Optimization of production of nucleopolyhedrovirus of Helicoverpa armigerathroughout larval stages

Studies were carried out to optimize production of nucleopolyhedrovirus of American bollworm, Helicoverpa armigera (Hubner), by treating larvae indivi dually with an inoculum dose that allowed maximal larval growth and also ga ve the highest occlusion bodies (OB) yield/larva The maximum virus yield of 12.2x10(9) OB/larva was obtained when 6-day-old larvae were fed individual ly with a dose of 1x10(3) OB. Topical spiracular treatment of larvae as old as 8 days with 10 mul of 2x10(7) OB ml(-1) gave the highest yield, of 15.2 x10(9) OB from 13-day-old larvae, of 12.8x10(8) OB from prepupae and of 1.4 9x10(8) OB from pupae at the time of their death. These studies showed that dietary inoculum is the best route for 6-day-old larvae and topical spirac ular treatment is the best for 8-day-old larvae.