Why Are My Apple Fruits Full of Maggots?

Cutting into an apple to find a caterpillar tunnel bored through the flesh toward the core, packed with brown frass and often with a small pinkish-cream caterpillar still inside, is one of the most recognisable and frustrating apple pest problems. Codling moth (Cydia pomonella) is widespread throughout temperate apple-growing regions and can ruin a significant percentage of the crop in bad years if not actively managed. The damage is done entirely invisibly inside the fruit — there is no way to tell from the outside which apples are affected until you cut them open or until the larvae exit and the fruit drops early.

The codling moth lifecycle

Codling moth adults are small, grey-brown moths that begin flying in late spring (May–June in the UK). Females lay eggs singly on developing fruitlets or nearby leaves. Larvae hatch and bore immediately into the fruitlet, feeding through the flesh toward the core and seed cavity. After four to six weeks feeding, the mature larva exits through a hole in the fruit and descends to overwinter as a pupa in crevices of the bark, under loose bark, or in the soil near the tree base. There may be one or two generations per year depending on climate.

Using pheromone traps

Pheromone traps contain a synthetic version of the female moth's attractant pheromone. Hang traps in the tree from late April. Monitor catch numbers weekly — when catches rise significantly, adult moths are flying and eggs are being laid. Treatment timing is based on three weeks after the first significant catch (larvae have hatched by this point but not yet bored deep). Traps alone do not control the pest but give precise timing for other control measures.

Control options

Spray kaolin clay (a fine white mineral) onto developing fruitlets starting from fruitlet stage — the coating deters egg-laying females. Apply codling moth grease bands around the trunk to catch descending mature larvae before they pupate. Hang corrugated cardboard traps on the trunk to provide pupation sites — peel off and burn in autumn. The biological insecticide spinosad is highly effective against newly hatched larvae if applied at the correct timing window and is approved for organic use in many countries.