxicity reference dose (NOEL) reported for the species (or closest s u rrogate spe c ies) for which toxicity testing has been conduct e d (Table 5- 1). When possible, we used the NOEL deri ved for the sa me

expos ure pathwa y for which a dose was esti mated to calculate ‘ p athway-spe cific’ hazard quotie nts. When pathway-speci fic NOEL’s we re not available, we use d the m o st conservative NOEL fr om the literature for all of the exposure pathways consi d ered, defaulting to the one-c ompart m e nt model assumption f o r uptake and elimination kinetics.

Based on pa st toxicologi cal research and the phys ical che m i s try of i m az apyr, it is assum e d that uptake of i m azapyr into an ani m al follows a first compart m ent m o de l with f i rst-order elim ination kinetics. That is, it is assum e d that once expose d, the im azapyr does not pr ef erentially concentrate

in one tissue over another, and that it is eli m i n ated from all tissues at eff e ctively the same rate. Under a one-compartment model, uptake of imazapyr by one path way will have an equivalent

effect as the sa m e dose acquired by another pat h way. Thus, the most co nservative t oxicological criteria would be applicable to all means of exposure

. However

, in practice, even with a onecompart m ent conceptual m odel

, this scenario is rarely obse r ved and di fferenc e s in the doses required to elicit a toxicological response are ofte n observed a m ong di ffer ent exposure pathways.

For e x a m ple

, ski n barrier s may preve n t full a b sor p tion of a de r m ally appli e d do se, or portions of an ingested quantity of herbicide ma y pass through an animal’s system without systemic absorption in

the small intestine.

5.0.1 M a m m a l Ri sk

As dis c usse d in cha p ter 3 the ac ute oral toxi city of imazapyr to m a mmals is rated as practicall y
non-t oxic , based on the EPA criteria outlined in Table 2-1 (i.e., an acute oral LD 50 of > 2,000, mg/kg-body weight)

. None of the ex posure doses esti m a ted in chapte r 4 (se e Table 4-3) exceeded a hazard quoti e nt of 1 for any of the species or exposure pathways modeled relative to the NOEL (Table 5-1) , with the e x c e ption of the deer mouse spill scenari o exposure ( H Q = 1.198) . The spill scenario modeled (i.e., where an ani m al woul d e ffectively drink undil u ted spilled spray solution) is highly conse r vative and unlikely to be realized in situ because best m a nagem e nt practices would

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O c tob e r 200 3 Pag e 74Table5-1:Hazardquotient calculationsfromestimatedexposure dosesofimazapyrto terrestrial wildlife.*EcologicalReceptorAcuteDietaryUpperExposure1AcuteDietaryTypicalExposure1ChronicDietary UpperExposure2Chronic DietaryTypicalExposure2Dermal/Contact UpperExposure3Dermal/ContactTypicalExposure3DrinkingWater (Spill)UpperExposure4Drinking Water(Spill) TypicalExposure4DrinkingWater(Runoff)UpperExposure4DrinkingWater(Runoff)TypicalExposure4DeerMouse0.00842140.0005240.0149464290.0078428570.027032540.01802171.197733330.598866670.00022676.667E-06Norway Rat0.0005240.0001720.000930.0004880.010657890.00710530.3952520.1976260.00007480.0000022CottontailRabbit0.00275040.00090280.0122035380.0064035770.135162680.09010850.349261280.174630646.61E-051.944E-06RedFoxM0.00072260.00023720.0051300570.0026919010.053289430.03552630.30182880.15091445.712E-051.68E-06RedFoxF0.00072320.00023740.005134140.0026919010.032018370.02134560.30885860.15442935.845E-051.719E-06MarshWren0.05528520.0181470.0661333330.0347022220.019569410.01304637.076757443.538378720.00133933.939E-05BobwhiteQuail0.01150830.00377750.0137664470.0072236840.021283890.01418932.805872251.402936120.0005311.562E-05Scaup M0.01523260.00087030.0054069770.0028372090.168162890.11210860.963626610.481813310.00018245.364E-06Scaup F0.0170130.0009720.0060389610.0031688310.062527310.04168490.995031250.497515630.00018835.538E-06Mallard DuckM0.10025510.00572810.0355867350.0186734690.036860320.02457350.85520470.427602350.00016184.76E-06Mallard DuckF0.11774930.00672770.04179650.0219319270.038314380.02554290.659628990.32981450.00012483.672E-061:acute dietaryreference NOEL = 5,000mg/kg-bw formouse, rat, rabbit, andfox; 1149 mg/kg formallard andscaup; and674 mg/kgforquail andwren2:chronic reference NOEL dose formouseand rate= 1,000 mg/kg;forrabbits = 400mg/kg; fordogs = 250 mg/kg;for avianspecies = 200mg/kg3:dermal/contact NOELdose formouse& rat=2,000 mg/kg; 400mg/kg forrabbit.No dataonfox oravian species, so assumed rabbitvalue of 400mg/kg4:same reference doses as acute oralFINALOctober 2003Page 75be e m pl oyed i mmediatel y to clean up spilled her b icide, and t h e disturbance of the cle a nup action

woul d discourage wil d life from the a r ea. All ot her expos ure scenarios and esti m a te d doses for the

terrestrial ma mmals modeled yielded hazard quotient s two to four orders of magnitude lower than the NOEL values for the species or guild from which toxicol ogical data were derive d. This result s indicates insigni ficant r i sk to these receptors can be expected from i m azapyr treat m ents.
Characterizi ng risk based on absol u te lethal thresholds such as the LD 50 is not possible for mammals because the dose ranges adm i ni stered ove r the var i ety of tests perfor med have never yielded lethality in mammals. Thus, the estimates of the LD

50 , as r e ported i n Table 3-9, a r e prefaced wit h the ‘>’ sign, and no empirical result s are available to substantiate these values.

Substa ntial conservatis m was factored into the e xpos ure ass e ss m e nt suc h that the modeled dose s can be assumed to over estim a te the conditions in-situ , particularly for c h ronic expos ures beca use applications will occur only every ot her year and tidal f l ushing over the Spartina results in the loss

of the herbic ide over ti me. Conserva tis m was als o f act ored into the hazard quotient cal c ulations, i n that most NOELs re port e d si mply re ferenc ed t h e hi ghest dose tested ( H DT), and there f ore were not
based on act ual e m pirical findi ngs fr om a dose-r espons e cur v e. It is the r efore the c onclusion of

this assess ment that the use of i m a zapyr at th e indicated a pplication ra te of 1.5 lbs/acre (0.68 kg/acre) will not pose a risk to m a mmalian ecologi cal receptors, even under the wor s t case (upper )

expos ure sc enarios. No threatene d or enda nge red ma mma lian species occupy ha bitats wher e Spartina is distributed or where i m azapyr c ould be applied. Sinc e the che mical does not bioaccumulate, and best manageme nt practices will prevent signifi cant drift off-sit e , it can be

reasonabl y assumed t h at such speci es occurring o ff- site would not be af fected by the use of

i m azapyr in the estuary setting.

5.0.2 Avi an Ris k

As discussed in chapter 3 the acute oral toxic ity of imazapyr to birds is also rated as practically

non-t oxic , based on the EPA criteria outlined i n Table 2- 1. None of the exposure doses esti mate d in chapter 4 (see Table 4-3) yielded a hazard quotie nt of 1 or greater for any of the species or
exposure pat h wa ys mode led relativ e t o the NOEL except, a g ai n fo r the spill scenario where both

the m a rsh wren and bobwhite qua il had upper lim it expos ure HQs of approxi mat e ly 7 and 3, respectively, and lower l i m it HQs of 3.5 and 1.4 (T able 5-1). The sa m e argument holds true for

avian wildlife as it woul d for terrestrial wildlife regarding t h e spill sce n ario—na mely that best

mana ge ment practices that obligat e WSDA t o i m mediate clean-up ac tions create dis t urbance t h a t
woul d be expected t o greatly eli m inate exposu re to birds of this guild when herbicide

concentrations are at thei r highest. The more r eal isitic exposure scenarios- - run-off dri nking water, dietary and direct contact yielde d hazard quotients generall y two to thr e e orders of m a gnitude below 1, indicating insignif icant risk to these receptors can be expected.

Sim ilar to mammals, characterizing ri sk based on lethal thresholds is not possible for birds. Like

ma mmals, i n the toxicity tests conducted wher e survival wa s a m e a s ure m ent endpoi nt, the dose

ranges a d mi nistered di d not yield toxicity (lethality), so the estim a tes of the LD 50 , as reported i n Table 3-10, are preface d with the ‘>’ sign, and no e m pirical results are available to substantiate

these values . Substa ntial conservatis m was there f ore fact ore d into the e xposur e asse ss m e nt such

that the modeled doses can be assu m e d to overestim ate the conditions in-situ , pa rticularly for chronic exposures. By considerin g avian species with a range of li fe his t ory be haviors and dietar y habits, we have screene d for a range of avian r e ceptors that could be exposed t o i m azapyr in t h e environme n ts where it might be a p plied. It is th e concl u si on of thi s a ssess ment that the use of

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O c tob e r 200 3 Pag e 77i m azapyr at the indicated application rate of 1.5 lbs/acre wil l not pose a risk to avian receptors,

even under the worst ca s e exposure s cenarios.

5.0.3 Insec ts

I m azapyr is practically non-t oxic to honey bees (BPA 2000). Direct contact exposure resulted in

an esti mate d dose of 0.0223 mg /kg and 0.0335 mg/kg for typical, a n d upper li mit expos ure, respectively. The esti mated NOEL for i n s ect s is 1000 mg/kg (the HDT), and the LD 50 is

considere d > 1,000 mg/ k g. On th is basis, the haz a rd quotient s would be 0.00022 3 and 0.000335, respectively, and the risks can be characterized as insignif i cant to terrestrial insects, even f r om the

“worst case” contact exposure scenar io.

5.0.4 Rep t il es a n d Amph ibia ns
No imazapyr toxicity values have been reporte d f o r reptiles and amphibians f o r imazapyr, and

expos ure par a m e ters have not been fully de velope d, as disc us sed in Secti on 4. Although a for m al dose (and hence risk calculation) can not be extrapolated, the lif e history behaviors of the herptiles

native to we stern Washi ngton sugge sts that risk fo r reptiles and amphibians is insigni fi cant because they would not be found in the brack ish water and estuarine habitat where Spartina could be

treated wit h i m azapyr, a n d thus expos u re is pre c luded, as de scr i bed in secti on 4.2.

5.0.5 Fish

Risk to aquatic ecologi cal receptor s from expo sure to a potentially hazardous substance is

deter m ined by two equa lly important factors: dur ation of exposure and t h e concentra tion or dos e of t h e che m i cal (whic h is a function of the pote n c y or toxicit y of the c h e mical).The a c u te toxicity (LC 50 ) concentration f o r rainbow trout, bluegill sunf ish, and channel catf ish was f o rmerly reported

at >100 m g / L (the HDT), and as such the herbicide has bee n considered practically non toxi c based on EPA hazar d criteria (Table 3-12) . As disc ussed in t h is assessment, more recent toxicity testing has established an e m pirica l LC 50 of 22,305 mg-i maza pyr ae/L using the Arsenal tm for m

ulati on. This toxicit y value actually exceeds the i m aza p yr concentrati on in a neat (undiluted) spray sol u tion applied at the nor mal 10 gal/acre ap plication rat e (i.e., 17,966 mg-i m a z a pyr/L), a nd is within one order of magnitude of t h e neat conc en trations if applied at the ultra-low rates of 5 or 2.5 gal/acre (35,931 and 71,862 m g / L , respectively). Based on the wor s t case, upper lim it and typical exposure concentrations outlined in chapte r 4.0 (Table 4-1), as de veloped f r om empirical studies, t h e hazard quoti e nts fo r wat e r expos ures to rainbow trout would be 0.00258, 00152, a n d 0.000045, re spectively ( T able 5-2). These valu es represent insigni ficant ri sk to fis h.

It should also be underst ood that thes e exposures are relevant only for an acute expos ure scenario. No signific a n t chronic e xposur es should occ u r due to the ti dal exchange of waters in the areas

where Spart ina is di stributed. Bas e d on the dissi pation e xper i m e nts of Pa tten (2002), all readily

solubilized i m aza pyr a p plied during a typical a pplication would be dis s i pated (dilut e d be yond detection) in approxi mat e ly 40 hours or less—roughl y four to five tidal exchanges i n the coastal

w a ters of W a shington. T h is duration of exposure is less than half the tim e of a typical 96-hr toxicity test.

Risks to Thr e atened and Endanger e d Fis h

Based on t h e hazard quotient calcul a tions descri bed above, and the t h reat ened and endangered species se nsitivity fish t oxicity study recen tly c onducte d (Sappingt on e t al. 2000), it can be

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O c tob e r 200 3 Pag e 78reasonabl y a ssumed, wit h high certa inty, that exposure to the activ e ingredients in i m az apy pose no signif i cant risk to the Columbia River ESU chum sal m on, chinook sal m on, or ca ndidate coho

sal m on st oc ks, nor t o a ny of the Puget Sound sal m onid stocks t h at ar e listed a s t h reatened or endangered under t h e ESA. Only under the a ccident al spill sc enario of undiluted neat solution that

was to be a pplied at a r a te of 2.5 or 5 gal/acre is there pote n tial to exce ed the acute l y toxicity

criteria f o r salm onids (as active ingredient). Ho wever, if a spill were to occur in an aquatic

environme n t where sal m on were inhabitants (i.e., as opposed to a bare mud-fl at at low tide), wate r must be pres ent. Thus, s o me dilution woul d occu r i mmediatel y and the dilution would likely lower

the concentr ation bel o w t h e toxicity t h reshold.

5.0.6 Aqu a ti c In v e rteb rates

The re porte d acute t oxi city LC 50 concentration for the water flea Daphnia magna is >100 mg/L and the reported acute toxicity LC 50 concentration for the eastern oyster growth inhibi tation is > 132 mg/ L (s ee section 3.1.9). On t h e basis of t h ese toxicity m eas ure m e n ts, i m azapyr woul d be

considere d practically non-t oxic to both fre s hwater and marine inverte b rates accor d ing to EPA hazard screening criteria (Table 3-11) . However, si m ilar to mammal studi es, and most fish studies (beyond those recently conducted by Smith et al. 2003) it should be re cognize d that no for m al

meas ure m ents have bee n doc umented that esta blis h i m azapyr concentrations that were e m pirically toxic or yielded sub-lethal eff ects such as growth inhibition. Thus, the measures of > 100 and > 132 mg/ L pr ovide only screening val u es for thi s cu rrent e f for t . To di ffere n tiate risks from motile epibenthic or pelagic i n vertebrates from benthic infauna we used the pore water concentrations depicted in Table 4-1. No sediment quality data ha ve been derived to enable risk characterization from potenti a l sedi ment conta m inati on, although ep ibenthic i nvertebrates such as t h e oyster and crayfis h have been tested. Using these toxicity measures and t h e esti m a ted worst case, upper li m i t and typical e xposur e concentrations from Ta ble 4- 1, the hazar d quotients have been summarized in

Table 5-2.

As depicte d in Table 5-2, conservative risk m o deling assuming ac ute e xposure conditions most likely to be experience d by invertebr a tes yielded hazard quoti e nts two to three orders of magnit u d e below 1 for the active ingredient of i m aza pyr. Thes e results s uggest that i nvertebrate expos ure to
i m azapyr in water represents an insignificant risk.

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O c tob e r 200 3 Pag e 79Table 5-2. Haza rd Quo t ien t Calc ul atio ns fro m Es tima ted Aqu a ti c Bio t a Expo su res*

Species Worst Case Exposure Upper L i mit Exposure T y p i ca l Expo sure

Rain bow Tro u t (LC50 = 22 ,30 5 mg/L) 0.00 2 5 8 0

. 0 0 1 5 2 0

. 0 0 004 5

Rain bow Tro u t, Arse na l (w/1 %

s u rfactant)
a) Hast en 113 mg /L LC50
b) W/Agr i d e x: 4 59 mg/L
LC50 a) 0.51 1 b) 0.12 6 a) 0.30 1 b) 0.07 4 a) 0.00 88 b) 0.00 21

Marine Invertebrates ( s urfac e water e x p o s ure, NOEL = 100 mg/L) 0.05 7 7 0

. 0 3 4 0.00 1

M a ri ne B e nt hi c In f a un a Inverte b rate s ( p o r e water

exp o sure; NOEL = 10 0 mg /L) 0.03 2 9 0

. 0 2 9 4 0

. 0 0 0 4 2

Non-targ et algae (e.g ., U l va

s p

., et c. —E C50 = 7 1 m g /L i n Sel e n a strum ) 0.07 6 0

. 0 4 4 7 0.00 1 3

Non-targ et va scu l ar plant s (e.g., eelgrass , Sa li co rni a ; EC50 =0. 021 4 m g /L in

duckwe ed for gro w th) 2 7 0 1 5 9 4

. 7

*Hazard quo tient def in ed as: e s t i mate d e x po su re c o nc en t r at io n / s u b

- l e t h al E C 50 , or est i m a te d e x p o sure con c e n trat io n/LC 50

5.0.7 Non -ta rg et Aqu a ti c Ve geta t io n Ri sk

It is not surprising that risks to non- target aquati c vegetation appear to pose the most significa nt
risk elem ent from the potential use of i m azapyr , as the herbic ide has been engineered as a broadspectrum agent to contr o l unwanted plant growt h. Risks to algae, ba s e d on hazar d quotient calculations, are insigni ficant

— within the same or der of magnitude a s risks chara c terized for aquatic inve rtebrates (Ta b le 5-3). Ri sks to vascul ar plants s u c h as eelgra s s (e.g., Z. marina and Z. japonic a ) may be signi ficant, based on EC 50 concentrations develope d in duckwee d, a floating vascular plant and expected w a ter concentrations of the herbicide. H a za rd quotients exceeded 1.0

under eac h of the expos u re scenarios considere d fo r va scular plants, ranging fr om 4.7 fold a bove

the EC 50 for duckweed gr owth inhi bitation for typi cal ex posure s to 270 for “worst case” exposures

. The i m pact of i m azapyr use on non-t a rget vegetat i on should be largely controllable by the use of

best m a nage ment practic es that li m it the potential for non-target vegeta tion expos ur e. Patte n (2003) showed that even after direct exposure t o the herbici d e, re growth of eel g rass to its preapplication state was evident less than one year af ter treatment. This effect was observe d in eelgrass spe c ifically tre a ted with the herbicide

, not treated through e xposur e to water as is

considere d t h e most re alistic m e ans of e xposure in this context. The monoc ulture growt h typical o f Spartina reduces the pote n tial for non-target plant expos ure dur i ng her b icide application.

