Decline of Eastern Hemlock due to Hemlock Woolly Adelgid Sophia DeMaio April 25, 2007.
-
date post
21-Dec-2015 -
Category
Documents
-
view
214 -
download
0
Transcript of Decline of Eastern Hemlock due to Hemlock Woolly Adelgid Sophia DeMaio April 25, 2007.
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
Population control
• Early freezing (spring generation)
• Cold winters (-25) with little snow (overwintering sistens)
• Predation– Native environment– here
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 20100
5
10
15
20
140150160170180190
Sanford
Number of -25C events in Sanford, ME
Kathleen S. Shields and Carole A. S-J. Cheah. USDA Forest Service, Hamden, CTConnecticut 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
Health Management Plan