Cotesia marginiventris Cresson

Cotesia marginiventris, a larval parasitoid of Spodoptera frugiperda (J.E. Smith) in its original home was imported into India in 1981 for trials against Helicouerpa armigera and Spodoptera litura. The parasitoid was found to parasitise 2nd instar larvae of S. litura and H. armigera.

Cotesia marginiventris is produced by exposing its mated females to 3 day old Spodoptera litura larvae. The adult parasitoids after mating are held without hosts for 24 hrs and then exposed to hosts. For mating 1 female: 2 to 3 males are released in a vial. 100% honey streaks are placed in the vials as food for the adults. The larvae is exposed by holding on a soft camel hair brush in glass vials (15 x 2.5 cm).

Larvae of Spodoptera can be exposed collectively by releasing them on castor leaves and introducing adult parasitoids in jars.

A transparent plastic container (20 x 16 cm) is converted into a rearing unit. One hundred second instar Spodoptera litura larvae are released on inner side of the lid and five mated females of Cotesia marginiventris are added into this unit. After exposure for 24 hrs females are collected back and a gap of 2 hrs is given. One set of 5 females is used for six exposures. The parasitized larvae are reared on bouquet of castor leaves. In general one parasitoid, is released for every 25 larvae for 24 hrs (1:25), after which the adult parasitoids are transferred to fresh jars with hosts (the detail for making bouquet is given under Spodoptera litura rearing). The leaves are changed twice a week. After 7-8 days of parasitisation the parasitoid grubs emerge from the host and the host dies 48 hrs after the emergence of the parasitoid grubs. The grubs of the parasitoid emerged turn into cocoon within 2 hrs time. The adults from the cocoons emerge in 5-6 days. Although the adults live for 15-18 days, yet their parasitising ability declines after 3rd day of parasitism and the females are used for exposing S. litura larvae only for 6 days, thereafter they are discarded. On an average 2300 cocoons are produced in 10 rearing units described above by 6 exposures and by just utilizing two man hours/day. Cotesia marginiventris could also be multiplied on Plusia signata.