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Raspberries: Raspberry fruitworm

Raspberry fruitworm (Byturus unicolor) prefers red and purple raspberries. Fruitworm adults limit their feeding to between the veins, skeletonizing unfolding leaves.

Raspberry bush with developing fruit and green leaves. Some leaves have no leaf tissue in-between veins. Thin strips of leaf veins can be seen near eaten sections as the tender tissue surrounding veins was eaten first.
Raspberry fruitworm damage to leaves. Photo courtesy of Heather Faubert, URI Extension.

Adults also feed on buds, and open flowers but the damage is usually minimal. Eggs are deposited on swollen unopened flower buds, inside buds or on developing fruit.

Close-up of closed raspberry buds. A brown-bodied beetle is hanging upside-down on one bud; beetle is same size as raspberry bud. A single green egg is on the raspberry bud. The egg is an elongated pill shape with rounded corners and is as long as a raspberry thorn. .
Adult raspberry beetle and a single egg on the unopened bud.

Larva hatch and bore into the receptacle tissue. When harvest fruit is picked larva often remain attached to the cup-like interior of the fruit and become a contaminant to harvested berries.

Ripe raspberry fruit with a c-shaped larva on surface. Larva is as long as one drupelet. There is a hole and tunnel burrowed into the detached receptacle, leading to the inside of the berry.
Raspberry fruitworm (Byturus unicolor) larva, with entry tunnel visible on receptacle.

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