 Larvae of the mustard saw fly defoliate the crop at early stage i.e. 15-20 days after sowing.  Population is increases as the temperature and relative humidity increase in environment.  The larvae are dark green in color and have eight pairs of legs on its abdomen.  Larva on slight disturbance, falls down on the ground and behave just like a feign death and at the same time, it also expels irritant liquid and get protection from its natural enemies.  If incidence occurs every year, raise white mustard, reddish or cress or turnip of 2-3 rows around the mustard field as attractant.  More than one larva can be seen on plants and do damage by making numerous holes on leaves.  Under higher incidence, they defoliate the plants and necessity arises for re-sowing.  Give seed treatment with imidacloprid 70 WS @ 700 g per 100 kg of seed.  Maintain weed free field and follow interculturing periodically as far as possible.  If infestation seems to be increasing, give irrigation. Most of the larvae die due to drowning effect.  Collect & destroy the larvae at morning and evening hours.  On initiation, spray neem oil or bitter guard oil or ready to use neem base pesticides.  Spray Bouveria bassiana, fungus base powder @ 40 g per 10 lit of water.  On having the larval population of 2 larvae per sq. feet (ETL); spray dimethoate 30 EC @ 10 ml or quinalphos 25 EC @ 20 ml per 10 lit of water.  Dust formulations can be adversely affected not only to the environment but also to its natural enemies; hence we have to avoid such insecticides.