Answer: Sounds like the larvae of the Oriental fruit moth. Adults are gray with dark-brown bands on their wings. The mature larvae are about 1/2 inch long. They become active when disturbed, crawling rapidly over the fruit surface.
The winter is passed in the larval stage in a cocoon under the bark, in dried fruit or in ground debris. Following pupation in the spring, the adults emerge and deposit flat, whitish eggs on leaves and twigs shortly after peaches bloom. The larvae feed in the succulent new growth of the twigs. In the summer, when tender growth is no longer available, the larvae of later generations attack the fruit, feeding around the seed. If succulent growth and fruit are absent later in the summer, a "suicide" generation probably occurs, since the larvae cannot find food satisfactory for their development. Consequently, only a few survive and damaging infestations rarely occur the following year.
Be sure to clean up any fallen fruit and rake up the leaves to remove any trace of the critters and lessen the problem of affected fruit next season.
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