SREF-FH-012 May 2019

Unlike other hemlock species, eastern Biology and Management of the Hemlock Woolly and Carolina hemlock are susceptible to severe impact from HWA21. Adelgid in the Eastern U.S. Carolina hemlock has a more limited range than eastern hemlock, growing AUTHORED BY: ELIZABETH McCARTY, GREG WIGGINS, in small, isolated populations on drier AND DAVID COYLE mountain sites16. Thus, most of the focus on HWA damage has centered a.a grow in the eastern U.S. These have great ecological and on eastern hemlock, which is more cultural value in . However, widely distributed and sometimes the invasive hemlock woolly used in the landscape industry. adelgid ( tsugae or HWA) is decimating hemlock populations throughout much of the trees’ native DISTRIBUTION AND BIOLOGY range, altering landscapes, and threatening these iconic species Hemlock woolly adelgid is native to in both rural and urban areas. China, Japan, and western North America11. The population in the b Identification and Biology eastern U.S. was likely accidentally introduced to on ornamental from Japan as early as the HEMLOCK DESCRIPTION 1920’s. HWA has now expanded AND DISTRIBUTION from Virginia to 20 eastern states (Fig. 2, next page). Eastern hemlock is a slow growing, long-lived, and shade tolerant Adelgids are soft-bodied, -like . Hemlocks may live up to . HWA adults are purplish- blackish in appearance and produce 800 years and grow as high as 175 a white protective woolly material feet tall. Hemlock needles are ½ - 1 that covers their bodies20. A hemlock inch long with two whitish stripes branch infested with HWA will appear running longitudinally along the Figure 1. Hemlock needles with striped to have small cotton balls on the underside (a) and a hemlock cone (b). underside of the needles (Fig. 1a). branches where the needles meet the They attach singly along thin, flexible twig (Fig. 3). twigs. Hemlock bark appears grayish Introduction in color, and the tree has a cone- like silhouette. Small brown cones Hemlock trees in eastern forests are about an inch long (Fig. 1b). In are late successional tree species eastern North America, hemlocks that provide shade for the grow from northern and understory. Globally, there are ten Alabama north into Canada. In the species of hemlock, with populations southeastern U.S., eastern hemlock is located in Asia and eastern and often found growing in damp valleys western North America12. Eastern or on the eastern and northern slopes hemlock ( canadensis) and of hills and mountains5. Carolina hemlock () Figure 3. HWA appear as white woolly mass- es on hemlock twigs.

www.southernforesthealth.net/insects 1 Hemlock woolly adelgid has a complicated life cycle, with two generations per year (called sistens and progrediens, Fig. 4). Females do not need to mate to reproduce, and each female lays up to 175 eggs that stay within her woolly mass (ovisac). In the southeastern U.S. the sistens generation lives for about 10 months, from early summer to the following spring. This generation aestivates, or becomes inactive, during the summer and begins feeding in late fall. The progrediens generation lives about three months, from early spring to early summer. The first instar, or life phase, is called a crawler (Fig. 5), and this is the only HWA instar that can move, other than a winged female – all other life stages are sessile (i.e., fixed in one place). Crawlers cannot move far on their own, but they can be carried longer distances by wind, wildlife, or humans. Generally, crawlers move along a branch and find a spot at a needle base. They insert their long, straw-like mouthpart Figure 2. Hemlock woolly adelgid distribution map in the eastern U.S. Different colors into the hemlock and begin feeding. represent different amounts of hemlock basal area, while counties where the adelgid Once HWA is feeding, they will grow has been reported are outlined in black and begin producing the protective wool. When mature, adults lay eggs under the protective wool (Fig. 6). The progrediens generation also includes production of winged females, which cannot reproduce in North America.

Figure 4. Hemlock woolly adelgid lifecycle.

