United States 

Department of 

Agriculture

Marketing and 

Regulatory

Programs

Animal and 

Plant Health 

Inspection 

Service

Release

Beetle 

coniferarum

Coccinellidae),

Biological Control of

the Hemlock Woolly

Adelgid (

in the Eastern United 

States

Environmental Assessment

Febr

Release of the Predatory 

Beetle Scymnus 

coniferarum (Coleoptera: 

Coccinellidae), for 

Biological Control of

the Hemlock Woolly

Adelgid (Adelges tsugae

in the Eastern United 

tates

Environmental Assessment

February 2012

Predatory 

(Coleoptera: 

Adelges tsugae)

in the Eastern United 

Environmental Assessment,
Release of the Predatory Beetle 

Scymnus coniferarum (Coleoptera: 

Coccinellidae), for Biological Control 

of the Hemlock Woolly Adelgid 

(Adelges tsugae) in the Eastern 

United States

Environmental Assessment, 

February 2012

Agency Contact:

Shirley Wager-Page, Branch Chief

Pest Permitting

Plant Protection and Quarantine

Animal and Plant Health Inspection Service

U.S. Department of Agriculture

4700 River Road, Unit 133

Riverdale, MD 20737–1236

The U.S. Department of Agriculture (USDA) prohibits discrimination in all 

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with disabilities who require alternative means for communication of 

program information (Braille, large print, audiotape, etc.) should contact 

USDA’s TARGET Center at (202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil 

Rights, Room 326–W, Whitten Building, 1400 Independence Avenue, SW, 

Washington, DC 20250–9410 or call (202) 720–5964 (voice and TDD). 

USDA is an equal opportunity provider and employer. 

Mention of companies or commercial products in this report does not imply 

recommendation or endorsement by the U.S. Department of Agriculture 

(USDA) over others not mentioned. USDA neither guarantees or warrants 

the standard of any product mentioned. Product names are mentioned 

solely to report factually on available data and to provide specific information.

This publication reports research involving pesticides. All uses of pesticides

must be registered by appropriate State and/or Federal agencies before they 

can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, 

desirable plants, and fish or other wildlife–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.
Table of Contents

I. Purpose and Need for the Proposed Action....................... 1

II. Alternatives ........................................................................... 2

III. Affected Environment........................................................... 7

IV. Environmental Consequences............................................. 9

V. Other Issues ........................................................................ 15

 

VI. Agencies, Organizations, and Individuals Consulted...... 15

 

VII. References........................................................................... 17

Appendix A............................................................................... A-1

Appendix B............................................................................... B-1
1

I. Purpose and Need for the Proposed 

Action

The U.S. Department of Agriculture (USDA), Animal and Plant Health 

Inspection Service (APHIS), Plant Protection and Quarantine (PPQ) Pest 

Permitting Branch (PPB) is proposing to issue permits for the interstate 

movement and release of the predatory beetle Scymnus (Pullus)

coniferarum (Coleoptera: Coccinellidae). This species is native to the 

western United States and would be used by the applicants for the 

biological control of the hemlock woolly adelgid ((Adelges tsugae)

(Homoptera: Adelgidae)) (HWA) in the eastern United States. Before 

permits are issued for release of S. coniferarum, the APHIS–PPQ PPB

needs to analyze the potential impacts of the release of this agent into the 

eastern United States.

This environmental assessment1(EA) has been prepared, consistent with 

USDA–APHIS' National Environmental Policy Act of 1969 (NEPA) 

implementing procedures (Title 7 of the Code of Federal Regulations 

(CFR), part 372). It examines the potential effects on the quality of the 

human environment that may be associated with the release of S. 

coniferarum to control HWA in the eastern United States. This EA 

considers a “no action” alternative and the potential effects of the 

proposed action.

The applicant’s purpose for releasing S. coniferarum in the eastern United

States is to reduce the severity of damage caused by HWA. HWA is

native to eastern Asia and western North America (Havill and Foottit, 

2007). The HWA was accidentally introduced to the eastern United States 

and is destructive there to the eastern hemlock, Tsuga canadensis, and 

Carolina hemlock, T. caroliniana. This sucking insect feeds at the base of 

the needles causing needle loss and abortion of buds which leads to 

decline in crown health and tree death after several years (Orwig et al.,

2002; Eschtruth et al., 2006). It is destructive to hemlocks in landscapes 

and forests and has affected federal parks, recreation areas, and forests; 

state-managed forest lands; commercial and private landowners; and urban 

and suburban communities (Evans et al., 2011; Krapfl, 2011).

To date, four predatory beetles have been introduced to the eastern United 

States for biological control of HWA and two (Laricobius nigrinus and 

Sasajiscymnus tsugae) are considered to be established (Cheah et al.,

2004). However, because, HWA has a group of natural enemies that 

control it where it is native, a full complement of predators are needed to 

 

1

Regulations implementing the National Environmental Policy Act of 1969 (42 

United States Code 4321 et seq.) provide that an environmental assessment “[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). 
2

more effectively control HWA in the eastern United States where it is an 

invasive pest. Adelgids, such as HWA, have complex multigenerational 

lifecycles with multiple forms appearing at different times. Specialized 

predators, such as S. coniferarum, that are part of the full complement of 

natural enemies where HWA is native, attack different lifecycle forms of 

HWA at different times of the year. For these reasons, the applicant has a 

need to move S. coniferarum from the western United States and release it 

into the eastern United States in order to provide an additional predator to 

the complement of natural enemies currently in place for more effective 

control of HWA. 

