Ceutorhynchus pleurostigma Marsham Turnip gall weevil

This weevil is a common but local pest of brassica crops, especially culinary swede and turnip, and late-sown or late-planted cabbage and cauliflower. The larvae feed in galls on the roots, and damage of greatest significance is caused to young plants (seedlings or transplants) during the autumn and early winter; plant growth is checked severely if infestations are heavy. Well-established crops are rarely harmed but extensive galling on culinary swedes and turnips may be troublesome.

BIOLOGY

Adults are active throughout the late spring and summer. Eggs are deposited mainly in August and September, each in a small hole excavated by the egg-laying female in the roots of host plants. The eggs hatch 1-2 weeks later. As the larvae feed, they become enclosed in conspicuous marble-like galls (Plate 5e). These galls occur just below the soil surface and, unlike those caused on brassica roots by club-root disease, are partly hollow (Plate 5f). Larvae complete their development in the following spring, and emerge from the galls in March or April to pupae in the soil. Adults appear a few weeks later.

DESCRIPTION

Adult 2-3 mm long, mainly black with a distinct spur on each femur. Egg 0.4 x 0.3 mm, oval and translucent. Larva up to 6 mm long; body whitish; head brown. Pupa 2-3 mm long, white.

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