Figure 5. Hemlock woolly adelgid crawler on Figure 6. Hemlock woolly adelgid eggs and Figure 7. Hemlock woolly adelgid adult re- a hemlock needle, as noted by the red arrow. wool. moved, shown with long mouthpart visible.

www.southernforesthealth.net/insects 22 ECOSYSTEM FUNCTION nearby streams. living so hemlock renewal from seed in hemlock canopies no longer have germination many years later is Eastern hemlock is a foundation, or habitats after hemlock trees die. unlikely24. Currently, hemlock keystone, species in eastern forests, Bird communities are altered when removal from a forest, along with the creating an environment necessary for hemlock is not a part of the forest negative effects on the ecosystem, is 9 28 the survival of other organisms . The canopy . Hemlock is replaced by permanent – especially since no other loss of hemlock impacts many other either hardwood tree species, such as native evergreen tree species can fill 26 plants and in eastern forests. birch, oak, maple, and/or tulip tree , hemlock’s ecological role. Hemlocks produce deep shade and or in the Southeast rhododendron acidic litter, which affect the can begin to dominate forests ECONOMIC DAMAGE temperature, moisture, and nutrients after hemlocks die. Unfortunately, of the forest floor14, as well as stream rhododendron thickets tend to Tourism, hazard tree removal costs, flow rates and water quality8. Many be very dense, restricting light to property values, and the ornamental animals live in hemlock canopies, and the forest floor and inhibiting the and nursery industries can all be hemlock is an important source of 30 growth of other species . negatively affected following hemlock food during the winter – for example, Declining hemlocks result in changes loss due to HWA. Forests with a small mammals like squirrels and in soil nutrients and greater light hemlock component are popular rabbits feed on the bark, and availability on the forest floor when destinations for tourists. Dead porcupines eat twigs. Hemlock 14 rhododendron is not present . More hemlock “skeletons” littering views occurs in several different forest light reaches streams when hemlocks and hazard trees located near trails types, with many different co- have died and the canopy is opened, and campgrounds detract from a occurring plant species depending on which leads to higher stream tourist’s outdoor experience (Fig. 9). the particular habitat and location. temperatures30 and subsequent impacts on fish. Hemlock water Dead hemlocks in public areas Hemlock Woolly Adelgid Damage use varies seasonally from that of such as parks, campgrounds, trails, hardwoods, resulting in different roads, and yards are hazards to 8 annual water balances . In addition, public safety. Federal and state PHYSICAL DAMAGE TO HEMLOCK stream communities can parks, transportation departments, become less diverse as the overstory Hemlock woolly adelgid uses its municipalities, and residents must pay changes from hemlock-dominated to for hazard tree removal. This expense straw-like mouthparts (Fig. 7) to hardwood-dominated1,27. retrieve carbohydrates from hemlock is often a great financial burden to storage cells31. Once the tree’s private entities, municipalities, and Unfortunately, hemlock seeds are ultimately taxpayers. carbohydrate reserves are reduced, only viable for about four years, the hemlock will begin to decline. The visible symptoms of HWA Hemlocks add aesthetic and feeding are greying needles, dead economic value to urban forests branches, and eventually canopy and other residential areas. The thinning (Fig. 8). Hemlocks can die presence of yard trees accounts for from HWA feeding, leaving gray, approximately 1 – 5% of residential needle-less hemlock tree “skeletons” property value. Hemlock defoliation scattered across the landscape (Fig. and subsequent mortality cause 9). In the Southeast hemlocks can decreases in property value for die from HWA feed in as little as 2-4 years. Some trees, especially in more northern areas, can take up to a decade to die, while other trees may never die.

