United States

Department of Agriculture

Marketing and Regulatory Programs

Animal and

Plant Health Inspection
Service 

# Proposed Field Release of

L a r i cobius osakensis ( Coleo ptera: Derodont i dae)

,

a Predatory Beetle for Biological Control of

Hemlock Woo l ly Adelgid ( Adelges tsugae

), in the

Continental United States

Environmental Assessment,

June 20 102



# Proposed F ield Release of

Laricobius osakensis (Coleoptera:

D erodontidae)

, a Predatory B eetle for Biological Control of Hemlock Woolly Adelgid (

Adelges tsugae

), in

the Continental United States

Final Environmental Assessment,

June 20 10

Agency Contact:

Shirley A W ager

- Page , Chief , Pest Permit ting Branch
Plant Protection and Quarantine Animal and Plant Health Inspection Service U.S. Department of Agriculture 4700 River Road, Unit 133 Riverdale, MD 20737

– 1236

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– if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers.3 

## Table of Contents

I. Background and Introduction

................................ ..................... 4

II

. Purpose and Need for the Proposed Action

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

II I

. Alternatives

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

I V

. Affected Environment

................................ ............................. 11

V. Environmental Consequences

................................ ................. 1 7

V I

. Other Issues

................................ ................................ ........... 2 7

V I I

. Agencies, Organizatio ns, and Individuals C onsulted

............. 2 8

V I II. References

................................ ................................ ............ 2 9

Appendix 1

................................ ................................ .................... 384 

## I. Background and Introduction

The hemlock woolly adelgid (HWA) ( Adelges tsugae Annand) is a n introduced insect pest destructive to forest and ornamental hemlock trees ( Tsuga spp.) in the eastern United States. The adelgid feeds at the bases of needles, causing them to d ry out and result ing in needle loss . This prevents trees from producing new buds for the next year’s growth , and lead s to
branch dieback and often eventual death of the tree. Heavy infestations

hav e killed trees in as little as four years, but some survive longer with only a sparse amount of foliage at the very top of the crown (McClure et
al

. 2001)

. HWA has become a very important pest of eastern hemlock, Tsuga canadensis

, and Carolina hemlock, T. caroliniana in the eastern

United States because of the damage and mortality to trees ranging from landscape shrubs to old

, large

, forest trees . This pest has impacted federal parks, recreation a reas, an d forests; state

- managed f orest lands ; commercial and private landowners; and urban and suburban

communities.

T he first report of HWA in eastern U nited S tates came from the Virginia Department of Agriculture and Consumer Services in 1951 on planted

easter n hemlock in Richmond, VA (Stoetzel 2002). HWA now infest s 18

states and it is estimated that approximately 40 percent of the T.

canadensis range and 100 percent of the T. caroliniana range within the

United States i s infested ( Tighe et al. 2005). Becaus e HWA is adapted to high elevations in Japan w here winter temperatures commonly drop below

- 35°C (

- 63°F), it should continue to spread in eastern North America until it occupies the entire r ange of T. canadensis (see Appendix 1).

HWA infestation is fatal to eastern hemlocks of all ages, regardless of health prior to infestation ( McClure 1990 ), with tree mortality occurring

between four and ten or more years after infestation , dependin g on environmental conditions ( Orwig and Foster 1998 , McClure et al. 2001 ).

Mode s of dispersal for HWA include birds, deer, humans (via movement of nursery stock), or wind ( McClure 1990 , McClure et al. 2001).

Existing management options for HWA are ineffective, expensive,

temporary, or have nontarget impacts. For these reas ons, forest managers

and the U nited S tates D epartment of A griculture (USDA) Forest Service have sought to identify an effective, host specific biological control organism and release it into the environment for the control of HWA.5 

## II. Purpose and Need for the Proposed
Action

The USDA Animal and Plant Health Inspection Service (APHIS) is proposing to issue permit s for the release of a predatory beetle,

L aricobius

. osakensis (Coleoptera: Derodontidae). The agent would be used by the applicant for the biological control of HWA in the continental United States. Before permits are issued for release of L. osakensis

, APHIS must analyze the potential impacts of the release of this agent into

the continental United States.

The applicant’s purpose for r eleasing L. osakensis is to reduce the populations and the severity of infestations of H WA where it occurs in the

United States

. The HWA is a nonnative invasive pest in eastern North

America on eastern hemlock and Carolina hemlock causing damage and

morta lity to the trees

.

This en vironmental assessment 1 (EA) has been prepared, consistent with USDA, APHIS' National Environmental Policy Act (NEPA) implementing procedures (Title 7 of the Code of Federal Regulations (CFR), part 372). It examines the potentia l effects on the quality of the human environment that may be associated with the release of L

. osakensis to control infestations of HWA within the continental United States. This EA considers the potential effects of the proposed action and

its alternati ves, including no action



## I I I . Alternatives

This section will explain the two alternatives available to APHIS: no action

, and the action to issue permits for environmental release of L

. osakensis . Although APHIS’s alternatives are limited to a decisi on on whether to issue permits for release of L. osakensis , other methods

available for control of HWA are also described. These control methods are not decisions to be made by APHIS and are likely to continue whether or not permits are issued for environ mental release of L

. osakensis . These are methods presently being used to control HWA by public and private

entities

.

1 Regulations implementing the National Environmental Policy Act of 1969 (42

United States Code 4321 et seq. ) provide that an environmental assessm ent “[shall include brief discussions of the need for the proposal, of alternatives as required by section 102(2)(E), of the environmental impacts of the proposed action and alternatives, and a listing of agencies and persons consulted.” 40 CFR § 1508.9.6 A third alternative was considered, but will not be analyzed further. Under this third alternative, APHIS would have issued permits f or the

field release of L. osakensis

, but the permits would contain special provisions or requirements concerning release procedures or mitigating

measures. Due to the small size of L. osakensis, and the probability that it may disperse on its own after release, mitigating measures for containment

or retrieval would not be feasible

. No issues have been raised that would indicate that special provisions or requirements are necessary.



### A. No A ction alternative

Under the “No A ction ” alternative, APHIS wou ld not issue permits for the

field release of L

. osakensis

, so t he release of this agent would not take place in the United States

.

The following methods are presently being used to control HWA, and

these methods will continue under the no a ction altern ative and will likely continue even if permits are issued for release of L

. osakensis

.

