Insecta, Hymenoptera, Tenthredinidae .
Description, Biology, Life Cycle, Damage, Common Names, Images
- Adult: emerges in May and June, leaves the ground and mates on the same day. Egg laying commences a few days later. After feeding, the females laterally incise the leaves in a sawtooth pattern and deposit their eggs one by one in the small chambers, constructed for preference on yellow leaves. Fecundity of the females is approximately 300 eggs.
- Egg: embryonic development lasts 6 to 8 days. Unfertilized eggs produce male larvae.
- Larva: at 20°C, the larvae consume twice their own weight in 24 hours. After moulting, the exuviae remain on the leaf. Pupation occurs after 10 to 13 days in the upper layers of the ground at a depth of 1 to 5 cm, inside a cocoon.
The final larval stage hibernates underground in a cocoon.
- There can be up to 3 generations per annum.
- In July-August, the second sawfly generation appears and lays its eggs on plants grown as green manure and fodder crops. Under favourable weather conditions, a third generation occurs, causing damage to winter rape.
Wind-assisted, this sawfly is able to undertake long migratory flights.
- A low percentage of the population may enter diapause at the pupal stage.
- The young larvae strip the underside of leaves or make holes in them (economic damage insignificant), whereas older larvae, dark in colour, eat the leaves from the underside and from the edge, leaving only the veins (skeletization) (*) .
In the event of swarming, total defoliation may occur (*) .
- On Sinapis alba, the oldest larvae also devour the pods.
Spread from Europe to the Far East (Korea), North and South Africa and also North America.
DE: Kohlrübenblattwespe, Rübsenblattwespe ES: Oruga de los nabos FR: Tenthrède de la rave IT: Tentredine delle crucifere PT: Atália do nabo GB: Coleseed sawfly, Turnip sawfly
HYPPZ on line : Species (scientific name), Pests (common names), Glossary, Crops.