Hemlock Woolly Adelgid
MODERATEAdelges tsugae
Overview
A tiny aphid-like insect native to Asia that feeds on hemlock sap at the base of needles. It has devastated eastern hemlock populations from Georgia to Maine. Trees typically die within 4-10 years of infestation.
- Type
- Insect
- Severity
- MODERATE
- Source
- iNaturalist
Symptoms
White woolly egg sacs at the base of needles on the undersides of branches, grayish-green needle discoloration, premature needle drop, thinning canopy, branch dieback
Affected Species
Geographic Spread
Treatments
Imidacloprid Soil Drench
Systemic insecticide applied as a soil drench around the base of hemlocks in fall or early spring. Effective for individual landscape trees but impractical for large forest stands.
Predator Beetle Release (Laricobius nigrinus)
Release of the predator beetle Laricobius nigrinus from western North America, which feeds on HWA during winter months. USFS has released millions across the eastern range of hemlock.
Horticultural Oil Spray
Dormant oil sprayed directly on infested branches to smother adelgids. Effective on small, accessible trees. Requires thorough coverage and may need repeated application.
Recommended Products & Tools
Helpful supplies for managing Hemlock Woolly Adelgid. Always read and follow label directions, and confirm a diagnosis before treating.
Knocks down soft-bodied pests like aphids, mites, and scale crawlers.
Smothers overwintering eggs and crawlers; dormant or summer rates.
Soil-applied protection taken up by the tree for season-long control.
Sharp, clean cuts to remove affected wood — a tree-care essential.
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Frequently Asked Questions
What is Hemlock Woolly Adelgid?
A tiny aphid-like insect native to Asia that feeds on hemlock sap at the base of needles. It has devastated eastern hemlock populations from Georgia to Maine. Trees typically die within 4-10 years of infestation.
What are the symptoms of Hemlock Woolly Adelgid?
White woolly egg sacs at the base of needles on the undersides of branches, grayish-green needle discoloration, premature needle drop, thinning canopy, branch dieback
Where is Hemlock Woolly Adelgid currently found?
Hemlock Woolly Adelgid is currently active in Connecticut, Delaware, Georgia, Kentucky, Massachusetts, Maryland, Maine, Michigan, North Carolina, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Vermont, West Virginia. It has been reported in 20 total states across the United States.
What plants are affected by Hemlock Woolly Adelgid?
Hemlock Woolly Adelgid affects Eastern Hemlock, Western Hemlock. Susceptibility varies by species.
How do I treat Hemlock Woolly Adelgid?
Treatment options for Hemlock Woolly Adelgid include: Imidacloprid Soil Drench, Predator Beetle Release (Laricobius nigrinus), Horticultural Oil Spray. Treatment approaches may include chemical, biological, cultural, and mechanical methods depending on the severity and context.
Compare with Similar Ailments
Not sure if it's Hemlock Woolly Adelgid? Compare it side-by-side with similar ailments.