ECOLOGICAL DAMAGE

Hemlock mortality changes forest ecosystems from the canopy all the way down to the forest floor and nearby streams. Arthropods living Figure 8. Declining hemlock tree. Figure 9. Dead hemlocks on the landscape.

www.southernforesthealth.net/insects 3 Table 1. Comparison of HWA management options. Management tactic Benefits Limitations Concerns Use location - entire hemlock canopy must be covered - areas with easy access - fast acting - short-term control Horticultural Oil - harmful to other insects - landscapes - generally considered less toxic - two applications each year - nurseries - should not be applied adjacent to water Contact insecticides - entire hemlock canopy must be covered - areas with easy access Organophosphates - short-term control - fast acting - toxic to other insects - landscapes - two applications each year - Carbamates - nurseries - Pyrethroids - should not be applied adjacent to water - Avermectins - longer acting - areas with easy access Neonicotinoid - systemic control - persistence in the environment - toxic to other insects - landscapes insecticides - can be used in remote areas - should not be applied adjacent to water - environmental persistence - nurseries - ease of application - forests - longer systemic control - effective slowly - lightly to moderately infested - Imidacloprid - approx. 5 - 7+ yrs - three months for HWA mortality hemlocks - effective quickly - shorter systemic control - Dinotefuran - heavily infested hemlocks - one month for HWA mortality - approx. 1.5 - 2 yrs. - long time for effective control - may not be effective - no insecticides introduced in - forests - robust effectiveness has not been before hemlocks die Biocontrol the environment - applied by trained personnel demonstrated - possible interaction with - more sustainable control with appropriate expectations - not appropriate for all sites native insects - locations where control - no insecticides or non-native - hemlocks will die - hemlock mortality No control measures are not used species introduced to the - numerous ecological effects of hemlock - permanent ecological - usually a result of financial implemented environment mortality in forests effects limitations or state regulations

Table 2. Most common predators assessed for biological control of HWA in the eastern U.S. Insect Insect type Scientific name Region of Origin Release Status Site objectives and management (Coleoptera: Sasajiscymnus tsugae Japan Widespread goals will determine which Lady ) (Coleoptera: Scymnus management options are best for Lady beetle* China Localized Coccinellidae) camptodromus each location. Treating forest-grown (Coleoptera: Western North Scymnus coniferarum Localized hemlocks two miles from a road Lady beetle* Coccinellidae) America entails a different set of challenges (Coleoptera: Scymnus sinuanodulus China Localized Lady beetle* Coccinellidae) than treating a single hemlock Predaceous (Coleoptera: Western North in an ornamental setting. Thus, nigrinus Widespread Fungus Beetle ) America different management options must Predaceous (Coleoptera: Japan Localized be considered for each situation. Fungus Beetle Derodontidae) When using an integrated pest (Diptera: Western North Silver fly Leucopis argenticollis Assessment ongoing Chamaemyiidae) America management (IPM) approach in (Diptera: Western North non-hemlock scenarios, insecticide Silver fly Leucopis piniperda Assessment ongoing Chamaemyiidae) America use is generally a last resort choice. *While these three Scymnus spp. lady do feed on HWA, establishment of beetle However, for most sites, insecticides populations after a release has not yet been demonstrated. may be the only option for hemlock preservation. Always read and the parcel on which the hemlocks industry, which boasts over 200 cultivars follow the pesticide label for are located as well as adjacent of eastern hemlock, has significantly specific information concerning property13. declined in the eastern U.S. applications near water and in sensitive areas, non-target injury, Hemlocks are important and valuable Management Strategies application rates, and application ornamental plantings. Hemlock guidance. Keep in mind that it is management or replacement in Options for hemlock management illegal to use pesticides in a manner yards is costly for residents. In currently include contact insecticides, that is inconsistent with the label. It addition, nurseries must control systemic insecticides, biological control, is highly recommended to contact HWA in nursery plants and navigate and doing nothing (Table 1), though a professional when working with quarantines for shipping hemlock silvicultural management strategies are pesticides. between infested and uninfested being developed15,17. areas. Hemlock in the nursery

