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Winter moth

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Winter Moth, Operophtera brumata

Overview

  • Winter moth are currently a problem to apple and pear growers in eastern Connecticut and Massachusetts, Rhode Island, and coastal Maine.
  • Caterpillars hatch from overwintering eggs around McIntosh green tip. Caterpillars wriggle into buds without feeding.
  • Once inside buds caterpillars feed, destroying flower parts. 100% of apple crop can be destroyed by these inch worms.
  • Mature caterpillars (1 inch long) drop to the ground on silken threads in late May.
  • Caterpillars pupate in the soil and remain there until late November when moths emerge. Male moths are light brown and attracted to lights; female moths are flightless and not easily seen.

Monitoring

  • Set up tree wraps before moths emerge in November. Tree wraps encourage females to deposit eggs on tree trunks below the wrap.
  • Check winter moth eggs for color change from orange to blue, indicating eggs will hatch in 1-3 days. Apply pesticide when eggs first begin to hatch. A Bt insecticide such as DiPel will not control hatching winter moth caterpillars.
  • Scout flower buds at tight cluster and pink bud stages and apply inseciticide if many caterpillars are found.
  • Winter moth caterpillars look identical to green pug moth caterpillars until caterpillars are half grown, then green pug moth caterpillars develop a burgundy-colored stripe. Green pug moths do not tend to build up to damaging levels.

Control

  • Apply Imidan, Delegate, Entrust, Neemix, or Altacor when eggs begin to hatch, usually around McIntosh green tip.
  • If egg hatch is delayed by cold weather, additional spray may be needed.
  • If easily finding green inchworm caterpillars at tight cluster or pink, apply Imidan, Delegate, Entrust, Neemix, Altacor, or a Bt insecticide such as DiPel.
Winter moth caterpillars damaging apple buds.
Full size winter moth caterpillar about 1 inch
Tree wrap set up early November to congregate eggs for monitoring egg hatch in Spring
Male winter moth found Nov-Dec
Female winter moth found Nov-Dec
Winter moth eggs turn from orange to blue just before hatching in early Spring