II. Alternatives

This section will explain the two alternatives available to the APHIS–PPQ

PPB—no action (no issuance of permits) and issuance of permits for 

interstate movement and environmental release of S. coniferarum in the 

eastern United States wherever HWA becomes established. Although 

APHIS’ alternatives are limited to a decision of whether to issue permits

for interstate movement and release of S. coniferarum, other methods 

available for control of HWA in the eastern United States 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 

environmental release of S. coniferarum. These are methods presently 

being used to control HWA in the eastern United States where it is not 

native and has established as a pest. 

A third alternative was considered, but will not be analyzed further. 

Under this third alternative, the APHIS–PPQ PPB would have issued 

permits for the field release of S. coniferarum, however, the permits would 

contain special provisions or requirements concerning release procedures 

or mitigating measures, such as limited release of S. coniferarum. No

issues have been raised which would indicate that special provisions or 

requirements are necessary.

A. No Action 

Under the no action alternative, the APHIS–PPQ PPB would not issue 

permits for the field release of S. coniferarum for the control of HWA—

the release of this biological control agent in the eastern United States 

would not take place. The following methods are presently being used to 

control HWA in the eastern United States; these methods will continue 

under the “no action” alternative and are likely to continue even if permits

are issued for release of S. coniferarum. 

Chemical insecticides provide an effective method to reduce HWA 

populations on individual hemlocks. Spraying infested trees thoroughly

1. Chemical 

Control
3

with insecticidal soap or horticultural oil is commonly used and highly 

effective in killing adelgids but two spray treatments each year are usually

necessary (McClure et al., 2001). The large equipment used for spraying 

make this method impractical for forests. Systemic insecticides applied to 

the soil or tree trunks can reduce HWA populations for several years and 

is one of the options used to control HWA in National Parks (Webb et al., 

2003; Cowles et al., 2006; Webster, 2010). 

Certain states have enacted quarantines to prevent the transport of HWA 

infected hemlock from infested states to uninfested areas in their states. 

Some states also restrict the import of hemlock timber with bark. States 

may allow shipment of nursery stock or hemlock timber if accompanied 

by a certificate of inspection that the items are HWA free or other 

compliance agreement (Gibbs, 2002). These restrictions to interstate 

commerce are likely to remain in place until HWA becomes widely 

established in these states.

The susceptible Carolina hemlock has been cross-pollinated with the very

resistant Chinese hemlock to produce a hybrid cross with high resistance 

to HWA (Montgomery et al., 2009). Clones of these are in field trials and 

a new, resistant hemlock cultivar would not be available to the nursery

industry for several years. Efforts are being made to identify resistant 

hemlocks in HWA infested stands of eastern hemlock (Caswell et al., 

2008; Ingwell and Preisser, 2011). 

Efforts have been made to develop effective fungus-based pesticide 

formulations using Lecanicillium muscarium (formally Verticillium 

lecanii) and Beauveria bassiana (Cheah et al., 2004; Gouli et al., 2008). 

Shortly after it was recognized as a significant pest, McClure (1987) noted 

that several native predators attack HWA in the eastern United States, but 

none were of any significance in reducing HWA density. A quantitative 

assessment of the resident natural enemies of HWA in Connecticut was 

made in 1993-1994 prior to the intentional release of exotic agents for 

biological control of HWA (Montgomery and Lyon, 1996). Two 

predatory beetles, Laricobius rubidus (LeConte) and Scymnus (Pullus) 

suturalis Thunberg were recovered. Laricobius rubidus is native to North 

America while S. suturalis is native to Europe. Both of these beetles were 

collected in about equal numbers from the foliage of eastern hemlock, 

white pine, and Scotch pine. Although it is likely that L. rubidus evolved 

on the pine bark adelgid (Pineus strobi (Hartig)), which attacks white 

pine, and S. suturalis evolved on the European pine adelgid (Pineus pini

(Macquart)), which attacks Scotch pine, both beetle predators can utilize 

several adelgids, including HWA as hosts. Host range tests found that S. 

suturalis and L. rubidus feed readily and equally on HWA and P. strobi in 

no-choice situations, although S. suturalis is attracted more to pine foliage 

3. Development 

of Resistant 

Hemlocks 

2. Restriction of 

Interstate 

Movement of 

Nursery

Stock

4. Bioinsecticides

5. Biological 

Control
4

than to hemlock foliage (Montgomery et al., 1997). Larvae of both beetle 

species were found on HWA in the field, but the number per branch 

decreased with distance from pine (Montgomery and Lyon, 1996). 

Although this survey indicated that resident predators associated with pine 

adelgids could switch to an exotic adelgid on hemlock, recent surveys, 15 

years later, have found far fewer of these two predators on hemlock 

(Montgomery, unpublished). A survey of natural enemies in 1997-1998 in 

North Carolina found several families of predators, but their numbers were 

too low to have any noticeable effect on HWA density (Wallace and Hain,

2000).

Because of the lack of effective natural enemies of HWA in eastern United 

States, natural enemies of HWA were imported from Japan, China, and 

western Canada (Cheah et al., 2004). A summary account of the predators 

imported and released follows. 

The first predator released was the lady beetle Sasajiscymnus tsugae 

(Sasaji and McClure) (formerly Pseudoscymnus tsugae) collected in Japan 

and first released in 1995 in Connecticut (Cheah and McClure, 2002). 

More than 2 million adult S. tsugae beetles have been released at 513 

locations in 13 states (Roberts et al., 2010). Although it is established in 

several states, its impact on HWA has been difficult to discern (Cheah et 

al., 2005; Hakeem et al., 2010). 

