Life cycle of the codling moth

Codling moths are a serious pest, damaging apples, pears and walnuts throughout the Pacific Northwest.

If you know what stage of life the insects are in, you can tailor your pest management strategy to susceptible forms.

The following outlines the insect life cycle:

1. Mature larvae overwinter in a silken cocoon under loose bark, in soil or in debris around the base of the tree.
2. When the first blossoms show pink the larvae change into pupae.
3. At about the full bloom, adults emerge from the pupae and begin laying eggs on leaves and sometimes on the fruit.
4. Larvae emerge from the eggs in 6–20 days, depending on temperatures. Larvae at hatch are about 0.1 inches long. The larval stage lasts three to four weeks. This is the damaging stage of the codling moth. The larvae can create a “sting” on the side of the fruit, which produces a small wound. Or, they can burrow into the center of the fruit, usually from the flower end (the end where the flower remains are) or from the side. This entry area will show frass, or larval excrement, as the larvae feed and grow.
5. Once the larvae are mature, they spin a silken cocoon and either overwinter or immediately pupate for two to three weeks. They hatch into adults in mid-July and August.
6. Adults of the second generation fly in July and August and lay their eggs. The larvae hatch from this generation is the one that does the most damage.

Controlling the first generation of codling moth well allows you to limit damage from the second generation.

See Solve Pest Problems for information on identification and treatment, or for more technical information see The Pacific Northwest Insect Management Handbook.