The cherry fruitworm, Grapholita packardi (Zeller), overwinters as large larvae in cavities usually made in the dead wood on the bush. The small, dark-gray moths with brown banded wings emerge in the late spring. The green-white flattened eggs are laid on the undersurfaces of leaves and on the fruit. After hatching, the larvae enter the berries. The 3/8-inch, pink and red larvae usually feed on one berry at a time and then penetrate and feed on another. Unlike cranberry fruitworms, the cherry fruitworms seal entrance holes with silk so that frass is not visible outside the berries, and an infestation is evidenced only by prematurely blue, shrunken berries webbed together by silk.
Both fruitworms can be controlled with two broad spectrum insecticide sprays. Apply the first at petal fall on a variety-by-variety basis to avoid poisoning bees. It is important to remove bee hives from the area before any insecticide spraying takes place. Spray again about 10 days later.