Winter Moths

Key Points

  • Winter moth infestations can cause damage in terms of fruit yield and quality
  • Lorsban WG timing varies by crop, check the label for appropriate timing
  • Applications of Lorsban WG can control Winter moths and many other fruit pests

Introduction

Infestation with caterpillars of Winter moths used to cause significant damage to fruit trees and bush fruits. With the adoption of appropriate insect management programs, incorporating effective insecticides, losses caused by these caterpillars now rarely occur.

Damage results from caterpillars feeding on leaves, flower buds and developing fruitlets. Most harm is caused when young caterpillars burrow in to unopened leaves and fruit buds. Attacked fruit is misshapen with corky areas at the site of attack, sometimes with a deep cleft where the caterpillar has eaten to the core. In severe cases no fruit is produced in the year of attack and production in the following year is seriously reduced.

Biology

The first Winter moths — Operophtera brumata — emerge from soil-borne pupae towards the end of October, emergence peaking about four weeks later. Male and female Winter moths are very different in appearance. The male is grey-brown with a wingspan approaching 25mm, but the female only has vestigial wings and is unable to fly. Females have to crawl up tree trunks to lay their eggs on small branches and shoots. Each female can lay up to 200 eggs, placed singly or in small batches, in bark crevices or in bud clusters. Newly-laid eggs are light green in colour but soon become orange.

Egg hatch normally occurs from bud break to the late green cluster stage but can sometimes continue to beyond pink bud. Newly-emerged caterpillars have black heads and olive-green bodies, turning brighter green with white stripes as they grow. They can be distinguished from caterpillars of other species by their characteristic looping action as they move. By the end of May mature caterpillars move to the soil and pupate. Adult moths emerge from these pupae during the following autumn and winter.

Product Choice

Lorsban* WG (active ingredient chlorpyrifos) is approved for the control of Winter moths in apples, pears and plums. Timing of application varies with crop. Repeat applications may be necessary where further generations re-infest crops. Do not apply to crops in flower or to those in which bees are actively foraging. Do not make applications when flowering weeds are present.