200 likes | 311 Views
Decline of Eastern Hemlock due to Hemlock Woolly Adelgid. Sophia DeMaio April 25, 2007. 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.
E N D
Decline of Eastern Hemlock due to Hemlock Woolly Adelgid Sophia DeMaio April 25, 2007
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
Eastern Hemlock • Range: Great Lakes to New England • Cool, moist climates • Acidic soils • Very shade tolerant • Long-lived
Eastern Hemlock Importance • Economic • Tanning • Lumber • Pulp • Ornamental varieties • Ecological • Dense canopies • Vertical structure • Horizontal structure • Nutrient cycling • Ecological research
Symptoms • Needles dry • Turn grayish green or yellow • Thinning of foliage • Crown and branch dieback
Forest Impacts • Tolerant conifer replaced by hardwoods • Stand structure • Stand density • Microclimate • Wildlife habitat • Nutrient cycling
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
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
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
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
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
Inciting factors • Transport of eggs or crawlers to suitable feeding site • Spread by wildlife, human activities, wind • HWA Feeding and reproduction
Contributing factors • Drought • Fungal infection • Other insect pests and diseases • Elongate hemlock scale • Hemlock looper • Spruce spider mite • Hemlock borer • needlerust
Control-preemptive • Quarantine • Increase hemlock vigor (5 yrs before infestation) • Manage for white pine over hemlock in drought-prone sites • Decrease spread by vectors
Monitor and Survey • Public outreach education • Take a stand • Costa protocol
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
Reactive control-biological • Beetles • Sasajiscymnus tsugae • Scymnus • Laricobius nigrinus • Fungi • Beauveria bassiana • Metarhizium anisopliae • Verticillium lecanii • Paecilomyces sp. • Ideal? http://www.invasive.org/hwa/
Feasibility • Ecological • Conservation of threatened species • Economic • Pesticides for ornamental and vector trees