Rape Winter Stem Weevil
The adults are 2.5-4mm long, metallic black with reddish/brown tips to the legs. The white larvae have brown heads, are legless, are 4-5mm long and 'C' shaped.
The main shoots or whole plants can be killed by the larvae tunnelling and feeding in the stems. In the spring, at the beginning of stem extension, plants remain stunted and produce lateral shoots and the larvae can be found feeding in the stems when cut open.
The adults move into oilseed rape crops in late September and October and lay eggs on the upperside of the leaf petioles. Egg laying can continue throughout the winter as long as weather conditions remain mild. The larvae tunnel into the stems and feed throughout the winter until exiting in March/April to pupate in the soil. The adults emerge in the summer and after a resting phase move into oilseed rape crops to feed and lay eggs in the autumn.
Up until 1982 this pest was relatively uncommon in the UK, but has increased locally in parts of Lincolnshire, as far north as Scotland and may be becoming more common in East Anglia.