Laricobius nigrinus, from the beetle family Derodontidae, was imported 

from Vancouver Island, British Columbia beginning in 1997 and several 

years of evaluations (Zilahi-Balogh, 2001) preceeded its field release in 

2003. More recently, L. nigrinus adults are being collected in the Seattle, 

Washington area (McDonald, 2010) and in Idaho (Mausel et al., 2011) for 

direct release in eastern states. To date, more than 100,000 adult beetles 

have been released at 267 locations in 13 states (Roberts et al., 2010). Its 

establishment has been very good with a slow but steady yearly increase in 

population density of the beetle (Mausel et al., 2010; McDonald, 2010). 

Another derodontid beetle, Laricobius osakensis Montgomery & Shiyake, 

native to Japan, has recently been approved by APHIS for environmental 

release (USDA, APHIS, 2010).

More than 50 species of “Neopullus” lady beetles have been collected

from HWA-infested hemlocks in China (Yu and Montgomery, 2008). Of 

these, three species that were abundant and fed specifically on adelgids 

were imported (Cheah et al., 2004). These species in the genus Scymnus, 

subgenus Neopullus have been difficult to mass rear. Field releases have 

been made with Scymnus sinuanodulus Yu & Yao and Scymnus 

ningshanensis Yu &Yao, but neither is known to have established. A third 

species, Scymnus camptodromus Yu & Liu, is undergoing further study in

quarantine. 
5

B. Issue Permits for Environmental Release of 

S. coniferarum.

Under this alternative, the APHIS–PPQ PPB would issue permits upon 

request and after evaluation of each application for the interstate 

movement and environmental release of S. coniferarum for the control of 

HWA in the eastern United States. These permits would contain no 

special provisions or requirements concerning release procedures or 

mitigating measures.

Insect Taxonomy

Order: Coleoptera

Family: Coccinellidae

Genus: Scymnus

Species: Scymnus coniferarum

Common name none

Scymnus coniferarum Crotch (Coleoptera: Coccinellidae) was described in 

1874 from specimens collected from pine in California. The typespecimen is at the Museum of Comparative Zoology, Harvard University 

(MCZ). Vouchers (male and female adults) have been deposited at the 

National Museum of Natural History, Washington, D.C. (NMNH) and the 

University of Georgia Arthropod Collection, Athens, GA (UGAC).

Scymnus coniferarum is a small lady beetle, about 2 millimeters in length,

covered in fine, short hairs, with reddish-brown wing covers edged in 

black. Whitehead (1967) and Gordon (1976) provide full descriptions 

with figures. Scymnus larvae are covered with white woolly wax.

In the laboratory, S. coniferarum has been reared for several successive 

generations on HWA growing on eastern hemlock. Its life stages consist 

of egg, four larval instars, pupa, and adult. During the spring months, a 

female lays about 1 egg per day in a bud scale, male flower, or near a 

HWA ovisac (egg-containing capsule). At 20° C, development is rapid 

with the egg, larval, and pupal stages lasting about 6, 19, and 9 days, 

respectively (Schwartzberg et al., 2009). The beetle also develops well at 

15° C.

To understand the relationship of this predator to its preferred host, HWA, 

the life cycle of HWA must also be understood. Adelgids, such as HWA,

have complex, multi-generational, life cycles, with multiple forms, and 

several types of life cycles even within a single species (Havill and Foottit, 

2007). The lifecycle of HWA varies depending on region. In Japan and 

China, where it is native, HWA is “holocyclic” and migrates between 

hemlock and a species of spruce. This holocycle takes two years with 

sexual reproduction and the formation of galls (abnormal swellings of 

plant tissue caused by insects) occurring on spruce, and three

1. Taxonomic 

Information 

for S. 

coniferarum

2. Description 

and Biology

of

S. 

coniferarum
6

parthenogenetic (a form of reproduction in which an unfertilized egg 

develops into a new individual) generations occurring on hemlock (Havill 

and Foottit, 2007). In western North America, where HWA is also 

native, HWA is “anholocyclic” and it does not migrate to spruce—it has 

only two alternating, asexual, wingless generations on hemlock; the 

“sistens” which diapauses (a period of inactivity during which 

development is suspended) during the summer and develops during the 

fall, winter, and spring, and the “progrediens” generation which develops 

during spring and early summer. In the eastern United States, the life 

cycle is similar to that in Japan, but there is no spruce host in eastern 

United States on which it can reproduce (McClure, 1989).

The seasonal occurrence of S. coniferarum and another predator, L. 

nigrinus, as well as their host, HWA, was monitored on western hemlock

in the Seattle, Washington area from October, 2010 to June, 2011. In

early October, S. coniferarum adults were more abundant on western 

hemlock than adults of L. nigrinus, but both species were equally 

abundant by the end of the month. Both species were found during the 

cold winter months. By April, adults of L. nigrinus were no longer 

present, but S. coniferarum adults were abundant. The larvae of L. 

nigrinus were most abundant during April whereas larvae of S. 

coniferarum were most abundant during June. The larvae of L. nigrinus

coincided with the eggs of the overwintering generation (sistens) of HWA 

and the larvae of S. coniferarum coincided with the eggs laid by the late 

spring generation (progrediens) of HWA. The larvae of L. nigrinus enter 

the soil in April to become adults and remain in the soil until the fall,

whereas the larvae of S. coniferarum become adults in June and remain on 

the tree throughout the year.