1. Chemical c ontrol

Hemlock woolly adelgid infested hemlocks in the urban environment can

be chemically controlled by thoroughly spray ing infested trees with an appli cation of insecticidal soap, horticultural oil, or any one of numerous

other insecticides specifically labeled for this use. Oil and soap have been commonly used and are highly effective in killing adelgids but t wo spray treatments each year are usually ne cessary (McClure et al. 2001) and not

e conomically practical on larger scales. For example, the hydraulic application equipment required to spray larger trees cannot be used in rural forest situations without adequate access roads.

More recently

, system ic treatments of the insecticide imidacloprid

, using

either soil drench, soil injection or trunk injection techniques have been frequently adopted , with combinations of soil and trunk injections being most effective over both short and long term (Doccola e t al. 200 8 )

. T he soil or truck injection techniques do not require large equipment and appli cations of imidacloprid have been performed on specific high value

forested sites in many areas.

An integrated approach in the Great Smokey Mountain National P ark was employed on approximately 2

, 700 combined acres using foliar applications in developed areas (roads, campgrounds picnic areas, and drench applications in undeveloped sites, applied based on a priority system including site and infestation factors (J ohnson et al

. 2008).7 2. Silvic ultural c ontrol

Silviculture involves the management of forest areas or stands using techniques aimed at controlling the establishment, growth, composition, and quality of trees and other forest vegetation for certain obje ctives such as timber, wildlife

, or other ecological attributes. H emlocks are slow growing and their value is mainly environmental and not economic . Thus

, for most hemlock stands, s ilvicultural objectives are designed to ensure long term health of the as sociated ecological aspects of the site rather than for the production of timber. With essentially no ability to control the various modes of HWA dispersal, infestation cannot be prevented.

Further more, HWA feeds on all ages of hemlock tree s, and virtual ly all trees are susceptible to damage by the insect, regardless of age or site condition category

. Therefore the options for using silvicultural techniques to specifically mitigate HWA infestations are limited. S ilviculture for

HWA simply emphasizes good tree care, in as much as it can be accomplished

, by maintaining healthy trees on individual sites

.

3. Biological c o ntrol

Biological c ontrol efforts against HWA began in the early 1990’s. Typically, searches for natural enemies begin with seeking avai lable and new parasitoids (organisms that are parasitic on just one host, eventually killing it as the parasitoid completes development). However, t here were no parasitoids known worldwide , and in eastern United States, only generalist predators were obse rved to feed on HWA, and there were occasional fungal infections, also by non

- specific species. Foreign exploration for natural enemies of HWA began in 1992 in Japan)

, then

continued in China in 1995 , and in cluded western Canada starting in 1997 (Cheah et al

. 2004) as depicted in Figure 1 below

.8 Figure 1 Worldwide occurrence of Hemlock (red) with arrows showing where biological control agents were collected for importation to the United States.

More than 6 0 species of lady beetles (Coccinel l idae) we re eventually

collected in China (Yu and Montgomery 2008 ) , with most being in the subfamily Scymninae, the largest subfamily of lady beetles. The s e

p redator y beetles are quite small ( less than 3 m illi m eters ) and are “specialized predators” in that they att ack only certain groups of sucking insects (Homoptera) such as scales

, aphids

, mealybugs

- and adelgids.

T his group of tiny lady beetles contains t he genera Sasajiscymnus and Scymnus

. Both genera are found naturally only in Asia

. Sasajiscymnus

tsugae (S asaji and McClure) (formerly Pseudoscymnus tsugae ) (Coleoptera: Coccinellidae) was collected in Japan

, and t hree species of Scymnus were brough t to the United States from China. The Scymnus species were studied in quarantine and proved to be very speciali zed adelgid predators

– the adults fed on aphids to some extent but otherwise they fed on all stages of adelgids (such as HWA) and t he larvae could not survive unless fed adelgid eggs (Cheah et al

. 2004)

.

L. nigrinus

, from the beetle family Derodontida e
, was collected i n western Canada

. Thi s is also a very small predatory beetle that appears to be a specialized predato r

.

L. nigrinus

, Sasajiscymnus tsugae

, and Scymnus sinuanodulus have been

released at numerous locations in eastern United States star ting with S.

tsugae in 1995

, and after 2000 for the other two species

. Establishment

has been achieved by all three species , although establishment and build

up of S

. tsugae has been very limited despite the release of over two

million individuals of diff erent stages (Salom et al

. 2008). The degree to
which these predators will suppress HWA populations has yet to be determined, however, since t he majority of releases have been relatively recent ( during just the last 5 years )

.9 Other biological control efforts include additional sp ecies of predatory

beetles , and are in various stages of evaluation and research. Current

efforts also include the development of effective fungus

- based pesticide formulations using Lecanicillium muscarium (formally Vericilliu m lecanii ) and Beauveria bassiana ( Cheah et al. 2004, Gouli et al. 2008)

.



### B

. Second Alternative: Issue p ermit s for
environmental r elease of Laricobius osakensis

Under this alternative, APHIS would issue permit s for the field rel ease of

L. osakensis . Th ese permit s would contain no special provisions or requirements concerning release procedures or mitigating measures.

1. Description and Taxonomy of Laricobius osakensis

Laricobius osakensis Montgomery and Shiyake is a newly des cribed species (see Montgomery et al. in press

, for additional information). Traditional morphological and molecular techniques have been used to identify L

. osakensis

. Voucher specimens are currently located at the Osaka Museum of Natural History in Osa ka, Japan, the USDA Forest Service, Northern Research Station in Hamden, CT, and the Beneficial Insects Quarantine Laboratory at Virginia Tech in Blacksburg, VA

.

2

. Life history

B ased on weekly field sampling that has been conducted for the past year

in Japan, a dults emerge from the ground in the fall and go to hemlock

trees. Adults feed on HWA through out the fall and winter months. Egg laying begins in December and continues through March. Larvae are active and feeding on HWA eggs from January through A pril. As

p repupae, they drop to the ground, and bury into the soil for pupation. As adults, they enter diapause (dormancy) for the summer months

.

T he life histories of L

. osakensis and HWA are synchronized

, although

HWA has two generations per year and L

. osakensis just one. The life history of HWA is characterized by the aestivation (summer dormancy) of

the first stage nymphs during the summer (approx imately June through September), with growth resuming in the fall , and continuing through

winter and s pring. HWA eggs are present typically from March into May and again in June (McClure et al. 2001). Laricobius larvae are likewise present during late February through May (see Figure 2 )

. Larval development is completed and adults emerge by June , but the adults go into a period of dormancy during the summer as well

, then resume activity

and feed during the f

all and winter on all stages of HWA which are

present.10 Figure 2 Summarized presence of L. osakensis life stages from sampling HWA

infested hemloc k in the Osaka region of Japan 2007 and 2008

.

