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Mustard Sawfly has become a serious pest of mustard, attacks all types of plants in family Brassicaceae like mustard, rapeseed, cabbage, cauliflower, knol-khol, turnip, radish etc. It is a pest of cold weather and is generally active during October to March. The female fly lays the eggs singly on the young leaves, close to the margin. Under favourable conditions, hatching takes place in 5–7 days, and the larval stage lasts about 13–15 days. There are six larval instars, and the pupation takes place in the soil. The whole life-cycle is completed in about 30–39 days. The larvae alone are destructive and feed from the margin of the leaf towards centre. The grown up larvae make holes, preferably on young leaves, and skeletonise them. Sometimes, they also feed on the epidermis of the tender shoots, flowers and fruits.
Sawflies are distinguishable from most other hymenopterans by the broad connection between the abdomen and the thorax, and by their caterpillar-like larvae. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay their eggs. Large populations of certain sawfly species can cause substantial economic damage to forests and cultivated plants. The larvae that do not feed externally on plants are grub-like, without prolegs. When harassed, many sawfly larvae are able to squirt a foul liquid from their last segment.
Spotted on Oct 1, 2014
Submitted on Nov 11, 2014