The in vivo production of Spodoptera littoralis nuclear polyhedrosis virus

The in vivo production of the nucleopolyhedrovirus (NPV) of the Egyptian cotton leafworm Spodoptera littoralis was studied experimentally. Larvae (7 days old) of 30-50 mg were experimentally infected with a range of NPV doses then harvested alive at various times after dosing to determine the effect of dose and incubation time on NPV productivity. Maximum NPV production achieved after 7 days incubation was 1.86 x 10(9) polyhedral inclusion bodies (PIBs) per larvae using an inoculum of 1 x 10(4) PIBs. Adjusting the inoculum dose had limited impact on NPV productivity but the correct selection of harvesting time was crucial in maximising the yield, both to achieve peak NPV production in individual larvae and to avoid losses from the death and disintegration of larvae if harvesting was delayed too long.