www.southernforesthealth.net/insects 4 CONTACT INSECTICIDES are near freezing. Check with state of an introduced pest2. Because forestry agencies to receive guidance they are from the same native range Many broad-spectrum contact on treatment timing in specific areas. as the pest, some natural enemies insecticides, such as horticultural will have very close or exclusive oil, organophosphates, carbamates, Systemic insecticides do not provide associations with the pest species, pyrethroids, and avermectins, immediate HWA mortality because perhaps only feeding on the pest can be used to suppress HWA. the insecticide takes time to move or requiring the pest to complete Contact insecticides provide fast from the roots to the canopy. their life cycle. Although many HWA mortality. Applying a contact Imidacloprid takes three months to natural enemies in the native range insecticide involves coating the reach efficacy, but control lasts for of a pest may be identified, only entire canopy with a foliar spray. up to seven years4,6. Imidacloprid those that are determined as host- They should be applied twice a year application can be optimized for specific to the target pest, through and must be timed appropriately the size of the hemlock, resulting controlled testing in laboratory and to target the mobile crawler stage. in precise insecticide dosages, field studies, are selected for release Applicators often use high-pressure which reduces overall insecticide against the pest. Classical biological sprayers to coat larger trees. Some use (application guidance available control programs require much effort practical limitations of contact online3). to identify natural enemies and insecticides include difficulty with considerable time to evaluate their uniform foliar coverage, lack of Dinotefuran has quicker uptake, suitability for release. residual effectiveness, and tree becoming effective in less than a accessibility. Contact insecticides month, but control only lasts for A classical biological control program are a management option for smaller two years at most18. Imidacloprid against HWA began in the 1990s25. landscape trees, hedgerows, and is a good choice for light to This effort is centered on establishing nursery settings. Although many of moderate infestations. Treated a complex (multiple species) of these products are labeled for forest hemlocks can survive HWA feeding biological control agents to reduce settings, contact insecticides are until imidacloprid begins killing HWA populations to non-injurious not often used in forests due to site HWA. Dinotefuran is a better levels. The native ranges of HWA accessibility issues. choice for hemlocks with heavy have been explored, and several HWA infestations, because it will predators of HWA have been SYSTEMIC INSECTICIDES quickly reduce HWA populations. identified and evaluated for use as Sometimes both products will be biological control agents (Table 2). Imidacloprid and dinotefuran are used for heavily infested hemlocks in Several laboratories in the eastern systemic neonicotinoid insecticides remote sites, because it is much more U.S. are responsible for raising and that are most commonly used difficult to go back and treat trees coordinating releases of predators for HWA suppression. Systemic with imidacloprid the next year due of HWA25. The most widely released insecticides are applied to either to site accessibility. natural enemies of HWA have been the soil or the hemlock trunk. The and Sasajiscymnus tree’s vascular tissue moves the BIOLOGICAL CONTROL tsugae, and both species have insecticide to the canopy, where established in some areas of HWA feeds. The systemic activity Biological control is the use of release10,19. However, other species, of these products allows greater natural enemies to reduce pest such as L. osakensis23 and Leucopis flexibility with application methods, populations and keep them at low spp.22, currently are being assessed such as soil drench, soil injection, levels. It is generally employed for for wide-scale releases to increase the trunk injection, and trunk spray7. In long-term management of a pest, diversity of introduced predators that addition, imidacloprid can be applied as populations of the natural enemy feed on HWA. in a slow-release tablet formulation. require time to grow large enough to Both products can be used in impact pest populations. Typically, Several factors must be considered either landscape or forest settings. biological control is applicable over a before the use of biological Treatment time recommendations large area (landscape scale), because control against HWA. Due to the may vary depending on geographical ideally natural enemies will reproduce developmental nature of this effort, location. For example, in the South and disperse in search of their target biological control of HWA has typically treatments are generally not applied pest or prey2. been conducted on public lands by during the summer, while in some trained personnel, and some natural northern areas treatments are not Classical biological control employs enemy species may not be available applied when soil temperatures natural enemies from the native range for use on private lands.

