Pest description and crop damage The cane maggot is the larva of a small fly. It feeds on the cambial tissues of red raspberry, blackcap, loganberry, and occasionally blackberry. The larvae are white and legless.
The larvae feed downward in new canes. Canes are usually 1 to 3 ft long when attacked. Young shoots wilt suddenly, and a purple discoloration appears where the maggot girdles the cane. This causes a distinct drooping condition. Canes also may show a characteristic swelling where feeding is occurring.
Biology and life history The insect overwinters as a pupa in the soil. The adult flies emerge in April. The female deposits eggs near the tops of the young canes. After hatching, the young maggots burrow into the pith of young shoots and tunnel downward. Later feeding involves girdling the cane just under the bark.
Scouting and thresholds Remove and burn wilted canes as soon as they are seen. Cut canes off near the base. Very little loss is caused by this pest even when 60% to 70% of new canes are infested.
No chemical control is advised. Parasites control this pest most years.