Investigations on nuclear polyhedrosis of black hairy caterpillar, Pericallia Ricini fabricius (Arctiidae: Lepidoptera)

Abstract

Detailed investigations were carried out on the nuclear polyhedrosis of the black hairy caterpillar,Pericallia ricini (Arotiidae) covering symptomatology, larval susceptibility, effect of the virus on the larval moulting, changes in the number of circulating haemocytes in the infected larvae, nature of causative agent, effect of temperature and sunlight on the infectivity of the virus and the cross infectivity of the virus to other species of lepidoptera. The virus infected larvae exhibited a ll the typical symptoms of nuclear polyhedrosis infection as reported from other lepidopterous larvae. The larvae infected in the early instars appeared paler and thinner. The infected larvae showed loss of appetite and became sluggish. The dead or dying larvae showed the characteristic symptom of hanging head downwards from the top o f the containers with the aid of prolegs. In the advanced stages of infection the cuticle became fragile and it ruptured liberating the liquefied body contents. The susceptibility of the larvae to virus infection decreased with increase in the age of the larvae. The averageincubation period varied from 5*24 days for the second instar to 8 days for the sixth instar larvae. The virus infection inhibited moulting in the later stages of the disease. No significant difference was observed in the THC of healthy larvae and virus infected larvae up to 24 hours after inoculation; there was significant reduction in the THC of diseased larvae after 24 hours of inoculation.