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O c tob e r 200 3 Pag e 805.1 R e lative Hazard and R i sk Charact erization of Imazapy r , Gly phosate,
Surf act ant s , Inert I n gredients, An d T h e Use of No Chemical Control Or Other Ag ent s F o r Sp artin a Eradicatio n

Glyp hosate

The full suit e of ec ologi cal hazards and risks as sociated wit h glyphosate use to control Spartina

were thor oughly addre s s e d in the ori g inal EIS ( W SDA 1993). The c o nclusion of t h at docume n t

was t h at the use of th e compound to control Spartina had lim ited risks associated with it to ecological receptors and t h erefore onl y thos e ele m ents releva nt to a compar ison with i m azapyr will

be evaluated here. On the basis of the m u ltitude of f

actors evaluated in this assessm e nt it can be

summarized that i m azapyr presents a substanti a lly i m proved rela tive risk scenario to aquatic

ani m als over that of glyphosate. Reported LC 50 values for gl yphosate i n r a inbow trout range over

two or ders of magnitude, from lo w values of 2 to 50 mg/L ( F ol m a r et al. 1979, Hilde nbrand et al

. 1982, Wan et al. 1989— as cited in Pa n et al . 2002) , to hi gh val u es of > 1,000 mg/L (Geisy et al. 2000) . As presented in t h is report, the m o st rec e nt (unpublis hed) data from EPA standard (1991)

96-hour static renewal te sts of gl yphosate (Rode o tm ) with rai nbow trout conducted c oncurrently with a comparison to i m azapyr yielded an LC 50 of 782 mg/L fo r Rodeo ( 95% confide n ce interval of 719-845 mg/ L ), relati ve to the LC 50 of the A r senal tm he rbicide for m

ulation of 77,716 mg/L (22,305 mg imaza pyr/L) (Grue, C., pe rsonal communication 2003). Becaus e these latter tests were

conducted with fi sh fr om the sa me origin and ag e, in the sa m e labor atory, the re lative toxicity comparison is perhaps t h e most re le vant of all t h e pre v ious tes ting conducted. Base d on these results, the i nherent aqua tic toxicity of Rodeo ma y be appr oxi mately 28.5 to 99- fold more acutel y toxic to fis h than i m az apyr—depe ndi ng on whether th e comparison is m a de to the active ingredient

or the herbicide for m

u l ation, respectively. Us i ng the more conserva tive toxicity esti m a tes established by the other researchers previously re fe renced, this difference c ould increas e up to two
orders of ma gnitude mor e than th at develope d from the data of Sm ith et al . (2002) and Grue (pers comm). The wide varia ti on in glyphosate’s aquatic toxicity has been attributed to the dilution water, temperature, for m

ulation, and the a m ount of suspe n ded sedi ment in the water. Toxicity
appears t o i n crease wit h temperature, and decr ease with el evated pH a nd s u spende d sedi me nt ( W SDA 1993E, Schuette 1998).

A si milar c o mparison of the relative hazards to invertebrate s between glyphosate and i m a z apyr cannot be provided bec a use no test s have been conducted with inverte b rates at hi gh enoug h

concentrations of im azapyr to elicit mortality (i.e., NOEL and LC 50 val u es represented were the highest dose s tested). Howe ver, the relationship be twee n fis h and aquatic invertebrate toxicity for a given chemical rarely differs by more than an order of m a gnitude (generally less than 1⁄2) so it is

reasonable to expect a si m ilar relat i onship t o e x ist for the relative invertebrate hazards f r om glyphosate verses i m azapyr.

Glyphosate i s an orga nophosphate c o mpound, but it does not inhibit acet ylcholinester a se activity like organophosphate insecticides such as Nuvan tm or Diazi n on tm because the herbicide is m i ssing

an ester in its chem ical structure (Pan et al. 2002) . It elicits its herbicidal activity by inhibiting the enzyme 5-e nolpyruvyls h iki m ate- 3- phosphate synthase, whic h is ne e d ed by pla n ts t o synt hesize

choris mate —neede d in turn for pr otein synthesi s in plants. Although hi ghly soluble like i m aza p yr (solubility = 11,600 mg/ L at 25 o C) with low potential for bi oaccumulati on, glyphos a te—unlike

i m azapyr—i s not degraded signi ficantly in water by photodegradation (Sc huette 1998). It appears to adsorb readily to sediment, with half-lives on t h e order of 1.5 to 11.2 da ys, and s e di ment a ppear s to be the principal environm enta l sink for t h i s widel y us ed he rbicide. By comparison with

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O c tob e r 200 3 Pag e 81i m azapyr, gl yphosate has a low organic carbon pa rtition coeffi cient indicating it can be expected to

be substa ntially less mobile than i m aza pyr. I n an estuar y setting, the physical c h e m istr y of glyphosate s u ch as its la ck of phot odegradation and rea dy a d sorption to sedi ment, s uggests that glyphosate will be mor e persistent than i m azapyr. Recent results in Spartina treated meadows

have de monstrated that the rhizome concentra tions of glyphosate increa sed 231 to 591% over a three year pe riod, while s e di m e nt concentrations a d jacent to t h e plots de clined 88 to 96% (Kilbride

and Pa vegli o 2001) . These recent results show that the residual bioma ss of Sparti na could als o

serve as a re sidual comp art m ent of gl yphos ate for even tual rele ase to the int e rtidal envir o nment.

Although significa n tly more toxic t h a n i m a zapyr , th e aquatic toxicity ha zar d rating of the herbicide would still qualif y as pr actically non-toxic to slightly toxic based on EPA toxicity cr iteria (Table 3-12) and the species te s t ed. ( T he te rrestrial wild lif e toxicity rates sim ilar to im azapyr--practically non-toxic) . However

, at issue in t h e relative ris k comparis on is not si mply the i nhe rent aquatic toxicity of t h e compound, but also the esti m a ted application rates relative to im azapyr. According

to recent results by Patten and Ste nvall (2002), effective control with glyphosate was obtained onl y with m i ni mum applicati o n rates of 18 kg ae/ha, 10.7- fold great er th an the 1.68 kg ae/ h a needed for

control with i m az apyr. Thus , based on active i ngredient concentrations required for herbicide efficacy and inherent t o xicity, the use of gl yphos ate reduces the margi n of safet y relative to potential environmental expos ure concentrations by up t o thr ee orders of magnitude —irrespecti ve of the other associated ri sks from t h e surfa c tants r e quired for a pplication.

Surf a ctants

The inherent risks of usi ng either her b icide (i.e., imaza pyr or glyphosate) rises signi fi cantly when

mixe d wit h surfa c tants, t hus the choi ce of which surf a c tant is used is not t r ivial. In addition spray

volumes re quired di ffer by her b icide

. Glyphosa t e applications require 80 to 100 ga l/acre for efficacy, i n comparison to the 5 t o 20 gal/acre that can be used for i m azapyr to yield equivalent

results. As s p ecifie d on the product l a bel, glyphosate (as Rodeo tm ) require s the use of a non-ionic

surf actant f o r application. These would includ e surfa c tants s u ch as R-11 and LI- 700, whic h, as previousl y discusse d, are one to two orders of magnit u de more toxi c to rainbow trout tha n surfa c tants s u ch as Ha ste n or Agridex that can be used wit h imaza pyr ( se e Table 3-16). Figure 5- 1 depicts the range of pot ential hazar d quotients of f our sur f actants used with eit h er i m azapyr or glyphosate under the range of applic ation rates c o mmonly us ed. Thi s mode ling, conducted at an

assumed wat e r depth of 0.1 m ( 10 c m or appr oxi mately 4 i n che s ) shows how at least one sur f actant used, R-11, has potential to ex ceed a hazard quotient of 1.0, when equated to the 96-hr LC 50 toxicity val u es developed by Sm it h et al. (2003) for juvenile rainbow trout. The potential

exceedance in the sea-surface micr olayer on th e incom i ng tide woul d yield even higher hazard quotients, if only for a short period until dilution was achieved. However, as demonstrated in Figure 5-1, the crop-oil surfa c tants Agri- D ex a n d Ha sten pr ovide a subs tantial m a r g in of sa fet y relative to their application rates to ensure that neither would pose a toxic risk during application,

even at high application rates ab ove those required for adequate Spartina control with i m a z apyr.

FINAL

O c tob e r 200 3 Pag e 820 0. 2 0. 4 0. 6 0. 8

1 1. 2 1. 4

2. 5 5 10 20 40 80

Ap p l i cat i o n R a t e ( g al / acr e )Hazard Quotient R- 1 1

LI

- 7 0 0

H A ST EN

AG R I

- D EX

Figure 5-1: Haz a r d quotie nt (HQ) estimati on based on r a inbow trout LC50 val ues of
these surf act ant s as devel op ed b y Smith et al. (2003), w h ere HQ = estimated w a ter

co ncentr at ion/L C 50.

5.2 Un certaint ies and Data Gap s

Every ec ological risk a ssess ment has inherent uncertainties that can only be addressed f r o m additional st udies. The funda mental question in addressing t h e signi fica nce of the uncertainty in any risk ass e ss m e nt is t h e degr ee to whic h it c o uld qualify t h e risk c onc lusi ons. That is, in this
report we r e viewed the m o st recent data devel oped on the toxicity, fate, and degr adation o f

i m azapyr. These results i ndicated that i m azapyr has insigni ficant toxicity to aquatic and terrestrial

wildlif e , is not environmentally persi s tent, and does not bioc oncen trate or bioaccum ulate. W h ile

the risks t o ecological r eceptors appear extremel y low, sever a l data gaps exist. The followi ng bullets summarize some of the ma in data ga ps t h at, i f resol v ed,woul d e l i m inate ele m ents of the uncertainty in this assessm e nt. Uncertaintie s associated specificall y with the m a nner o f preparation and c onclusi ons of this ri sk assessment are summarized in Table 5-4.

• Studies pert aining to the effect of imazapyr on aquatic or water-depende nt species ot her

than f i sh are lim ited. No studies exam ining the toxicity of i m azapyr to a m phibians and reptiles were discovered in our literature review. No studies on the toxicity of imazapyr to marine fish typical of th ose areas where invasive Spartina is distributed in W a shington

State ha ve been conduct e d.

• Speci fic data on the toxicity of i m azapyr to se di ment-associate d orga nis m s typical of northte m p erate marine envir onm e n ts is ge nerally l acki ng and repre s ents a signi ficant data ga p.

• Residues of i m azapyr in treated Spart i na , and the degradation of t h e her b ic ide over ti me in plant tissue were not ide n tified in t h e literature. Exposure c a lculations i n this assessment

FINAL

O c tob e r 200 3 Pag e 83therefore relied on estimated concentrations in the plant tissue. Em pirical residues f r om plants woul d increase co nf idence in the exposure and risk estimates.

• Effe cts on the m i corhiz os phere and microflora in a treated estuary have not been explored. This subject area has not been investi g ated th oroughly for any herbicide us ed in a n est u ary setting to our knowledge . Long ter m

i m plications of herbici d e use on nutrient dyna mic s could e f fect microflora

.

• Effe cts on non-target sal t

- m ar sh plants native to areas Sparti na has c o lonized are poorly

understood. Li m ite d data on only a fe w s p ecies ha ve bee n reported.

• Persistence and stability of i m azapyr in dead and decayi ng Spartina is not known. Ca n leachate fr om decaying vegetation retain herbicid al activity thereby potent i ally delaying the recovery of native salt marsh plant s ?

• Dri f t conce n trations of i m azapyr off-site by treat m ent method (e .g., backpack, boom sprayer, etc.,) have not been quantif i ed. However, worst-case scenario exposure conditions

in direct a p plication sites did not indi cate signi fic a nt risk.

• Effe cts on marine phyt oplankt on: c ould her b ici d e treat m e nt s effect nutr i ent trans f er

to higher trophi c levels i f ph ytoplankton are inhibited?

• Effe cts on se a-surfa ce m i crolayer associated organism s a nd microf l ora in this surf ace water
fil m are not known.

While t h e a bove data ga ps represent uncertainty, the existing infor m ati on on the toxici ty and fate

of t h e comp ound i s subs tantial and s uggests t h at signi ficant negative i m pa cts would be unlikely i n studies to address the above data gaps—with the possible exc e ptions of e f fects on ot he r non-target plants and phytopla nkton.

FINAL

O c tob e r 200 3 Pag e 84Table 5-4: Unc e rtai nti es as soc iated w i th e c o l ogic a l ris k mode ling fo r i m azap y r

.

Parameter Source and Re sults
Missing
Informatio n (data gap s) Informatio n gap s where sour ces or stress ors are not ide n tifi ed or important aspe cts of the eco l og y are not known can a ffect ri sk conc lu sions. Al though it is be lieved tha t the imp o rtant p o tential sources of
adverse ef fects have been addr essed, i t is p o ssi ble that there w e re unmeasur ed or uncons idere d
chemical co nstit uents in the b a y that ar e cont rib u ting an uneval uated deg ree of risk to r e ceptor s in target ar eas. Conceptual

Model If rela tionshi ps b e tween sour ces and recep t ors ar e missing or inc o rrectly identi f ie d, risks could be
under- or overe s timated. To re duce this uncer t a inty, a concep t ual model wa s d e veloped that id entified

all known pathw ays (both compl e te and incompl e te) and recepto r trophic level s

. The overal l imp a ct of

this sour ce of u n certaint y on r i s k conclusi ons is unknown.

Use of Uncertainty (Safety) Fa ctors
for Calcul ating
TRVs Uncertainty (saf ety) fac t ors use d to der ive TRV s may not accur a tely re flect site condition s. Ho wever, the UFs app lied were conside r e d realist i c bas ed on data from va rious pub lished studies. Since published TRVs were not availa ble for all ROIs

, UFs were appl ie d. Risk estimat e s could be und er- or over-estima t ed using th is appr o a ch, as the UFs applied wer e co nsidered r eason able.

Laboratory
verses Fiel d Populatio ns Species u s ed i n labora t ory tox i city tests are n o t neces sarily s ubjected to the same de gree of nonchemical relat e d stresses as receptors in nat ural conditi ons. As such, cumulative effe cts of multiple

stressors (inclu ding chemic als) are not necess a rily th e same. It is d i ffic u lt to p r edict t he ef fect on ER A
results since la boratory versus natural conditi ons may stress species diffe rently. Due to likel y differenc es in t he health of la boratory p opula t ions and those inhabit i ng tar g et areas, diffe r ences in genetic d i versit y (hence res i stan ce to stre ssors), and possi ble im pacts of n on-ch emical stres s ors

, some unavoidabl e unc ertainty exists w hen extra polati n g laborat ory der i v ed data to f i eld situatio ns.

Use of Representat ive or Surrogat e Species Toxicologic a l st udies used spec ies that are r e lat ed to ta xa pres e n t in t he tar get a r eas, but are n o t
identica l . I n gen eral, th e grea ter the taxo nomic di fference, the gre a ter the uncert a i n ty in a pplica t io n of laboratory toxic i t y data t o recep t ors. I t is n o t kno w n whether l abo ratory te st spec i e s or rece ptors i n target ar eas are the most sensit i v e to a given ch emical cons titue n t.

Feeding Rat e s Feeding ra tes w e re assumed no t to var y

with se ason, bre eding condition , or wi t h other local fact ors. Reported f eedin g rates u ndoubt edly vary with a l l of thes e fac t ors because me tab o lic need s chan ge as does food avail a bility. Where p o ssible, estimate s of aver age fe e d ing rate s were derived f r om stu d ies that repo rted for multiple season s and are a s to c o mpensate for t h is poten tial unc ertainty . As s u c h

, while uncer taint y is int r oduced , t he effec t on ER A conclusi ons (i f any) is not q u a n tifiabl e.

5.3 Con c lu sion s and Reco mmen datio ns

With current technologie s, non-native Spartina er adication ca nnot be reali z ed in Was h ington State

without some elem ent of chem ical control f actored into the W S DA i n te grated pest mana ge ment

progra m . Current m e c h anical and bi ological contro l m e thods have not be en wholly effective

, and

the distributi on of Spartina is spreading at a rate of approxi mately 20 percent per year in som e locations. As Spartina spreads, cri tical habitat for shor ebir ds , j uvenile fish and shellf ish is lost.

These i m pacts directly or indirectly i m pact th r eatened species such as chinook sal m on, and commerical enterprises such as she llfish culture . The use of Rodeo tm (glyphosate) is the only currently a p proved herbi c ide for Spartina treatments, but its eff i cacy is hindered by mi ni m u m drytim e limits that are not possible under all est u ary conditi ons where Spartina is considered a

noxious wee d. Additional contol m e ans are unde r investigation, and the use of i m azapyr has be e n explored in t h is report as another pos s i ble che m ica l control me ans.

FINAL

O c tob e r 200 3 Pag e 85W e examined the potential ecologi cal risks from the use of i m az a pyr in an est u ar y setting t o control and eventually eradicate non-native Spar tina in Was h ington Stat e. Realistic im azapyr

exposure sc enarios in t h e estuary settings envisioned for Spartina contr o l did not yield aquatic concentrations or terrestrial doses that would pose significa nt risks to aquat i c or terrestrial wildlife

, even under t h e i m proba ble “upper li mit” conditi ons modeled. Onl y for sp ill scenarios where it was

assumed that avian and mammalia n wildli fe coul d ingest undilu ted spray solution was there the potential for signif i cant risk identif i ed, but wildli fe behavioral mechan isms m a ke this ri sk scenario largely unte nable.

Both i m az apyr and glyphosa te can be effective at Spartina control and both are essential l y sa fe for terrestrial and aquatic ani m als i f used in ac corda n ce with ma nufacturers recomme nda tions wit h adequate dr y-ti m e . However

, the use of i m az a pyr improves the margin of saf e ty relative to potentially t oxic e nvironm e n tal concentrations by three to four orders of ma gnitude over the existing use of gl yphosat e—depe nding on which s p ecies is considered in the risk assessment. This

im provement is due to the lower toxicity of imazapyr, lower active ingredient concentration

needed for Spartina cont rol, lower s p ray volumes of the her b icide/sur f acta nt solution r e quired for

eff ective treatm ent, and the ability to use crop-o il based surfactants which are them selves one to

two orders of ma gnitude less toxic tha n the non-io nic sur f acta n ts required for glyphosat e use.

I m a zapyr is highly mobil e , per s iste nt in soil s, a nd is a broad- spectrum herbi c ide. Although risks to

ani m al s fr om i m aza pyr use are insi gni fic a nt , it s us e ca n ca use signi f ic a n

t im pa c t s to no n

- ta r g e t vegetation i f ina ppr opriat ely applie d. T h ese risks are particularly ac ute for vasc ular plant s (li k e Spartina )

, although risks to algae ap pear to be signi f ica n

t l y less . In sedi me nt , ima zapyr is significantly less persistent than in soils, but it can still be expected to be de tectable for several

wee k s a f te r t r eat me nt. It s hould ther e f ore be applie d only to target species, avoi ding dri f t or see p a g e

to non-ta rget speci es a n d sedi me nt through obs er vation of we ather patter n s suc h as hi gh rai n s or wind. I m a z a pyr shoul d be us ed pri m arily i n area s where total vegeta tion control or eradication is

desir e d, or i n is olate d spot a ppl i cations due to re ports of its pote n tial to “leak” out of t a rget plant

roots int o s o il that c ont ai ns non- targe t plants . Ha nd s p ra y a p plications s h ould be use d on Spartina
clones a nd on the peri phery of Spart i na me adows to mini miz e spra ying of non-tar g et plant s and

poor c a nopy inter cept i on. Br oad cast system spraying can be cond ucted in the central portions o f Spartina me ado w s wit h

mi ni mal ris k o f dri f t a

n d ma xi mu m e f fic acy for Spartina control.

