Viruses of Heliothis armigera (Hübner) (Lepidoptera : Noctuidae)

Abstract

Bibliography: pages 249-271.Heliothis armigera (the bollworm) is a pest of agricultural importance in Southern Africa. It is often simultaneously infected with several insect viruses: nuclear polyhedrosis virus (NPV), granulosis virus (GV), and cytoplasmic polyhedrosis virus (CPV). Both NPV and GV have been previously studied because of their ready availability and their potential use in pest control. However, there have been no recorded studies of CPV in H. armigera because of the small amounts of virus present in the naturally infected larvae. Particular emphasis was therefore placed in this study on the CPV of H. armigera. CPV was successfully separated from naturally occurring NPV by a combination of techniques, such as differential centrifugation, density gradient zone electrophoresis and absorption with antibody to NPV. The CPV was then successfully propagated by passage in larvae reared on synthetic media. Pure CPV having been obtained, its replication and physico-chemical properties could be studied. Serological studies using immune electron microscopy and immune osmophoresis were used to detect and identify viruses of H. armigera and examine relationships between different CPVs. The gross morphological appearance of viral infections in H. armigera were studied. Distinctive features were observed both in larvae infected by NPV and in those infected by GV, but CPV-infected larvae were not markedly different in appearance from uninfected larvae. Larvae died readily from NPV or GV infection indicating their suitability for use in controlling H. armigera, but there was no larval mortality following CPV infection