 

The known native geographical range of S. coniferarum is western North 

America (Gordon, 1985). Specimens have been collected from various 

species of pines in British Columbia, Arizona, California, Colorado, 

Idaho, Nevada, New Mexico, Oregon, South Dakota, Utah, and Wyoming 

(Gordon, 1976). Recently, several hundred specimens have been collected 

from western hemlock in Washington State (Montgomery et al., 2009;

McDonald, 2010). It has recently been recovered from Monterey pine in 

Chile and Peru (Gonzalez, 2006); probably an accidental introduction

since pine and adelgids are not native to South America. There is a report 

of it in the eastern United States (Malkin, 1945), but this may be a 

misidentification. Gordon (1976) recorded it in Pennsylvania, but later 

clarified that these were S. suturalis (Gordon, 1985). Considering that the 

species has spread intercontinentally, has been found in the Rocky

Mountains as far east as the Black Hills, South Dakota, and occurs in a 

variety of habitats in western North America, it is possible that it is 

already established in eastern North America.

3. Geographic

Range of

S.

coniferarum
7

In the field, the adults of S. coniferarum and L. nigrinus feed on all HWA 

stages, except nymphs that are in diapause during the summer. Diapause 

is a period of inactivity or rest, during which development is suspended. 

The larvae of both S. coniferarum and L. nigrinus target the egg stage of 

HWA. Larvae of L. nigrinus primarily attack the spring generation eggs 

laid in late winter to early spring while the larvae of S. coniferarum

primarily attack eggs laid in later spring to early summer. Because these 

two species attack the eggs of separate HWA generations, they

complement each other in reducing HWA populations. By releasing S. 

coniferarum in the eastern United States, the spring HWA generation will 

have a predator that it currently lacks and additional pressure will be 

provided to reduce HWA populations.

III. Affected Environment

A. Areas Affected by Hemlock Wooly Adelgid

The HWA is native to eastern Asia and the western North America (Havill 

et al., 2007). It is not considered a pest in these regions (Furniss and

Carolin, 1977; Cheah et al., 2004). 

The first report of HWA in eastern United States came from the Virginia 

Department of Agriculture and Consumer Services in 1951 on planted 

eastern hemlock in Richmond, Virginia (Stoetzel, 2002) and has since 

spread to 18 eastern states (USDA, FS, 2011). Currently, HWA infests all 

of the U.S. counties with Carolina hemlock and 50 percent of the U.S. 

counties with eastern hemlock (USDA, FS, 2011). It is the only adelgid 

that feeds on hemlock and its distinctive white woolly wax makes it easy

for non-specialists to distinguish it from other insects on hemlock.

Eastern North America has two native hemlock species, Tsuga 

canadensis, eastern hemlock and Tsuga caroliniana, Carolina hemlock, 

and these species serve as the primary hosts of HWA. Eastern hemlock

grows on almost 19 million acres in the United States, while Carolina 

hemlock is limited to the Blue Ridge of the southern Appalachian 

Mountains. Both hemlock species are long-lived species that, if left 

undisturbed, eventually dominate tree stands. 

Eastern hemlock, may take 250 to 300 years to reach maturity, live for 800 

years, and attain heights of 150 to 175 feet. It 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, hemlock is a late successional, "climax" tree 

that can dominate a forest for centuries. Ward et al. (2004) provides an 

overview of the species and its ecological and commercial values. Eastern 

hemlock forests provide important habitat for a wide variety of wildlife. 

2. Present 

Distribution in 

the United 

States

3. Hemlock 

Resources in 

Eastern North 

America

4. Impact of S. 

coniferarum

on Hemlock 

Woolly

Adelgid

1. Native and 

Worldwide 

Distribution
8

In the northeastern United States, 96 bird and 47 mammal species are 

associated with hemlock forests (Yamasaki et al., 2000). Of these, at least 

eight species of birds and ten species of mammals have strong ecological 

linkages with hemlock forest habitat. Hemlock is an important winter 

habitat for white-tailed deer. Many native plant species thrive in hemlock 

stands, including leatherwood, rattlesnake plantains, bunchberry, Canada 

mayflower, goldthread, bluebeard, and wood sorrels (Evans et al., 1996).

Hemlock stands are very popular recreational sites for fishing, hiking,

camping, hunting, and bird watching. Hemlock is not a valuable timber 

species, but it is used widely for pulpwood and utilitarian uses (such as 

pallets). Hemlocks are valued landscape plants and are one of the most 

cultured and cultivated landscape trees in the United States (Swartley,

1984). 

B. Insects Related to HWA and S. coniferarum

There is considerable uncertainty about the taxonomy of adelgid species, 

which is further complicated by the several forms produced on primary

and secondary host plants (Havill and Foottit, 2007). Review of the 

literature indicates that there are as many as 25 species of adelgids in 

North America, but only 16 may be valid species, with 10 species of these 

native to North America (see Appendix A). In eastern North America, 

there are no native adelgids in the genus Adelges, but there are six nonnative species in this genus. There are nine adelgid species of Pineus in 

eastern North America: three are Eurasian (P. cembrae, P. pineoides, P. 

pini), two are considered to be native to North America (P. pinifoliae, P. 

similus), two species are native to western North America (P. boerneri, P. 

coloradensis,) and two species are native to eastern North America (P. 

floccus, P. strobi). Pineus strobi is the most common pine adelgid in 

eastern North America and it has spread worldwide. Pineus boerneri and 

P. coloradensis were pests 30 years ago on red pine in Connecticut 

(McClure, 1989). All the adelgids present in eastern states are considered 

to be pests, with the non-native species more damaging than native species. 

Although S. coniferarum belongs to the subgenus Pullus, which has more 

than 80 species in the United States, it is unlikely to interact with native 

lady beetles. No other native Scymnus lady beetle is known to feed on 

adelgids to any appreciable extent. A non-native species, Scymnus

(Pullus) suturalis Thunberg, present in the northeastern United States is 

similar to S. coniferarum (Gordon, 1985). These two species and S. 

impexus—a native of Europe introduced for biological control of the 

balsam woolly adelgid in the 1960s—form a distinctive group with similar 

form and structure and have adelgids as hosts (Whitehead, 1967). 