3 . Native geographical r ange

L. osakensis has been recorded from only eight of Japan’s 72 prefectures (provinces) . It has been collected from well below 34° N latitude to just above 36° in Japan and at alti tudes ranging from 300 to almost 7000 ft

. Given the latitude s and altitude s from which this species has been

recor d ed, it is predicted that it will survive throughout most of the HWA

infested range of Tsuga spp. in the eastern U nited S tates

. Furthermore, lab rearing indicates that L. osakensis is capable of surviving very low

temperatures ; as it lays eggs at 0°C and continues to feed at

- 7°C (A

. Lamb, personal observation)

.

4 . Impact on HWA

HWA is not a pest in the areas of Japan where L. osakensis h as been

collected. As explained below, L. osakensis has an observable direct effect on the target host A. tsugae . Exclusion cages deployed throughout the winter months in Japan show a large decrease of HWA on branches exposed to L. osakensis compared to caged branches where HWA remained, but predators were excluded

. A f ield s tudy was conducted during the winter months in Japan at three locations with sufficient HWA populations

. T he stage and number of adelgids, as well as dead adelgids

and the cause of d eath was recorded ( i.e., caused by a chewing insect, sucking insect, fungus, or during aestivation). During that time, L.

osakensis was the only predato r present on the hemlock trees, and predator11 abundance was positively correlated to percent mortality o n a site by site

basis (Lamb et al. 2008). In the lab, L. osakensis appears to feed more voraciously on HWA than L. nigrinus , and also larval development rates

are faster, with only 75 percent and 62 percent as much time in the larval

stage as L. nigrinus at 9°C and 12°C

, respectively (Lamb et al. 2008)

.



## I V . Affected Environment

A. Native North American Species

1. Species related to the Hemlock woo l ly adelgid

There are 13 described species of Adelgidae known to be native to No rth America (Havill and Foottit 2007) , and at least three introduced specie s besides HWA , including two known pests, the balsam woo l ly adelgid ( Adelges piceae ) and the e a stern spruce gall adelgi d ( Adelges abietis ) ( Johnson and Lyon 1991 ). Identified h osts of these 16 species ar e s pruce,

p ine, f ir, D ouglas

- f

ir, l arch

, and hemlock. The HWA is the only adelgid species in North America, and possibly the world, which utilizes hemlock.

Adelgids have complex life cycles which can be divided into two types: species with only parthenog enetic (no sexual reproduction) cycle s; and holocyclic species, which are species with both parth en ogenetic and

sexual cycles

. Havill and Foottit (2007) provide the following description of adelgid life cycles and habits: Five generations make up the typic al adelgid holocycle. Three are produced on the primary host, where sexual reproduction and gall formation occur; two are produced on the secondary host that supports a series of asexual generations. The entire cycle takes two years to complete. Spruce ( Pi cea spp.) is always the primary host and another conifer genus (

Abies

, Larix

, Pseudotsuga

, Tsuga , or Pinus ) is always the secondary host. Adelgids are highly host specific: A given species can survive and reproduce only on certain tree species within a sin gle primary and secondary host genus. For example, Pineus orientalis can alternate between Picea orientalis and Pinus silvestris , but it cannot

survive on Picea abies, Pinus strobus , or Pinus cembra

.

The primary hosts for HWA in Japan appear to be the spr uce species

Picea jezoensis hondoensis and P. polita, neither of which occurs in eastern north America, so HWA cannot complete the sexual cycles in the

eastern United States.

2. Hemlock Woo l ly Adelgid12 a. Native range of hemlock woolly adelgid

HWA is na tive to Asia and likely also western North America ( Cheah et al. 2004, Havill et al. 2006). The population of HWA in the Pacific

Northwest of North America was first described on western hemlock by Annand (1924)

. Havill et al (2006) determined that this population is molecularly distinct from populatio ns in Asia and the eastern United States, and thus likely native to the region

. It is present throughout this region of western North America, but at typically harmless densities ( Furniss and Carolin 1977

, Tait et al. 1985 ).

b. Present distribution of HWA in eastern North America
In eastern North America, HWA has spread gradually from the

introduction in Richmond VA and presently is known to occur in 18 states from Maine to Georgia (see Appendix 1 ). A pp roximately 40 percent of

the T. canadensis range within the U nited S tates and 100 percent of the T.

caroliniana range i s infested ( Tighe et al. 2005 ).

c. HWA life history in eastern United States Basically, t here are three parthenogenetic generations of HWA each year

on hemlock in eastern United States: an overwintering generation that occurs from July through April in the northeast, and two spring generation s that occur simultaneously from April through June. All three of these generations have six stages of development: the egg; four nymphal instars (size stages) ; and the adult. One spring generation remains on hemlock, the other migrates to spruce, but the nymphs that hatch and begin to feed on spruce in July all die within a few days; none

develo p beyond the first instar on any of 15 different north American

spruce species ( McClure 1987, 1991 ) . The adults from the spring generation (all female) each lay a cottony egg sack sometime in June or July

. The crawlers (first stage nymphs) that hatch mi grate to new growth

on the tree and settle to feed but enter aestivation that lasts until October when they resume feeding (McClure 1996).

3 . Species related to Laricobius osakensis

Species in the genus Laricobius (Coleoptera: Derodontidae) feed only on Adelgidae. The remaining species of Derodontidae in North America feed on various species of fungus during their entire life cycle. Laricobius is represented in North America by 4 species : L. erichsonii Rosenhauer, L.

laticollis Fall, L. nigrinus Fend er and L. rubidus LeConte

. L. erichsonii

,

was introduced from Europe as a biological control agent of the balsam woolly adelgid, Adelges piceae (Ratzeburg ). L. laticollis has been infrequently collected in the northwest and host associations are not

kno wn ( Zilahi

- Balogh et al. 2003 b) . The remaining t wo species of

Laricobius

, L. rubidus (eastern N orth A merica ) and L. nigrinus (western13 N orth A merica )

, have been noted feeding on HWA. Laricobius rubidus completes development, and survives well on a diet of HWA (Zilahi

Balogh et al. 2005 ). It is present in Connecticut (Montgomery and Lyon 1996), North Carolina, Virginia (Wallace and Hain 2000), Maine, New Hampshire, Massachusetts, District of Columbia, Pennsylvania, New York, Michigan, Quebec, Ontario, and N ew Brunswick (Lawrence 1989, Downie and Arnett 1996). The primary host of L. rubidus is the pine bark adelgid, Pineus strobi Hartig (Clark and Brown 1960) , and is not commonly observed feeding on HWA

.

