UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

MEMORANDUM

JUN 0 9 2010 OFFICE OF

CHEMICAL SAFETY AND POLLUTION

PREVENTION

SUBJECT:

FROM:

T H RU :

TO:

Evaluation of a Request for a Public Interest Finding for the Conditional

Registration of AminocyclopyracWor and Aminocyclopyrachlor Methyl for

Weed and Brush Control (DP#376722) 01

William Phillips, II, Ph.D., Agronomist

Biological Analysis Branch

Biological and Economic Analysis Division (750 3P)

Arnet Jones, Chief ~v() -" -'vQ:/ j

Biologica l Analysis Branch

Biological and Economic Analysis Division ( 3P)

Mindy Ondish

Herbicide Branch

Registration Division (7505P)

PRODUCT REVIEW PANEL: June 02, 2010

S UMMARV

A request was submitted to the United States Environmental Prote ction Agency

(Agency) by the registrant E.I. DuPont de Nemours and Company (DuPont) to determine

whether a request for the conditional registrati on of a new acti ve ingredient for the broadleaf

herbicide am inocyclopyrachlor acid (DPX-MAT2 8) and meth yl (DPX-IU M44)

(aminocyclopyrachlor) is in the pub lic interest. The herbicide will be used in turfgrass (TG)

and vegetat ion management (VM) are as such as rights-o f-way , fence rows. ditch banks.

wildlife areas, native grass and turf areas. There will be 15 end-use products and 5 techn ical

active ingredients (15 EPs and 5 TGAIIMUP). Such a publ ic interest finding has many

compone nts; however, BEAD 's role in this process wa s to foc us on determining ifthere is a

need for this new pe sticide that is not currently being met by regist ered pesti cides and if

the be nefits from the new pesticide are greater than those from currently registered

pesticides or non-chemi cal control measures.

1
Overall, the data submitted was incomplete with respect to herbicide efficacy

comparisons and data rigor, and as such, the information provided by the registrant for

aminocyclopyrachlor failed to meet the requirement that the herbicide controls weed species

that are not controlled by currently registered herbicides. While mentioned in the registrant's

submission, but not a primary focus, the volatility of 2,4-0 and dicamba is important to

consider when being used around valuable ornamental plant materials. Because these two

herbicides are a staple ofthe commercial turf industry, if field use of aminocyc lopyachlor is

determined to have a lower volatility than 2,4-0 or dicamba it will be important to consider

this potential advantage as meeting the criteria that there is a benefit ofthis herbicide

registration over those from currently registered herbicides or non-chemical measures.

Future data submissions provided to BEAD will be evaluated to determine if

aminocyclopyrachlor meets the two criteria: 1)that there is a need for the new pesticide that

is not being met by currently registered pesticides, or 2)that the benefits from the new

pesticide are greater than those from currently registered pesticides or non-chemical

control measures. Until more information is provided regarding results of efficacy trials,

BEAD is unable to determine ifthis herbicide meets these criteria.

PUBLIC INTEREST FINDING POLICY

FIFRA section 3(c)(7)( c) authorizes the issuance of a conditional registration for a

new pesticide with specific restrictions. This interim registration allows temporary use of

a pesticide while full reg istration is being pursued. All three ofthe following conditions

must be met for a conditional registration to be granted: 1) insufficient time has elapsed

for the generation of data, since the requirement for that data was imposed; 2) use ofthe

pesticide will not cause unreasonable adve rse effects; and 3) use ofthe pesticide is in the

public interest.

The conditional registration of a new pesticide ingredient is presumed to be in the

publi c interest if one or more of the following criteria are app licable. I) it involves a

rep lacement for another pesticide that is of continuing concern to the Agency; 2) it

involves a use for which a section 18 emergency exemption has been granted, ifthe basis

for the exemption was the lack of a suitable alternative; or 3) it involves a use against a

pest of public health significance.

For pesticides that do not meet the criteria listed above for the presumption of

public interest, one ofthe following three criteria must be met. 1) there is a need for the

new pesticide that is not being met by currently registered pesticides, 2) the new pesticide

imposes less risk to human health and the environment than currently registered

pesticides, 3) benefits from the new pesticide are greater than those from currently

registered pesticides or non- chemical control measures. To determine ifthe criteria are

met with respect to currently registered pesticides, BEAD's rev iew for this part ofthe

public interest finding (PIF) will focus on items I and 3.

