Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: the wild or cultivated brassicas.
- Adult: the young adult appears in May-June. It nibbles the leaves as well as the green pods. Then, sheltered under the foliage of various wild plants situated on the border of fields, in the cool, it enters into summer diapause (aestivation). When it resumes activity, it flies toward recently sown rape fields and attacks the germinating seeds, the seedlings and the young leaves. After 10 to 15 days, the female starts to lay then stops when the temperature falls below 0°C, to start again at the end of the winter. Total fecundity (ante-and post winter), 70 to 150 eggs.
- Egg: deposited on the surface or in the cracks of the ground, singly or in clusters of 2 to 8 in the immediate vicinity of the stems of plants.
- Larva: directly after hatching, it penetrates the plant by the upper surface of the petiole of one of the oldest leaves (*) . It gnaws within the pith (*) then passes into the stem and may also reach the terminal bud.
- Pupation occurs in the ground, at a depth varying between 0.5 and 8 cm.
- 1 annual generation.
- The adult having aestivated, resumes its activity at the end of August - beginning of September with important variations depending on the regions, the years and the climatic conditions, a rainy period favouring a mass appearance. Egg-lLaying begins in autumn and with a break in mid-winterresumes from February to mid-March.
- Adult attacks on rape seedlings can totally destroy the crop (*) .
- Later, the adult attacks the leaves of older plants, weakening them.
The plants attacked by the larvae become bushy and stunted. Maturity is irregular and the yield is reduced.
HYPPZ on line : Species (scientific name), Pests (common names), Glossary, Crops.