Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: the adults feed on various brassicas but laying only occurs on rape, rape (Brassica campestris oleifera), cabbage, turnip, coleseed (Brassica rapa).
- The adult hibernates in the soil of fields in which rape had been growing in previous years. As soon as the weevil emerges, it feeds on wild brassicas. During sunny days, it flies to new rapeseeds fields. It leaves the field borders and progresses rapidly through the crop. Laying begins 10 to 20 days after the first emergence.
- Egg: the female lays inside very young stems which are beginning their elongation, just below the terminal bud. The embryonic development lasts several weeks.
- Larva: 3 larval instars which last 30 to 40 days on winter rape. It feeds on the stem pith (*) ; having reached maturity, it leaves through an exit hole formed in the stem level with the petiole of a low leaf and buries itself in the soil.
- Pupa: pupal development lasts about 25 days.
- 1 generation per year.
- The adult remains in its pupal cell until the beginning of winter and leaves the ground only when activity resumes. The first adults occur, depending on the year and the region, from end of January to the end of March.
- This weevil is extremely harmful to rape. The damage is essentially caused by egg laying. The presence of the egg in the stem (*) induces a canker in the growing tissue, which will lead to characteristic deformations: dwarfism, twisting, bursting (*) , as well as a premature drying up often caused by the invasion of a secondary organism such as Phoma.
- The sensitivity of rape is greatest when laying occurs during growth resumption at the end of winter, (stems from 2 to 20 cm).
HYPPZ on line : Species (scientific name), Pests (common names), Glossary, Crops.