Scymnus suturalis’ primary host seems to be Pineus pini on Scots pine, 

but it can complete development on HWA (Montgomery and Lyon, 1996). 

1. Insects 

Taxonomically

Related to 

HWA

2. Insects 

Taxonomically

Related to S. 

coniferarum
9

IV. Environmental Consequences 

A. No Action

The infestation and damage caused by HWA in urban and forest 

landscapes has received considerable attention from landowners and land 

managers, 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 insecticides, development of 

bioinsecticides and resistant hemlocks, and biological controls at current 

levels would be expected to continue if the “no action” alternative is 

chosen. The current rate of spread, and levels and trends of eastern 

hemlock mortality and other environmental consequences from infestation 

by HWA will likely continue if the “no action” alternative is chosen. 

These environmental consequences may also continue at some level even 

with the establishment of S. coniferarum in eastern hemlock forests, 

depending on its efficacy in reducing HWA populations.

a. Continued decline and mortality of eastern hemlocks 

Currently, about 50 percent of the counties with hemlock in the eastern 

United States are infested by HWA (USDA, FS, 2011) and HWA is 

expected to continue to expand its range. Damage in the southern range of 

the hemlocks appears to be more severe (Evans et al., 2011). This may

reflect the absence of low winter temperatures which can reduce HWA 

populations (Trotter et al., 2009). Although HWA can quickly cause a 

decline in the crown condition of hemlock, mortality can be rapid or take 

many years, depending on site conditions (Orwig et al., 2002). For 

example, in Shenandoah National Park, some sites experienced 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 direction a 

slope faces (Blair, 2002). Although the rate of spread and mortality is 

variable, the overall expectation is that most of the hemlock in the eastern 

United States may be lost without more and better options to control 

HWA.

b. Loss of economic, social, and recreational value

Yearly monetary loss caused by HWA is estimated to be over 

$200,000,000 (Aukema et al., 2011). About one-half of this is

expenditures by governments and citizens for control of the pest and 

removal of damaged trees. Loss of residential property values due to 

damage by HWA is estimated to total $100,000,000. 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., 2005). Forest timber 

1. Impact of 

Hemlock 

Woolly

Adelgid on 

the 

Environment
10

loss to landowners is estimated to be on $1,100,000 per year (Aukema et 

al., 2011). Hemlock has little value for lumber or pulp but has an 

important ecological role in forests. 

Hemlock mortality can have considerable impact on recreational use of 

forests. Consequently, large federal parks and forests 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 (this park 

was originally 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 Smoky Mountains National 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).

c. Continued impacts on ecosystems

Evans (2002) commented 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 from 

chestnut blight” due to the fact that hemlock would not be replaced 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., 2002; 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 chemistry (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, affecting temperature, and moisture 

microhabitats. In the Southern Appalachian area, hemlock has an

ecohydrological function that no other forest tree can fill (Ford and Vose,

2007).

Reduction in the number and variety of species 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), and water quality (Yorks et al., 2003).
11

Current levels of the current control methods would continue if the “no 

action” alternative is chosen, and may continue even if permits are issued 

for environmental release of S. coniferarum.

a. Chemical Control

Control of HWA with available chemical insecticides is expensive, has

environmental restrictions, and is not long lasting. The no action 

alternative will likely increase reliance on chemical methods to control 

HWA.

b. Restriction of interstate movement of nursery stock

Restrictions to interstate commerce are likely to remain in place until 

HWA becomes widely established in eastern states. No action may

shorten the time for uninfested states to become infested.

c. Development of resistant hemlocks

The susceptible Carolina hemlock has been cross-pollinated with the very

resistant Chinese hemlock to produce a hybrid cross with high resistance 

to HWA (Montgomery et al., 2009). Clones of these are in field trials and 

a new, resistant hemlock cultivar would not be available to the nursery

industry for several years. Collections of hemlock seed are being made 

from several geographical areas in order to conserve the genetic resources 

of the eastern hemlocks until a permanent solution is found to reduce 

hemlock mortality caused by HWA (Jetton et al., 2008; Potter et al.,

2008). 

d. Bioinsecticides

Bioinsecticides for control of HWA are expensive and not long lasting. In 

addition, these are still experimental so efficacy has not been established. 

Biopesticides must be as effective as conventional pesticides if they are to 

be successful but can decrease the potential for adverse chemical 

insecticide impact.

e. Biological Control

The biological control agents released show promise to reduce populations 

of HWA, but more time is needed to find if they will be successful in 

providing the level of control desired. However, the addition of S. 

coniferarum that is expected to complement L. nigrinus would not occur 

and would reduce the potential for successful biological control of HWA.

These environmental consequences may occur even with the 

2. Impact from 

the Use of 

Other Control

Methods
12

implementation of the biological control alternative, depending on the 

efficacy of S. coniferarum to reduce HWA infestations in the eastern 

United States.

B. Issue Permits for Environmental Release of S. 

coniferarum

a. Host specificity testing

Scymnus coniferarum did not feed on any prey offered in the laboratory

other than adelgids (Appendix B). Non-preferred prey included woolly 

alder aphid (Paraprociphilus tessellates), linden aphid (Eucallipterus 

tiliae), Taxus mealybug (Dysmicoccus wistariae), and elongate hemlock 

scale (Fiorina externa) (Montgomery and McDonald, 2010). 

