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

2. Life Cycle

3. Early infestation

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

5. 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,

6. 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.

7. 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

8. HWA Detection
Look for gray foliage tint from afar

9. 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

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

11. Aestivating HWA Sistens In Summer

12. Early infestation

13. Middle of infestation

14. Late infestation In Summer

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

16. USFS, Northern Research Station, 2008

18. Scott McDonnell, NYSDEC. 2014.

19. Ecological Impact

20. Ecological Impact

21. 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

22. Ecological Impact

23. 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

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

25. Watkins Glen State Park October 2012

27. 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

28. 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

29. Northeast Regional Climate Center, Cornell University, 2014

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

31. 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?

32. 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)

33. 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

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

35. Laricobius nigrinus releases

36. 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

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

38. Hemlock Recovery in North Carolina

39. 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

40. 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?

41. 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”

42. 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.

43. 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

44. 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.

45. 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!

46. nyis.info Mark Whitmore Dept. of Natural Resources Cornell University