Photodegra dation of i m a zapyr in wat e r is extre m ely rapid. I n the tidal e xhange conditions where Spartina is found, diluti on is also e x tre m ely ra pid due to t h e fre quenc y of tidal exchange. For example, in W illapa Bay, the primary area where Spartina spp. is distribute d and poses t h e greatest
threat to ha bitat, there are generall y two high and two low tides within a 24-hour period. The average di fference between the high and low tide in W illapa ranges from 8.1 to 10.2 feet, with an average tida l pris m of 4.8 x 10 8 cubic yards (cy) and an average tidal f l ow discharge of 25,000 cy/second. Potentially toxic co ncentrations to aquatic animals will not occur under the range of application rates considered in this risk asse ssment and the dilution pr of iles presented in the estuary settings where Spartina occurs. The time of exposure is also reduced because of tidal exchange rat e s inherent t o W a shingt on’s coastal environments. The ove r all weight of e v idence

f r om this analysis suggests that i m a zapyr can be a safe

, highly eff ective treatm ent for Sparti na control and eradication in an estuary setting, and of fers a significantly i m proved risk sc enario ove r existing treat ment regi me s.

FINAL

O c tob e r 200 3 Pag e 86

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FINAL

O c tob e r 200 3 Pag e 94

### Appendix A

No Action Alternative for S p artina ControlTABL E OF CONTENT S

1.0 INTRODUCTION

............................................................................................................. ..... 1

2.0 OVERVIEW OF NO ACTION ALTERNATIVE

................................................................. 2

2.1 Im pacts of Spartina

.......................................................................................................... 2 2.2 Description of NAA

........................................................................................................ .. 3

3.0 DESCRIPTION OF NO ACTION ALTERNATIVE (NAA)

............................................... 4

3.1 Spartina Description

......................................................................................................... 4

4.0 DESCRIPTION OF CURRENT CONTROL METHODOLOGIES AND

EFFECTIVENESS .................................................................................................................

.... 8 4.1 Physical Removal

.......................................................................................................... ... 8

4.2 Mechanical

................................................................................................................ ........ 8

4.3 Che m ical

.................................................................................................................. ....... 10 4.4 Biological

................................................................................................................ ........ 11

5.0 IMPACTS OF CONTROL METHODS

............................................................................... 13 5.1 Physical Methods

.......................................................................................................... .. 13

5.2 Mechanical Methods ....................................................................................................... 1 3

5.3 Che m ical Methods

.......................................................................................................... 13

5.4 Biological Control Methods

........................................................................................... 13

5.5 Integrated P e st Managem e nt Plan

.................................................................................. 14

6.0 DISCUSSION

............................................................................................................... ........ 18

7.0 REFERENCES

............................................................................................................... ...... 22

LIST OF FIGURES

Figure A1. Locations of known Spartina spp. infestations in Puget Sound, Hood Canal and San Juan Islands (source: W S DA, 2002)

.......................................................................... 5 Figure A2. Locations of known Spartina spp. infestations and treatm ent sites in

W illapa Bay (source: WSDA, 2003)

........................................................................................ 6 Figure A3. Locations of known Spartina SPP. infestations in Grays Harbor (Source: W S DA 2002)

............................................................................................................ . 7

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No Ac tion Al t erna t ive for S part i n a Co nt ro l Pag e iLIST OF T ABLES

Table A-1. Physical Control Methods (source WSDA 1993)

........................................................ 8

Table A-2. Mechanical Contro l Methods (source W S DA 1993)

................................................ 10

Table A-3. Che m ical (Glyphosate) Cont rol Methods (source W S DA 1993)

............................... 11 Table A-4 . Biological Control Methods (source WSDA 1993)

.................................................. 12 Table A-5a. Potential Physical Habitat Im pacts of Different C ontrol Methodologies (USFW S 1997)

................................................................................................................... .... 15 Table A-5b. Potential Biological Im pacts of Control Methodol ogies (USFWS 1997)

............... 16

Table A-5c. Potential H u m a n Im pac t s (USFW S 1997)

............................................................... 17

Table A-6. Total Treatm en t Area and Methodology for Spartina in W a shington State

from 1997 through 2002 (WSDA 2002)

................................................................................ 18

Table A-6. Total Treatm en t Area and Methodology for Spartina in W a shington State

from 1997 through 2002 (WSDA 2002), Continued.............................................................. 19 Table A-7. Potential Efficacy of Treatm ent Meth ods on Spartina Infestations in W a shington State (source: W S DA 1993)

................................................................................................... 20

Table A-8. Summ ary of the m o st cost-effectiv e, integ r ated Spartina Managem e nt Practices (Norm a n and Patten, 1997)

.................................................................................................... 21

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No Ac tion Al t erna t ive for S part i n a Co nt ro l Pag e ii1.0 INTRODUCTION

This appendix provide s a descri ption of the No Action Alterna tive (NAA) for smooth cordgrass ( Spartina spp.) c ontrol a s practiced by the W a shi ngton St ate Depart ment of Agricult ure ( W SDA).

The NAA i s described as the progr a m that is presently be ing e m ploye d to eradica t e Spartina species. The W a shingt on State Sparti na control progra m is a cooperative effort betwe e n federal, state, local, tribal and private entitie s to eradicate this invasive weed. Sparti na is rapidl y colonizing

critical m u df lat habitat that is used extensively by native shellf ish, cultured shellf ish, salt m a rs h plants, migr atory birds

, juvenile fish and other wildli fe ( W SDA, 2002). The e f fica cy of current methods is not as high as desired to cont rol the invasion of this exotic species and Spartina

infestati on al ong Was h ington State ‘s coastal area s is spreadi n g rapidly. Current contr o l m e a s ures have inhere nt costs and environmental risks a ssociated with the m which a ddit i onal and/or alternative methods may alle viate, and thereby facilitate greater eff i ciency in Spartina control.

The focus of the NAA de scription is control of Spartina by herbicides and mechanical and physical methods. The Ecologic a l Risk Asse ss m e nt (ERA) pr esents infor m ati on for a potenti al change in the existing integrated pest m a nage ment plan (I PMP) for t h e purpos e of providing more e f fecti v e means of Spartina contr o l. The focus of the ERA is to evaluate the risks of using a more eff ective

control thr o ugh changes i n the c h e m ic al (herbicide ) component of the existi ng pr ogra m

.

Glyphosate ( i .e. Rode o® ) is currently the onl y che m ic al re gist ered for a q uatic use in the U.S. an d

its use has c e rtain shortc om ings. Glyphosate rea d ily binds t o s e di m e nt part icles, which reduces the translocation (transfer) of chem i cal down to the roots

. Daily i nundati on by tides cover plants wit h

mud and dir t , reducing herbicide e f fe ctiveness

. In addition, application must be timed with tidal fluctuations to allow glyphos ate to dry in roughl y 6 hours

. Decrease d drying ti m e i s directl y related to decreased efficiency or success in el i m i n ating t h e pl ant (IVM Te chnical Bull etin 2003). Hand spra yi ng with Rodeo re quires re-treat m e nt, is poorly adapted to l a rge meadows and t h e logistics of water transport are probl em atic. The efficacy of broadcast spra ying of Rodeo has been questiona ble and the aerial spraying of Rode o does not wor k

well (Patten 2002) . Phys ical control

methods are labor intensive, expens ive, and ha ve sm all effective areas of control. Mechanical

control is eff ective if used correctly but is limi t e d by sedi ment type ( s oft mud) and by se ason. Changes that have bee n sugge sted to i m prove the prese n t progra m include a cost-effe c tive

che m ic al control and/or a relatively inexpensiv e large-scale mechanical control (USFWS 1997). Patten (2002) sugge sts that a soluti on may be a che m i cal c ontr o l that is applied in low volumes an d

sm all concentrations in salt water, tha t has a m i ni mal non-target impa ct wit h no aquatic risk, is able to treat large areas with a m i ni mal need for re-tre at m e nt and is non-per s istent in the water. One

chem ical that m a y fit t h ese criteria is i m az apyr, available in the for m

ulations Ars e nal tm and Chopper tm , a m ongst ot hers. The ec ological haz a rds a nd ris k s fr om the use of i m az apyr are the pri m ary subject of the Ec ological Ris k Asse ss ment for which t h is NAA is a ppended.

The objective of this appendix is to present a desc ription of t h e IPM P in c ontrolling populations o f Spartina spp. in Washi n gton State inc l uding e f fect iv eness and potential environmental im pacts o f the progra m . This following sections pr ovide 1) a general ba ckground of the Spartina proble m in

Was h ington State, 2) a description of the pres ent control progra m , 3) th e potential environmental

i m pacts of t h e control me thods, and 4) th e e f ficacy of these cont rol m e t hodol ogies.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 12.0 OVERVIEW OF NO ACTION ALTE RNATIVE

The goal of the NAA is to eradicate Spartina usi ng conventi onal mecha n ical, physica l , biological

and che m ic a l m e thods ( g lyphos ate) . The proble m is that Spart i na sprea d s quickly and is extre m ely

diff icult to eradicate. The purpose of th e NAA pr ogra m is to control the s p read of Spartina using

methods wit h m i ni mal e nvironmenta l i m pa cts and greatest cost effectiveness.

Prior to the present era d ication progra m , passi ve m a nage me nt was use d t o contr o l Spartina s pp. inf e stations. Natural processes involving envi ronmental variables, pla n t genetics and bioti c interactions were thought to re gulate distribution and spread of Spartina spp. ( W SDA 1993)

. Agencies were to moni t o r infestations of Spartina spp. and part icipate in public outreac h activities

under what c a n be descri bed as a no c ontrol alterna tive. The no control progra m was characterized

as not bei n g successful i n the eradicating or slowing t h e spr ead of Spart i na infestati ons ( U SFWS 1997)

.

The 1995 Le gislature de s i gnated Wa s h ington Stat e De part ment of Agricult ure ( W SDA) as the lead
agency t o develop a Statewide Spar tina Mana ge ment Plan. Since t h at ti m e , WSD A ha s since served as the lead state agency for t h e eradication of Spartina . To acc o mplis h this, six area-wide Spartina ma nage ment pl ans (one for each water body covere d by a per m it) were develope d by WSDA for North Puget Sound, South Puget Sound, Hood Canal/ Cent ral Puget Sound, Grays

Harbor and W illapa Bay (Figur e A1). These programs were developed in c onjunction with

Was h ington Depart me nt of Fish a nd Wildli fe ( W DF W), Was h ington Depart me nt of Nat u

ral Resources (DNR)

, Unit ed States Fish and W ild li fe Ser v ice (USFWS) , Washington St ate Noxious

W e ed Control Board, tribal co mmu nities, and private landowne rs. These managem e nt plans

detailed hist orical infor m ation on known infest ati ons, past treat m e nt e f forts

, and pl ans for fut u

r e control seas ons. WSDA consoli d ate d infor m ation fr om the si x area-wi de mana ge ment plans int o a single dra f t document

. The State w ide Spartina M a nage ment Plan is update d yearly as new c ontrol and survey data/techniques become available. Current m e thodologies in pl ace to control Spartina

in Washi ngt on State incl ude digging, mowi ng, mowi ng in combination with herbicide, herbicide use only, see d ling re moval, and va rious mecha n ic al control methods.

The NAA presently in operation is referred to as the Integrat ed Pest Management (IPMP) plan.

The IPMP is based on the coor dinated use of multiple preventa tive, biological, mechanical, physical, and che m ical t r eat m e nts methodol ogies to contr o l a nd eradicate the Spartina inf e station in Washingt on State.

2.1 IMPACTS OF SPARTI N

A

Spartina can alter ecological process e s that gove rn wetla nd e c osyste m function. I n fes t ations ca n alter the physical aspect , structure, a n d spatial configur ation of wetlands t h rough dense growt h and

sedim e nt accumulation

. The four species now found in W a shi ngton State out com p ete and displace beneficial native vegetation and also thr eaten to severely i m pact economicall y i m portant
shellfish cult ures. Shell f i s h are i m pacted by Spart i na encroac h ing on the a v ailable area for oyster

cultivation and reduction of oyster growth by de creasing the am ount of nutrients reaching the oyster be ds ( W SDA 2002). This oc curs as t h e plants trap sedi m e nt, which reduc es the flow o f water through river c h a nnels and c h anges t h e el evation of m udflats. Although t h e a m ount of

sedi m e nt accumulation is variable from site to site, Spartina' s dense root a nd ste m s e ffectively trap

sedim e nt at higher rates than nor mal, altering water m ovement by f illing shore lines and river deltas

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 2and possibl y causi ng fl ooding during peri ods of hea vy rai n. Spartina spp. de stroy i m portant migratory shorebird and waterf owl habitat by reduc ing their ability to move, rest and forage on open mudfla ts. Spartina also aff ects f i sheries because f i sh utilize estuaries as nursing grounds or

fora ging site s . Spartina can also ove r take intertidal sea grass beds that pr ovide i m port a nt habitat

for juvenile fish (USFWS 1997).

2.2 DESC RIPTI O N OF NA A

Spartina pos es challenge s to imple m enting contr o l m e th odol ogies and is particularly difficult to eradicate because it grows in soft mud and has an exte nsive r oot net w ork. It also spreads rapidly i n areas that are hard to t r averse and apply treat ment

. These large infestations of Spartina are difficult to c ontrol with present met hodol ogies a nd no indivi dual method currently being used is

able to eff e ctively control Spartina i n festations ( U SFWS 1997). Curre ntly there are over 15,000

acres infeste d in Willapa Bay, over 4,000 acres in Snohomish Co unty a n d m i nor infe stations in eight other c ounties i n wester n Was h ington ( W SDA 2002)

.

The c u rrent control pr ogra m involves active In tegrated Pest Mana ge m e nt I P M to c o mbat

infestati ons of Spartina s pp. usi ng me chanical, physical, biological , che m i cal and/or a combination

of thes e m e t hods. The I P MP was chosen as the c u rrent progr a m contr o l methodology because it is a comprehensive approach that co mbines a ma nage ment pr ocess wi t h the best comp onents of the other methods ( W SDA 2002). The c u rrent er adic ation progra m involve s four steps:

1. Preventing an existing inf e st ation from producing seed;

2. Treating a n existing infe station for se veral consec utive years using I P M;

3. After successful eradicati on is achieve d, monitoring the area and removing new seedlings to ensure no re- e st ablishment occurs and; and

4. Conti nuing t o survey s h orelines, educ ate the publi c and follow-up on possi ble sightings

of ne w infe stations.

This is the most promising approach to re gionally sta b ilize and decrease noxious we ed

distributions . The curre nt progra m i nvolves t h e de liberate se lection, inte gration, and directed use of pla n t population suppression meas ures on the ba sis of pre d icted economic, environmental

, and sociological conse quenc es. When these measur es are succ essfully a p plied, plant populations should be prevented from attaini n g economical ly and/or e nvironmenta lly da maging densities (USFWS 1997).

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 33.0 DESCRIPTION OF NO ACTION ALTERNATIVE (NAA)

3.1 SPARTI N

A DESCRIPTI O N

Spartina is commonly known as cor dgrass and i s an invasive weed that inhabits mudf lats, salt

marshes and estuaries thr oughout Wa shington Sta t e’s coastal a r eas. There are now four species of Spartina found in Wa shi ngton’s wate rs including Spartina alt e rniflora, Spar tina patens, Spartina anglica and a ne wly dis c overed spe c ies fou nd i n the fall of 2001, whic h is Sparti na densiflora. Spartina spp. are curre ntly disrupti ng several native P aci fic coastal ecosystems i n western

Was h ington

.

Spartina is a success f ul i nvader beca use of its hi gh ra te of spr ead, its tall a nd dense canopy that c a n shade out other plants, a nd its ability to colonize low intertida l regions (Daehler and Strong 1994; WSDA 1993). The stems are stout and the rhizom es for m

a n extensive r oot syste m t h at is roughl y five ti m e s la rger than its above ground biomass

. Once establi s hed, Spartina spreads vegetatively,

for m ing ring-shaped clumps of indi vidual clone s

. These cl ones are tall and c onspic uous a g ainst open mudfla ts. New ste m s grow al ong the outer edge of the r i ng, gr aduall y increasing its dia m eter with each growing seas on, while ol d, dying ve geta tion can be found i n the m i ddl e . As clone s spread, the y grow into e ach other, for m ing a de nse Spartina m o noculture that overgrows native plants (Da e hler and Strong 1994). Zi pperer (1996) has documented the potential of exotic species to change t h e physical structure and alter the ecological functioning of re gional ecosyste m s

. Spartina f o llows this pattern well sinc e it out competes and physica lly displaces native vegetation by converting littoral mudf lats to salt m a rshes. This invasion could mani f e st into large-scale ecological changes t h at t h reaten to adversely i m pact f

i sheries, shellf ish be ds, water f owl m i grations

and ot her wi ldlife depe ndant on nati ve coastal ma rshes.

3.1.1 Origin and Geographic Area

Spartina alterniflora typifies an i nvasive spe c ies by ha ving a wide tolerance to habitat require ment s, fa st disper sal rate, clonal reproduc ti on (fr o m a s i ngle plant s p reading as e xually) and

fe w to no natural predat ors in its invaded range ( Z ipperer 1996). Spartina alterniflora w a s m o st likely introduced to the W a shington coast when it was used in the packing of oysters from the Eas t
Coast for shi pping duri n g the late 1800s. Spartina alterniflora was also int e ntionally pl anted by a gun cl ub be tween 1941 and 1946 t o stabilize bank er osion on t h eir property i n Padilla Bay. Spartina anglica wa s also intentiona lly introduce d to stabilize dikes and provide forge for cattle in

Port Sus a n Bay (Fi g. A- 1). The pat h wa ys of introduction for both Sparti na patens a n d the newly

discovere d S. densiflora are not curre ntly known. Spartina s p ecies have s p read throughout coastal Washington State and pr esently, te n counties i n western Was h ington have one or more infestations

of Spartina alterniflora, Sparti na anglica, Spartina pate n s or Spartina densiflora ( F igures A1 through A3)

. These incl ude Cla lla m, Grays Harbor, Is land, J e fferson, Ki ng, Kitsap, Paci fic, San Juan, Ska g it and Snohomish c ounti e s. Spartina infestati ons range from one col ony in Clalla m County measuring 50 f e et in diam eter to m o re than 7,800 solid acres spread throughout W illapa Bay in Paci fic County ( F igure A2)

. Spartina infests over 8,000 s o lid ac res and has spread over

more than 20,000 total a c res in Wa shington State.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 4Fi gure A 1

. L o ca ti o n s of kn ow n Spa r tina spp. in fes t ations in P u ge t S o und, H o od Canal and S a n Juan Islands (Source: WSDA 2002)

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 5Fi gure A 2

. L o ca ti o n s of kn ow n Spa r tina spp. infestations and tre a tm ent si tes in Willapa B a y (Source: WSDA

2 003 )

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 6Fi gure A 3

. L o ca ti o n s of kn ow n Spa r tina SPP. inf e st at io ns in Gray s Ha rbo r ( S o u rce: WSDA 200 2)

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 74.0 DESCRIPTION OF CURREN T CONTROL METHODOLOGIES AND
EFFECTIVENESS

Current cont rol m e thods vary in effectiveness, depending on size of infestation, age of plants

, topogra phy, and pr oxi mit y to a g ricult ural , aquacul t ural, or buil t environme n ts.