The known distribution of L. nigrinus ranges from nort hern California to

British Columbia, Alberta, and northern Idaho ( Furniss and Carolin, 1977;

Lawrence 1989). An extensive 2 year survey of predato rs of HWA in Washington and British Col umbia resulted in the collection of 55 species of predators. Just thr ee species, Laricobius nigrinus

, Leucopis argenticollis Zetterstedt, and Leucopis atrifacies (Aldrich) (Diptera: Chamaemyiidae) comprise 59 percent of all the predators collected, with L. nigrinus being the most abundant (Kohler et al. 2008).

Laricobius nigrinus has one gen eration per year which is very well synchroniz ed with HWA throughout the year (Zilahi

- Balogh et al. 2003 a ). Both the predator and prey are active in the fall, winter, and spring, and

both diapause in the summer. A dults emerge from the soil in the fall, disperse to hemlock branches

, feed on HWA nymphs, adults, and eggs (available during early

- mid spring) , and then die. In the lab oratory tests conducted at Virginia Tech

, L. nigrinus completed development on HWA

but not on several other e astern adelgids and a phids tested. Because of its specificity to HWA, L. nigrinus was release d from quarantine by USDA

APHIS (Zilahi

- Balogh et al. 2002) , and has subsequently been released

in 16 eastern states where HWA is present.



### B. Hemlock R eso urces in North America

Eastern hemlocks

, T. canadensis

, are long

- lived, late successional climax trees that, if left undisturbed, eventually dominate stands. Easter n hemlock, may take 250

- 300 years to reach maturity

, live for 800 years

, and attain height s of 150

- 175 feet. E astern hemlock is the most shade tolerant tree species in North America, capable of surviving underneath a shaded forest canopy for as long as 350 years (Quimby 1996). Because it is so shade tolerant and long

- lived, hemlo ck is a late successional (or "climax") tree that can dominate a forest for centuries. Eastern hemlock forests create distinctive microclimates and provide an important habitat for a wide variety of wildlife. In the Northeast, 96 bird and 47 mammal species are associa ted with hemlock forests ( Yamasaki et al. 2000). Of these, at least eight species of birds and ten speci es of14 mammal s have strong ecological linkages with hemlock forest habitat. In

Connecticut alone , a lmost 90 species of birds use hemlock as a food

sour ce, nesting site, roost site, or winter shelter (McClure et al. 2001)

. Examples of birds include black

- throated green warbler

, blackburnian

warbler

, blue

- headed vireo , winter wren, red

- breasted nuthatch, ruffed grouse, and the northern goshawk. Examples of mammals include black

bea r, bobcat, snowshoe hare, red squirrel, and southern red

- backed vole.

Hemlock is a n important winter habitat for white

- tailed deer. M any native plant species thrive in hemlock stands, including leatherwood, rattlesnake plantains, bunchberry, goldthread, b luebeard, Canada mayflower, wood

sorrels ( Evans et al. 1996, McClure et al. 2001)

.

Hemlock forests are often a critical factor in supporting native brook trout populations, by main taining cool stream temperatures and stable flows

. A study conducted by Snyder et al. ( 2001 ) in the Delaware Water Gap

National Recreation Area showed that s mall streams in hemlock forests are three times more likely to support native brook trout populati ons than similar streams in hardwood forests in the park

. The study showed that

small streams in hemlock forests are typically 1

- 2 ° C (2

- 3.5 ° F) cooler in the

summer than similar str eams in hardwood forests. Furthermore, hemlock forest streams typically su pport about 65 species of aquatic insects, compared to only about 35 species in hardwood forest streams. About 15 species of aquatic insects seem ed to occur almost exclusively in hemlock

forest streams in this park ( Snyder et al. 2001 ).

For these and othe r reasons
, h emlock stands are very popular recreational sites for fishing

, hiking , hunting and bird watching

. H emlock is not a valuable timber species, but it is used widely for pulpwood and utilitarian

us es (such as pallets)

. Hemlocks are valued landsca pe plants , however:

with 274 cultivars of eastern hemlock, it is one of the most cultured and cultivated landscape trees in the United States (McClure 2001)

.



### C. Relationship of HWA with eastern hemlocks

1. Continued s pread of hemlock woolly adelgid

McClure and Cheah (1999) reported that f rom 1985 to 1999, the rate of spread of HWA averaged nearly 30 km (19 miles) per year. A later report by Evans and Gregoire ( 2007) calculated an average rate of spread of 12.5 km (7.8 miles) per year since 1990. Ho wever, several factors influenced this rate of spread, the most important being exposure of the HWA nymphs to temperatures of around

- 25°C (

- 13°F). Thus the average rate of spread is only 8 km (5 miles) per year for Pennsylvania and north, and 15.6 km (9. 7 miles) per year for areas further south. Winter mortality of15 HWA has been observed on many occasions. The lowest temperature tolerated by a sample of individuals from both northern and southern US sites appears to be approximately

- 18°C (0°F), with som e variation between individuals, and more individuals in northern sites tolerating temperatures slightly lower than 18°C ( Costa et al. 2008 ). Nevertheless, i t is widely considered that HWA will eventually occupy all of the natural range of eastern hemloc ks (see Appendix 1 )

2. Impact on hemlock resources

a. Tree decline and mortality Eastern hemlock is classified as highly susceptible to HWA (Hoover et al. 2008). HWA has caused significant mortality of hemlock trees over the last 20+ years. As HWA in festations rapidly spread to other states in the 1980’s, and these HWA outbreaks had steadily grown in size, impacts from HWA infestation appeared to be worsening and by the mid 1990’s tree mortality was being reported from at least four states.

Tree de cline and mortality is highly variable site to site and year to year, often showing cycles of decline and regrowth and decline for individual trees and stands, mainly in response to HWA induced changes in nutritional quality of the tree on which they feed (McClure et al. 2001). Site and weather factors (i.e., drought) plus secondary pests attacking the weakened trees, are thought to influence when and where mortality occurs ( Souto et al. 199 6). For example, in Shenandoah National Park, some sites experien ced a rise in mortality from 8 percent to 48 percent in just two years, with several site factors deemed to be important including, elevation and which cardinal direction a slope faces (Blair 2002).

