ENTOMOPOXVIRUSES OF GRASSHOPPERS AND LOCUSTS - BIOLOGY AND BIOLOGICAL-CONTROL POTENTIAL

Entomopoxviruses (EPVs) are insect poxviruses that are often found inf ecting grasshoppers and locusts. Nearly 15 grasshopper and locust EPVs have been reported in the literature. This review describes our curre nt knowledge of the biology of grasshopper and locust EPVs including v irus ultrastructure, host range, production in cell culture, pathology , process of infection, epizootiology, and field evaluations of the Vi ruses to assess their potential as biological control agents. The most extensively studied has been the Melanoplus sanguinipes EPV (MsEPV). Trypsin-like protease activity has been identified in association with MsEPV occlusion bodies but its importance in the infection process is not known. Mortality from MsEPV has been found to occur in two distin ct time frames over 6 weeks or longer. MsEPV is also the only grasshop per EPV that has been grown in vitro and been shown to produce virus t hat is both infectious and virulent to M. sanguinipes. Horizontal tran smission of grasshopper EPVs is apparently by consumption of infected cadavers. Field evaluations of MsEPV at an application rate of 1 x 10( 10) occlusion bodies per hectare resulted in a 23% prevalence after 13 days despite a considerable amount of dispersal of grasshoppers betwe en plots. Epizootiological studies of EPVs will continue to be an area requiring additional research. Virus production and a limited host ra nge are the two most critical issues affecting the development of EPVs as microbial control agents.