Codling moth

Identification

A nocturnal moth with a wingspan of 15-20 mm; the forewings are grey-brown with a characteristic coppery, glossy patch at the tip. The caterpillar is whitish to pinkish with a brown head, grows to about 18 mm and tunnels right into the core of an apple or pear (less often quince or walnut). Symptoms: 'maggoty' fruit, entry holes with brown, sawdust-like droppings, and premature fruit drop. The caterpillar has five pairs of abdominal prolegs - the key feature distinguishing it from the larva of the apple sawfly, which has six or more. The codling moth overwinters as a full-grown caterpillar in a dense cocoon hidden in bark crevices, under loose flakes of bark, in the soil at the base of the trunk or in fruit crates; in spring it pupates, and the moths usually emerge from the end of apple blossom (May-June). Flights take place at dusk and at night, when the air temperature rises above about 15C. Females lay eggs singly on the fruit and on leaves nearby; after about one to two weeks the caterpillars hatch and, after a short wandering, bore into the fruit and head for the seed cavity, feeding on the flesh and the seeds. Under Polish conditions there is usually one full generation, and in warmer years and in the south of the country a partial second one whose feeding reaches harvest. Damaged fruit rots, drops prematurely and is unfit for storage.

Treatment

Pheromone traps for monitoring the moths' flight and timing the treatment, corrugated-cardboard trap bands fitted around the trunks (attracting caterpillars seeking a pupation site, which are then destroyed), and systematic collection and removal of fallen fruit. In larger orchards, pheromone mating disruption together with biological products (granulosis virus CpGV, Bacillus thuringiensis) and the encouragement of insect-eating birds. The success of control depends above all on hitting the right timing: the treatment targets the eggs and freshly hatched caterpillars before they bore into the fruit, where they become inaccessible to most products. This moment is determined from catches in pheromone traps, supported by temperature sums. Trap bands, by contrast, work at the end of the season: under Polish conditions (usually one generation) they attract full-grown caterpillars seeking an overwintering place in a cocoon, where they overwinter and pupate only in spring - which is why they are taken off and destroyed in autumn. The granulosis virus (CpGV) is highly selective and safe for beneficial insects, but it breaks down in UV light and requires several treatments at short intervals as well as precise timing; Bacillus thuringiensis works less well against the codling moth, because the caterpillar moves very quickly from the surface into the interior of the fruit and stops ingesting the product. Among chemical products, groups acting on the eggs and young larvae are used - anthranilic diamides (ryanodine receptor modulators) and insect growth and development regulators (IGR) - and, as needed, contact-and-ingestion products (spinosyns) or contact pyrethroids, the latter acting only briefly and being harmful to predators and pollinators. The codling moth readily develops resistance to repeated substances, so it is essential to rotate groups with different modes of action and to combine methods (monitoring, bioproducts, trap bands, orchard hygiene) as part of integrated pest management.

How to tell it apart from look-alikes

Control — organic and chemical methods

We give active-ingredient groups and modes of action, not brand names — specific products and their approval vary by country and are sometimes withdrawn. Always check and follow the current label.