By about 2005, hemlock mortality and logging in antici pation of mortality had become so widespread that there was concern about the future viability and preservation of the species. However, there appears to be some innate resistance in a small minority of surviving hemlocks from devastated stands, based on propagating and then challenging these apparently resistant trees with HWA infestation (Casswell et al. 2008).

b. Economic, Social and Recreational Impacts

Landowne rs today have several options for monitor ing and manage ment HWA and tree mortality ( Ward e t al. 2004, Orwig and Kittredge 2005

, Costa and Onken 2006). However, no practical options are available to prevent h emlock decline in forest settings, and thus, these stands are transitioning to hardwoods and invasive plants ( Orwig and Foster 1998, Orwig et al. 2002, Eschtruth et al. 2006).

Loss of hemlock landscape trees due to HWA infestations in residential properties has been estimated at $2,000

– $7,000 per home (Holmes et al.16 2005). Hemlock l osses as a forest product resource have not been

estima ted due to the fact that hemlock is not an especially valuable or unique forest product resource.

Hemlock mortality in the forest does have significant impact on recreational use, and large federal parks have engaged in integrated pest management (IPM) programs to address the varied recreational and ecosystem needs on their properties. For example, long term monitoring, ecosystem studies, and management efforts were begun at the Delaware Water Gap National Recreation Area in 1993 (the Park was originall y infested in 1989). Monitoring has shown a rapid decline and mortality and as of 2006, 28 percent of originally healthy plot trees had died and none of the remaining trees were in healthy condition (Evans and Shreiner 2008). The Great Smokey Mountains N ational Park has engaged in an aggressive IPM program to respond to the infestation which threatens over 35,000 acres of hemlock dominated forest (Johnson et al. 2008).

3. Ecosystem impacts of HWA

Richard Evans (2002) of the National Park Service comme nted that the “decline and loss of our remaining eastern hemlock stands could be more ecologically significant than the loss of American chestnut ( Castanea

dentata ) in the early 1900s due to chestnut blight” due to the fact that hemlock would not be replac ed by ecological equivalent species as occurred with the loss of the American chestnut. The large scale removal of hemlock trees due to HWA caused mortality, and in some cases the resulting salvage logging of stands is well documented ( Kizlinski et al.

20 02, Orwig et al. 2002, Foster and Orwig 2006)

Impacts include negative effects on brook trout (reversal of cooler summer and warmer winter stream temperatures), carbon cycling ( Nuckolls et al. 2009), soil and water c hemistry (Yorks et al. 2003). Loss of foliage and tree mortality in hemlock dominated stands often results in the invasion of exotic and native species which provide less shade and cover during the summer and winter seasons, significantly impacting temperature and

moisture microhabitats.

Redu ction in biodiversity after tree mortality due to HWA has been reported extensively ( Yamasaki et al. 2000

, Brooks 2001 , Evans 2002, Snyder et al. 2002, Tingley et al. 2002, Ross et al. 2003, Ross et al. 2004, Buck et al. 2005, Ellison et al. 2005, Lishawa et al. 2007) . Hemlock mortality is also changing ecosystem processes, structure, and function ( Jenkins et al. 1999, Stadler et al. 2005, Cobb et al. 2006, Stadler et al. 2006), wa ter quality (Yorks et al. 2003).17 

## V

. Environmental Consequences

A. No a cti on

The infestation and damage caused by HWA in urban and forest landscapes has received considerable attention from landowners and landmanagers, both public and private. Several management tactics have been implemented to reduce the infestation level of HWA and the damage and mortality it causes. The use of chemical insecti cides and biological

controls at current levels would be expected to continue if the “no action”

alternative is chosen. These environmental consequences may also occur even with the implementation of the biological control alternative, depending on the efficacy of L. osakensis to reduce infestations HWA and levels of damage to eastern hemlocks

.

Similarly, the current rate of spread, and levels and trends of eastern

hemlock mortali ty and other environmental consequences from infestation by HWA are expected to continue if the “no action” alternative is chosen. Likewise, these environmental consequences may also continu e at some
level even with the implementation of the biological co ntrol alternative

1

. Impact f rom u se of other control methods

a. Chemical control In recent years chemical control of HWA in both ornamental and forest situations has predominantly utilized imidacloprid applied as a soil drench, soil injection or tr unk injection. The injection techniques use a Kioritz injector (soil) or any of a variety of inject ion systems for trunk injection.

S ome proprietary designs have been specifically developed for application against HWA (Doccola et al. 2008). Imidacloprid acts systemically ( taken up by the hemlock tree and is translocated via the plants vascular system )

. Typically pest suppression is evident for more than one year after application ( Webb et al. 200 3 ).

It appears that very little to no run off occurs fr om properly applied soil injections (Churchel et al. 2008). Further, h emlocks frequently grow in

stream

- side locations and in steep, rock y ravines with little intact soil

, and trunk injection is used instead of soil injection in t hese situations

. Another avenue for imidacloprid entry into the environs outside of the live tree is

v ia leaf fall in deciduous trees. H owever with the needle retention of hemlock, this is less of a concern. Other insecticides will have different

environmental fate scenarios.

Predatory organisms feeding on HWA on treated plants have the potential18 to be exposed to insecticide s , including imidacloprid, through ingest ion of contaminated prey. For example, predator poisoning was observed in o ne laboratory trial that investigate d t his issue . However, a strong feeding preference for health y (untreated) adelgids was shown by L. nigrinus and Sasajiscimnus tsuga (Eisenback et al. 2008)

. A secondary impact could

result from ingesting poorer quality prey items (i.e., less preferred and less suitable prey species) in treated areas

.

b. Biological c ontrol

I nformation from surveys of native parasites and predators of HWA

, indicates there are no parasites

, and that the predators attacking HWA are generalist species, most of which were pred atory flies in the families Cecidomyiidae, Syrphidae, and various lacewings ( C h rysopidae, and

Hemerobiidae ) . Only two co l eoptera n predators were noted, the invasive

la d ybeetle

, Harmonia axyridis , and Laricobius rubidus . However

, predator abundance was n ot great enough to exert any controll ing effect (Montgomery and Lyon 1996; Wallace et al. 2000; Salom et al. 2008).