4.1 PHYSI CAL REMOVAL

The Physical Re moval M e thod pri m ar ily involves manu al labor m e thods. Cu rrent phys ical control

methods bei ng us ed in clude the following:

• Hand pulling, Digging

This method is e f fective for s m all pat c hes and on young pla n ts

.

• Covering

This i nvolve s layering ( c overing) Spartina inf e stations with geo-te xtile f a

bric mats that inhibit light penetration i n order to stop phot osynt hesis. This method is only used for s m all patches of Spartina

.

Most physic al control methods are la bor intensiv e and ti me consuming but m a nual re moval can be

effective for removing seedlings and very s m all infestati ons or to prevent seed production and spread (Table A1). Volunteer organizations a nd tribal agencies have conducte d s m all-scal e

re m o val proj ects succe ss fully.

Table A-1. Ph y s ica l Co ntrol Meth o ds (source WSD A 1993)

Physi cal
Control

Method Current

Use M o s t Prac ti ca l Applicati ons / Us e in pr esent

program Use Constraints

Hand pul lin g or dig g in g y e s Eradic a t i on of s m a ll, is o l at ed

c l umps , s e e d li ngs

, or s pars e infes t a t io ns / l i mi te d us e Lab or-int ens iv e; m u lti p le tre a tm ents may be req u ire d ; pla n ts

mus t b e ac c e s s i bl e by fo ot; pul li ng l i m ite d t o s e e d li ngs s m all

eno ugh to pu ll

Cov e ring y e s Eradic a t i on of s m a ll c o lo ni es /

limi t ed us e Lab or-int ens iv e ov er a l a rg e ar ea; wi nd or wav e s may dis l od ge

c o v e rs ; moni tori ng duri ng tr eat me nt r equ ired; bi od egra dab le

mater i als are pref erred; no n-bi od egr ada ble ma teri als will re quir e

remov a l aft e r us e ; c o v e rs may be bur ied by s edi men t
Dewatering/

Draini ng n o E r a d i c a t i on of me diu m -s iz e d

c o loni es , etc Not prac tic a l for la rge ar eas or gra d u a l s l o pes n ear s e a lev e l;
diffic u lty in ob tai n i ng p e rm its ; eff i c a c y unk nown

Floo din g /

inu nda tin g no Eradic a t i on of me diu m - s i z ed

c o loni es / e t c

. Not prac tic a l; s hor elin e t opo gra phy mus t b e a m en ab le ; dif f ic ulty
in o b ta ini ng per mit s

Burni ng/f l a m in g no Eradic a t i on of me diu m - s i z ed

c o loni es Treat men t s h o u ld be d o n e pr ior t o s eed s e t, d u rin g dry weath e r, and whe n win d b l ows s m ok e away f r om i n h abit ed are a s ;

s m ok e mi ght be to x i c to work ers ; fla m in g is l abor- i nt en s i v e ; difficu lty in o b tai n i ng p e rmits

4.2 MECHANICAL

This methodology i nvol ves the use of m a c h inery to contr o l Spartina from a large area. Machines

include t ool s with powe r sources and range from hand- hel d brus h c u tters to a m phibious trac k vehicles and barge- mounted dredge s. State and federal age n cies have aggressivel y pursued the

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 8treat m e nt of Spartina meadows usi n g m e chanical control. The goal of m e chanical ly treating Spartina m e adows is to reduce curre nt seed production, kill Spartina plants, stress the rem a ining plants suffic iently to reduce seed production in subseque nt years, and reduce the a m ount of herbicide used in future applications while in crea sing spray e f ficacy a nd reducing c o s t (USFWS 1997; WSDA 2002) . This m e t hod is not selective and can da ma ge desira ble vegetation and distur b

soil. This method is nor mally used only on e v e n terrain wi th few obst a cles. As with manual

re m o val, control e f forts are nor mal l y ti m e d to pre-e m pt se ed producti on. Me cha n ical control

efforts are a l ways followed by m e a s ures ( m ec ha nical or other) to kill shoots from resprouting plants and s eedlings s p r outing from the seedban k. Mec h ani cal control methods e v a l uated in the EIS ( W SDA 1993) include dredging, diggi ng, plowing, rototilling, crus hing, mowing, and harvesting ( T able A-2) . Current mec h ani cal contr o l methods being us ed include:

• Mow i ng
Repeated mowing in late spring and summ er ca n preve n t se ed production, dela y col o ny expansi on, weake n root vigor and r e duce sa me season re-gr o wth. Mowing can incr eas e susceptibility to other control methods and can reduce the am o unt of herbicide needed to

control Spar tina

.

• Mechanical sub-soiling and Rototill ing

Mechanical sub-soiling and rototilling in volve the m e chanical disruption of Spartina, its
root syste m , and the supporting substr ate by a ripping i m ple m e n t m o unted t o a a m phibi ous tracked vehi cle ( W SDA 1993) . This is effecti v e on some upl and wee d s because it results

in the desiccation of roots. Rototilling can in crease susceptibility to other control methods

and can reduce the am ount of he rbici d e nee d ed t o control Spar tina

.

• Crushi ng
This method destroys the abovegr ound portion, a n d can affe ct the below gr ound root ma ss. Crushi ng is only use d in solid m e adows of Spar tina . Treat m ent of Spartina clones woul d

involve ha ving to transit across ope n m u dflat fr om one clone to another. Som e of the potential e n vironmental i m pacts may be mi ni mi zed since this method is only used on

meadows and not used on clone s.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 9Table A-2. Me cha nica l Con t rol Methods (source WSD A 1993)

Mech ani cal

Control

Method Current

Use Most Pra c tic a l A pplic ations Use Constrai nts

Mowin g y e s Prev enti on or re du c t ion o f s e e d s e t;
del ay of ex pans i o n of s m all to lar ge

mon o ty pic c o l oni e s Mult ipl e tr eat men t s requir ed t o k ill pl ants ; l abor
inte ns iv e if ha ndh eld eq uip m e n t us e d ; tre a tm ent
befor e s e e d s e t Diggi ng y e s Eradic a t i on of s m a ll m o n o ty pic c o lo ni es where s e d i m ent h a s ac c r eted Mus t b e ac c e s s i bl e fro m s hor e; m i g h t n o t b e
pos s i ble on s o ft s e dim ents

Crus hing y e s Prev enti on or re du c t ion o f s e e d s e t;
reduc ti on of s m a ll to l a rge mo noty p ic

c o loni es

. Mult ipl e tr eat men t s requir ed f o r er ad ic atio n;

c r us hing by foot s hou ld be l i m i te d to s m all c l ones

, whereas mec h a n i c al c r us hers c an b e us ed for larg e

c l ones ; h eav y mac h in ery not ap propr iate d f o r us e in s o ft s u bs trates ; lab o r i n te ns iv e if don e by f oot;

treat men t s h o u ld b e do ne ear ly in t h e growin g

s eas on if pos s i bl e. Rototi lli ng y e s Prev enti on or re du c t ion o f s e e d s e t;
del ay of ex p ans io n of s m all to lar ge

mon o ty pic c o l oni e s Effec t iv e d u rin g wi nter but ex trem ely s l ow;

ex pens iv e t o o per ate mac h i nery

Dredgi n g n o Eradication of la rge monotypic
infestations wher e s edi me nt ac c r eti on has des troy e d n a v i ga ble c h an nels M u st be a cce ssi b l e from wa te r

Harv es ting no Prev enti on or re du c t ion o f s e e d s e t Requir e s mark et f o r pro duc ts ; c oul d only b e d one where c o l ony s p re ad wo uld no t b e pr obl ema t ic ;

s hould be c ond uc t ed t o a u g m en t c o n t rol e fforts and

not t o m a x i m i z e y i eld.

4.3 CHE MICAL

The Was h ington State Depart m e nt of Agricult ure ( W SDA) has legislative responsibil ity over the

control of noxious a nd invasive weeds in the State of Washi ngt on. Under t h is mandate , the age n c y is authorized to use herbicides selectively to c ontr o l invasive weeds

. Gl yposate ( R odeo®) and 2,4- dichlorophe noxya cetic acid (2,4- D) were the t w o che m icals e v aluated in t h e Envir o nmental I m pa ct
State m ent ( E IS) ( W SDA 1993). 2 ,4-D has not been use d since it is not registere d for use for Spartina control in marine environme n ts in Was h i ngton State. Rodeo® ha s be en r e gist ered for use

in the m a ri ne environme n t. It is a non-selectiv e herbicide that affects the growth processes i n plants. Glyphosate (the active ingredient) tightly binds to soil particles, reducing its ability to contaminate groundwater while microorganisms br eak it down in water and sedi ment. Rode o® i s an effe ctive and relativel y non-toxic herbicide tha t is effective on a wi de range of pla n t species but

it m u st be used wit h a nonionic surfactant (R-11 ® Spreader Acitvator, X-77 ® Spreader , or LI-700 ® ) to help c ove r the plant a nd reduce t h e sur f ace t e nsion of spray droplet s ( W SDA, 2002). Two

differe n t met hodol ogies a r e used to a p ply the he rbi c ide (Ta b le A-3) a s summarized below.

• Herbicide (handheld gr ound applic ation)

Ground application of gl yphos ate fr om a backpac k unit, low pressure or hi gh pressure unit,

is eff e ctive for treati ng cl ones a nd me adows.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 10• Herbicide (broadcast ground appli c ation)

Applicati on by precision sprayer ve hicle or airb oat is tim e d to coinci de with the maximum susceptibilit y of the plant to increase efficacy (i.e. applicat ion at low tide). Broadcast application is ef fective f o r treating clones and meadows.

• Herbicide (aerial application) –

Aerial application by helicopter is timed to coincide with the maxi mum susceptibility of the plant to incr ease efficacy (i.e., application at lo w tide). Aerial application is effecti v e at seed pre v ent i on, a nd i n upper elevation Spartina meadows, c a n reduc e pla n t densit y.

Table A-3. Che m ic al (Gl y p h o sate ) Contro l Metho ds (source WSD A 1993)

Chemic al
Control Most Practical A pplications Use Constraints

Aerial Spray Eradic a t i on of larg e mo noty p ic
infes t a t io ns where s edim ent

ac c r etion has d e s t roy ed

nav iga b l e c h a nne l s Helic opt er: quic k f o r lar ge area ; s p ra y ball c a n m i ni miz e drif t a nd

o v e r sp ra y. Bo at, Tru ck, ATV Sp ra yi n g : more co ntrol th an h e lico p ter ; reduc ed p o s s i bility of dr ift ov ers p ray ; more tim e a nd la b o r th an helic o p ter

. Ground Applic a t io n Eradic a t i on of s m a ll m o n o ty pic

c o loni es where s e dim ent has

ac c r eted Wic k i ng: m a y req u i re l e s s herbic i de f o r c ontro l; no pos s i bil i ty of

ov ers p ray ; may re quire s e v e ral pas s e s ac ros s plant ; l a bor i n te ns iv e. Bac k

- pac k Spray : alm o s t twic e as ra pid ap plic at ion as wic k i ng;

eas ier t h a n wic k i n g ; s o m e dri ft or ov ers p ray c ould oc c u r.

In several st udies, gl yphosate applica tions have ha d m i xed e ffectiveness (e fficacy ra nged fr om 0 t o 100 perce n t ) in controlling Spartina . Short dryi ng ti m e s caus e the tides to wash gl yphosate off the treated plants and thus limit its eff i cacy in controlling Spartina . A rece nt study in Willapa Bay

found no si gnific a nt re duction i n Spartina ste m de nsity whe n applie d by helicopter using a 5 percent solution. Howe ver, the sa me concentrat ion of Rode o® (5 perce n t Rode o®, 95 percent

water/surf actant) applied with a hand-held wand resulted in an 84 perce n t reduction in Spartina

ste m de nsity ( W SDA 2002). Killbri de et al., (1995) also indi cated that gr ound rather than aeria l

treatm e nts obtained greater control

. Ground treat m e nts al so increased herbicide contact by applying higher conce n trations of che m ical with a brush a nd by the clea ni ng action of wiping the

che m ic al on the plant le aves. Wipi ng her b icide onto plants both cle a ns the dirt off plants a n d applies herbicide, but is labor intensive. Ground, compared to aerial applications decreases the

a m ount of herbicide dri f t

.

Appl ying t h e herbicide t o plants be fore seeds ar e produced a nd when t h e weed i s most susceptibl e is crucial to the eff ectiveness of the treatm e nt. The herbicide m u st be a p plied during an outgoi ng tide for ma xi mum drying ti m e . Gly phosate is eff e ctive f o r clone an d see d l i ng control i f using high rate and spra y volume. It is also good for hi gh me a dows where drying ti me is greater than 12 hour s but is probl e m atic in intertidal m e a dows with s hort dry ti mes (Patten 2002). Decr eased dryi ng tim e usually results in decreased eff i c i ency (I VM Technical Bulletin 1987)

.

4.4 BIOL OGICAL

The Biol ogi cal m e thods involve the use of bi ologically base d controls, s u ch as pathogens, insects

, livestock, ge netic engine ering, and c o mpetitive plan t species to m a na ge infe stations of noxious species (Table A-4). The purpose of biological c ont rol is not to eradicate weeds, but to reduce the

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 11infestati on a nd ke ep t h e m at low, manageable le vels

. After t h eir introduc tion, biocont rol agents ca n take 5 to 12 years to be com e esta bli s hed and i n c r ease to numbers large enough to c a use da mage

. There is al so a long t i m e fra m e to complete te sting and gain regulatory approvals. Once established, effective biological controls provid e an inexpensi v e, long-te r m , and non-toxic means to control weed populati ons

. The pl anthopper, Prokelisia marginata, was sele cted as the most

prom i s ing natural enemy because of i t s known pot ency against Spartina alt e rniflora a n d its narrow host range. This insect sucks the sap f r om the leaf veins of Spartina , depl eting its energy supply. In addition, P. marginata har m s Spartina by inse rting its eggs between the leaf layers, scarring the

leaves and c a using struct ural da m a ge to the va scul ar syste m . Appr oxi mat e ly 200,000 planthoppers

were release d in 2001 and obser vations indicated these insects have reproduced and the i r offs pring are currently fee d ing a n d developi ng on the pla n ts (Grevsta d 2001). Prokelisia marginata , ha d an unusually de vastating effect on Spartina alterniflora from Will apa Bay and da mage to t h e plant s i s just beginning to be vis i ble (Grevst a d 2001). Release d of Prokelisia marginata we re m a de t o a

re m o te population of Spartina angli c a in Puget Sound during 2003. Potential insect agents f o r control of S. densiflora a nd S. patens have not be e n investi g ate d.

Direct grazi ng by domestic livestock c ould a f fect the health and vigor of Spartina infes t ations and might be a possible biological cont rol m echa n is m where the m udflat substrate would suppor t grazing lives tock.

Table A-4 . Bio l ogi cal Con t rol Methods (source WSD A 1993)

Biological

Control

Method Most Practical A pplications Use Constraints Targe t Ins e c t Plant ho pper

, Prok elis ia mar g in ata , h o lds

prom is e for larg e- s c a le c ontro l of s e ed prod uc tion in Spar tina alt e rn iflor a Need t o re leas e in s e c t s at many s i t e s throug ho ut t he
infes t e d ar ea to bu ild up hig h d ens it ie s need ed to c o ntro l Sparti na L i ve sto ck
Graz ing Eradic a t i on of s m a ll c o l oni es

m o no sp e c i f i c st and s o f Sp arti na Soft mud s ubs trat e will hi nder graz i n g

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 125.0 IMPACTS OF CONTROL METHODS

5.1 PHYSI CAL METHODS

Environmental impacts associated with phys i cal m e thods include soil erosion, sedi m e nt mobilization, non-tar g et species mort ality, noxiou s plant dispe r sal, soil compacti on, di sruption of aquatic food webs , and safet y of la borers. The severity of i m pacts is dependent both on the speci fic physical m e t h od chos en a n d size of ar ea treated. I m pacts associated wit h all physical methods would be expe cted to incr ease wit h the size of ar ea treated. Depe nding on treat m ent method, many impacts can be mitigated by using appropriate procedures and materials and by

carefull y ti ming treat ments (USFWS 1997)

.

5.2 MECHANICAL MET H ODS

Signi ficant i m pacts include noxious plant disper s a l, soil compaction, sedi ment mobili zation, nontarget plant and ani m al mortality, increased wat e r turbidity, and disr upti on of a quati c food we bs.

The extent of t h ese i m pacts varies with treat me nt met h od and siz e of treat m e n t area. Many

im pacts can be m itigated by using appropriate procedures and m a te rials, and by carefully tim i ng

treat m e nts

. Harvesting does not halt infe station sp read a nd r e quires a market for pla n t product s , but coul d be bene ficial a s a method of c ontro lling seed pr oduc tion. Diggi ng, rototilling, crushi ng, and/or mowi ng woul d be appli cable in some situations f o r

some species ( U SFWS 1997).

5.3 CHE MICAL METH OD S

The potentia l impacts fr om use of glyphosate result fr om the t oxicity of the herbicide or from ot her

factors

, such as loss of ve getati on, algal blooms, loss of oxyge n in water, and erosion and sedi ment instability f r om loss of plant cover. The m a gnitude of the toxic impacts depends on the concentration of glyphosate in the environment, t h e toxicity of glyphosate, and the extent to whic h humans, wil d life, a nd nontarget pla n ts could be expose d to glyphosate. Although no significa nt
i m pacts from glyphos ate are expect ed for wildl i fe and humans, there c ould be toxic effects o n eelgrass and algae.

Biode gradati on and toxici ty studies in fish, inverte b rates, a nd ma mmals of the s u rfacta n ts approve d

f o r use in W a shington and chem icals sim ilar to th e surf actants, indicate that the environmental

concentrations of sur f act ants that would result fr om s p raying are not expected to ha ve signi ficant

adverse i m p acts to huma n health or the environment. If the herbic ide is not applied appropriately,

it could a f fe ct non-tar g et vegetation. However

, re su lts of human healt h ris k asse ss ments indicate

that the concentrations of glyphosate to which t h e public could be exposed are expected to be

below levels of co ncern. (USFWS 1997).

