Codling moth

What is codling moth?

Codling moth is a small moth whose caterpillars bore into the fruits of apple and pear trees during mid- to late-summer.

Symptoms

• The caterpillar’s exit hole is often visible in the side of the ripe fruit or at the 'eye' end (opposite to the stalk)
• When the fruit is cut open, the tunnel and feeding damage inside the core can be seen, together with the caterpillar’s excrement pellets

Control

Non-chemical control

• A pathogenic nematode (Steinernema carpocapsae) is available by mail order from some biological control suppliers. This is a microscopic worm-like creature that enters the bodies of caterpillars and infects them with a fatal bacterial disease
• The nematode should be sprayed on the trunk and branches, and also the soil under the branches, in September-October, after the caterpillars have left the fruit
• This treatment gives no protection next year against female codling moths flying in from nearby gardens, and so may not be worthwhile in areas where apples and/or pears are widely grown

Chemical control

• Codling moth caterpillars can only be controlled on apple and pear with insecticides before they enter the fruits
• On trees small enough to be sprayed, the newly-hatched caterpillars can be killed by using deltamethrin (Bayer Provado Ultra Fruit & Vegetable Bug Killer) or lambda-cyhalothrin (Westland Plant Rescue Fruit & Vegetable Bug Killer).  Use one of these sprays in about the third week of June, with a second application about three weeks later.
• In some years, egg hatching may be earlier or later, due to the weather conditions
• It is not worthwhile spraying quince or walnut as the level of infestation in these fruits is rarely significant
• Spray applications can be more accurately timed by using a codling moth pheromone trap, which is available from most garden shops or from a biological control supplier. This consists of an open-sided box that is hung in the tree in early May. The bottom of the box has a sticky sheet on which the pheromone pellet is placed. This exudes a scent similar to that produced by virgin female codling moths to attract mates. Male codling moths are lured into the trap and get stuck
• By counting the trapped males every week and following the instructions that come with the trap, the best time to spray can be calculated
• A pheromone trap on its own cannot control codling moths, but on isolated trees it may catch enough males to reduce the females' mating success, resulting in fewer fertile eggs being laid
• Pheromone traps sold by Agralan are designed to prevent birds entering the trap and getting caught by the sticky sheet

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A pheromone trap for codling moths. Credit: RHS/Entomology.

Biology

• Adult codling moths emerge in late May-June and lay eggs on or near developing fruits from June to mid-July
• After hatching, the small white, brown-headed caterpillar bores into a fruit and feeds in the core region
• This pest overwinters as non-feeding caterpillars in leaf litter or under loose flakes of bark and they pupate in the following spring