Laboratory choice tests did not find any consistent preferences between 

pine adelgids (European pine adelgid, Pineus pini and pine bark adelgid, 

Pineus strobi) and HWA as prey. Although the beetle laid eggs on the 

pine bark adelgid that feeds on eastern white pine, only 16 percent of the 

eggs survived to the adult stage (Appendix B). 

Laboratory feeding tests indicate that S. coniferarum is a voracious 

predator of HWA. Adult S. coniferarum, given 10 eggs, 10 nymphs and 2 

adult HWA, consumed an average of 8.9 eggs, 3.4 nymphs, and 1.0 adult 

in 24-hours. By contrast, an adult consumed an average of only two larch 

adelgid eggs in 24 hours. Late instar larvae consumed all of the 25 HWA 

eggs they were provided within 24 hours (Schwartzberg et al., 2009.) 

b. Field observations

Field observations in its area of origin indicate that S. coniferarum feeds 

on both pine and hemlock adelgids and does not use other homopterans or 

arthropods associated with hemlock or other woody plants as alternative 

food. Even though the adult stage of S. coniferarum was collected from 

western white pine infested with Pineus pinifolia, only one larva was 

collected from this host. It seems that adelgids on white pine are 

supplemental rather than primary hosts. 

1. Impact of 

S. coniferarum 

on Non-target 

Insects
13

a. Success in establishment in eastern United States 

The climate in the Seattle area differs from the release areas of the 

Southern Appalachian region, primarily in having a more temperate 

environment and in the seasonal pattern of rainfall. That L. nigrinus

collected from the Seattle area has been successfully established in several 

states in the Southern Appalachian region and is a strong indication that 

climatic differences should not be a barrier to the establishment of S. 

coniferarum. A model that predicts the effects of climate on species,

CLIMEX, indicates that S. coniferarum has a high probability of 

establishing in much of the eastern United States.

b. Extent that native adelgids will be attacked

Establishment of S. coniferarum in the eastern United States would result 

in possible contact with only one adelgid species, Pineus floccus, that is 

not present in the western United States (Appendix A). This species has at 

least one generation on spruce (DeBoo and Weidhaas, 1967; Walton, 

1980). S. coniferarum has not been found on spruce. Other adelgid 

species may be attacked to a limited extent, because S. coniferarum feeds 

on other adelgid species in the western United States that are also present 

in the eastern United States. Western conifers from which S. coniferarum

has been collected include ponderosa and lodgepole pine. These conifers 

are host to Pineus coloradensis, which has been reported as a pest of white 

pine and red pine in Eastern States (Doane, 1961), but this adelgid has not 

been reported in many years. In a laboratory test S. coniferarum readily

ate the eggs of what is presumed to be this species (Appendix B).

Although there are many uncertainties concerning the adelgids that S. 

coniferarum may prey upon, the relationships it is expected to have with 

the adelgids in the eastern United States is expected to be similar to the 

relationships it has with these same adelgids in the western United States. 

c. Success in reducing HWA populations 

Only 12 percent of the introductions of biological control agents against 

pests have led to “complete” control of the target pests (Greathead and 

Greathead, 1992). Actual impacts on HWA populations by S. coniferarum 

will not be known until after release occurs and post-release monitoring 

has been conducted. 

2. Uncertainties 

Regarding the 

Environmental 

Release of S. 

coniferarum. 
14

d. Competition or interference with established adelgid 

predators

The previously introduced L. nigrinus seems to be the biological control 

agent that is present in greatest number and most widely distributed 

(Mausel et al., 2010). Based on the co-existence of L. nigrinus and S. 

coniferarum in the western United States and differences in their life 

history, they are expected to coexist and have additive impact on HWA in 

the eastern United States. Likewise, L. osakensis, which has been 

approved for environmental release, and S. coniferarum should have a 

complementary effect on HWA, based on their life histories.

The lady beetle from Japan, Sasajiscymnus tsugae, has been widely

released in the eastern United States, but its numbers remain low. It preys 

on other adelgids (Jetton et al., 2011) and has been recovered in Japan 

from marshes and on pines far from hemlock (Sasaji and McClure, 1997;

Shiyake et al., 2008). This species has a life history similar to S. 

coniferarum; thus, these two lady beetles could compete for resources. 

The most direct interaction may be with a lady beetle in the same 

subgenus that was accidently introduced from Europe, Scymnus (Pullus) 

suturalis. Scymnus suturalis also feeds on both pine and hemlock 

adelgids, although it is seldom recovered from hemlock. 

There have been no adverse interactions reported for adeligid predators. 

Flowers et al. (2007) studied the interactions between three predators of 

HWA (L. nigrinus, S. tsugae, and Harmonia axyridis, a generalist lady

beetle predator) and found that they had little impact on each other and 

recommended multiple-predator releases for HWA.

“Cumulative impacts” is defined as the 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 other actions” (40 CFR 1508.7).

Many states and counties, as well as federal, state, local, and private 

property ownerships conduct their own programs to manage HWA along 

with other invasive forest pests. Chemical, bioinsecticidal, and biological 

controls, along with resistant hemlock development and restrictions on 

movement of nursery stock as described previously in this document are 

used in a wide range of habitats.

Release of S. coniferarum is not expected to have any negative cumulative 

impacts in the continental United States because of its specificity to 

adelgids. If effective, biological control of HWA would have beneficial 

effects for forest and ornamental pest management programs, and may

result in a long-term, non-damaging method to assist in maintaining native 

 Cumulative 

Impacts

3. Cumulative 

Impacts
15

hemlock trees and hemlock stands in good health.

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 

and endangered species, or result in the destruction or adverse

modification of critical habitat. 

APHIS has determined that based on the host specificity of S. coniferarum 

and because 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. No federally listed threatened or 

endangered insects belong to the insect family Adelgidae (USFWS, 2012). 

