CANNIBALISM ON NUCLEAR POLYHEDROSIS-VIRUS INFECTED LARVAE BY HELIOTHIS-ARMIGERA (HUBN) AND ITS EFFECT ON VIRAL-INFECTION

Studies on cannibalism by Heliothis armigera (Hubn.) larvae on nuclear polyhedrosis virus (NPV)-infected larvae and feeding on virosed cadav ers indicated that feeding was significantly higher on 4-day-old viros ed cadavers followed by 1-day-old cadavers than on healthy or NPV-infe cted living larvae. The data revealed that cannibalism was significant ly higher on NPV-infected (3 days post inoculation) larvae than either healthy larvae or those which had been just inoculated. However, the extent of feeding was higher on healthy larvae (cannibalistic feeding) than on cadavers. Significantly more number of larvae became infected by NPV when they fed on NPV-killed cadavers than on NPV-infected livi ng larvae. Some of the larvae which had fed on either virosed cadavers or NPV-infected larvae survived. But, the disease was expressed in th e pupal stage. Pupal mortality was significantly higher in larvae whic h fed on NPV-inoculated larvae (3 days post inoculation). The multiple choice test to find out the feeding preference of the larvae showed t hat the larvae had a greater preference to feed on virosed cadavers th an either the healthy larvae or the host plant. The role of cannibalis tic behaviour in the dissemination of the virus disease under field co nditions is discussed.