2
PJ;BL.lC INTEREST FINDING REQUEST

Dupont, the registrant ofthe herbicide aminocyclopyrachlor, has requested that the

Agency review its submitted information to determine if a conditional registration ofthis

herbicide is in the public interest. In support of its request for the Agency's review for

conditional registration, BEAD has received the following information:

I. a statement in support of a public interest finding

2. a list of university investigators

3. a summary report of comparative efficacy data for some of the more difficult to

control weed species that will appear on the product labels

4. 15 end-use product labels and 5 technical active ingredient labels (15 EPs and 5

TGAIIMUPs).

The registrant has stated that the primary basis for its request for the VM registration is

that this new herbicide will control certain invasive and noxious brush weed species that no

currently registered pesticides controls. The basis for the TG use registration is that this

herbicide has a higher efficacy on difficult to manage broadleaf weed species (BLW) as well

as herbicide resistant BLWas compared to other registered herbicides. Secondarily, for both

of these general use sites the registrant maintains that its herbicide will reduce the amount of

pesticides used to control brush and TG species due to its lower use rate. The registrant

believes that together these stated benefits of aminocyclopyra chlor make it in the public

interest to grant the conditional registration.

BIOLOGI CAL A~ALYSt ISTRODUCTION

Aminocyclopyrachlor is a pyrimidine carboxylic acids that belongs to the family of

synthetic auxins. The herbic ide labels will include uses in golf courses. sod production,

residential turf, and other TO uses as well as VM are as, which will include rights-of-way.

fencerows, ditch banks, wildlife areas, and native grass areas (Table I). Labeled rate s and

maximum number of applications will be 0.284 Ib acid equivalent (ae)!A with an annual

maximum of one application for VM, and 0.108 lb ae ! A with a maximum of three

applications or a total annual amount of 0.324 1b ae/A for TO. Application methods will

include ground boom for both sites, with the addition of aerial and basal bark applications,

injection, cut-surface, soil applied, and cut stubble/stump applications for VM. Labels for

these products will include lists of weed species controlled that will including weeds varying

from small annual weeds to tree and brush species. The use sites and weed spectrum are

similar to those of other herbicides in the same chemical family (Table 2).

3
Table 1. Aminocyclopyrachlor herbicide requested use sites for the control of annual,

broadleaf and brush weed species.

Sites for Use Examples of Specific Sites

Uncultivated Private, public and military lands such as airports, highway, railroad and

Nonagricultural utility rights-of-way, sewage disposal areas, etc.);

Uncultivated

Agricultural areas

Industrial sites

Natural areas

Release or

Restoration

Residential Turf

Industrial and

Professional Turf

Non-crop producing - such as farmyards, fuel storage areas, fencerows,

non-irrigation ditchbanks and waterways (de-watered), barrier strips, etc.

Lumberyards, pipeline, tank farms, etc.

Wildlife management areas, wildlife openings, wildlife habitats,

recreation areas, campgrounds, trailheads and trails

Native perennial grasses

Lawn maintenance - herbicide/fertilizer combinations

Unimproved turf established around manufacturing and industrial areas

as well as established turf in golf courses, athletic fields, sod farms, and

residences.

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Table 2 '. Selected potential alternative herbicides to arninocyclopyrachlor

Herbicide Sites Weeds Controlled

Aminocyclopyrachlor Rangeland. permanent grass, pastures. Annual and Per ennial Broadleaf Weed s and

rights-of-way. roadsides. and non-irrigation Wood ylBrush Speci es

ditch bank s, wildlife management areas.

natural recreat ion areas, cam pgrounds.

trailheads. tra ils. and turf (crop, gol f, and

resident ial)

Amin cpyralid

BromacH"

2,.1-0'-

Dicamba

Picloram"

Mecoprop

Clopyrlid

Glyphosate

Imazapyr

Rangeland, permanent grass, pastures,

rights-o f-way, roadsides , and non-irrigation

ditc h bank s, wild life management areas.

natural recreation areas, campgrounds.

nailheads, and trails

Cultivared and Non-crop land. and industrial

sites

Aquatic. cultivated and fallow cro p land ,

pasture. industrial, CRP land, turf{crop.

golf. and residential)

Cultivated and fallow crop land, pasture.

industrial, CRr land , turf (crop, golf. and

residental)

Rangeland, perm ane nt grass, pastures,

forestry, righ ts-of-way. roadsides. and nonirrigation ditch banks. wildli fe man agement

areas. natura l recreation areas, campgrou nds.