5.4 BIOL OGICAL CONTROL METHODS

There is an ecological risk involve d in introduc tion of non-indigenous bio-control organis m s

. These orga nis m s mi ght cause possible death or inju ry of native species or agricultural grasses. Livestock grazing might negatively impact sediments, soils, water quality, and non-target biota .

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 135.5 INTEGRAT ED PEST MANAGE ME NT PLAN

I m pacts due to i m ple m e n tation of t h e IPMP cont rol m e thods can ha ve c o mbined i m pacts from

i m ple m entat i on of the individual methods, with som e method combinat ions having additiona l synergistic e f fects. Combin ation of methods can e xpose Sparti na to m u ltiple stresses, resulting in a

reduction in environmental i m pa cts and frequenc y of use of each c ontrol m e thodol ogy ( U SFWS 1997)

Tables A-5a through A5c summ ari ze the i m pacts of the diff ere n t control m e t h odologies on Willapa Bay (USFWS 1997). These tables are excerpted from the EA c onducte d by USFWS i n 1997 (EA based on the 1993 EIS for western Was h ington coastal are a s). These i m pacts ar e specif i c to W illapa Bay but they can be generalized and extra polated to include all of the Sparti na infested areas along the Washington coast.

The USFWS, (1997) has indicated that Spartina is cha ngi ng ha bitat for fis h spe c ies. Spartin a

converts us a b le intertidal habitat to high m e a d ow that is available to fish only during the highest

tides. There is concern t h at the Spart i na m e a d ows are less comple x fr om an ecologica l perspective and will negatively i m pa ct fish. The r e are also c oncerns that control met hods negati vely i m pact
f i sh. The primary concern is that chemicals used to kill Spartina mi g h t i m p a c t o r c o mp r o mi s e fi s h

health.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 14Table A-5a

. Po ten t ial Ph y s ic al Ha b i tat Im pacts
of Diffe r en t Con t rol Methodo logi es (USFWS 199 7)

Physi cal
Issu es IPMP Physi cal/ M e c han i cal Onl y Chemic al Onl y

Soils and Topograph y Sparti na -f ac ilit ate d s edim ent
buil d u p i n s c a ttere d c l on es an d

mea dows woul d b e s l owed or halt ed in t he s h ort e s t am oun t of

time . L o w c onc ent ratio n s of

c hemic als wo uld b i nd to s o i l a nd

then bre a k down

. Sparti na -f ac ilit ate d s edim ent

buil d u p i n s c a ttere d c l on es woul d
be s l owe d or ha lte d , b u t s o m e

mea dows woul d c onti n u e to

c apture s e di men t

for m any y ears Sparti na -f ac ilit ate d s edim ent bu ild up in s c a tter ed c l o n e s and mea dows
would be s l owed o r halt ed, b u t ov er a lo ng er p e rio d of time th an wi th

I PMP. Ch emic a l s would bi nd t o s o i l
and the n br eak d o w n.

Hydrology Altera tio n of na tur a l fl ow p a tter n s would be s l owed o v er the nex t few y ears an d rev e rs ed i n th e long- run. Altera tio n of na tur a l fl ow p a tter n s would lik ely be s l o w ed ov er t he

nex t few y e ars

. Ch ang es in wa ter

mov e m ent du e to Sparti na wo ul d

c ontin ue in areas where c o n t rol

c ould not be ac c o mpl i s hed. Altera tio n of na tur a l fl ow p a tter n s would be s l owed o v er the nex t
dec ad e, a nd pos s i bly rev e rs ed

ev entu a lly

.

Water Qual ity Poten t ia l f o r s hort- term herb i c i de

c ontam in atio n. Gr eates t pot ent ial
for re duc in g te mp eratur e inc r eas es an d c h a nges i n s a li nity

and ox y gen lev e ls

c aus ed by Spartina

. Greates t l o c a liz e d inc r eas es in

s u s pende d s e d i m ents

. Re duc ed pote n ti al f o r t e mp e r ature
inc r eas es an d c h a nges i n s a li nity

and ox y gen lev e ls

, but to a l e s s e r degr ee t h a n ot her meth ods

. Poten t ia l f o r her bi c i de

c ontam in atio n. Re duc ed pot ent ial
for te mp erat ure i n c r eas es and

c hang es in s a l i ni ty and ox y gen lev e ls

.

Ambient
Sound Short t e rm inc r eas ed a m b i en t
nois e lev e ls as s o c i ate d wit h us e of a i rcraft, airb oats

, weed cutters,

etc

. A hig her r e li anc e on l a rge

mac h i nery th at c o uld w o rk nig h t
and day wo uld lik e l y res u lt i n

more no is e th an ot her m e th ods

. Even with use o f a i rcraft, t h is
meth od w oul d g e n e rate les s tot a l
nois e t h a n ot her m e tho d s ma inly
bec aus e of re duc e d work

opp ortu nity . Grou n d -bas ed c hem ic al

app lic ati on mac h i n ery tends t o
gen erat e l e s s nois e th an

mec h a n ic al met h o d s

. Air Quality Of met hods

, leas t pote n ti al f o r a i r poll u ti on from c o m bus tio n of
fos s il fu els du e t o hig her

e ffi ci en cy.

Les s pote n ti al for herbic i de drift

than Che m ic al O n l y Meth od. Of met hods

, hig h e s t pote n ti al f o r poll u ti on from c o m bus tio n of
fossil fu els. Of met hods

, ther e would be a hig her pote n ti al f o r h e rbic ide s p r a y drift du e to to tal rel i anc e on c hemic a l c ontr o l.
Pollu tio n fr om bur nin g fossil f u e l s may be comp ara b l e to tha t of th e Ph ysi ca l / M e ch an i c a l Me tho d

.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 15Table A-5b

. Po ten t ial Biolog ica l Im pacts o f Co ntrol Meth o d olo g ies (USFWS 199 7)

Biological

I s s u e s P M P Physical/Mecha n i c a l O n l y C h e m i c a l O n l y Vegetati on The greatest acreage of native plant habitat would be preserved and eventually restored. All existing mudflat habitat supportin g macroalgae and eelgrass
would be maintained. Some Spartina dominated areas
would be converted to
mudflat and some would

convert to native saltmarsh.
Exist i ng native saltmarsh would be preserved. Impacts to vegetation du e to Spartina spread would be minimized. Of the methods, this will preserve the smallest acreage of native plant habitat. Mudflats supporting eelgrass and macroalgae would be
maintained. So me Spartina meadow would likely remain and expand on tidela nds. Less
efficient at contr o lling Spartina

tidelands would have more impacts to adja c ent vegetation
than other meth ods. Mudflat supporting eelgrass and macroalgae on the would be maintained. Most of the existing Spartina meadow would convert
to native saltmar s h. Seed production would likely be stopped over time, reducing impacts an adja c ent areas.

Spartina Spartina would not increase. Seed production could be stopped within a short
timeframe. Spart i na meadows and clones would be mostly elimin ated. Spartina expansion would be slowed. Seed production would be stopped. So me Spartina meadows would likely remain after years of control effort. Seed production would likely be stopped in about a decade.
Meadows would be eliminated and greatly reduced.

Wildlife Exist i ng mudflat and native
saltmarsh habita t would be
maintained. Former areas of this habitat, now occupied by Spartina would revert mostly
to native saltmar s h. Wildlife

use would be su stained. Some existing m udflat habitat

would continue t o be lost to Spartina . Nearly all Spartina

meadow killed b y this method
would convert to native saltmarsh. Of the methods, this would preserve the least mudflat habitat for migratory bird use. Most of the exist i ng mudflat and

native saltmarsh habitat would

be maintained. Former a r eas of this habitat, now occupied by Spartina would revert mostly to
native saltmarsh

. Wildlife u s e would be sustain ed.

Fish More habitat wo uld be protected for existing fish populations than in other
methods. Some habitat would become
unusable for fish due to this
method’s li kely i nability to fu ll y control Spartina

. Most of the habit a t would be protected for existing fish populations.

Invertebra t

es Potential for trampling of

invertebrates at work sites.
More habitat for the existing invertebrate community would be protected than with
other methods. Potential for trampling of

invertebrates at work sites.
Where Spartina is not controlled, species composition would change. This action would have the least potential for trampling of

invertebrates at work sites. Most
of the habitat for the
existing inverteb rate community would be protected.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 16Table A-5c

. Po ten t ial Human Imp a cts (USFWS 199 7)

Social

Issues IPMP Physical/Mecha n ical Only Chemical Only

Huma n Health Health problems associated

with Spartina pollen production and
Mosquitos that b r eed in Spartina meadows would be reduced by Spartina control. This method provides the greatest opportu nity to reduce such impact s

. There could be some reduction in pollen product i on and in mosquito habitat however, this
method’s inabilit y to fully control Spartina would allow these problems to persist to a degree.
Greate r risk of injury to control

workers. Health problems associated with Spartina pollen production and mosquitos that b r eed in Spartina
meadows would be reduced by this method, but to a slightly
lesser extent tha n I PMP.

Concer ns Concerns about chemical u s e would be reduced to the degree that control would not depend

Exclu s ive l y on chemical
methods. Spartina spread would be stopped, reducing
concerns over the loss of aquatic resources. The absence of chemical u s e would remove concerns about
chemical risk. Spartina spread would be slowed, but not as
much as with I PMP or chemical only. Concerns about chemical risk would be greatest under this
method. Concerns about Spartina spread would be reduced.

Recreation Noise from airboats, hovercraft, and aircraft.
Disturbance of waterbirds

would reduce bird
Observations. In the long term, would be b eneficial to

recreational uses. Due to reduced control, some recreational opportunities would
decline. Noise d i sturbance to
recreational users would like be greater than with other methods. Noise would be generated by airboats, hovercraft, and aircraft,

but over shorter periods of time.
Disturbance of waterbirds would

reduce bird observations. In the long term, would be beneficial to

recreational uses.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 176.0 DISCUSSION

WSDA ha s been devel o ping regional m a nage ment plans si nce 1998. The State w i d e Spartina

mana ge ment plan provides infor m ation for the e f fects of Spar tina on the i n tertidal ecology of the s e areas, describe previous control efforts/results, an d outline the control strate gy for the com i ng years (Table A-6) . In 2002, the WSDA Spartina er adication pr ogra m work ed collaboratively with partner agencies to continue Spar tina control, as outlined in f i ve regional integrated pest

mana ge ment plans. The progra m included hirin g, equippi ng and coordi nating wor k ers to treat
infestati ons i n Clalla m, J e fferson, Kit s ap and Ki ng counties. WSDA also assisted the Swi n omish and Suqua mish tribal c o mmunities with c ontrol wo r k

on their property and worked cooperativel y with the WDFW and DNR on infe stations in Willapa Bay. W S DA worked cooper a tively with Ecology to devel op a NPDES per m it for a quatic noxi ous wee d c ontrol, providing NPD E S coverage to numerous federal

, stat e and local governme ntal agencies, and private entities for

herbicide a p plications to both ma rine and fres hwat er ( W SDA, 2002)

.

Table A-6. Tota l T r ea tment Are a and Meth od olog y fo r Spartina

in Wa shi ngton Sta t e fro m 199 7 thro ugh 2 002 (WSDA 20 02 )

County Spartina Prese nt i n 2002 Spartina Treate d

, 1997 - 2002 2002 Treatme nt Methods
Pacific (Willapa Bay) Over 6,800 solid acres spread over > 15,000 acres ‘97 – approx. 742 solid acres
‘98 – approx. 450 solid acres
‘99 – approx. 600 solid acres
‘00 – approx. 800 solid acres
‘01 – approx. 900 solid acres
‘02 – approx. 1804 solid acres Mow/herbicide, herbicide, seedling remova l, various
mechanical cont rol (rototilling, sub-s o iling, etc).

Grays Harbo r Scattered clones and seedlings

0.25 acres in size ‘97 – all treated

‘98 - all treated

‘99 – all treated

‘00 – all treated

‘01 – all treated

‘02 – all treated Herbicide, seedling removal,

mow

Snohomish Approx. 350 solid acres spread over > 4,500 acres ‘97 – approx. 89 solid acres
‘98 – approx. 126 solid acres
‘99 – approx. 90 solid acres
‘00 – approx. 158 solid acres
‘01 – approx. 75 solid acres
‘02 – approx. 238 solid acres Mow/herbicide, herbicide, seedling remova l, dig, mechanically cru s h, mow

Island Approx. 350 solid acres spread over >1,000 acres ‘97 – approx. 250 solid acres
‘98 – approx. 160 solid acres
‘99 – approx. 155 solid acres
‘00 – approx. 130 solid acres
‘01 – approx. 72 solid acres
‘02 – approx. 180 solid acres Mow/herbicide, herbicide, seedling remova l, mechanically cru s h, mow

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 18Table A-6. Tota l T r ea tment Are a and Meth od olog y fo r Spartina

in Wa shi ngton Sta t e fro m 199 7 thro ugh 2 002 (WSDA 20 02 ), Con t in ue d

County Spartina Prese nt i n 2002 Spartina Treate d

, 1997 - 2002 2002 Treatme nt Methods
Skagit Approx. 40 solid acres spread over > 2,000 acres ‘97 – approx. 91 solid acres
‘98 – approx. 57 solid acres

‘99 – all treated
‘00 – approx. 60 solid acres
‘01 – approx. 33 solid acres
‘02 – approx. 37 solid acres Mow/herbicide, herbicide, seedling remova l, dig, mow

Clallam 1 infestation < 0. 001 acres

in size ‘97 – treated twice

‘98 – treated three times

‘99 – treated twice

‘00 – treated three times

‘01 – treated four times

‘02 – treated four times Dig

Jefferson 14 infestations – approx. 0.01 solid acres total ‘97 - all treated

‘98 - all treated twice

‘99 – all treated t w ice

‘00 – all treated t w ice

‘01 – all treated t h ree times

‘02 – all treated t h ree times Mow, mow/he rbicide, dig, seedling remova l

Kitsap 8 infestations - a pprox. 1
solid acre total ‘97 - all but 2 tribal sites

‘98 - all treated

‘99 – all treated t w ice

‘00 – all treated

‘01 – all treated

‘02 – all treated t w ice Mow mow/he rbicide, dig, seedling remova l

King 2 infestations – single
clones and a fe w seedlings ‘97 – monitored

‘98 – all treated

‘99 – all treated

‘00 – all treated t w ice

’01 – all treated t w ice

‘02 – all treated t w ice Dig

San Juan Re-gro wth found at one
site. 2 other site s clean for
four consecutive years ‘97 - all treated

‘98 - all treated

‘99 – monitored

‘00 – all treated

’01 – all treated

‘02 – all treated Survey, dig

The potential ef f i cacy of the control methods is outlined in Table A-7. Mowing and herbicide application seem t o have the highest ef ficacy for containmen t and reduction of Spartina

.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 19Table A-7. Potential Effica c y o f T r eatm ent Me thod s o n Spartin a Infe sta t ion s in W ash ing t on State (s ource: W S DA 1 993 )

Potential Effica cy /

Infes t ati on Thr eat Objec t ive Manage men t M e th od Small Area Large
Area Plant Growth Stage

Herbicide Low to High Low to High Active ly growing, especially pre-flowering

C u t t i n g / m o w i n g M e d i u m t o High Medium to High Pre-flowering o r early flowering, every month

Mechanical crushing Low to High Low to High Pre-flowering o r early flowering, May through August Established
Invader Core Containment,

Reduction

Covering Medium Low All stage s during growing

season

Herbicide Low to High Low to High Seedlings, pre-flowering

Hand pulling Medium to High Medium to High Seedlings to small plants Established
Invader Outliers Containment or
Control

C o v e r i n g H i g h M e d i u m t o High All stage s during growing season, treatments repeated every month

Herbicide Low to High Low to High Seedling, pre-flowering

Hand pulling/dig g ing Medium to High Medium Seedling to small plants

C o v e r i n g H i g h M e d i u m t o High All stage s during growing season, treatments repeated every month New Invader Eradication, Reduction, Containment,
Control

Mechanical crushing Low to High Low to High Pre-flowering o r early flowering, May through August

Education/awareness Medium to High Medium to High All Infestat ions Prevention (applies to all infestations) S u r v e y s M e d i u m t o High Medium to High

Patten (1997) has indicated that m o wing followe d by herbicide application provides t h e highest efficacy but at an increased cost ( T able A-8) . Aerial applicati on is more cost effective and covers

wider are a s but the e ffic acy is questi onable.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 20Table A-8. Sum m a r y o f th e m ost c ost-effectiv e, inte grate d Spa r t i na Ma nage men t Prac tice s (Norm an a nd Patten , 19 9 7 )

M e t h o d % K i l l ( E f f i c a c y ) A c r e a g e $ / A c r e Mow only 95 low 312

Mow + Rodeo 98 low 431
Rodeo hand wipe 91 low 310
Rodeo hand spray 81 low 585
Rodeo aerial spray ? high 165

WSDA ha s de monstrate d that Sparti na eradicati on is fea s ibl e . The curre nt strategies for control i n each region are founde d upon th e 1998 plans. Many of these plans are proving success f ul

, especially in North Puget Sound wher e the strategy has resulte d in a 27% decline in the overall size

of the infes t ation ( W SDA, 20 01a; WSDA, 2002). The overall Puget Sound infe station wa s reduced by 10% fr om 1997 to 1999, Spartina est a blishment i n Grays Har bor has bee n prevented, and populati ons of Spart i na at select sites in W i l l apa Bay ha ve been era d icated ( W SDA, 2001b;

W S DA, 2002). This is the positive aspect concerning th e present program, but the Spartina

infestati on c ontinues to grow. At c u rrent levels , it could ta ke decade s to eradicate Spartina in Puget Sound and it may never be eradi cated in Will apa Bay ( W SDA, 2002).

Methodol ogi es and equipm e n t for e r adicating Spartina have evolved over ti m e wi th treat m ent efforts. The agencies now use ai rboats to tr ansport e q uipm e n t and personnel, large-scale

am phibious mowing m a chines to stop seed produc tion, s m all tracked vehicles to shred and ri p apart isolate d infestations, hi gh pr essure spra y syste m s t o treat large clones a n d fri nges of meadows, a nd voluntee r s, landowners and studen ts to dig seedlings (W SDA 2002). W S DA (2002) , conc luded that , l a rge-scale mechanical er adication of Spartina is not f e asible at this tim e

. A potential alternative at this ti m e , might be an effective chemical control. The chemical control

solution would need to be a cost -effective chemi cal that can be applied i n low volumes and small

concentrations in salt water and woul d integrate mini mal non-target im pact with acceptable aquatic risk and non-persistent in the wate r. This would allow for large ar eas t o be treated wit h a mini mal

need for re-t reat m e nt

.

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No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 217.0 REFERENCES

Daehler

, C.C. a nd D.R. St rong. 1994. Variable re productive output a m ong clones of Spartina alterniflora (Poacea) invading San Francisco Bay, Cali fornia: t h e influen ce of herbivory, pollination, and esta blishm ent Site. American Jour nal of Bota ny 81( 3):307- 313.