www.southernforesthealth.net/insects 5 Because HWA can cause tree and negative consequences. Any insecticides and biological control mortality quickly, especially in the decision regarding are currently the management tactics southern U.S., predator populations management will involve making best suited for hemlocks growing in often cannot grow large enough to trade-offs between the benefits and forests or other natural areas. decrease HWA populations if the limitations of management options. infestation is too great. Also, the use Conclusion of natural enemies to manage HWA Management Perspective is not suitable for individual trees or if immediate reduction in pest Hemlock woolly adelgid is a small The approach to managing HWA insect that kills a mighty tree. The populations is required. on hemlock is dependent on the landscapes of eastern forests will be location and site goals. The use forever changed as a result of the NO HWA MANAGEMENT of appropriate tools depends on introduction of this invasive species. whether the goal is preserving one While every hemlock cannot be Treating individual trees with systemic tree in a landscape setting or the saved, there are several management insecticides can be expensive, and it integrity of an entire forest system. tactics to suppress HWA and is not possible to save every hemlock Single-tree management is generally preserve hemlock resources. in the forest29. In addition, many land a landscape/ornamental issue. Hemlocks can be protected for management programs cannot treat Proper tools include horticultural oil, numerous years using one systemic hemlocks, either due to the cost, or contact insecticides, and systemic insecticide treatment. Biological because state regulations prohibit insecticides (Table 1). The cost control predators are being assessed the use of insecticides in forests. of treating a tree is far less than for their ability to reduce HWA However, doing nothing results in the cost of removing a dead tree populations. Landowners have loss of hemlock, a foundation species that has become a safety hazard. the option of using insecticides to from the forest. Hemlock loss will However, the purpose of preserving protect hemlock resources now while have many negative ecological hemlocks in forested areas is not biological control tactics are being consequences. In residential and just preservation of a single tree, but studied. Conserving hemlock trees park settings, hazard tree removal rather the preservation of an entire is beneficial for overall forest health is costly and is a consideration forest ecosystem. Unfortunately, and is less costly than the expense of when determining whether to treat. many methods used in ornamental removing trees in landscape settings. Every management tactic, including landscapes are either not allowable doing nothing, has both positive or not practical in forests. Systemic

AUTHORS: Elizabeth McCarty, University of Georgia, D.B. Warnell School of Forestry & Natural Resources, Tifton, GA

Greg Wiggins, National Institute for Mathematical and Biological Synthesis, University of , Knoxville, TN

David Coyle, Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC

We thank Lori Chamberlin, Robert Jetton, Rusty Rhea, Katlin Mooneyham, Nathan Havill, and Kelly Oten for earlier reviews of this document.

SREF-FH-012 | www.sref.info A Regional Peer Reviewed Technology Bulletin published by Southern Regional Extension Forestry

Southern Regional Extension Forestry (SREF) is a diverse team of trained natural resource educators, IT specialists, graphic designers, communi- cations and marketing experts, and media and content producers. SREF works closely with the Southern Land Grant University System, US Forest Service, and state forestry agencies to develop content, tools and support for the forestry and natural resource community. To find out more about SREF programs please visit www.sref.info.

www.southernforesthealth.net/insects 6 Oklahoma Cooperative Extension Service: Resources http://www.oces.okstate.edu/ Clemson Cooperative Extension (South Carolina): http://www.clemson.edu/extension/ For the location and phone numbers of state agencies in the southeastern U.S. providing forestry assistance and University of Tennessee Extension: information, see the following websites: https://extension.tennessee.edu/ Texas A&M AgriLife Extension: http://agrilifeextension.tamu.edu/ Alabama Forestry Commission: http://www.forestry.alabama.gov/ Virginia Cooperative Extension: http://www.ext.vt.edu/ Arkansas Forestry Commission: http://forestry.arkansas.gov/Pages/default.aspx To locate a consulting forester: Florida Forest Service: http://www.floridaforestservice.com/ Association of Consulting Foresters: Georgia Forestry Commission: http://www.gatrees.org/ http://www.acf-foresters.org/acfweb.