tra ilhead s. trai ls and forests

Commerci al and Residential Turf

Rangelan d. permanent grass, pastures,

forestry, rights-of-way, roadsides, Non-erop

and industrial sites

Cultivated and fallow crop land, pasture,

indu strial, CRP land

Aquatic, rangeland, permanent grass,

pastures, right s-of-way, roadsides, and nonirrigation ditch banks, wildlife management

areas. natural rec reauon areas. campgrounds.

nailhead s. trails. and turf'(crop, golf, and

resident ial). man y others

Cultivated and fallow crop land. forest!')'.

rights-of-way. roadside s. and non-irrigation

d itch banks, wildlife management areas

Annual and Per enn ial Broad1caf Weeds and

WoodylBru sh Species

Annual and Per ennial Broadleat wced.

Grass w eeds, Sedges. and WoodylBrush

Species

Annual and Perennial Broadleaf Weeds and

WoodylB rush Species

Annual and Pere nnial BroadJeafWeeds and

Brush Species

Annual and Per ennial Broad1eaf Weeds and

Wood ylBrush Species

Annual BroadleafWeeds

Ann ua l and Perennial BroadleafWeeds and

WoodylBrush Species

Ann ual and Perennial BroadleafWecds and

WoodylB rush Species

Ann ual and Perennial Broadte ar w ccd .

Grass Weed s, Sedges, and Woody/Brush

Species

Annual and Peren nial Bmadleaf and Grass

Weed s and WoodylBrush Spec ies

Note: Sites and weed s controlled are not com prehensive lists.

' Herbicide Handbook. Weed Science Society of Amcrica. Eighth Edition-2002 , Weed Scien ce Society. 810 E. 10th Street.

Lawrencc.KS 66044-889 7. USA

"Specifi c herbi cides discu ssed by registrant as bein g a "Replacement of Higher Use Rate Products," (See registrants

submission: R.M. Ashley. DuPont Crop Protection Subm ission, Publ ic interest finding stat ement in support of registration

ingred ients, amin ocy clopyrachlor and aminocyclopyrachlor methy1.)

5
D ISCUSSI01\

The registrant has stated that the primary basis for its request for the VM registration is

that aminocyclopyrachlor herbicide will control certain invasive and noxious brush weed

species that no currently registered pesticides controL The basis for the TG use registration is

that this herbicide has a higher efficacy on difficult to manage broadleaf weed species as

compared to other registered herbicides. Secondarily, for both of these use sites, the

registrant maintains that its herbicide will reduce the amount of pesticides used to control

brush in VM and TG areas due to its lower use rate. The registrant believes that together

these stated benefits of aminocyclopyrachlor make it in the public interest to grant the

conditional registration.

Efficacy and Alternatives

The efficacy data provided by the registrant was a collection oftrial results from 24

university researchers. The information included only means for treatments selected from

these herbicide trials and not the raw data. The results were not statistically evaluated across

trials. In order to facilitate a comparative assessment, a statistical analysis was needed. It is

for this reason that BEAD's review of the efficacy data regarding this herbicide use in VM

and TG data can only be discussed on a cursory level.

It is understandable that it would not be practical for the registrant to submit all of the

university research trial results to the Agency for evaluation, nor would the Agency be able to

evaluate all of the individual research reports. However, given the data sheets that were

provided it is clear that the registrant has access to, and most likely ownership of, the trial

data and should be able to use this data to conduct some type of meta-analysis in order to

provide some statistical rigor to their herbicide comparison claims. BEAD would evaluate

this type of analysis if it were to become available.

As stated earlier, the basis for this request is specific to the two general use sites, VM

and TG for this herbicide. The research efficacy data that was submitted includes weed

species that occur in both VM and TG sites as well as brush species that are key in VM sites.

The species found in both sites are mare's tail, russian thistle species, kochia, knapweed

species, and leafy spurge. In these studies, aminocyclopyrachlor was generally applied as a

foliar spray, but applications to brush species included basal bark treatments; however, data

was not submitted for the other application types that will appear on the VM product labels

(e.g. injection, cut-surface, soil applied, cut stubble/stump).

An attribute that the registrant states in its application is that this herbicide can

,·... control invasive and noxious weeds while allowing native grasses and other plants to

flourish, providing desirable understory f or wildlife." However, there was no information or

data provided regarding the issues of native grass safety or "Flashback" (passive loss through

roots) from the control of brush when restoring ecosystems and/or native habitats. These are

considerations with other herbicides in this chemical family and may need to be evaluated for

this herbicide.