Three species of predators have been released in eastern United States against HWA: Laricobius nigrinus (from northwestern U nited S tates ),

and Sasajiscimnus tsuga, and Scymnus sinuanodulu s (both from Asia )

. Many of these releases have been in recent years, thus, recovery and establishment is limited or not yet confirmed in many areas (Grant 2008, McDonald, et al. 2008). Recovery of the Asi an coccinellid predators has

been limited despite widespread releases and the release of over 2 million

S. tsugae

. However, Laricobius nigr inus has been recovered in 60 per

cent of release sites ( Mausel et al. 2008). Population buildup of this species ha s been noted in a few sites, for example in northwestern North Carolina (McDonald et al. 2008).

Research of other biological control agents continues, including release and recovery efforts for the three species mentioned above (Salom et al. 2008)



### B. Issue permit s for environmental release of L.
osakensis

1. Effe ct s on target non target prey species

a. Scientific literature and sources The genus Laricobius is kno wn to be specific to Adelgidae ( Zilahi

- Balogh

et al

. 2003b )

. Museum specimens at the Osaka Museum of Natural History were all collected on Tsuga sieboldii and T. diversifolia infested

with HWA. Hundreds of adult s , eggs, and larvae of L. osakensis have also19 been collected from HWA on T. sieboldii during 2006 and 2007 visits to Japan for re search

.

L. nigrinus likewise may have become somewhat specialized on HWA in

western North America. Zilahi

- Balogh et al. ( 2007) reported that L

. nigrinus highly preferred HWA over three other adelgid

, two aphid and one scale species, and that it could not complete larval development on

these alternate hosts yet was successfully reared on HWA.

b. Field Observations

L. osakensis appears to be well adapted to this host

, feeding specifically on it. The seasonal cycles of the life histories of the two spec ies are tightly synch roniz ed as is evident in several regions in Japan. For example, during autumn 2008 in northern Japan , HWA became active on Oct ober

14 and predators were found feeding on it , while at the same time in the Kansai area, regular sampling h ad revealed that HWA was still in diapause on October 13 and no predators were found.

L. osakensis appeared to have an observable direct effect on HWA

. This

was shown by a fie ld test in Japan in winter 2007

- 2008 using cages on hemlock branches which prev ented the free living L. osakensis in the area from feeding on the HWA inside the cages. There was a large decrease of HWA on branches exposed to L. osakensis compared to caged branches.

c. Host specificity testing Host range testing was conducted usin g adelgid species and other related species available in North America

. Several adelgid hosts were used, as well as two scale species, and a woolly aphid. These alternate hosts were chosen because they are closely related to HWA, or are on hemlock trees,

or because they have a specific non

- target concern. The results indicate

that HWA

, A delges t

sugae
, is the preferred host. Following is additional information about these species and results from these tests.

i. Species tested Adelgid species

Balsam woolly adelgid ( BWA ), Adelges piceae (Ratz.)

, is of European origin but is now distributed in eastern and western North America and

attacks various firs trees ( Abies spp. ). Pine bark adelgid ( PBA ), Pineus

strobi (Hartig), is native to the eastern U nited S tates

, and mainly attacks eastern white pine, Pin us strobes, but occasionally attacks other species of pine ( Pinus ). Larch woolly adelgid ( LWA ), Adelges laricis Vallot, is native to Europe and attacks larch ( Larix spp. ) in North America. Eastern

spruce g all adelgid ( ESGA ), Adelges abietis (Linneaus), introduced from Europe, primarily attacks white spruce ( Picea abies ) and Norway spruce ( P. glauca )

.20 Woolly a p hid and scales Woolly alder aphid ( WAA ), Paraprociphilus tessellates (Fitch), is generally cons idered a pest, but it may be an insect of concern for non

targets effects because it is the host of the only carnivorous Lepidopteran in North America, the harvester butterfly, Feniseca tarquinius (Fabricius). WAA is found east of the Mississippi river an d requires both alder and silver maple to complete its lifecycle. This aphid is woolly, therefore

there has been some concern that Laricobius would be attracted to it. Elongate hemlock scale ( EHS ), Fiorina externa Farris, is a scale of Japanese origin tha t is found in several eastern states where it has been introduced and spread. It attacks both eastern and Carolina hemlocks, T.

canadensis and T. caroliniana , thus

, it i s freq uently in the same areas as

HWA. It is considered a pest and contributes to the decline in hemlock

trees. Pine needle scale ( PNS ), Chionaspis pinifoliae (Fitch), is a native scale that is commonly a pest on coniferous trees.

ii. Tests conducted:

No

- Choice Tests

– Adult Feeding and Oviposition

Female L. osakensis were placed indi vidually on HWA, BWA, or PBA for 5 days at 12°C

, and the number of host eggs eaten and the number of eggs

laid was recorded (see Table 1). Female L. osakensis were placed individually with WAA for 7 days , and the number of aphids eaten was

recorded

. Adu lt feeding and o viposition (egg laying) was higher on HWA than either of the other hosts ( Tables 1 and 2 )

Table 1. M ean (±SD) host eggs consumed and oviposition rate by

L. osakensis when offered hemlock woolly adelgid (HWA), balsam woolly adelgid (BWA) or pine bark adelgid (PBA) during a 5

- day no

choice test.

H ost n L. osakensis Feeding

(host eggs/day) L. osakensis Oviposition (eggs/day)

HWA 8 17.3 ± 5.6 a

_ 3.7 ± 1.9 a

BWA 10 2.1 ± 2.7 c 0.1 ± 0.1 b

PBA 11 7.1 ± 3.8 b 0.5 ± 0.8 b

T able 2

. Mean (±SD) number of woolly alder aphid s eaten in 7 days when given no choice.

Host n Feeding

WAA 10 0.7 ± 0.82

Choice Tests

– Adult Feeding A series of choice tests measuring feeding and oviposition on HWA and

one alternate host were conducted at 10°C for 7 days. For each test, a single adult was placed in each of 10 petri dishes with a sufficient amount
each HWA and the alternate host. In each test, the number of HWA eaten21 was significantly greater than the number of alte rnate hosts eaten ( Table

3 .)

Table 3

. The mean number of hosts eaten in a 7

- day choice test using hemlock woolly adelgid and an alternate host. Alternate hosts include pine needle scale (PNS), balsam woolly adelgid (BWA), woolly alder aphid (WAA), elongat e hemlock scale (EHS), and pine bark adelgid (PBA).

