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Palmerworm

Dichomeris ligulella[3]

The palmerworm is a small moth caterpillar that skeletonizes the leaves of oaks, cherry, basswood and apple; most years it goes unnoticed, but occasional outbreaks after hot, dry springs can defoliate whole stands for a season or two.[1][2]

Group
Insect
Order
Lepidoptera
Family
Gelechiidae
US records
33 states
Sources
3 cited
Updated
2026-10-19

No licensed photo of this species is available yet; the identification notes below describe what to look for.

On this page
  1. Identification
  2. Where it lives
  3. Biology
  4. Damage and signs
  5. Health risk
  6. Control
  7. Related profiles
  8. Common questions
  9. Sources

How to identify it

  • Full-grown caterpillars are about 1/2 inch long, olive green with pale stripes along the back and sides.[1][2]
  • They skeletonize leaves and may fold or roll them as they feed.[2][1]
  • Adult moths are grayish to brownish and small; in outbreak years swarms of them flush from shrubs and small trees when disturbed.[2]

Where it lives

It occurs in the northeastern United States, on forest and orchard trees, including in Connecticut apple orchards.[2][1]

US map: public records from 33 states since 1990 (GBIF).

Biology and life cycle

Adult moths spend the winter; in spring females lay eggs singly on the expanding leaves.[2][1]

Caterpillar feeding peaks in June, they pupate in early July at the feeding site, and most new adults are out by the end of July. There is one generation a year.[2][1]

Damage and signs

  • Outbreaks rarely last more than one or two years and usually follow unusually hot, dry springs; even when defoliation is noticeable, trees rarely suffer permanent damage.[2]
  • On apples, palmerworms skeletonize leaves and sometimes injure young fruit.[1]

Health risk

It feeds only on plants; the Connecticut station and the Forest Service guide mention no risk to people.[1][2]

Control

Prevention

Numbers swing widely from year to year, and the Connecticut station notes the damage usually doesn't justify an insecticide application.[1]

Common questions

Why are my oak leaves suddenly skeletonized this spring?
Palmerworm outbreaks are one possible cause, especially after a hot, dry spring; they rarely last more than a year or two.[2]
Should I spray palmerworms on my apple tree?
Usually not; the damage is normally too small to justify spraying.[1]

Sources

  1. Connecticut Agricultural Experiment Station, “Plant Pest Handbook: Apple (Malus).” portal.ct.gov/caes/plant-pest-handbook/ppha/apple-malus (accessed 2026-10-19)
  2. USDA Forest Service, Northeastern Area State and Private Forestry, “Palmerworm, in A guide to common insects and diseases of forest trees in the northeastern United States (NA-FR-4, 1979; archived on the Bugwood wiki).” wiki.bugwood.org/Archive:Northeast/Palmerworm (accessed 2026-10-19)
  3. iNaturalist, “Dichomeris ligulella taxon page (order and family).” www.inaturalist.org/taxa/1072105 (accessed 2026-10-06)

Updated 2026-10-19. Built from sourced records. Spot an error? Tell us.