6
The primary basis for the registrant's request for the VM registration is that this new

herbicide will control certain invasive and noxious brush weed species that no currently

registered pesticides control. Specifically stated, "Aminocyclopyrachlor also provides

excellent control 0/a number ofbrush species including Boxelder (Acer negundo), Hackberry

(Celtis occidentalis), and Sugarberry (Celtis laevigata) that currently are not being

effectively controlled by any other registered brush herbicides or herbicide programs." This

statement should be considered under the first criteria with which BEAD is charged, that

there is a need for the new pesticide that is not being met by currently registered pesticides.

Several herbicides in Table 2 are in the same family as aminocyclopyrachlor and have

the same basic weed spectrum. Data or information for a few ofthese herbicides and their

relative efficacy were provided in the trial results submitted by the registrant. The herbicides

that listed in Table 2 that were included in the list oftrial data were not included in all trials,

nor for all species tested. In many cases, the comparative efficacy ofmost ofthese herbicides

would have been important in order to evaluate the efficacy ofthis herbicide. The only

manner with which to consider the comparative efficacy of this herbicide is to discuss the

relative percent weed control using the industry standard of an acceptable control level of

>70%. However given the uncertainty regard ing the relative nature of the data, in this

document the standard of >80% will be used.

The only herbicide that does appear consistently throughout the efficacy package

submitted is imazapyr. Because the registrant singled out the three brush species (box elder,

hackberry, and sugarberry), the discussion below is focused on these species. Data for other

brush species was included in the registrant's submission; howeve r, the data for these species

followed the same method of evaluation and data presentation by the registrant, and overall

did not yield results much different from for those species below. Based on the registrant's

submitted data, box elder contro l with aminocyclopyrachlor was >80% as were imazapyr and

aminopyralid. Herbicides that would also be considered as potential alternatives such as

those in Table 2 were not included alone in the data, or were included but only in

combination with aminocyclopyrachlor. Hackberry was another species evaluated with

imazapyr but was not evaluated with other potential alternatives. In this group of data,

imazapyr contro l was <80% while the registrant's herbicide was greater. Applications made

to sugarberry included imazapyr, which did not meet the standard of 80% contro l as did

aminocycIopyrachlor.

While the data presented for the three "invasive and noxious brush weed species"

indicates perhaps what is probably good to excellent control, the data is incomplete with

respect to herbicide comparisons and data rigor, and as such, fails to indicate that

aminocyclopyrachlor contro ls brush weed species that are not controlled by currently

registered herbicides. The data does seem to indicate that this herbicide will be an important

component in an integrated pest management program, along with other herbicides in this

chemical family.

7
The basis for the TO use registration is that this herbicide has a higher efficacy on

difficult to control broadleaf weed species as compared to currently registered herbicides.

This statement should be considered under the first criteria with which BEAD is charged that

there is a need for the new pesticide that is not being met by currently registered pesticides.

The registrant discussed the comparative efficacy of its chemical with respect to

picloram, bromocil, and 2,4-0. In the case of picloram the registrant stated that "[t]he weed

and brush spectrum of aminocyclopyrachlor has demonstrated close, ifnot equivalent,

control of these species to picloram at use rates up to 4 times lower than picloram." The

comparison made for bromocil was that "[ilt is especially useful in situations where there are

ALS resistant species such as marestail, pigweed, kochia and Russian thistle.

aminocyclopyrachlor has similar activity on these ALS resistant species and would be used at

a much lower use rate f or control of these tolerant species as compared to Bromacil." As for

2,4-0 , ''" [a]minocyclopyrachlor has a similar range of spectrum on broadleafweeds and

superior control ofhard to control species including leafy spurge, Sericea lespedeza, the

thistle complex, and knapweeds, and would be used at a lower use rate than 2,4-D.

Given the statements in their submitted application, the registrant provided

contradictory information that the herbicide controls weed species that are not controlled by

currently registered herbicides. However, the use of this herbicide along with others in this

chemical family in controlling ALS and glyphosate resistant species will be important.

PEST ICI DE REDUCTION

The second basis for which the registrant has focused on is that its herbicide will

reduce the amount of pesticides used to control VM and TG weed species is due to its lower

use rate. While this statement seemingly meets the criteria that the benefits from the new

pesticide registration exceed those from currently registered pesticides or non-chemical

control measures, this qualification would make it necessary to determine whether the

volume of a pesticide product is related to toxi city. It is, however, out of the purview of

BEAD to discuss the toxicology of a pesticide; BEAD defers to the Environmental Fate

and Effects Division and the Health Effects Division for this determination.

