Advice
RHS Help & Advice
Raspberry beetle (Byturus tomentosus)
A common pest on the berries of cane fruit.
Hosts
Raspberry, blackberry, loganberry, tayberry and other hybrid cane fruit.
Symptoms
Damaged ripe berries dry up at the stalk end and turn greyish-brown. A brownish-white grub, up to 8mm long, may be found inside the fruit.
Biology
The 4mm long adult beetles are brown and they lay eggs on the flowers in May to mid-July. The young larvae feed at the stalk end of the developing fruit, but later move inside to feed on the central plug.
In late summer, the fully fed larvae move into the soil where they overwinter as pupae. Early fruit on autumn raspberries may be damaged, but those ripening after late August are unaffected.
Control
Rotenone* (Bio Liquid Derris Plus* or Vitax Derris Dust*) can be used to control raspberry beetle. Spray or dust raspberries when the first pink fruits are seen, with a second application two weeks later. Treat hybrid berries at 80% petal fall and blackberries when the first flowers open. Apply rotenone* in the evening when bees are not active on the flowers.
*Rotenone/derris-based products are being withdrawn from sale in September 2008 (date to be confirmed). Gardeners can use up rotenone/derris-based products for 12 months after the last selling date.