Test 

### n Mean HWA Eaten Mean Alternate Host Eaten

HWA vs PNS 10 6 +/

- 0.68a 0 b

HWA vs BWA 10 6 +/

- 0.92a 1.7 +/

- 0.21 b

HWA vs WAA 10 7.9 +/

- 1.18a 1.3 +/

- 0.45 b

HWA vs EHS 10 3.6 +/

- 0.27a 0.5 +/

- 0.22 b

HWA vs PBA 10 3.8 +/

- 0.39a 2.0 +/

- 0.47 b

M eans with the same letter within a row are not significantly different (p=0.05 Student T

- test).

No

- Choice Tests

- Larval Development

L. osakensis eggs were placed on HWA and 5 alternate hosts , B WA, PBA,

LWA , ESGA, and WAA. Individuals were held at 9°C and survival of each individual was assessed every 2

- 3 days (Table 4)

. L. osakensis was able to complete development from the egg stage through all larval stages to adult only on HWA (see trail # 1)

. There was no survival beyond the first larval stage (no feeding) when fed LWA and WAA (Trail #1).

Cohort s urvival to prepupal stage was below 20% on BWA (7%)

, and PBA (see Trials #1 and #3)

, while cohort survival on HWA exceeded 50%

in two of three t rials. Trail #2, (average 43%). L. osakensis survival from egg to prepupal stage averaged 31% on PBA , and was 43 % for ESGA.

Despite limited data , it is clear that there was no development on the only

non

- adelgid species tested (WAA), while development to prepupa occurred on four of the five adelgid species tested. Regarding development being restricted to adelgids, t hese data are consistent with

results from similar trials with L. nigrinus and three other adelgids (BWA, ESGA, PBA), and two aphid species ( Zilahi

- Balogh et al. 2002)

.22 Table 4

. The number and percentage of individuals of L. osakensis surviving to each life stage for each test prey species in No Choice conditions.

Trial #1 Stage HWA LWA WAA

n % survival from egg stage n % survival

f rom egg stage n % survival from egg stage Egg 9 20 20

L1 9 100 20 100 20 100

L2 8 88 0 * 0 0 * 0

L3 7 78 0 0 0 0

L4 7 78 0 0 0 0 Prepupae 5 56 0 0 0 0 Pupae ? ? 0 0 0 0

Adults 4 44 0 0 0 0

* L1 larvae did not feed on LWA and WAA and did not develop to L2

Trial #2 Stage HWA ESGA PBA

n % survival from egg stage n % survival from egg stage n % s urvival from egg stage Egg 28 14 29

L1 28 100 14 100 29 100

L2 24 86 14 100 26 89

L3 11 39 12 86 21 72

L4 7 25 8 57 18 62 Prepupae 5 18 6 43 13 44 Pupae ? ? ? ? ? ?

Adults 0 0 0 0 0 0

Trial #3 Stage HWA BWA PBA

n % survival from egg stage n % survival from egg stage n % survival from egg stage Egg 11 14 18

L1 11 100 14 100 18 100

L2 10 91 2 14 12 67

L3 9 82 1 7 12 67

L4 9 82 1 7 10 56 Prepupae 6 55 1 7 3 17 Pupae ? ? ? ? ? ?

Adults 0 0 0 0 0 023 iii

. Summ ary and Discussion: Host specificity of L

. osakensis

The life history pattern of L. osakensis indicates that it is naturally synchronized with the life history pattern of HWA , including a period of aestivation in the summer followed by active feeding and development in the colder months of September to June, which itself is synchronized with the annual pattern of growth and transpiration of the hemlock hosts (very high rates in the early spring). The literature shows that Laricobius species are specialist predator on adelgids

. Results from the laboratory tests on L.

osakensis a nd the native L

. nigrinus demonstrate a very narrow host range.

L. osakensis is not expected to be able to survive on a diet of prey of other North American species related to HWA. Although L. osakensis adults may feed on these other adelgids, the results from paired choice test show they are not preferred. The synthesis of this information

– specialized life history, and high deg ree of prey choice preference among the alternate ho sts tested, coupled with the inability to survive on prey other than HWA, suggest very minimal direct impact on other potential prey species in the environment in

North America.

d. Competition with other predators The life history of Laricobius osakensis appears to be similar to L. nigrinus

. This was confirmed by w eekly field sampling conducted in

2007

- 2008, and is summarized as follows. In the fall, after the summer aestivation ends, the adult L. osakensis emerge from the ground and go to hemlock trees, where they feed on HWA throug hout the fall and winter

months. Female L. osakensis begin begin laying eggs in December and continue through March. Beginning in January, larvae hatch and feeding on HWA eggs through April. The larvae finish their growth an d drop to the ground during late March and April and bury into the soil for pupation.

A dults emerge from the pupal stage by early s ummer
, but remain in the

soil in aestivation for the summer and into early fall when they become active and start the cycle a gain

.

Since this species is active in the winter, and aestivates in the summer, it does not interact or compete with other predators on hemlock except perhaps the biological control agent L. nigrinus which has been introduced

and established in the easter n U nited S tates

. This s pecies may also

interact with the native L. rubidus that feeds on pine bark adelgid but is

known to occasionally feed on HWA

. The pot ential interactions of all

three species are currently being studied at Virginia Tech. Laboratory studies of adult beetle interaction among all three species show no negative interactions to the impact on the target host ( see Fig. 3 below )

and in the number of predator eggs deposited in HWA ovisacs (egg clusters) (Fig. 4 ). Additionally, survivorship among the three species appears unaffected (Fig. 5 ).24 Figure 3. Mean number of HWA ovisacs disturbed by adult Laricobius spp. when placed in groupings by themselves or all together in the laboratory. All

treatments containe d a total of 3 adult beetles. “ L. sp. N. ” = L. osakensis.

T reatments denoted by different letters are significantly different from each other (Tukey’s studentized test; p <0.05).

Figure 4. Mean number of eggs deposited by Laricobius spp. when placed i n groupings by themselves or all together in the laboratory. All treatments
contained a total of 3 adult beetles. “ L. sp. N. ” = L. osakensis. Treatments denoted by different letters are significantly different from each other (Tukey’s studentized test; p <0.05).25 Figure 5. Survivorship of each predator species when placed in groupings by themselves or all together in the laboratory after 6 days. “ L. sp. n

. ” = L.

osakensis. No differences in treatments were observed (ANOVA; p > 0.05)

Based on these results with high but typical density of host ovisacs, no negative interactions are apparent. Under lower densities, preliminary

results show no statistical differences at densities 1⁄2 and 1⁄4 of the tests depicted above. There is some tendency for each spe cies to consume their own and competitor’s eggs. Again preliminary results show a t rend (not significant) where L. nigrinus may prefer L. osakensis eggs somewhat to their own, but both L. osakensis and L. rubidus seemed to prefer their own eggs. In summa ry
, there is no evidence of negative interspecific competition among these three specialized predators.