Herbicide Chemistry Issues

As compared to herbicides used in TG and VM, this herbicide differs only slightly in

its mechanism of action but not in its mode of action. The mechanism of action for

aminocyclopyrachlor is the alteration of gene expression, which is the same as for the benzoic

acids, phenoxys, and the pyridine carboxylic acids. However, the registrant stated that the

mechanism of action for this herbicide is that "[t]he herbicide has unique fe atures acting via

a distinctive mechanism that targets a family ofauxin receptor complexes. " The mode of

action for aminocyclopyrachlor is uncontrolled cell division and growth, which is the same as

the benzoic acids, phenoxys, and pyridine carboxylic acids.

When comparing the mechanism and mode of action ofthe herbicides in this chemical

family, there is little difference. The registrant stated, however, that aminocyclopyrachlor is

B
" ...non-volatile and control[s] most broadleafweeds in turf without the need for phenoxy

herbicides." A study conducted by Strachan et all compared the volatility of

aminocyclopyrachlor methyl with dicamba, and aminopyralid. The research concluded that

the active ingredient did indeed have a low volatility in the laboratory; however, when mixed

with methylated seed oil (MSO) under the same laboratory conditions the volatility of

aminocyclopyrachlor methyl was comparable to that of dicamba. When the study was

replicated in the field the effects of aminocyclopyrachlor + MSO on soybean and kidney bean

was lower than dicamba. The conclusion of the research was that there needs to be more

research to understand the vapor movement of aminocyclopyrachlor under field condition.

The use of an herbicide for BLW control on golf courses and residential use sites with

a low volatility reduces the phytoxic effects to valuable ornamental plants. fffieid use of

aminocyclopyachlor demonstrates a lower volatility than 2,4-0 or dicamba it will be

important to consider this potential advantage as meeting the criteria that there is a benefit of

this herbicide registration over those from currently registered herbicides or non-chemical

measures. BEAD defers to RD, EFED, andlor HED to make this determination.

CONCLUSIO:ooiS AND FINDlJ'IlGS

Overall, the data submitted was incomplete with respect to herbicide efficacy

comparisons and statistical data rigor, and as such, the information provided by the registrant

for aminocyclopyrachlor failed to meet the requirement that the herbicide controls weed

species that are not controlled by currently registered herbicides.

Regarding the second basis for which the registrant focused, the determination that a

reduction in the amount of pesticides used to control weed species due to this herbicides

lower use rate is not in the purview of BEAD. Th is use rate reduction benefit claimed by the

registrant may be focus on a reduction in environmental loading of pesticides. BEAD

defers to the En vironmental Fate and Effects Division and the Health Effects Division for

this determination.

The potential low volatility of this herbicide in TG could be important in golf courses

and other sites where difficult to control BLW species are near and around expensive

ornamental plantings. While mentioned in the registrant's submission, but not a primary

focus, the volatility of2,4-D and dicamba is important to consider when being used around

valuable ornamental plant materials. Because these two herbicides are a staple of the

commercial turf industry, if field use of aminocyclopyachior is determined to have a lower

volatility than 2,4-D or dicamba it will be important to consider this benefit as meeting the

criteria that there is a benefit ofthis herbicide registration over those from currently registered

herbicides or non-chemical measures. BEAD defers to Registration Division, Environmental

Fate and Effects Division, and the Health Effects Division on this determination.

1 Strachan, S.D., M.S. Casini, K.M. Heldreth, J.A. Scocas, SJ . Nissen, B. Bukun, R.B. Lindenmayer, D.L.

Shaner, P. Westra, and G. Brunk. 2010. Vapor movement ofsynthetic auxin herbicides: aminocyclopyrachlor,

amtnocyclopyrachlor-methyl, dicamba, and aminopyralid. Weed Sci. 58:103-108

9
Future data submissions provided to BEAD will be evaluated to determine if

aminocyciopyrachlor meets the two criteria: 1)that there is a need for the new pesticide that

is not being met by currently registered pesticides, or 2)that the benefits from the new

pesticide are greater than those from curre ntly registered pesticides or non-chemical

control measures. Until more information is provided regarding results of efficacy trials,

BEAD is unable to determine ifthis herbicide meets these criteria.

10