One generation hatches each year. Cranberry fruitworm infestations can be difficult to detect early. Look for a pin-sized entry hole near the stem of any small shrunken berries that have turned blue, and then open adjacent berries to find the larva. The distinctive frass and webbing do not appear until later in the larva s lifetime when it begins to move between berries. Repeated disking to eliminate weeds and trash also helps in its control.
Pesticides used for plum curculio also usually result in control of cranberry fruitworm.
The small, dark grey 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. 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 insecticide sprays.