Codling Moth Larva

The codling moth larva is the caterpillar stage of Cydia pomonella, a small moth in the family Tortricidae and one of the best-known fruit pests worldwide. Originally native to Eurasia, the species has spread with apple and pear cultivation to nearly every temperate fruit-growing region on Earth.

The larva is responsible for the familiar experience of biting into an apple and finding a tunnel leading to the core, an association so well known that the phrase 'worm in the apple' almost universally refers to this species. It bores from the fruit surface directly toward the seed core, where it feeds and develops.

Because of its close association with commercial apple and pear production, the codling moth has been the subject of extensive agricultural research, and its life cycle timing is closely tracked by orchardists in many growing regions.

• Body is pinkish-white to cream, with a distinct light brown head capsule
• Reaches about 2 cm (0.8 in) in length at maturity
• Body appears smooth and lacks obvious hairs or spines
• Most reliably identified by its damage: a small entry hole on the fruit surface, often plugged with reddish-brown frass (excrement), leading to a tunnel through the flesh to the core
• Distinguished from other apple-feeding caterpillars by its habit of boring straight to the seed core rather than feeding superficially on the surface

Found wherever apples and pears are grown, including commercial and backyard orchards across temperate regions of North America, Europe, Asia, and other continents where the species has been introduced. Larvae are active inside fruit from late spring through harvest, depending on the number of generations in a given region.

Newly hatched larvae seek out developing fruit and bore inward, tunneling directly to the core where they feed on seeds and surrounding tissue. A single larva can render an entire fruit unmarketable, and infested fruit often drops prematurely. After completing development within the fruit, the mature larva exits and searches for a sheltered site, such as bark crevices or leaf litter, to spin a cocoon. As a specialist on pome fruit, the species has essentially no ecological role outside of orchard settings but supports a range of specialist parasitic wasps used in biological monitoring programs.

Adult moths emerge in spring and lay flat, disc-shaped eggs on leaves or developing fruit. Newly hatched larvae bore into fruit within days, feeding internally for several weeks before emerging to pupate in a silk cocoon in bark crevices or ground litter. Depending on climate, one to three generations occur per year, with the final generation of larvae overwintering as fully grown larvae inside a cocoon rather than as pupae, before completing pupation and emerging as adults the following spring.