Chemical control is the principal means of control in UK orchards. A wide range of insecticides are approved for control of caterpillar pests on apple. The pest is sensitive to insecticides and can be controlled cheaply and effectively.
- It was common practice for growers to apply a pre-blossom spray of a broad-spectrum insecticide, usually chlorpyrifos (no longer approved on apple), to control early season caterpillars and aphids.
- A spray of an approved insecticide should be applied at the green cluster to pink bud growth stage.
- Later spraying is preferable because late hatching larvae are more likely to be killed.
- Broad-spectrum chemicals are harmful or dangerous to bees and should not be applied during blossom.
- Many other insecticides when applied before blossom will also control winter moth and have varying degrees of activity against different pests.
- Indoxacarb (Steward or Explicit) is a selective material which is likely to control caterpillars only, and have little effect on aphids.
- Pyriproxyfen (Harpun) is approved for use on apples for codling moth control but may offer incidental control of winter moth. It inhibits egg hatch, metamorphosis of nymphs to adults and reduces the fecundity of adult females. However, as a new product to the UK in 2020, further experience is required to inform growers and agronomists of its efficacy at controlling winter moth.
- Spinosad (Tracer) may also be effective.
- The synthetic pyrethroid deltamethrin (Decis Forte etc) is also highly effective against winter moth but its use should be avoided because it is harmful to important orchard natural enemies including the orchard predatory mite.
- Bacillus thuringiensis is the only material approved for organic orchards. It can be fairly effective, providing that temperatures are warm at and shortly after application so that caterpillars are feeding actively.