How to Manage Pests

Pests in Gardens and Landscapes

Seasonal development and life cycle—Apple maggot

Apple maggots overwinter as pupae in the soil. Generally there is one generation a year, although there may be a partial second generation in warm years. Adults emerge in mid-June to early July; emergence usually peaks between mid- and late July and is over by late August. In some places, some of the pupae may remain in the soil and will not emerge until the following year.

When flies emerge in summer, they are sexually immature and must feed on honeydew produced by aphids, psyllids, and scales before they are ready to mate. Female flies lay eggs singly under the skin of apples and then mark the apple with a pheromone to keep other females from laying eggs. Females lay about 300 eggs over a 30-day life span. Eggs hatch in 2to 10 days, depending on temperature. Larvae are cream colored with a blunt posterior and a tapered front end that contains two black mouth hooks. They feed within the apple and pass through three instars before completing developing in 20 - 30 days. Infested fruit fall to the ground; larvae leave the fruit, burrow into the soil, and molt into a fourth instar and then into a pupal stage to overwinter.

Maggot larvae tunneled into apple flesh
Maggot larvae tunneled into apple flesh

Statewide IPM Program, Agriculture and Natural Resources, University of California
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