Grevsta d, F. 2001. Sparti na Biocontr ol—Bac kground a nd Progre ss. Uni v e r sity of Was h ington, Olympic Nat u

ral Re sourc e s Ce nter. Website:

ht

t p :// www.wi ll apabay .org/

~ coast a l / nospartina/ bi ocont rol/ bi ocont rol _overvi e w2001.p d f

IVM Technical Bulletin, 1998 . Smooth Cordgras s ( Sparti na ). I n Integrate d Pest Ma nage ment
Practitioner' s Association: Bio-Inte gral Resource Center (BIRC)' s I PM P Ac cess: Noxio u s Wee d Inte grated Vegetat i on Manage ment Guide: IVM Technica l Bulletin. W e bsite:

http://www.efn

. org/~ip m p a

/N oxspart.htm l

. Visited: 6/5/ 03.

Killbride, K.M, F.L. Paveglio, a nd C.E. Grue. 1995. C ontrol of smooth cordgr ass with Rodeo in a

southwester n

Washi ngton estuary. Wildlife Society Bulletin 23(3): 520- 524.

Major III, W. and C.E. Grue. 1997. Control of Spartina alterniflora in W illapa Bay, W a shington: efficacy of mechanical and ch em ical control techniques and their off target i m pacts on eelgrass (Z. j aponic a ). Se cond I n ternational Sparti na Conf . Proc. 1997: 76- 81.

Nor m an, M. and K. Pa tten. 1997. Cost-effi cacy of integrated Spartina control practices in W illapa Bay, Washi n gton. 1997. Second Inter national Spartina Confer ence Procee dings 1997: 89-

92.

Patten, K. 2002. I m aza pyr- efficac y, t oxicity, cost s and registr a tion. Prese n tation at Spartina

Confere n ce, May 13-14. Ol ympia

, WA. Website:

ht

t p :// www.wi ll apabay .org/

~ coast a l / nospartina/ conferences/conf20 02/ conference_ m a y 2002.htm Visited:

6/5/03.

U

. S

. D e partm e nt of A g riculture ( U SDA). 1995. I m aza pyr: Pesticid e Fact Sheet

. Prepared by

Venture s , I n c. Nove mbe r 1995. We bsite: htt p : //i nfovent ures.co m / e -hlt h/

pest ci de/ i m a zapy r .h tm l
Visited: 6/5/ 03.

U.S. Fish and W ildlif e Servi ce (USFWS). 1997. Environmental Asse ss me nt for Contr o l of Smooth Cordgrass ( Spartina Altierniflora ) on W illapa National W ildlife Refuge. U.S. Fish and

Wildli fe Ser v ice. Was h i ngton.

Was h ington State Depart ments of Agricultu re, ( W SDA). 1993. Noxious e m ergent pla n t

mana ge ment : final envir onm e n tal i m pact stat ement. State of Washi ngton. Olym pia

. 204 pp
+ app

.

Was h ington State Depart ment of Agri culture ( W SDA). 2000, Spartina and Purple Loosestrif e Report to the Legislat ure Eradication a nd Contr o l Progra m s (a s required by RCW 17.26.015). 44 pp.

J:\Divisions\Plan t Prot ecti on\ S p a r t i na \ H ab it a t E c o R is k A ss e s s m e n t \ A p pe nd ix A Rp t. do c Appe ndix A

No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 22Was h ington State Depart ment of Ag ri culture ( W SDA). 2001a . 2001 Spart i na Manage ment Plan

for North Puget Sound. Prep ared by WSDA in cooperation wi th the North Puget Sound Spartina Task Force.

Was h ington State Depart ment of Ag ri culture ( W SDA). 2001b. 2001 Spart i na Manage ment Plan

f o r W illapa Bay. Prepared by W S DA in cooperation with the W illapa Bay Spartina Task

Force.

Was h ington State Depart ment of Agri culture ( W SD A). 2002. Report to the Legislat ure. State of

W a shington. O l ym pia.

Zipperer, V.T. 1996. Ec ological Effe cts of the Int r oduced Cor dgrass, Spartina alternif lora, on the

Benthic Communit y Str u cture of Wi llapa Ba y, Was h ington. Masters of Science The s is.

Univer sity of Wa shingt on.

J:\Divisions\Plan t Prot ecti on\ S p a r t i na \ H ab it a t E c o R is k A ss e s s m e n t \ A p pe nd ix A Rp t. do c Appe ndix A

No Ac tion Al t erna t ive for S part i n a C o ntr o l Pa ge 23

### Appendix B

Exposure Calculation W o rksheet sAPPENDIX B:Exposure Calculation WorksheetsDermalAbsorbed DoseTerrestrial ReceptorAR mg/cm2Body Weight SA Upper Amnt Typical Amnt Upper Dose Typical DoseDeer Mouse 0.0168 0.021 90.11 1.14 0.76 54.07 36.04Norway Rat 0.0168 0.300 507.52 6.39 4.26 21.32 14.21Cottontail Rabbit 0.0168 1.286 1307.16 16.47 10.98 12.81 8.54Red Fox M 0.0168 5.250 3261.57 41.10 27.40 7.83 5.22Red Fox F 0.0168 4.130 2790.55 35.16 23.44 8.51 5.68Marsh Wren 0.0168 0.011 60.06 0.76 0.50 67.27 44.84Bobwhite Quail 0.0168 0.190 377.15 4.75 3.17 25.01 16.67Greater Scaup M 0.0168 0.860 1006.35 12.68 8.45 14.74 9.83Greater Scaup F 0.0168 0.770 936.57 11.80 7.87 15.33 10.22Mallard Duck M 0.0168 1.225 1266.52 15.96 10.64 13.03 8.68Mallard Duck F 0.0168 1.043 1140.80 14.37 9.58 13.78 9.19W = body weight (kg); SA = exposed surface areaEstimated Absorbed Dose = Dabs = Amnt/WTypical Amount deposited on the animal (Amnt) = 0.5 x SA x ARUpper Amount Deposited On the Animal (Amnt) = 0.75 x SA x ARApplication Rate AR= 0.0168 mg/cm2Exposed Surface Area SA= 1110(W)0.65Amt Deposited on Animal (mg) Dose Absorbed (mg/kg-bw)Page 1 of 1Appendix BEcologicalReceptorAcuteDietaryUpperExposure1AcuteDietaryTypicalExposure1ChronicDietaryUpperExposure2ChronicDietaryTypicalExposure2Dermal/ContactUpperExposure3Dermal/ContactTypicalExposure3DrinkingWater(Spill) UpperExposure4DrinkingWater(Spill)TypicalExposure4DrinkingWater(Runoff)UpperExposure4DrinkingWater(Runoff)TypicalExposure4Deer Mouse 0.0084214 0.000524 0.014946429 0.007842857 0.02703254 0.0180217 1.19773333 0.59886667 0.0002267 6.667E-06Norway Rat 0.000524 0.000172 0.00093 0.000488 0.01065789 0.0071053 0.395252 0.197626 0.0000748 0.0000022Cottontail Rabbit 0.0027504 0.0009028 0.012203538 0.006403577 0.13516268 0.0901085 0.34926128 0.17463064 6.61E-05 1.944E-06Red Fox M 0.0007226 0.0002372 0.005130057 0.002691901 0.05328943 0.0355263 0.3018288 0.1509144 5.712E-05 1.68E-06Red Fox F 0.0007232 0.0002374 0.00513414 0.002691901 0.03201837 0.0213456 0.3088586 0.1544293 5.845E-05 1.719E-06Marsh Wren 0.0552852 0.018147 0.066133333 0.034702222 0.01956941 0.0130463 7.07675744 3.53837872 0.0013393 3.939E-05Bobwhite Quail 0.0115083 0.0037775 0.013766447 0.007223684 0.02128389 0.0141893 2.80587225 1.40293612 0.000531 1.562E-05Scaup M 0.0152326 0.0008703 0.005406977 0.002837209 0.16816289 0.1121086 0.96362661 0.48181331 0.0001824 5.364E-06Scaup F 0.017013 0.000972 0.006038961 0.003168831 0.06252731 0.0416849 0.99503125 0.49751563 0.0001883 5.538E-06Mallard Duck M 0.1002551 0.0057281 0.035586735 0.018673469 0.03686032 0.0245735 0.8552047 0.42760235 0.0001618 4.76E-06Mallard Duck F 0.1177493 0.0067277 0.0417965 0.021931927 0.03831438 0.0255429 0.65962899 0.3298145 0.0001248 3.672E-061: acute dietary reference NOEL = 5,000 mg/kg-bw for mouse, rat, rabbit, and fox; 1149 mg/kg for mallard and scaup; and 674 mg/kg for quail and wren2: chronic reference NOEL dose for mouse and rate = 1,000 mg/kg; for rabbits = 400 mg/kg; for dogs = 250 mg/kg; for avian species = 200 mg/kg3: dermal/contact NOEL dose for mouse & rat= 2,000 mg/kg; 400 mg/kg for rabbit. No data on fox or avian species, so assumed rabbit value of 400 mg/kg4: same reference doses as acute oralCupper in mg/LClower in mg/LA W Upper TypicalDeer Mouse 3.4 0.1 0.007 0.021 1.133 0.033Norway Rat 3.4 0.1 0.033 0.3 0.374 0.011Cottontail Rabbit 3.4 0.1 0.125 1.286 0.330 0.010Red Fox M 3.4 0.1 0.441 5.25 0.286 0.008Red Fox F 3.4 0.1 0.355 4.13 0.292 0.009Marsh Wren 3.4 0.1 0.003 0.0113 0.903 0.027Bobwhite Quail 3.4 0.1 0.02 0.19 0.358 0.011Scaup M 3.4 0.1 0.053 0.86 0.210 0.006Scaup F 3.4 0.1 0.049 0.77 0.216 0.006Mallard Duck M 3.4 0.1 0.067 1.225 0.186 0.005Mallard Duck F 3.4 0.1 0.044 1.043 0.143 0.004Dose is calculated as (C x A)/WA = water consumed per day (in L); and W = average body weight (in kg)C = concentration of neat solution in spill (mg/L) based on application rates of 10 gal/acre (upper), and 20 gal/acre (typical)[note: lower application volumes result in higher neat concentrations of herbicide, hence higher concentrations)EcologicalReceptorDose Ingested fromCupper in mg/LClower in mg/LA W Upper TypicalDeer Mouse 17966 8983 0.007 0.021 5988.7 2994.3Norway Rat 17966 8983 0.033 0.3 1976.3 988.1Cottontail Rabbit 17966 8983 0.125 1.286 1746.3 873.2Red Fox M 17966 8983 0.441 5.25 1509.1 754.6Red Fox F 17966 8983 0.355 4.13 1544.3 772.1Marsh Wren 17966 8983 0.003 0.0113 4769.7 2384.9Bobwhite Quail 17966 8983 0.02 0.19 1891.2 945.6Scaup M 17966 8983 0.053 0.86 1107.2 553.6Scaup F 17966 8983 0.049 0.77 1143.3 571.6Mallard Duck M 17966 8983 0.067 1.225 982.6 491.3Mallard Duck F 17966 8983 0.044 1.043 757.9 379.0Dose is calculated as (C x A)/WA = water consumed per day (in L); and W = average body weight (in kg)C = concentration of neat solution in spill (mg/L) based on application rates of 10 gal/acre (upper), and 20 gal/acre (typical)[note: lower application volumes result in higher neat concentrations of herbicide, hence higher concentrations)Dose Ingested fromSpill Solution (mg/kg-bw)TerrestrialEcologicalReceptorChronic Dietary DoseTerrestrial Receptor Ctwaupper Ctwatypicalfood intake/day(kg/1000))Prop (W)UpperLimit DoseTypical DoseDeer Mouse 46.5 24.4 9 0.75 21 14.95 7.84Norway Rat 46.5 24.4 15 0.4 300 0.93 0.49Cottontail Rabbit 46.5 24.4 180 0.75 1286 4.88 2.56Red Fox M 46.5 24.4 362 0.4 5250 1.28 0.67Red Fox F 46.5 24.4 285 0.4 4130 1.28 0.67Marsh Wren 46.5 24.4 8 0.4 11.25 13.23 6.94Bobwhite Quail 46.5 24.4 15 0.75 190 2.75 1.44Greater Scaup M 46.5 24.4 50 0.4 860 1.08 0.57Greater Scaup F 46.5 24.4 50 0.4 770 1.21 0.63Mallard Duck M 46.5 24.4 250 0.75 1225 7.12 3.73Mallard Duck F 46.5 24.4 250 0.75 1043 8.36 4.39Time-weighted average concentration on Vegetation (Ctwa) = Co(1-e-kt)/(kT) (note: units in mg/kg)food intake per day is in kg/1000, from Wildlife exposure handbookW = body weight in kg/1000 Chronic Dietary Dose Absorbed (CD) = (Ctwa)(food intake/day)(Prop)/WAcute Dietary DoseTerrestrial Receptor CupperCtypicalAProp WUpper Dose(mg/kg-bw)Typical Dose(mg/kg-bw)Deer Mouse 131 43 9 0.75 21 42.11 13.82Norway Rat 131 43 15 0.4 300 2.62 0.86Cottontail Rabbit 131 43 180 0.75 1286 13.75 4.51Red Fox M 131 43 362 0.4 5250 3.61 1.19Red Fox F 131 43 285 0.4 4130 3.62 1.19Marsh Wren 131 43 8 0.4 11.25 37.26 12.23Bobwhite Quail 131 43 15 0.75 190 7.76 2.55Greater Scaup M 131 43 50 0.4 860 3.05 1.00Greater Scaup F 131 43 50 0.4 770 3.40 1.12Mallard Duck M 131 43 250 0.75 1225 20.05 6.58Mallard Duck F 131 43 250 0.75 1043 23.55 7.73Dose= AxC(Prop)/WA = daily food intake in gramsProp is unitless estimate of percent of total diet assumed from contaminated vegetationC = residue concentration in food (mg/kg)W = body weight in grams

