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Walnut Caterpillar: Gregarious Feeder on Walnut and Cherry

Identifying the Pest

Walnut caterpillar (Datana integerrima) larvae are distinctive for their gregarious behavior—dozens feeding together on leaf margins or clustering on tree trunks. They feed on black walnut, pecan, hickory, and occasionally black cherry.

Life Cycle and Behavior

Two generations per year in Georgia
Larvae feed in tight groups, skeletonizing leaves
When disturbed, they arch heads and tails in unison (defensive display)
Mature larvae descend to pupate in soil

Damage Assessment

While alarming to witness, walnut caterpillars rarely threaten tree health. They defoliate random branches but don't kill established trees. Natural enemies—especially hornets and paper wasps—provide significant biological control.

Management Options

Do nothing: Natural predators usually suppress populations
Spot spray: Bt (Bacillus thuringiensis) or spinosad on accessible clusters
Mechanical: Prune out and destroy infested branch tips

Walnut caterpillars feeding — Gregarious feeding cluster on walnut leaf

Walnut caterpillars on trunk — Larvae congregating on tree trunk

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