Kentucky Division of Forestry: Click on “Find a Forester”, then select your state in the http://forestry.ky.gov/Pages/default.aspx “People Search – Public” search page. Louisiana Department of Agriculture and Forestry: http://www.ldaf.state.la.us/ For more information on how to select a consulting Mississippi Forestry Commission: http://www.mfc.ms.gov/ forester, go to:

North Carolina Forest Service: http://www.ncforestservice.gov/ http://msucares.com/pubs/publications/p2718.pdf Oklahoma Forestry Services: http://www.forestry.ok.gov/ http://texashelp.tamu.edu/011-disaster-by-stage/pdfs/recovery/ ER-038-Selecting-a-Consulting-Forester.pdf Forestry Commission: http://www.uaex.edu/environment-nature/forestry/FSA-5019.pdf http://www.state.sc.us/forest/

Tennessee Division of Forestry: Additional information on the hemlock woolly adelgid is https://www.tn.gov/agriculture/section/forests available at: Texas A&M Forest Service: http://texasforestservice.tamu.edu/ http://southernforesthealth.net/ Virginia Department of Forestry: http://www.dof.virginia.gov/ http://protecttnforests.org/hemlock_wooly_adelgid.html https://www.nature.org/ourinitiatives/regions/northamerica/ For the location and phone numbers of University unitedstates/tennessee/explore/hemlock.xml Extension personnel in the southeastern U.S. providing https://www.fs.usda.gov/detail/r8/forest-grasslandhealth/insects- forestry assistance and information, see the following diseases/?cid=stelprd3842820 websites: https://www.nrs.fs.fed.us/disturbance/invasive_species/hwa/ Alabama Cooperative Extension System: http://www.aces.edu/main/ University of Arkansas Cooperative Extension Service: Photo Credits http://www.uaex.edu/

University of Florida’s Institute of Food and Agricultural Figure 1a, 1b, 3, 4, 6, and 7: Elizabeth McCarty, University of Sciences (UF/IFAS): Georgia. http://solutionsforyourlife.ufl.edu/ Figure 2: Samuel Lambert, USDA Forest Service. University of Georgia Extension: http://extension.uga.edu/ Figure 5: Vincent D’Amico and Nathan Havill, USDA Forest Kentucky Cooperative Extension Service: Service. https://extension.ca.uky.edu/ James Johnson, Georgia Forestry Commission, Louisiana Cooperative Extension Service: Figure 8: bugwood.org. http://www.lsuagcenter.com/ Camcore, State University. Mississippi State University Extension Service: Figure 9: http://extension.msstate.edu/ North Carolina Cooperative Extension: https://www.ces.ncsu.edu/

www.southernforesthealth.net/insects 7 References

1Adkins, J. and L.K. Rieske. 2015. Benthic collector and grazer communities are 16Jetton, R.M., W.S. Dvorack, and W.A. Wittier. 2008. Ecological and genetic factors threatened by hemlock woolly adelgid-induced eastern hemlock loss. Forests 6(8): that define the natural distribution of Carolina hemlock in the southeastern United 2719-2738. States and their role in ex situ conservation. For. Ecol. Manage. 255: 3212-3221.

