Walnut Caterpillar Outbreak on Black Walnut: Identification and Control

Large black walnut (50-60 ft) has clusters of fuzzy worms stripping leaves. Some on ground, not fuzzy. Owner fears for other walnuts.

Identification: Walnut Caterpillar (Datana integerrima)

Serious on young/transplanted trees. Mature trees tolerate defoliation, releaf, but lose growth/nut production.

Bt (Bacillus thuringiensis): spray foliage for young larvae.
Contact insecticides: carbaryl, cyfluthrin, acephate, neem for larger caterpillars.
Spray migrating groups on trunk as they descend.

Large trees rarely need treatment. Focus on valuable young trees.

Trees: Leaf Spots on Young Black Walnut: Harmless Fungi or Galls; Sooty Mold on Large Trees: Systemic Imidacloprid for Aphid Control; Citrus Fruit Drop in Mature Trees: Spray Schedule, Not Just Fertilizer; Black Rot on Grapes/Apples: No Threat to Walnut Trees; Linden Borers and Decay: Treat Borers, Accept Hollows; Preventing Catalpa Worms (Catawba Worms) on Catalpa Trees; Black Walnut Management: Lumber Value vs. Nut Uses; Walnut Aphid Honeydew: Sooty Mold on Leaves; Growing Grass Under Black Walnut Trees: Tolerant Species by Region; Black Walnut Tree Diseases: Recognition and Management

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