### Appendix C

A

v ian S p ecies in W illap a BayAPPENDIX C:Avian Species in Willapa BaySpecies Scientific NameLOONSSpring Summer Fall WinterRed-throated LoonGAVIA STELLATAc-ccPacific LoonGAVIA PACIFICAcrcuCommon LoonGAVIA IMMERcrcuGREBESSpring Summer Fall WinterPied-billed Grebe*PODILYMBUS PODICEPSuuuuHorned GrebePODICEPS AURITUScrccRed-necked GrebePODICEPS GRISEGENAr -ooWestern GrebeAECHMOPHORUS OCCIDENTALISauaaFULMARS, PETRELS AND SHEARWATERS Spring Summer Fall WinterNorthern FulmarFULMARUS GLACIALIS-rruPink-footed ShearwaterPUFFINUS CREATOPUS--rSooty ShearwaterPUFFINUS GRISEUSucaShort-tailed ShearwaterPUFFINUS TENUIROSTRIS---oSTORM PETRELS Spring Summer Fall WinterFork-tailed Storm-PetrelOCEANODROMA FURCATA--rLeach's Storm-Petrel*OCEANODROMA LEUCORHOA--rPELICANS AND CORMORANTS Spring Summer Fall WinterBrown PelicanPELECANUS OCCIDENTALISoccDouble-crested Cormorant*PHALACROCORAX AURITUSccccBrandt's Cormorant*PHALACROCORAX PENICILLATUSccccBITTERNS, HERONS AND EGRETS Spring Summer Fall WinterAmerican Bittern*BOTAURUS LENTIGINOSUSouuoGreat Blue Heron*ARDEA HERODIASccccGreat EgretARDEA ALBAo-oCattle EgretBUBULCUS IBIS--rGreen HeronBUTORIDES VIRESCENSrrrAbundance by seasonPage 1 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonWATERFOWLSpring Summer Fall WinterTundra SwanCYGNUS COLUMBIANUS- - u u"Trumpeter SwanCYGNUS BUCCINATOR- - u u"Greater White-fronted GooseANSER ALBIFRONSo-ooSnow GooseCHEN CAERULESCENSo-ooRoss' GooseCHEN ROSSIIr---Emperor GooseCHEN CANAGICAr-orBrantBRANTA BERNICLAaoccCanada Goose*BRANTA CANADENSISacaaWood Duck*AIX SPONSAuuuGreen-winged TealANAS CRECCAcrccMallard*ANAS PLATYRHYNCHOSccccNorthern PintailANAS ACUTAuracBlue-winged TealANAS DISCORSuruCinnamon Teal*ANAS CYANOPTERAuuuNorthern ShovelerANAS CLYPEATAuruoGadwallANAS STREPERAuruuEurasian WigeonANAS PENELOPE- -ooAmerican WigeonANAS AMERICANAcracCanvasbackAYTHYA VALISINERIAu-uuRing-necked DuckAYTHYA COLLARISu-uuTufted DuckAYTHYA FULIGULA---rGreater ScaupAYTHYA MARILAu-uuLesser ScaupAYTHYA AFFINISc-ccHarlequin DuckHISTRIONICUS HISTRIONICUSr-rrOldsquawCLANGULA HYEMALISo-roBlack ScoterMELANITTA NIGRAu-uuSurf ScoterMELANITTA PERSPICILLATAc o c c"White-winged ScoterMELANITTA FUSCAcoccCommon GoldeneyeBUCEPHALA CLANGULAu-ucBarrow's GoldeneyeBUCEPHALA ISLANDICAr--rPage 2 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonBuffleheadBUCEPHALA ALBEOLAc-ccHooded Merganser*LOPHODYTES CUCULLATUSuouuCommon Merganser*MERGUS MERGANSERcuuuRed-breasted Merganser r c c"Ruddy DuckOXYURA JAMAICENSISo - u u"VULTURESSpring Summer Fall WinterTurkey VultureCATHARTES AURAuuurOSPREY, KITES, EAGLES AND HAWKS Spring Summer Fall WinterOsprey*PANDION HALIAETUSuuurWhite-tailed KiteELANUS LEUCURUSouooBald Eagle*HALIAEETUS LEUCOCEPHALUSuuuuNorthern Harrier*CIRCUS CYANEUSccccSharp-shinned HawkACCIPITER STRIATUSuruuCooper's HawkACCIPITER COOPERIIuruuNorthern GoshawkACCIPITER GENTILISr-rrRed-tailed Hawk*BUTEO JAMAICENSISccccRough-legged HawkBUTEO LAGOPUSu-uuFALCONSSpring Summer Fall WinterAmerican KestrelFALCO SPARVERIUSuruuMerlinFALCO COLUMBARIUSu-uuPeregrine FalconFALCO PEREGRINUSu-uuGyrfalconFALCO RUSTICOLUS--rrGALLINACEOUS BIRDS Spring Summer Fall WinterRing-necked Pheasant*PHASIANUS COLCHICUSuuuuBlue Grouse*DENDRAGAPUS OBSCURUSuuurRuffed Grouse*BONASA UMBELLUSuuuuWild TurkeyMELEAGRIS GALLOPAVOrrrrNorthern Bobwhite*COLINUS VIRGINIANUSuuooPage 3 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonRAILSSpring Summer Fall WinterVirginia Rail*RALLUS LIMICOLAuuurSoraPORZANA CAROLINAr-rAmerican CootFULICA AMERICANAu-ucPLOVERSSpring Summer Fall WinterBlack-bellied PloverPLUVIALIS SQUATAROLAcuacAmerican Golden PloverPLUVIALIS DOMINICArrurSnowy Plover*CHARADRIUS ALEXANDRINUSuuurSemipalmated PloverCHARADRIUS SEMIPALMATUScccrKilldeer*CHARADRIUS VOCIFERUSuucuOYSTERCATCHERS Spring Summer Fall WinterAmerican Oystercatcher*HAEMATOPUS PALLIATUSuuuSHOREBIRDSSpring Summer Fall WinterGreater YellowlegsTRINGA MELANOLEUCAcuccLesser YellowlegsTRINGA FLAVIPES--rWilletCATOPTROPHORUS SEMIPALMATUSr -ooWandering TattlerHETEROSCELUS INCANUSuouSpotted SandpiperACTITIS MACULARIAuouWhimbrelNUMENIUS PHAEOPUScocLong-billed CurlewNUMENIUS AMERICANUSu-uoBar-tailed GodwitLIMOSA LAPPONICA--oMarbled GodwitLIMOSA FEDOAuourRuddy TurnstoneARENARIA INTERPREScocrBlack TurnstoneARENARIA MELANOCEPHALAuuuuSurfbirdAPHRIZA VIRGATAcrcrRed KnotCALIDRIS CANUTUSc-uSanderlingCALIDRIS ALBAacacSemipalmated SandpiperCALIDRIS PUSILLAor--Page 4 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonWestern SandpiperCALIDRIS MAURIaaacLeast SandpiperCALIDRIS MINUTILLAccauPectoral SandpiperCALIDRIS MELANOTOS--cSharp-tailed SandpiperCALIDRIS ACUMINATAr-uDunlinCALIDRIS ALPINAauaaStilt SandpiperCALIDRIS HIMANTOPUS--rRuffPHILOMACHUS PUGNAX--rShort-billed DowitcherLIMNODROMUS GRISEUSaac -Long-billed DowitcherLIMNODROMUS SCOLOPACEUSurcuSNIPESpring Summer Fall WinterCommon SnipeGALLINAGO GALLINAGOcrcuPHALAROPESSpring Summer Fall WinterWilson's PhalaropePHALAROPUS TRICOLOR--rRed-necked PhalaropePHALAROPUS LOBATUSuouRed PhalaropePHALAROPUS FULICARIArroJAEGERSSpring Summer Fall WinterParasitic JaegerSTERCORARIUS PARASITICUSrruGULLS AND TERNS Spring Summer Fall WinterBonaparte's GullLARUS PHILADELPHIAcucrHeermann's GullLARUS HEERMANNIoccMew GullLARUS CANUScrccRing-billed GullLARUS DELAWARENSIScucuCalifornia GullLARUS CALIFORNICUScuauHerring GullLARUS ARGENTATUS---rThayer's GullLARUS THAYERI---rWestern Gull*LARUS OCCIDENTALISccccGlaucous-winged Gull*LARUS GLAUCESCENSccccBlack-legged KittiwakeRISSA TRIDACTYLAuruuPage 5 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonSabine's GullXEMA SABINIrrrCaspian Tern*STERNA CASPIAcccCommon TernSTERNA HIRUNDOuruArctic TernSTERNA PARADISAEAr-rSEABIRDSSpring Summer Fall WinterCommon MurreURIA AALGEuccuPigeon Guillemot*CEPPHUS COLUMBAccurMarbled Murrelet* u u u"Ancient MurreletSYNTHLIBORAMPHUS ANTIQUUS--rrCassin's AukletPTYCHORAMPHUS ALEUTICUS--rrRhinoceros AukletCERORHINCA MONOCERATAouooTufted PuffinFRATERCULA CIRRHATAouooHorned PuffinFRATERCULA CORNICULATA---oDOVESSpring Summer Fall WinterRock Dove*COLUMBA LIVIAuuuuBand-tailed Pigeon*COLUMBA FASCIATAcccMourning DoveZENAIDA MACROURArrrOWLSSpring Summer Fall WinterBarn Owl*TYTO ALBAuuuuWestern Screech-Owl*OTUS KENNICOTTIIuuuuGreat Horned Owl*BUBO VIRGINIANUSuuuuSnowy OwlNYCTEA SCANDIACA---rNorthern Pygmy-Owl*GLAUCIDIUM GNOMAuuuuBurrowing Owl - r r"Barred Owl*STRIX VARIAuuuuLong-eared OwlASIO OTUSr-rrShort-eared OwlASIO FLAMMEUSuouuNorthern Saw-whet Owl*AEGOLIUS ACADICUSuuuuPage 6 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonGOATSUCKERSSpring Summer Fall WinterCommon Nighthawk*CHORDEILES MINORruuSWIFTSSpring Summer Fall WinterVaux's Swift*CHAETURA VAUXIcccHUMMINGBIRDS Spring Summer Fall WinterAnna's HummingbirdCALYPTE ANNA---rRufous Hummingbird*SELASPHORUS RUFUSaaorKINGFISHERSSpring Summer Fall WinterBelted Kingfisher*CERYLE ALCYONuuuoWOODPECKERS Spring Summer Fall WinterRed-breasted SapsuckerSPHYRAPICUS RUBERu-uuDowny Woodpecker*PICOIDES PUBESCENSuuuuHairy Woodpecker*PICOIDES VILLOSUSuuuuNorthern Flicker*COLAPTES AURATUSccccPileated Woodpecker*DRYOCOPUS PILEATUSuuuuFLYCATCHERSSpring Summer Fall WinterOlive-sided Flycatcher*CONTOPUS BOREALISccoWestern Wood-Pewee*CONTOPUS SORDIDULUSuuoWillow Flycatcher*EMPIDONAX TRAILLIIuuoPacific-slope Flycatcher*EMPIDONAX DIFFICILISccuWestern KingbirdTYRANNUS VERTICALISr---LARKSSpring Summer Fall WinterHorned Lark*EREMOPHILA ALPESTRISuuuoSWALLOWSSpring Summer Fall WinterPurple Martin* o r -"Page 7 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonTree Swallow*TACHYCINETA BICOLORccuoViolet-green Swallow*TACHYCINETA THALASSINAccuoNorthern Rough-winged SwallowSTELGIDOPTERYX SERRIPENNISuuoCliff Swallow*HIRUNDO PYRRHONOTAccoBarn Swallow*HIRUNDO RUSTICAcaoJAYS, MAGPIES AND CROWS Spring Summer Fall WinterGray JayPERISOREUS CANADENSISooooSteller's Jay*CYANOCITTA STELLERIuucuScrub JayAPHELOCOMA COERULESCENSo o o o"American Crow*CORVUS BRACHYRHYNCHOSccccCommon Raven*CORVUS CORAXuuuuCHICKADEES AND TITMICE Spring Summer Fall WinterBlack-capped Chickadee*POECILE ATRICAPILLUSccccChestnut-backed Chickadee*POECILE RUFESCENSccccBUSHTITSSpring Summer Fall WinterBushtit*PSALTRIPARUS MINIMUSorooNUTHATCHESSpring Summer Fall WinterRed-breasted NuthatchSITTA CANADENSISuruuCREEPERSSpring Summer Fall WinterBrown Creeper*CERTHIA AMERICANAu u u u"WRENSSpring Summer Fall WinterBewick's Wren*THRYOMANES BEWICKIIuuuuWinter Wren*TROGLODYTES TROGLODYTESccccMarsh Wren*CISTOTHORUS PALUSTRIScccuPage 8 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonKINGLETS, BLUEBIRDS AND THRUSHES Spring Summer Fall WinterGolden-crowned Kinglet*REGULUS SATRAPAccccRuby-crowned KingletREGULUS CALENDULAcrcuWestern BluebirdSIALIA MEXICANAr-rMountain BluebirdSIALIA CURRUCOIDESr-rTownsend's SolitaireMYADESTES TOWNSENDIorrSwainson's Thrush*CATHARUS USTULATUSccuHermit ThrushCATHARUS GUTTATUSu-uuAmerican Robin*TURDUS MIGRATORIUScccuVaried Thrush*IXOREUS NAEVIUScuccWAGTAILS AND PIPITS Spring Summer Fall WinterAmerican PipitANTHUS RUBESCENS--oWAXWINGSSpring Summer Fall WinterCedar Waxwing*BOMBYCILLA CEDRORUMucurSHRIKESSpring Summer Fall WinterNorthern ShrikeLANIUS EXCUBITORo-uuSTARLINGS AND MYNAS Spring Summer Fall WinterEuropean Starling*STURNUS VULGARISccccVIREOSSpring Summer Fall WinterSolitary Vireo*VIREO SOLITARIUSr-rHutton's Vireo*VIREO HUTTONIuuuuWarbling Vireo*VIREO GILVUSuuoWARBLERSSpring Summer Fall WinterOrange-crowned Warbler*VERMIVORA CELATAccuYellow Warbler*DENDROICA PETECHIAuur -Yellow-rumped Warbler*DENDROICA CORONATAcuucPage 9 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonBlack-throated Gray Warbler*DENDROICA NIGRESCENSccuTownsend WarblerDENDROICA TOWNSENDIc -uuHermit WarblerDENDROICA OCCIDENTALISr r - -"Palm WarblerDENDROICA PALMARUM--rrMacGillivray's WarblerOPORORNIS TOLMIEIr r - -"Common Yellowthroat*GEOTHLYPIS TRICHASccuWilson's Warbler*WILSONIA PUSILLAccuTANAGERSSpring Summer Fall WinterWestern Tanager*PIRANGA LUDOVICIANAuuoGROSBEAKS AND BUNTINGS Spring Summer Fall WinterBlack-headed Grosbeak*PHEUCTICUS MELANOCEPHALUSuur -TOWHEES AND SPARROWS Spring Summer Fall WinterRufous-sided Towhee*PIPILO ERYTHROPHTHALMUSuuccChipping SparrowSPIZELLA PASSERINAr-rSavannah Sparrow*PASSERCULUS SANDWICHENSISccuFox SparrowPASSERELLA ILIACAu-uuSong Sparrow*MELOSPIZA MELODIAccccLincoln's SparrowMELOSPIZA LINCOLNIIr-rWhite-throated SparrowZONOTRICHIA ALBICOLLISoo- -Golden-crowned SparrowZONOTRICHIA ATRICAPILLAc-ccWhite-crowned Sparrow*ZONOTRICHIA LEUCOPHRYScccuDark-eyed Junco*JUNCO HYEMALISccccLapland LongspurCALCARIUS LAPPONICUSr-crSnow BuntingPLECTROPHENAX NIVALIS- -ooBLACKBIRDS, MEADOWLARKS AND ORIOLES Spring Summer Fall WinterRed-winged Blackbird*AGELAIUS PHOENICEUSccccWestern Meadowlark*STURNELLA NEGLECTAuuuuYellow-headed BlackbirdXANTHOCEPHALUS XANTHOCEPHALUSr---Page 10 of 11Appendix CAPPENDIX C:Avian Species in Willapa BaySpecies Scientific Name Abundance by seasonBrewer's Blackbird*EUPHAGUS CYANOCEPHALUSccuuBrown-headed Cowbird*MOLOTHRUS ATERccurBullock's Oriole*ICTERUS BULLOCKIIo o r -"FINCHESSpring Summer Fall WinterPurple Finch*CARPODACUS PURPUREUSccuuHouse Finch*CARPODACUS MEXICANUSccccRed Crossbill*LOXIA CURVIROSTRAucuuCommon RedpollCARDUELIS FLAMMEA---rPine Siskin*CARDUELIS PINUScoccAmerican Goldfinch*CARDUELIS TRISTISuccrWEAVER FINCHES Spring Summer Fall WinterHouse Sparrow*PASSER DOMESTICUSc c c c"Notes: a = abundant, c = common, u = uncommon, o = occasional, r = rare, * = known to nest in the area"Page 11 of 11Appendix C

### Appendix D

T

e rrestrial and Amphibious W ildlife

in the W a llap a Bay W atershedAPPENDIX D: Terrestrial and Amphibious Wildlife in the Wallapa Bay Watershed

MARSUPIALS Virginia opossum DIDELPHIS VIRGINIANA

INSECTIVORES Vagrant Shrew SOREX VAGRANS Dusky Shrew SOREX MONTICOLUS

Marsh Shrew NEOSOREX PALUSTRIS Trowbridge's Shrew SOREX TROWBRIDGII

Shrew-Mole NEUROTRICHUS GIBBSII

Townsend's Mole SCAPANUS TOWNSENDII

Coast Mole SCAPANUS ORARIUS

BATS Little Brown Myotis MYOTIS LUCIFUGUS Yuma Myotis MYOTIS YUMANENSIS Long-eared Myotis MYOTIS EVOTIS Long-legged Myotis MYOTIS VOLANS California Myotis MYOTIS CALIFORNICUS

Silver-haired Bat LASIONYCTERIS NOCTIVAGANS Big Brown Bat EPTESICUS FUSCUS Hoary Bat LASIURUS CINEREUS

RABBITS AND HARES

Snowshoe Hare LEPUS AMERICANUS

RODENTS

Mountain Beaver APLODONTIA RUFA Townsend's Chipmunk TAMIAS TOWNSENDII Douglas Squirrel TAMIASCIURUS DOUGLASII Northern Flying Squirrel GLAUCOMYS SABRINUS

Beaver CASTOR CANADENSIS

Deer Mouse PEROMYSCUS MANICULATUS

Forest Deer Mouse PEROMYSCUS MANICULATUS GRACILIS Bushy-tailed Woodrat NEOTOMA CINEREA

Southern Red-backed Vole CLETHRIONOMYS GAPPERI

Townsend's Vole MICROTUS TOWNSENDII Long-tailed Vole MICROTUS LONGICAUDUS Oregon Vole MICROTUS OREGONI

Muskrat ONDATRA ZIBETHICUS Norway Rat RATTUS NORVEGICUS Pacific Jumping Mouse ZAPUS TRINOTATUS Porcupine ERETHIZON DORSATUM

Nutria MYOCASTOR COYPUS

CARNIVORES Coyote CANIS LATRANS

Black Bear URSUS AMERICANUS

Raccoon PROCYON LOTOR

Pine Marten MARTES AMERICANA Long-tailed Weasel MUSTELA FRENATA

Page 1 of 3 Appendix DAPPENDIX D: Terrestrial and Amphibious Wildlife in the Wallapa Bay Watershed

Mink MUSTELA VISON Striped Skunk MEPHITIS MEPHITIS

River Otter LUTRA CANADENSIS

Bobcat LYNX RUFUS Cougar FELIS CONCOLOR

WHALES, DOLPHINS, AND PORPOISES Gray Whale ESCHRICHTIUS ROBUSTUS Harbor Porpoise PHOCOENA PHOCOENA

SEALS AND SEA LIONS

Stellar Sea Lion EUMETOPIAS JUBATUS

California Sea Lion ZALOPHUS CALIFORNIANUS

Harbor Seal PHOCA VITULINA

Northern Fur Seal CALLORHINUS URSINUS

DEER

Roosevelt Elk CERVUS ELAPHUS ROOSEVELTI

Black-tailed Deer ODOCOILEUS HEMIONUS COLUMBIANUS

Columbian White-tailed Deer ODOCOILEUS VIRGINIANUS LEUCURUS

AMPHIBIANS

BULLFROG RANA CATESBEIANA

CASCADE TORRENT SALAMANDER RHYACOTRITON CASCADAE

CASCADES FROG RANA CASCADA E

COLUMBIA SPOTTED FROG RANA LUTEIVENTRI S

COLUMBIA TORRENT SALAMANDER RHYACOTRITON KEZERI

COPE'S GIANT SALAMANDER DICAMPTODON COPEI

DUNN'S SALAMANDER PLETHODON DUNNI

ENSATINA ENSATINA ESCHSCHOLTZI I

GREAT BASIN SPADEFOOT SPEA INTERMONTANA

GREEN FROG RANA CLAMITAN S

LARCH MOUNTAIN SALAMANDER PLETHODON LARSELL I

LONG-TOED SALAMANDER AMBYSTOMA MACRODACTYLU M

NORTHERN LEOPARD FROG RANA PIPIEN S

NORTHWESTERN SALAMANDER AMBYSTOMA GRACIL E

OLYMPIC TORRENT SALAMANDER RHYACOTRITON OLYMPICUS

OREGON SPOTTED FROG RANA PRETIOSA

PACIFIC GIANT SALAMANDER DICAMPTODON TENEBROSU S

PACIFIC TREEFROG HYLA REGILLA

RED-LEGGED FROG RANA AURORA

ROCKY MOUNTAIN TAILED FROG ASCAPHUS MONTANU S

ROUGHSKIN NEWT TARICHA GRANULOSA

TAILED FROG ASCAPHUS TRUE I

TIGER SALAMANDER AMBYSTOMA TIGRINUM

VAN DYKE'S SALAMANDER PLETHODON VANDYKE I

WESTERN REDBACK SALAMANDER PLETHODON VEHICULUM

WESTERN TOAD BUFO BOREA S

WOOD FROG RANA SYLVATICA

WOODHOUSE'S TOAD BUFO WOODHOUSII

Page 2 of 3 Appendix DAPPENDIX D: Terrestrial and Amphibious Wildlife in the Wallapa Bay Watershed