2Bellows, T.S. and T.W. Fisher. 1999. Handbook of Biological Control: Principles and 17Jetton, R.M., A.E. Mayfield III, W.A. Whittier, B. Mudder, R. Rhea, and G.R. Hodge. Applications of Biological Control. Academic Press, San Diego, CA. 2017. Silvicultural and genetic resource conservation strategies for management of the hemlock woolly adelgid. Proceedings of the 58th Southern Forest Insect Work 3Benton, E. and R.S. Cowles. 2017. Optimized insecticide dosage for hemlock woolly Conference. p. 27. adelgid control in hemlock trees. WSFNR-17-01. Warnell School of Forestry and Natural Resources. https://www.warnell.uga.edu/sites/default/files/publications/ 18Joseph, S.V., J.L. Hanula, and S.K. Braman. 2011. Distribution and abundance of WSFNR-17-01%20Benton_0.pdf Adelges tsugae (: ) within hemlock trees. J. Econ. Entomol. 104: 1918–1927. 4Benton, E.P., J.F. Grant, R.J. Webster, R.J. Nichols, R.S. Cowles, A.F. Lagalante, and C.I. Coots. 2015. Assessment of imidacloprid and its metabolites in foliage of eastern 19Mausel, D.L., S.M. Salom, L.T. Kok, and G.A. Davis. 2010. Establishment of the hemlock multiple years following treatment for hemlock woolly adelgid, Adelges hemlock woolly adelgid predator, Laricobius nigrinus (Coleoptera: Derodontidae), in tsugae (Hemiptera: Adelgidae), in forested conditions. J. Econ. Entomol. 108: the eastern . Environ. Entomol. 39: 440–448. 2672–2682. 20McClure, M.S. 1989. Evidence of a polymorphic life cycle in the hemlock woolly 5Burns, R.M. and B.H. Honkala, tech. coords. 1990. Silvics of North America: 1. adelgid, Adelges tsugae Annand (Homoptera: Adelgidae). Ann. Entomol. Soc. Am. ; 2. Hardwoods. Agriculture Handbook 654. U.S. Department of Agriculture, 82: 52–54. Forest Service, Washington, DC., 877 p. 21McClure, M.S., S.M. Salom, and K.S. Shields. 2001. Hemlock woolly adelgid. 6Coots, C., P.L. Lambdin, J. Grant, and R. Rhea. 2013. Spatial and temporal USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, WV. distribution of residues of imidacloprid and its insecticidal 5-hydroxy and olefin and FHTET-2001–03. metabolites in eastern hemlock (: ) in the southern Appalachians. J. Econ. Entomol. 106: 2399–2406. 22Motely, K., N.P. Havill, A.L. Arsenault-Benoit, A.E. Mayfield, D.S. Ott, D. Ross, M.C. Whitmore, and K.F. Wallin. 2017. Feeding by Leucopis argenticollis and Leucopis 7Cowles, R.S., M.E. Montgomery, and C.A.S.-J. Cheah. 2006. Activity and residues piniperda (Diptera: Chamaemyiidae) from the western USA on Adelges tsugae of imidacloprid applied to soil and tree trunks to control hemlock woolly adelgid (Hemiptera: Adelgidae) in the eastern USA. Bull. Entomol. Res. 107: 699–704. (Hemiptera: Adelgidae) in forests. J. Econ. Entomol. 99: 1258–1267. 23Mooneyham, K.L., S.M. Salom, and L.T. Kok. 2016. Release and colonization of 8Cowles, R.S., M.E. Montgomery, and C.A.S.-J. Cheah. 2006. Activity and residues Laricobius osakensis (Coleoptera: Derodontidae), a predator of the hemlock woolly of imidacloprid applied to soil and tree trunks to control hemlock woolly adelgid adelgid, Adelges tsugae. Northeastern Nat. 23: 141–150. (Hemiptera: Adelgidae) in forests. J. Econ. Entomol. 99: 1258–1267. 24Olson, J.S., F.W. Stearns, and H. Nienstaedt. 