The Hemlock Woolly Adelgid Adelges tsugae A formidable pest we CAN manage Mark Whitmore Dept. of Natural Resources Cornell University mcw42@cornell.edu

Life Cycle

Early infestation

Adult & Eggs Sistens more fecund than Progrediens Sistens egg hatch is more punctuated than Progrediens

Crawler & Nymph Kelly Oten, Bugwood.org After Egg hatch, the Crawler is the ONLY dispersal stage. The Crawler will find a feeding location and insert it’s mouthparts, staying in that spot for the rest of its life. With this change it is called a Nymph. After inserting its mouthparts into the host tissue the Sistens Crawler enters diapause for the summer,

Impact on trees Inserts stylets at base of needles and feeds on xylem ray parenchyma cells (woody part of twig) Feeding kills foliage & buds Usually kills trees within 6 to 10 years, it takes longer in cold areas. Old trees are first to die.

Hemlock Woolly Adelgid The Problem Parthenogenetic (all females) No Founder , or Allee Effect Small number of founders can start a new population High Reproductive Potential 2 generations per year & up to 200 eggs/female, but generally less 1 x 100 x 50 = 5,000 potential progeny from 1 female/yr. Native natural enemies are lacking in the eastern US Biocontrol efforts are ongoing No documented resistance by Eastern hemlock species Dispersal aided by birds, mammals, and humans

HWA Detection Look for gray foliage tint from afar

HWA Detection Look for the bug itself on twigs Inspect branches near ground – HWA will be found all through the crown Use binoculars to see higher? Be careful of glare and false positives Examine twigs that fall to the ground after a storm Be sure to check branches near water Birds are implicated as good long distance vectors

HWA Detection Examine bark of trees for tell-tale wisps of the waxy wool Woolly Whisps can also be seen on forest floor

Aestivating HWA Sistens In Summer

Early infestation

Middle of infestation

Late infestation In Summer

Host trees in North America Eastern Hemlock Tsuga canadensis Carolina Hemlock Tsuga caroliniana Western Hemlock Tsuga heterophylla

USFS, Northern Research Station, 2008

Scott McDonnell, NYSDEC. 2014.

Ecological Impact

Ecological Impact

Hemlock is a Foundation species in our forests Ecological Impacts Hemlock is a Foundation species in our forests They occupy the base of the food web They are critical species in the habitat they help create Generally so common that we take them for granted We depend on the ecosystems they build and maintain for a wide range of tangible and intangible services

Ecological Impact

Ecological Impacts Water resources Soils Moderate stream water temperatures for trout and other animals Provide a buffer for nutrient inputs to maintain water quality Soils Stabilize shallow soils especially in steep gorges Soil chemistry made more acidic Provide shelter for animals & plants Especially important in winter Critical habitat for migrating neo-tropical birds Acidic substrate for lichens Mortality opens stand to invasive plant species Can impede establishment of desired forest species

Skaneateles Lake, a AA unfiltered source of water for Syracuse, NY Photo Bill Hecht 2005

Watkins Glen State Park October 2012

Natural Control of Insect Populations Host Tree Resistance Many factors involved, most poorly understood for trees Abiotic Factors Temperature, humidity Biological Control Predators, Parasites, and Pathogens Additive effect of all agents involved

HWA and Cold Weather Severity and time of year are important. Parker et al. 1999; Skinner et al. 2003 In January and February, 3% of HWA from Holyoke, MA survived -22F (-30C); none survived -31F (-35C). Susceptibility increases later in the season (Feb – Mar) Tolerance of low temperatures genetically linked. Common garden experiment in MA with HWA from Maryland and MA. Butin et al. 2005

Northeast Regional Climate Center, Cornell University, 2014

Northeast Regional Climate Center, Cornell University, 2014 Taughannock State Park Mine Kill State Park Northeast Regional Climate Center, Cornell University, 2014

HWA and Cold Weather Taughannock State Park Mine Kill State Park Lowest temperature -8F (-22C) on 4 Jan 2014 91% mortality, n=3253 Mine Kill State Park Lowest temperature -24F (-31C) on 23 Jan 2014 82% mortality, n=2936 The colder location has less mortality! Are HWA populations adapting to the cold?

