Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: rape and wild brassicas.
- Adult: after a period of winter diapause, it invades fields of rape, first attacking the plants on the periphery and then progressing towards the middle of the field. It feeds on buds then on pods; the bite marks look like sting punctures.
Laying begins 15 to 20 days after the adults have emerged (*) and continues until seeds are formed in pods.
Fecundity: about 50 eggs introduced at a level of 1 to 3 per pod (*) .
- Egg: embryonic evolution lasts 10 to 12 days.
- Larva: they gnaw the epiderm of young seeds and then fed inside; having finished its development (22 to 26 days), it bores a hole in the pod wall, drops to the ground and pupates.
- 1 generation per year.
- Adults become active at the end of April, beginning of May, once the temperature reaches 15 °C. The females lay eggs in May and the larvae develop in the pods in June. The adults appear in July and, after a short feed on wild or volunteer brassicas, seek their winter shelter during the month of August and enter diapause.
- The feeding bites and punctures caused by egg laying (*) (*) do not affect yield, the plant fully compensating for any damage. As far as seed damage is concerned, the plant compensates for up to 20 % of attacked pods.
- The weevil can attack up to 60 to 70 % of the pods, resulting in a yield loss of around 30 % in humid years (favouring seed germination in the pods and the development of moulds).
- In addition, the feeding and egg laying stings enable the Cecidomyiidae, in particular the brassica pod midge (Dasineura brassicae), to deposit their eggs in large quantities. The larval activity of the Cecidomyiidae results in the busting of the pods and loss can then reach 50 % of the harvest.
HYPPZ on line : Species (scientific name), Pests (common names), Glossary, Crops.