Gypsy Moth Caterpillars: The Tree Defoliator Nightmare

Imported 1869 for silk—escaped. Now a century-long scourge in Northeast US/SE Canada.

Lifecycle & Damage

• Eggs hatch early spring → caterpillars feed nightly (daytime if heavy).
• 5–6 molts (instars). Appetite grows with size.
• Feeding peaks mid-June/early July. Then pupate → moths → mate → die.

Host Preferences

Favorites: oak, maple, elm. Also: apple, alder, birch, poplar, willow. Older larvae attack pines/spruces. Avoid: ash, sycamore, walnut, dogwood, balsam—but in outbreaks, nothing is safe.

Impact

• Light to total defoliation.
• Deciduous trees survive 1–2 years.
• Repeated attacks → fatal weakening → secondary pests, disease.

Management

Monitor. Band trees. Biological controls (Bt, nucleopolyhedrovirus). Professional treatment for high-value stands. Early action = saved canopy.