No federally listed species are known to depend on or use HWA. 

V. 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 and low-income populations. There are no adverse 

environmental or human health effects from the field release of S.

coniferarum and it will not have disproportionate 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 environmental health and safety risks 

to children. No circumstances that would trigger the need for special 

environmental reviews are involved in implementing the preferred 

alternative. Therefore, it is expected that no disproportionate effects on 

children are anticipated as a consequence of the field release of S.

coniferarum in the eastern United States.

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 development 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.

4. Endangered 

Species Act
16

VI. Agencies, Organizations, and 

Individuals Consulted

This EA was prepared by personnel from the Forest Service, Virginia 

Tech, and University of Georgia, and reviewed by APHIS. The addresses 

of participating APHIS units, cooperators, and consultants follow.

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Registrations, Identifications, Permits and Plant Safeguarding

4700 River Road, Unit 133

Riverdale, MD 20737

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Policy and Program Development

Environmental and Risk Analysis Services

4700 River Road, Unit 149

Riverdale, MD 20737

U.S. Department of Agriculture

Forest Service, Northeast Area, State and Private Forestry

Forest Health Protection

Morgantown Field Office

180 Canfield Rd. 

Morgantown, WV 26505

U.S. Department of Agriculture

Forest Service, Northern Research Station

Ecology and Management of Invasive Species and Forest Ecosystems

51 Mill Pond Rd.

Hamden, CT 06514

Virginia Tech

Department of Entomology

Blacksburg, VA 24060

University of Georgia, 

Department of Entomology

413 Biological Sciences Building

Athens, GA 30602 
17

Symbiont Biological Pest Management

194 Shull’s Hollar

Sugar Grove, NC 28679
18

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A–1

Appendix A. List of adelgid species in North America (NA); hosts column gives genus of 

the primary and secondary host—“None” means it is anholocyclic and “?” = believed to be 

holocyclic but host not identified; the right column gives current North American distribution. 

Species Taxon

Validity

Hosts

(1, 2)

Native Range Occurrence in 

North America

Adelges abietis (Linneaus 1758) Picea, None Europe Continental

Adelges aenigmaticus

 Annand 1928

?

1

?, Larix Eastern NA No records after 1928

Adelges cooleyi (Gillette 1907) None, 

Pseudotsuga

Western NA Continental

Adelges coweni (Gillette 1907) ?

2 None,

Pseudotsuga

Western NA Only in Europe?

Adelges diversis Annand 1928 ?

1

?, Larix Western NA No records after 1928

Adelges lariciatus (Patch 1909) ?

1 Picea, Larix North America Western

Adelges laricis (Vallot 1836) None, Larix Europe, NA? Continental

Adelges nordmannianae 

 (Eckstein 1890)

?

3 None, Abies Caucasus Mtns. Continental

Adelges oregonensis

 Annand 1928

?

1

?, Larix Western NA No records after 1928

Adelges piceae (Ratzeburg 1844) Picea, Abies Europe Continental

Adelges tsugae Annand 1924 Picea, Tsuga Asia,Western NA Continental

Pineus abietinus 

 Underwood & Balch 1964

None, Abies Western NA No records after 1964

Pineus boerneri Annand 1928 ?

4 None, Pinus Western NA? Continental

Pineus boycei Annand 1928 Picea, ? Western NA Western

Pineus cembrae

 (Cholodkovsky 1888)

Picea, Pinus Eurasia Eastern

Pineus coloradensis

 (Gillette 1907)

None, Pinus North America Continental

Pineus engelmannii

 Annand 1928

?

5 Picea, ? Western NA Western

Pineus floccus (Patch 1909) ? Picea, Pinus Eastern NA Eastern 

Pineus patchae Börner 1926 ?

6 Picea, ? North America Status unclear

Pineus pineoides 

 (Cholodkovsky 1903)

Picea, None Europe Eastern

Pineus pini (Macquart 1819) None, Pinus Europe Continental

Pineus pinifoliae (Fitch 1853) Picea, Pinus North America Continental

Pineus similis (Gillette 1907) Picea, None North America Continental

Pineus strobi (Hartig, 1937) None, Pinus Eastern NA Continental

Pineus sylvestris Annand 1928 ?

4

?, Pinus Western NA No records after 1928

Sources: Annand, 1928; Boerner and Heinze, 1957; Blackman and Eastop, 1994; Havill and Foottit, 2007)

1

variants of A. laricis (Blackman and Eastop, 1994); A. lariciatus and A. laricis DNA different (Havill et al., 2007)

2A. cooleyi (Blackman and Eastop, 1994)
A–2

3 A. piceae based on DNA barcodes (Havill et al., 2007; Zurovcova et al., 2010)

4

these species are closely related to P. pini, if not the same species (Blackman and Eastop, 1994)

5

sexupara of P. boycei (Boerner and Heinze, 1957; Blackman and Eastop, 1994)

6P. similis (Blackman and Eastop, 1994) 
B–1

Appendix B. Host range evaluation of Scymnus (Pullus) coniferarum (Montgomery and 

McDonald, 2010)

Field observations. 

The only hosts of S. coniferarum reported in the literature are adelgids that feed on pine (Pineus

spp.) (Whitehead, 1967), but while collecting L. nigrinus from western hemlock, it has been 

found to be common on hemlock. From samples of trees in landscapes in the Seattle,

Washington area, it was also found to be abundant on hemlocks infested with HWA and on 

western white pine infested with adelgids and aphids (Montgomery et al., 2009; McDonald,

2010). From October 9-19, 2004, 1,003 S. coniferarum and 1,417 L. nigrinus adults were 

collected from western hemlock (McDonald, pers. obs.). S. coniferarum was also recovered in 

low numbers on eastern hemlock, Carolina hemlock, and lodgepole pine growing in arboreta in 

the Seattle Washington area. The hemlocks were infested with HWA, the white pine with Pineus 

pinifolia, and the lodgepole pine with another Pineus adelgid that may be P. coloradensis. 

