Helicoverpa armigera was reared in the laboratory on
an artificial diet (Nagarkatti and Prakash, 1974). The
initial colony of the fruit borer was obtained from a
farmer’s field in 1997. Larvae were reared individually
on the diet by the method described by Raulston and
Lingren (1972). Adults were maintained in a nylon net
cage (40 cm20 cm diameter) for mating and oviposition.
Eggs deposited on the nylon mesh ofthe cage were
removed by washing in 0.2% sodium hypochlorite
solution in a small plastic bucket, and filtered with a
fine brass mesh screen. Eggs were then spread on a
20 cm20 cm filter paper, air-dried and then stored in a
plastic box (30 cm long, 14 cm broad, 12 cm high) at
2871C and 40–50% r.h. for hatching.