HWA Biological Control Program HWA detected in Eastern United States 1951? Classical Biological Control program initiated in 1993 No Parasitoids or specific pathogens? Work has focused on Coccinellid and Derodontid beetles from Eastern Asia and the Pacific Northwest. Seven species have been released to date, two in NY Only one species has become widely established: Laricobius nigrinus (Coleoptera: Derodontidae)

Laricobius nigrinus Native to Pacific Northwest Feeds ONLY on Adelgids Released in 16 states on east coast since 2003. Establishment found at many locations but impacts on HWA populations have been difficult to assess until 2012. Banner Elk, NC Spread over 20 miles since first introductions in 2003 Over 12,000 collected in two weeks for release Delaware Water Gap, Northern NJ and PA populations are growing since releases beginning in 2006 New York, first releases in NY 2009, established at two locations

Laricobius nigrinus releases in NY 2009 to 2013 14 locations: 2009, 2012, 2013 Two biotypes: Puget Sound Idaho Established at two sites – F5 generations

Laricobius nigrinus releases

Laricobius nigrinus Production Laboratory production in Virginia, Tennessee, Georgia, and New Jersey Complicated by shifting sources of HWA for food Estimate is $4 per beetle Most releases are wild collected in Puget Sound and Idaho Current push is to create field insectaries: Planting hemlocks in convenient locations across the state Utilize established hemlock hedges

Biocontrol in North Carolina Hemlock Hill, Banner Elk, NC – First release of Laricobius nigrinus 2003

Hemlock Recovery in North Carolina

Topical Chemical Control Mineral oil or soaps Thorough application required for adequate control Access is necessary for spray rigs Practical only in urban locations Impacts on non-target organisms detrimental Great Smoky Mountains National Park Resource Management Archive, USDI National Park Service, Bugwood.org

Systemic Insecticides Imidacloprid Various formulations and application techniques: Core Tect - time release tablets – NY restricted use Basal bark spray is recent innovation– NY restricted use Stem injection – NY restricted use Soil injection – NY restricted use Soil drench available to homeowners Effective for 7 years or more Problem: Slow movement through tree, up to one year. Dinotefuran (Safari) Basal bark spray. Fast movement. 1 or 2 years efficacy. Azidiractin (TreeAzin) Stem injection. Control for 1 year or more. Efficacy?

Basal Bark Spray Lower 5 feet of tree are sprayed until just before dripping wet Product moves through bark into conductive tissue without the aid of a bark penetrant In NY two products can be applied this way and are often used as a tank mix when infestations are advanced: Imidacloprid many generic formulations Dinotefuran “Safari”

Systemic Insecticides Current BMP’s Older trees showing decline Basal bark spray of Dinotefuran for rapid movement into the crown to preserve canopy Imidacloprid application at the same time for long term protection Core-Tect time release formulation Basal bark spray now registered in NYS so Imidacloprid and Dinotefuran can be applied at the same time with a tank mix Younger trees without much canopy deterioration can be treated with time release, soil drench, or basal bark spray of imidacloprid only.

Hemlock Recovery No need to treat until HWA observed, but… don’t wait too long! Upper crown will respond but lower crown may not recover

Integrated Pest Management of HWA Insecticide treatments are efficacious and relatively inexpensive. They are an important tool to keep select trees alive and thereby maintain a diverse gene pool. Classical biocontrol is a long process and results on the landscape are just becoming apparent. We need to step up efforts to establish and produce predators in New York. Integrate systemic insecticide treatment with biocontrol efforts in priority areas. Treat vulnerable large trees leaving younger trees to harbor HWA to feed predators.

Next steps for Management Need to develop region wide priorities for management Maintain genetic resources across the landscape with systemic insecticides PROTECT TREES! Detection and monitoring over the long haul Engage professional land managers and volunteers in management efforts Establish field insectaries to produce predators Hemlock hedges infested with HWA are needed!

nyis.info Mark Whitmore Dept. of Natural Resources Cornell University mcw42@cornell.edu