Decline of Eastern Hemlock due to Hemlock Woolly Adelgid

1. Decline of Eastern Hemlock due to Hemlock Woolly Adelgid Sophia DeMaio April 25, 2007

2. Susceptible Species • Carolina (Tsuga caroliniana) and eastern hemlock (Tsuga canadensis) • Western (T. heterophylla) and mountain hemlock (T.mertensiana) also become invested but do not decline

3. Eastern Hemlock • Range: Great Lakes to New England • Cool, moist climates • Acidic soils • Very shade tolerant • Long-lived

4. Eastern Hemlock Importance • Economic • Tanning • Lumber • Pulp • Ornamental varieties • Ecological • Dense canopies • Vertical structure • Horizontal structure • Nutrient cycling • Ecological research

5. Symptoms • Needles dry • Turn grayish green or yellow • Thinning of foliage • Crown and branch dieback

6. Forest Impacts • Tolerant conifer replaced by hardwoods • Stand structure • Stand density • Microclimate • Wildlife habitat • Nutrient cycling

7. Primary Stress • Hemlock woolly adelgid (HWA; Adelges tsugae) • Signs: fuzzy white spots underside of needles, late fall-early summer, crawlers spring and summer • Introduced from southern Japan to NJ->New England->Maine • Limited by T (39F spring generation, -25F winter generation) and vectors

8. Predisposing factors • Warm winters • Introduced pest • No time for tree to adapt or predator populations to build • Drought • Low precipitation (especially in summer) • Drought-prone sites (shallow rooting, southern slopes) • Other hemlock stressors

9. Life Cycle • Winter generation • Eggs hatch mid-summer • ~300 per adult • Crawler enter summer dormancy late summer • all adults are female=parthenogenesis) • Only moving and exposed stage • Find feeding sites on twigs • Resume development in October (2,3,4 instar nymphs) • Feed in place • White woolly covering • Spring generation • Eggs hatch early spring (20-75/adult) • Reach adulthood early summer • Some winged adults fly to alternate host (not available so die, but keep populations viable) • Density dependent population growth

10. Mechanisms for disruption • Depletes tree’s starch reserves • Inserts stylet into xylem ray parenchyma • starves to death • allocates E to external new shoots • New growth reinfested

11. Number of -25C events in Sanford, ME Population control • Early freezing (spring generation) • Cold winters (-25) with little snow (overwintering sistens) • Predation • Native environment • here Kathleen S. Shields and Carole A. S-J. Cheah. USDA Forest Service, Hamden, CT Connecticut Agricultural Experiment Station, Windsor, CT

12. Inciting factors • Transport of eggs or crawlers to suitable feeding site • Spread by wildlife, human activities, wind • HWA Feeding and reproduction

13. Contributing factors • Drought • Fungal infection • Other insect pests and diseases • Elongate hemlock scale • Hemlock looper • Spruce spider mite • Hemlock borer • needlerust

14. Control-preemptive • Quarantine • Increase hemlock vigor (5 yrs before infestation) • Manage for white pine over hemlock in drought-prone sites • Decrease spread by vectors

15. Monitor and Survey • Public outreach education • Take a stand • Costa protocol

16. Reactive control-Chemical and physical • Horticultural oils • suffocates adelgid • minimal impact other forest trees • widely spaced, manageable height • Stem/root injection • concentrated chemical • Systematic • drilling may further stress tree • Soil injection • Problem near streams • Soil organisms • Harvest vector trees • Salvage • Plant with white pine or other intermediate species on good sites

17. Reactive control-biological • Beetles • Sasajiscymnus tsugae • Scymnus • Laricobius nigrinus • Fungi • Beauveria bassiana • Metarhizium anisopliae • Verticillium lecanii • Paecilomyces sp. • Ideal? http://www.invasive.org/hwa/

18. Feasibility • Ecological • Conservation of threatened species • Economic • Pesticides for ornamental and vector trees

19. Health Management Plan