Plutella xylostella Linnaeus

Plutella xylostella is an important pest of crucifers. It has countrywide distribution. The female lays its eggs singly on the leaves. A total of 57 eggs may be laid by each female. The larva upon hatching from these eggs in about 3-4 days feed on the leaves for about 12-15 days and finally forms a cocoon in which it pupates. The adults from the pupae emerge in 6-8 days. The attacked leaves are sometimes badly defoliated and the attacked plants look pale sick, show larval feed holes and are soiled with the excreta of the larvae. Such cabbage heads do not fetch any value in the market and are discarded. The pest attains peak population during July to September around Bangalore, Karnataka.

To facilitate rearing of host specific parasitoids a method for rearing Plutella xylostella on mustard leaf powder based artificial diet has been tried. Water content was increased and sorbic acid added to prevent the growth of mould. As the diet is quite expensive therefore. cabbage seedlings or mustard seedlings are used for the mass multiplication of P. xylostella. Mustard Brassica juncea (Linnaeus) Czern seedlings are grown in small ice cream cups with vermiculite or in wooden trays containing a equal mix of red soil, sand and farm yard manure. The seeds dribbled by either way are allowed to germinate and proper moisture to ensure maximum germination of the seedlings is provided. Five days after germination the seedlings are placed in an insect rearing cage 3 x 2.5 x 2.5 meters all sides of the' cage are covered by nylon mesh but the top is covered by acrylic sheet. Two hundred P. xylostella pupae are kept in small petri plate and placed inside the cage. The emerging adults are fed on 30% honey and water soaked swabs. The adults are allowed to oviposit on the leaves of mustard for 24 hours. After this time the seedlings are removed and placed in trays in a cage. P. xylostella larvae upon hatching feed on mustard seedlings and the seedlings are completely eaten away by the larvae. The larvae from these seedlings are shifted to another set of fresh seedlings by chopping the remnents of the old seedlings and placing them on fresh seedlings. The 'pupae are formed in about 15 days time, they are collected and placed in an oviposition cage and the production procedure continues. The pupal stock in the oviposition cages is renewed once in 5-6 days, so that continuous supply of eggs or larvae could be maintained. The mustard seedlings or trays could be raised depending upon the need.