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Winter Moth

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Operophtera brumata

Overview

Winter moth caterpillars damage apple fruit by entering flower buds at Green Tip and then feeding on developing flower buds, destroying the flowers. Caterpillars continue feeding on opened flower clusters and leaves until late May.

Biology

  • 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.

Management

  • In orchards with high populations of winter moths, apply insecticide when eggs begin to hatch, usually around McIntosh Green Tip. Bt insecticides, such as DiPel, not effective against newly hatched caterpillars.
  • If egg hatch is delayed by cold weather, additional spray may be needed.
  • Apply insecticide if finding many green inchworm caterpillars Tight Cluster - Pink.