REPTILES

CALIFORNIA MOUNTAIN KINGSNAKE LAMPROPELTIS ZONATA

COMMON GARTER SNAKE THAMNOPHIS SIRTALI S

GOPHER SNAKE PITUOPHIS CATENIFE R

GREEN SEA TURTLE CHELONIA MYDA S

LEATHERBACK SEA TURTLE DERMOCHELYS CORIACEA

LOGGERHEAD SEA TURTLE CARETTA CARETTA

NIGHT SNAKE HYPSIGLENA TORQUATA

NORTHERN ALLIGATOR LIZARD ELGARIA COERULEA

NORTHWESTERN GARTER SNAKE THAMNOPHIS ORDINOIDES

PACIFIC GOPHER SNAKE PITUOPHIS CATENIFER CATENIFE R

PAINTED TURTLE CHRYSEMYS PICTA

POND SLIDER PSEUDEMYS SCRIPTA

RACER COLUBER CONSTRICTOR

RINGNECK SNAKE DIADOPHIS PUNCTATU S

RUBBER BOA CHARINA BOTTA E

SAGEBRUSH LIZARD SCELOPORUS GRACIOSU S

SHARPTAIL SNAKE CONTIA TENUI S

SHORT-HORNED LIZARD PHRYNOSOMA DOUGLASS I

SIDE-BLOTCHED LIZARD UTA STANSBURIANA

SNAPPING TURTLE CHELYDRA SERPENTINA

SOUTHERN ALLIGATOR LIZARD ELGARIA MULTICARINATA

STRIPED WHIPSNAKE MASTICOPHIS TAENIATU S

WESTERN FENCE LIZARD SCELOPORUS OCCIDENTALI S

WESTERN POND TURTLE CLEMMYS MARMORATA

WESTERN RATTLESNAKE CROTALUS VIRIDI S

WESTERN SKINK EUMECES SKILTONIANU S

WESTERN TERRESTRIAL GARTER SNAKE THAMNOPHIS ELEGAN S

Page 3 of 3 Appendix D

### Appendix E

Threatened and Endangered S p ecies and
S p ecies of Concern within W ashington S t ate,
and the Potential for Imazapy r Exposure from Spartina T r eatmentAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeCascades FrogRana cascadaeAmphibian FCo SM N Mountain meadows, streams, ponds, and lakes above 3,000' (900 m), in thewater and vegetation around it.Columbia Spotted FrogRana luteiventrisAmphibian FCo SC P Mountainous areas near cold streams and lakes, wetlands. Reported to moveoverland in springand summer.Columbia TorrentSalamanderRhyacotriton kezeriAmphibian FCo SC N Live on the edges of cold, clear mountain streams. Can be found under gravelor in waterfall spray zones. Sometimes found away from streams during rainyseason.Larch MountainSalamanderPlethodon larselliAmphibian FCo SS N Prefers lava talus slopes and outcrops in dense Douglas fir stands; 100-3,900'(30-1,189 m).Northern Leopard FrogRana pipiensAmphibian FCo SE N From freshwater sites with profuse vegetation to brackish marshes and moistfields; from desert to mountain meadow. Not found on West Coast.Olympic TorrentSalamanderRhyacotritonolympicusAmphibian FCo SM N Live on the edges of cold, clear mountain streams. Can be found under gravelor in waterfall spray zones. Sometimes found away from streams during rainyseason.Oregon Spotted FrogRana pretiosaAmphibian FC SE N Mountainous areas near cold streams and lakes, wetlands. Reported to moveoverland in springand summer.Red-legged FrogRana auroraAmphibian FCo none P Usually found near ponds or other permanent water with extensive vegetation.Also likes dampwoods.Tailed FrogAscaphus trueiAmphibian FCo SM N Usually clear, cold swift-flowing mountain streams; sometimes found nearwater in dampforests or in more open areas in cold, wet weather.Van Dyke's SalamanderPlethodon vandykeiAmphibian FCo SC N Streams, mountain seeps, waterfall splash zones, and talus slopes at 1,500-5,000'(457-1,524 m).Western ToadBufo boreasAmphibian FCo SC P Near springs, streams, meadows, woodlands on Pacific Coast.Beller's Ground BeetleAgonum belleriBeetle FCo SC N A terrestrial species, not found in estuary habitatsHatch's Click BeetleEanus hatchiiBeetle FCo SC N A terrestrial species, not found in estuary habitatsAleutian Canada GooseBranta canadensisleucopareiaBird FCo ST P An uncommon visitor to coastalPage 1 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeAmerican PeregrineFalconFalco peregrinusanatumBird FCo SS P Open country, especially along rivers; also near lakes, along coasts, and incities. Migrates chiefly along coasts. Breeds from Alaska and Canadian Arcticsouth locally through mountainous West, and sparingly in East. Winters coastal,north to British Columbia and Massachusetts.Several Subspecies also represented by the WDFW as species of concern;these include the Peale's Peregrine.Bald EagleHaliaeetusleucocephalusBird FT ST Y Common resident to Puget Sound and Coastal WABlack TernChildonias nigerBird FCo SM P Freshwater marshes and marshy lakes in summer; sandy coasts on migrationand in winter. No sightings recorded in Willapa, but suitable habitat.Brown PelicanPelecanusoccidentalisBird FE SE P Resident of Pacific Coast from southern California south to Chile, dispersingnorthward as far as southern British Columbia after nesting season. Also onAtlantic Coast from North Carolina south to Venezuela.Burrowing OwlAthene cuniculariaBird FCo SC N Plains, deserts, fields, and airportsCassin's AukletPtychoramphusaleuticusBird FCo SC N Open ocean. Nests on sea cliffs and isolated headlands.Ferruginous HawkButeo regalisBird FCo ST N Prairies, brushy open country, badlands.Harlequin DuckHistrionicushistrionicusBird FCo none P Swift-moving streams in summer; rocky, wave-lashed coasts and jetties inwinter.Loggerhead ShrikeLanius ludovicianusBird FCo SC P Grasslands, orchards, and open areas with scattered trees; open grassywoodlands; deserts in the West.Marbled MurreletBrachyramphusmarmoratusBird FT ST Y Breeds in coastal rain forests; inshore waters at other times.Northern GoshawkAccipiter gentilisBird FCo SC P Breeds in coniferous forests; winters in farmlands, woodland edges, and opencountry. Rarelyrecorded from Willapa.Olive-sided FlycatcherContopus borealisBird FCo none* Y Boreal spruce and fir forests, usually near openings, burns, ponds, and bogs.Page 2 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeOregon Vesper SparrowPooecetesgramineus affinisBird FCo SC P Prefers relatively dry and sparsely vegetated areas with scattered tall structuresused for songperches.Sage-grouseCentrocercusurophasianusBird FC ST N A rare shrub-steppe species of the Columbia Plateau in areas wheredisturbance factors have disrupted mature shrub-steppe habitatSharp-tailed GrouseTympanuchusphasianellusBird FCo ST N Found in the North Central Cascades at altitude. Not coastalShort-tailed AlbatrossPhoebastria albatrusBird FE SC N An open ocean piscivore. Does not frequent coastal areas along Washington'sCoast. An extremelyrare bird.Slender-billed Whitebreasted NuthatchSitta carolinensisaculeataBird FCo SC Y Large trees in deciduous and mixed forests.Snowy PloverCharadriusalexandrinusBird FT SE Y Sandy coastal beaches and shore of salt ponds and alkaline lakes, fromWashington to Baha, CaliforniaSpotted OwlStrix occidentalisBird FT SE P Wet, coniferous, old-growth forests; innermost tidal denditricchannels along theWillapa Bay coast retain some adjacent old growth habitat potentiallysupportable for spotted owlStreaked Horned LarkEremophila alpestrisstrigataBird FC SC P Grasslands and lowland prairies.Tufted PuffinFratercula cirrhataBird FCo SC P Nests on vertical sea cliffs, in colonies or singly. Feeds at sea.Willow FlycatcherEmpidonax trailliiBird FCo none* P Dense streamside thickets, swampy thickets, wooded lakeshores and streams.Yellow-billed CuckooCoccyzusamericanusBird FC SC $B,RI P Moist thickets, willows, overgrown pastures, and orchardsIsland MarbleEuchloe ausonidesinsulanusButterfly FCo SC P Grasslands and Garry oak woodlands.Makah (Queen Charlotte)CopperLycaena mariposacharlottensisButterfly FCo SC P Sedge dominated fens (prairie terrain) containing swamp gentian within thecoastal rainforests of the Olympic Peninsula.Mardon SkipperPolites mardonButterfly FC SE P Fescue-dominated native prairie grasslands.Oregon SilverspotButterflySpeyeria zerenehippolytaButterfly FT SE P Coastal meadows in salt spray zone. Spartina meadows have displaced somehabitats where its forage, Viola adunca, might otherwisegrow.Page 3 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeTaylor's (Whulge)CheckerspotEuphydras edithatayloriButterfly FC SC P Native grasslands, prairies, and oak woodlands of Vancouver Island, the PugetSound basin, and the Willamette Valley.Valley SilverspotSpeyeria zerenebremneriiButterfly FCo SC P Moist Garry Oak ecosystems.Bull Trout (Coastal/PugetSound)SalvelinusconfluentusFish FT SC Y Coastal and mountain streams; deep pool of large, cold rives; deep cold lakes;rarelybrackish and salt water.Bull TroutSalvelinusconfluentusFish FT SC Y Coastal and mountain streams; deep pool of large, cold rives; deep cold lakes;rarelybrackish and salt water.Bull Trout (ColumbiaBasin)SalvelinusconfluentusFish FT SC Y Coastal and mountain streams; deep pool of large, cold rives; deep cold lakes;rarelybrackish and salt water.Chinook Salmon (UpperColumbia SP)OncorhynchustshawytschaFish FE SC N Coastal streams and rivers, intertidal areas , and open ocean.Chinook Salmon (SnakeR. Fall)OncorhynchustshawytschaFish FT SC Y Coastal streams and rivers, intertidal areas , and open ocean.Chinook Salmon (PugetSound)OncorhynchustshawytschaFish FT SC Y Coastal streams and rivers, intertidal areas , and open ocean.Chinook Salmon (LowerColumbia)OncorhynchustshawytschaFish FT SC Y Coastal streams and rivers, intertidal areas , and open ocean.Chinook Salmon (SnakeR. SP/SU)OncorhynchustshawytschaFish FT SC N Coastal streams and rivers, intertidal areas , and open ocean.Chum Salmon (HoodCanal SU)Oncorhynchus ketaFish FT SC Y Coastal waters; enters streams to spawn. Naturally spawned populations inthe Columbia drainage and naturally spawned summer-run populations in theHood Canal and its tributaries in Olympic Peninsula rivers between Hood Canaland Dungeness Bay are classified as threatened in Oregon and Washington.Chum Salmon (LowerColumbia)Oncorhynchus ketaFish FT SC Y Coastal streams and rivers, intertidal areas , and open ocean.Coastal CutthroatOncorhynchus clarkiclarkiFish FCo none Y Small, cool headwater streams and larger rivers; ponds and lakes; sea-runform in intertidal areas and inshore marine waters.Page 4 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangePackific Hake (C. PugetSound)MerlucciusproductusFish FC SC Y Coastal Waters as juveniles: Open waters as adults.Pacific Herring(DiscoveryBay)Clupea pallasiFish FC SC P Frequently offshore, but usually inshore in harbors and large estuaries duringspawning.Pacific Herring (CherryPoint)Clupea pallasiFish FC SC P Frequently offshore, but usually inshore in harbors and large estuaries duringspawning.Pacific LampreyLampetra tridentataFish FCo none P Migrate as adults to ocean. Widespread and often well offshore. Found inshallow waters to 820 ft.River LampreyLampetra ayresiFish FCo SC P Migrate as adults to ocean. Widespread and often well offshore. Found inshallow waters to 820 ft.Rock BassAmbloplites rupestrisFish none none N Vegetated and brushy stream margins of lakes. Most common in clear, silt freerockystreamsSalish SuckerCatostromus SP.Fish none SM N Pools and runs of small cool headwaters and creeks.Sand RollerPercopsistransmontanaFish none SM N Quiet backwater and pool margins of small to large rivers.Sockeye Salmon (SnakeR.)Oncorhynchus nerkaFish FE SC N Streams and rivers; lakes; intertidal areas and open oceanSockeye Salmon (OzetteLake)Oncorhynchus nerkaFish FT SC N Streams and rivers; lakes; intertidal areas and open oceanSteelhead (UpperColumbia)OncorhynchusmykissFish FE SC P Clear, cool streams and rivers; lakes; intertidal areas and open oceanSteelhead (Snake River)OncorhynchusmykissFish FT SC P Clear, cool streams and rivers; lakes; intertidal areas and open oceanSteelhead (MiddleColumbia)OncorhynchusmykissFish FT SC P Clear, cool streams and rivers; lakes; intertidal areas and open oceanSteelhead (LowerColumbia)OncorhynchusmykissFish FT SC Y Clear, cool streams and rivers; lakes; intertidal areas and open oceanWestslope CutthroatOncorhynchus clarkilewisiFish FCo none N Small, cool streams and rivers; lakesPage 5 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeBlack Right WhaleBalaena glacialisMammal FE SE N A marine pelagic species.Blue WhaleBalaenopteramusculusMammal FE SE N A marine pelagic species.California Bighorn SheepOvis canadensisCalifornianaMammal FCo none N Semi-open, precipitous terrain with rocky slopes, ridges, and cliffs or canyons;from alpine meadow to hot desert.Cathlamet PocketGopherThomomys mazamalouieiMammal FC SC N Prairies to mountain meadows. Known only from the type locality in WahkiakumCounty. It maynow be extinct.Columbian White-tailedDeerOdocoileusvirginianus leucurusMammal FE SE P Coastal and inland floodplains, in woodlands and scrub. Some habitat alongWillapa Bay may be suitable for this species, if it expands from its currentrange.Destruction Island ShrewSorex trowbridgiidestrructioniMammal FCo none N Numerous habitats; most common in moist fields, bogs, marshes, and moistwoods.Fin WhaleBalaenopteraphysalusMammal FE SE N A marine pelagic species.FisherMartes pennantiMammal FCo SE N Not coastal--a species of mature, dense forested habitat.Fringed MyotisMyotis thysanodesMammal FCo SM N Oak, pinyon, and juniper forests; desert scrub. Roosts in caves, mines,buildings, and other protected locationsGray WolfCanis lupusMammal FT SE N Open tundra and forestsGrizzly BearUrsus arctosMammal FT SE N Only an occasional visitor to Washington wilderness habitat in the NorthCascades; not coastalHumpback WhaleMegapteranovaeangliaeMammal FE SE N A marine pelagic species.Kincaid's Meadow VoleMicrotuspennsylvanicusMammal FCo SM P Lush, grassy fields; also marshes, swamps, woodland glades, andmountaintops.Least ChipmunkTamias minimusMammal none none* P Pastures, piney woods, rocky cliffs, and sagebrush deserts; often abundant inopen coniferous forests.Long-eared MyotisMyotis evotisMammal FCo SM Y Variety of habitats, from sage to high-altitude coniferous forests; mostly foundin forested regions. Sometimes roosts in buildingsPage 6 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeLong-legged MyotisMyotis volansMammal FCo SM Y Mainly coniferous forests. In summer, roosts in trees, crevices, or buildingsLynxLynx canadensisMammal FT ST N Deep, coniferous forest interspersed with rocky areas, bogs, swamps, orthicketsMazama (Western)Pocket GopherThomomys mazamaMammal FC SC N Prairies to mountain meadowsOlympic Pocket GopherThomomys mazamamelanopsMammal FC SC N Prairies to mountain meadowsPacific Townsend's Bigeared BatCoryhorhinustownsendiiMammal FCo SC P occur in a variety of habitats from desert shrub to deciduous and coniferousforests at a wide range of elevationsPallid Townsend's Bigeared BatCoryhorhinusTownsendiiMammal FCo SC P occur in a variety of habitats from desert shrub to deciduous and coniferousforests at a wide range of elevationsPreble's ShrewSorex prebleiMammal FCo SM P Open areas, woodlands, forestsPygmy RabbitBrachylagusidahoensisMammal FE SE N It is patchily distributed in the sagebrush-dominated areas of the Great BasinSea OtterEnhydra lutrisMammal FCo SE N Coastal waters within a mile (1.5 km) of shore; especially rocky shallows withkelpbeds and abundant shellfishSei WhaleBalaenopteraborealisMammal FE SE N A marine pelagic species.Shelton Pocket GopherThomomys mazamacouchiMammal FC SC P Native grasslands, prairies and oak woodlands of Mason County, Washington.Small-footed MyotisMyotis ciliolabrumMammal FCo SM P Usually lives in arid, rocky habitats including forests and woodlands.Sperm WhalePhysetermacrocephalusMammal FE SE N A marine pelagic species.Steller Sea LionEumetopias jubatusMammal FT ST N Stellers are found throughout the North Pacific Rim from Japan to centralCalifornia. Unlike California sea lions, Stellers tend to remain off shore or haulout in unpopulated areas.Townsend's Big-earedBatCoryhorhinustonsendiiMammal FCo SC P Western deserts and dry pine forests.Page 7 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeWashington GroundSquirrelSpermophiluswashingtoniMammal FC SC P Sagebrush and grassland habitats in Southeastern Washington and small areaof Oregon in Gilliam, Morrow, and Umatilla Counties.Western Gray SquirrelSciurus griseusMammal FCo ST P Woodlands and coniferous forests, particularly Quercus garryana woodlands.WolverineGulo guloMammal FCo SC N A wide range of habitats with circumpolar distribution, North American primarilymontane coniferous habitats.Woodland CaribouRangifer tarandusMammal FE SE N Usually found in small herds in boreal forests from British Columbia toNewfoundlandYelm Pocket GopherThomomys mazamayelmensisMammal FC SC P Native grasslands, prairies and oak woodlands of western Washington.Yuma MyotisMyotis yumanensisMammal FCo none* P Yuma myotis occur in a variety of habitats including riparian, and scrublandsand deserts, and forests.California FloaterAnodontacaliforniensisMollusk FCo SC N Shallow areas of clean, clear lakes, ponds and large rivers. They prefer lowerelevations and a soft, siltysubstrate to burrow into.Giant Columbia SpireSnailFluminicolacolumbianaMollusk FCo SC N Relatively pristine colder, clear streams of the Snake-Columbia River systemwith a high dissolved oxygen content.Newcomb's LittorineSnailAlgamordasubrotundata45 FCo SC P Rocky shores in the upper intertidal zone of marine coastal environments.Fender's SoliperlanStoneflySoliperla fenderiOther insect FCo none N Fender's soliperlan stonefly nymphs are exclusively found in seeps in theheadwaters of small streams. As adults, stoneflies are poor fliers and live alongthe shores of the streams.Lynn's ClubtailGomphus lynnaeOther insect FCo none N Clear streams that have relatively open canopies. In Washington, sightings ofColumbia clubtail have only been confirmed along the Yakima River in BentonCounty,Washington.Green Sea TurtleChelonia mydasReptile FT ST N Open-ocean species; no breeding colonies in WALeatherback Sea TurtleDermochelyscoreaceaReptile FE SE N Open-ocean species; no breeding colonies in WALoggerhead Sea TurtleCaretta carettaReptile FT ST N Open-ocean species; no breeding colonies in WAPage 8 of 9Appendix EAPPENDIX E:Threatened and Endangered Species and Species of Concern within Wahsington State,and the Potential for Imazapyr Exposure fromSpartinaTreatmentCommon Name Scientific NameAnimalTypeFederalStatusStateStatusPotentialEstuaryPresence? Habitat and RangeSagebrush LizardSceloporusgraciosusReptile FCo SC N Primarily areas of sagebrush and gravelly soils or fine-sand dunes. Never farfrom shelter such as stony piles, crevices, animal burrows. Preferred habitatnot supported in estuarine conditions.Western Pond TurtleClemmys MarmorataReptile FCo SE P Ponds and small lakes with abundant vegetation. Also seen in marshes, slowmovingstreams, reservoirs, and occasionallyin brackish water.Note: Fco = federal species of concern; FT = federally listed as threatened; FE = federally endangered;FC = Federal Candidate SpeciesSE = State endangered; ST = state threatened; SC = state species of concern© 2003Washington Department of Fish and WildlifePage 9 of 9Appendix E