It was not found on 13 species of spruce, including the following which had live adelgid galls: 

Picea glehnii, P. koyamai, P. alcoquiana, and P. sitchensis. S. coniferarum also was not 

recovered from Douglas-fir infested with Adelges cooleyi and larch infested with Adelges laricis. 

It has not been found on broad-leaved trees, shrubs, or forbs infested with aphids, mealybugs or 

scale insects. 

Prey acceptance tests. 

Several species in the insect suborder Homoptera that occur in the eastern United States were 

evaluated in quarantine. First no-choice tests were conducted in which a single potential prey

species on its host is placed in a small covered-dish with an adult S. coniferarum lady beetle. 

The beetle’s previous food was HWA, but they were starved for 24-hours prior to the test. The 

number of prey on the host in each dish was counted at the start of the test and recounted the next 

day after confinement with an adult beetle. Each test had 10 replicates and was accompanied by

control dishes with an HWA adult and 10-15 eggs in the ovisac (most eggs were removed so that 

an accurate before and after count could be made and the adult feeding was disrupted so it 

stopped laying eggs). 

When confined with potential prey, S. coniferarum fed on all of the adelgid species tested and 

none of the other homopteran species (Table 1). Other Scymnus lady beetles that are considered 

adelgid specialists also feed on aphids, including P. tesselatus (Montgomery et al., 1997; Butin et 

al., 2004). 
B–2

Appendix B, Table 1. Feeding by adult S. coniferarum when confined for one day on a 

potential prey species that occur in the eastern United States. 

Prey Species Stage 

Tested

Host plant No. eaten Remarks

Adelgidae

Adelges tsugae Adult/egg Tsuga 

canadensis

1.0 adults 

18.0 eggs

Fed 3 adults and 25 eggs

" Nymph II " 9.9 Fed 10 nymphs 

" Neosistens " 0.6 Diapausing, not significantly. 

different from zero

Adelges piceae Adult, eggs Abies 

balsamea

0.4 adults 

4.3 eggs

Adelgid on bark

Pineus strobi Adult, eggs Pinus strobus 1.4 adults

2.4 eggs

Adelgid on twig

Pineus pini Adult, eggs Pinus

sylvestris

0.6 adults 

1.2 eggs

Adelgid at tip of twig

Aphididae

Eucallipterus 

tiliae

Adults, 

nymphs

Tilia

cordata

0.0 on underside of leaf

Paraprocipilulus 

tesselatus1 

Nymph I Alnus 

serrulata

0.0 Small colonies of the first 

instar nymph settled on twig.

Diaspididae

Fiorinia externa Adult T. canadensis 0.0 Crawlers not tested

Pseudococcidae

Dysmicoccus 

wistariae

Nymphs Taxus 0.0

1 Additional testing with this species, the woolly alder aphid, found no feeding after 10 days of confinement. Of the 

15 beetles confined with the aphid, 2 died, but none of the control S. coniferarum lady beetles reared on HWA died. 

Choice tests were conducted by confining adult S. coniferarum with a choice of HWA on eastern 

hemlock or a pine adelgid (Pineus sp.) on its pine host. The adelgids on pine are smaller, about 

three-fourths the size of HWA. There was no consistent preference for HWA compared to pine 

adelgids (Table 2).

Appendix 2, Table 2. Number of adelgids eaten when provided a choice between a pine adelgid 

and hemlock adelgid on their respective hosts.

Pineus species Source1Pineus HWA Prefer Variable measured

Pineus strobi East 49 39 ns # eggs eaten

" 24 9 Pineus sp. # adults eaten

Pineus pini East 28 60 HWA # eggs eaten

Pineus coloradensis2 West 125 47 Pineus sp. # eggs eaten 

1Collected in Washington State (West) or Connecticut (East)

2Tentative identification
B–3

Host preference for oviposition (egg laying) was examined by placing 10 recently received S. 

coniferarum in a one-gallon oviposition jar with a choice of HWA on eastern hemlock or Pineus 

strobi on eastern white pine (n = 5 jars). After five-days, the white pine foliage had an average 

of 14 beetle eggs whereas the hemlock foliage had an average of 58 eggs. This preference for 

hemlock to oviposit corresponds to the finding of more larvae on western hemlock than on 

western white pine in the Seattle area. 

Host suitability tests with the pine bark adelgid 

The pine bark adelgid, Pineus strobi Hartig, is native to eastern North America but occurs 

worldwide wherever species of white pine occur. It colonizes and feeds on both the tip of twigs 

and on the bark of eastern white pine, Pinus strobus. This pine often co-occurs with eastern 

hemlock in forests; thus, tests were conducted to determine if S. coniferarum could develop 

successfully on P. strobi. For this assay, S. coniferarum adult females were individually

confined with adults and eggs of P. strobi on white pine bark or HWA in Petri dishes at 15oC. 

On each host, S. coniferarum oviposited about 0.1 eggs per female per day. From these eggs, 19

S. coniferarum larvae, less than 24-hours old, were confined with P. strobi adults and eggs on 

white pine bark. Only 16 percent of the larvae successfully developed to the adult stage. While 

these data indicate that S. coniferarum will oviposit and can develop on pine bark adelgid, the 

low fecundity and survival is not indicative of a host that would be successfully utilized in 

nature.