1959. Eastern hemlock seeds and 9Ellison, A.M., M.S. Bank, B.D. Clinton, E.A. Colburn, K. Elliott, C.R. Ford, D.R. Foster, seedlings: Response to photoperiod and temperature. Bull. Conn. Agric. Expt. Sta. B.D. Kloeppel, J.D. Knoepp, G.M. Lovett, J. Mohan, D.A. Orwig, N.L. Rodenhouse, 620: 1–70. W.V. Sobczak, K.A. Stinson, J.K. Stone, C.M. Swan, J. Thompson, B. Von Holle, and J.R. Webster. 2005. Loss of foundation species: consequences for the structure and 25Onken, B., and R. Reardon. 2011. Implementation and status of biological control of dynamics of forested ecosystems. Front. Ecol. Environ. 3:479–486. hemlock woolly adelgid, USDA Forest Service, Morgantown, WV. https://www.fs.usda. gov/naspf/sites/default/files/naspf/pdf/bio_control-2012.pdf. 10Hakeem, A., J.F. Grant, G.J. Wiggins, P.L. Lambdin, F.A. Hale, D.S. Buckley, J.R. Rhea, J.P. Parkman, and G. Taylor. 2013. Factors affecting establishment and recovery 26Orwig, D. A., D. R. Foster, and D. L. Mausel. 2002. Landscape patterns of hemlock of Sasajiscymnus tsugae (Coleoptera: Coccinellidae), an introduced predator decline in New England due to the introduced hemlock woolly adelgid. J. Biogeogr. of hemlock woolly adelgid (Hemipter: Adelgidae) on eastern hemlock (Pinales: 29: 1475 – 1487. Pinaceae). Environ. Entomol. 42: 1272–1280. 27Snyder, C.D., J.A. Young, D.P. Lemarie, and D.R. Smith. 2002. Influence of eastern 11Havill, N.P., S. Shiyake, A.L. Galloway, R.G. Footitt, G. Yu, A. Paradis, J. Elkinton, M.E. hemlock () forests on aquatic invertebrate assemblages in Montgomery, M. Sano, and A. Caccone. 2016. Ancient and modern colonization of headwater streams. Can. J. Fish. Aquat. Sci. 59: 262–275. North America by hemlock woolly adelgid (Hemiptera: Adelgidae), an invasive insect from East Asia. Mol. Ecol. 25: 2065-2080. 28Tingley, M.W., D.A. Orwig, R. Field, and G. Motzkin. 2002. Avian response to removal of a forest dominant: Consequences of hemlock woolly adelgid infestations. 12Holman, G., P. Del Tredici, N. Havill, N. S. Lee, R. Cronn, K. Cushman, S. Matthews, J. Biogeogr. 29: 1505–1516. L. Raubeson, and C.S. Campbell. 2017. A new species and introgression in eastern Asian hemlocks (Pinaceae: Tsuga). Syst. Bot. 42: 1–14. 29Vose, J.M., D.N. Wear, A.E. Mayfield III, and D. Nelson. 2013. Hemlock woolly adelgid in the southern Appalachians: Control strategies, ecological impacts, and 13Holmes, T.P., A.M. Liebhold, K.F. Kovacs, and B. Von Holle. 2010. A spatial-dynamic potential management responses. For. Ecol. Manage. 291: 209–219. value transfer model of economic losses from a biological invasion. Ecol. Econ. 70: 86–95. 30Webster, J.R., K. Morkeski, C.A. Wojculewski, B.R. Niederlehner, E.F. Benfield, and K.J. Elliott. 2012. Effects of hemlock mortality on streams in the southern Appalachian 14Jenkins, J.C., J.D. Aber, and C.D. Canham. 1999. Hemlock woolly adelgid impacts Mountains. Am. Midl. Nat. 168: 112–131. on community structure and N cycling rates in eastern hemlock forests. Can. J. For. Res. 29: 630–645. 31Young, R.F., K.S. Shields, and G.P. Berlyn. 1995. Hemlock woolly adelgid (Homoptera: Adelgidae): stylet bundle insertion and feeding sites. Ann. Entomol. 15Jetton, R.M. and A.E. Mayfield III. 2018. Towards silvicultural management of the Soc. Am. 88: 827–835. hemlock woolly adelgid. 2018. Proceedings of the 59th Southern Forest Insect Work Conference. p. 33.

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