2. Uncertainties regarding the environmental r elease of L

. osakensis

Once a biological control agent such as Laricobius osakensis is released

into the environment and become s established, there is a slight possibility

th at it could move from its preferred prey ( HWA ) to preferentially attack

other nontarget p rey , such as PBA , or native woolly aphids

. Prey shifts by predators are not uncommon, especia lly opportunistic feeding on very abundant prey items in the environment. However, adaption to other prey by larval L. osakensis would require both nutritional as well as life history shifts in order to successfully survive on other prey, which significan tly

lowers the likelihood of such an occurrence

.26 If other insect species were to be attacked by L

. osakensi s , the resulting effects could be environmental impacts that may not be easily reversed. Biological control agents such as L

. osakensis generally s pread without intervention by man . In principle, therefore, release of th is biological

control agent at even one site must be considered equivalent to release over the entire area in which potential hosts occur and in which the climate is suitable for rep roduction and survival.

In addition, these agents may not be successful in reducing HWA populations in the continental United States. Approximately 12 percent of the introductions of biological control agents against pests have led to “comple te” control of the target pests ( Greathead and Greathead 1992 )

. Actual impacts on HWA populations by L

. osakensis will not be known until after release occurs and post

- release monitoring has been conducted. The environmental consequences discussed under the “no actio n” alternative may occur even with the implementation of the biological control alternative, depending on the effica cy of those agents to reduce

HWA populations in the continental United States

3. Cumula tive i mpacts

“Cumulative impacts are defined as th e impact on the environment which results from the incremental impact of the action when added to other past, present and reasonably foreseeable future actions regardless of what agencies or person undertakes such o ther actions” (40 CFR 1508.7).

Many stat es and counties

, as well as individual federal, state and local and private property ownerships conduct their own programs to manage HWA

as well as other invasive forest pests

. Chemical, mechanical, and biological controls, as described previously in this document are u sed in a wide range of habitats.

Release of L. osakensis is not expected to have any negative cumulative impacts in the continental United States because of its specificity to HWA

. Effective biological control of HWA will have beneficial e ffects for forest and ornamental pest management programs , and may result in a long

- term,

non

- damaging method to assi st in maintaining native hemlock trees and hemlock stands in good health

.

4. Endangered Species Act

Section 7 of the Endangered Species Act (ESA) and ESA’s implementing regulations require Federal agencies to ensure that their actions are not likely to jeopardize the continued existence of federally listed threatened endangered species or result in the destruction or adverse modification o f

critical habitat.27 APHIS has determined that based on the host specificity of Laricobius

osakensis

, and since there are no listed species related to HWA, or dependent on HWA, there will be no effect on any listed species or designated critical habitat in the continental United States



## V I . Other Issues

Consistent with Executive Order (EO) 12898, “Federal Actions to Address Environmental Justice in Minority Populations and Low

- income Populations,” APHIS considered the potential for disproportionately high and adverse human health or environmental effects on any minority populations a nd low

- income populations. There are no adverse

environmental or human health effects from the field release of L

. osakensis and will not have disp roportionate adverse effects to any minority or low

- income populations.

Consistent with EO 13045, “Protection of Children From Environmental Health Risks and Safety Risks,” APHIS considered the potential for disproportionately high and adverse environme ntal health and safety risks to children. No circumstances that would trigger the need for special environmental reviews is involved in implementing the preferred alternative. Therefore, it is expected that no disproportionate effects on

children are a nt icipated as a consequence of the field release of L.

osakensis i

.

EO 13175, ―Consultation and Coordination with Indian Tribal
Governments, was issued to ensure that there would be “ meaningful

consultation and collaboration with tribal officials in the deve lopment of Federal policies that have tribal implications.... ”. Consistent with EO 13175, APHIS sent letters of notification and requests for comment and consultation on the proposed action to tribes in Connecticut, Florida, Maine, Massachusetts, Michigan, Minnesota, Mississippi, New York, North Carolina, Rhode Island, South Carolina and Wisconsin . APHIS will

continue to consult and collaborate with Indian tribal officials to ensure that they are well

- informed and represented in policy and program decisions that may impact their agricultural interests, in accordance with EO 13175.28 

## VI I

. Agencies, Organizations, and
Individuals Consulted

North American Plant Protection Organization (NAPPO). A petition for cons ideration of release ref. NAPPO Standard RSPM No. 12 (available at: http://www.nappo.org/Standards/Std

- e.html ) to APHIS

and forwarded to the AAFC Biological Control Review Committee fro

review and recommendation. The Committee recommended that release

of Laricobius osakensis be approved with the conditions that: 1) a detailed

post

- release monitoring plan be provided; and 2) authoritatively identified voucher specimens of the L. osakensis population s released are deposited in the national entomological collections in North America. Agencies and organizations represented on the committee are: Agriculture and Agri

- Food Canada, Research Centre, Ottawa, ON (Chair);

Centro Nacional de Referencia de Contr ol Biológico, Enasica, Colima, Mexico; Pest Management Regulatory Agency, Ottawa, ON; Canadian Forest Service, Victoria, BC; North Carolina State University, Raleigh, NC

U.S. Department of Agriculture Animal and Plant Health Inspection Service

Plant Prote ction and Quarantine Registrations, I dentification s, Permits and Plant Safeguarding 4700 River Road, Unit 133 Riverdale, MD 20737

U.S. Department of Agriculture Forest Service, Nort h east Area

, State and Private Forestry

Forest Health Protection Morgant own Field Office

180 Canfield Rd. Morgantown, WV 26505

Virginia Polyt ech nic Institute and State University (Virginia Tech) Department of E n tomology Blacksburg

, VA 2406029 

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Broo ks, R. T. 2001. Effects of the removal of overstory hemlock from

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## Appendix 1

Map of hemlock woolly adelgid inf estations 2008
Map show s current and recently infested counties and native range of eastern hemlock ( Tsuga canadensis)

Source : http://na.fs.fed.us/fhp/hwa/maps/distribution.shtm

.