MODIFIED BEHAVIOR IN BACULOVIRUS-INFECTED LEPIDOPTERAN LARVAE AND ITSIMPACT ON THE SPATIAL-DISTRIBUTION OF INOCULUM

Quantifying the rate of dispersal of target insects when infected with a disease agent will aid the development of biorational pest control programs. The effect of nucleopolyhedrovirus (NPV) infection on the mo bility of second and fourth instar Mamestra brassicae larvae was inves tigated in the laboratory and field. NPV infection altered larval mobi lity, with the changes in behavior varying with the timecourse of infe ction. Diseased larvae moved three to five times further than healthy ones during the middle stages of infection. By the 7th day postinfecti on diseased larvae were less mobile than healthy counterparts. The sam e pattern of modified behavior was observed in both instars. Fourth in star larvae moved further than second instars under laboratory and fie ld conditions. In the field, infected larvae tended to die on the apex of the cabbage leaves. Bioassay of the leaves showed a linear decreas e in inoculum from central to peripheral plants within the plots, whic h occurred to the same extent for second and fourth instars. Leaves fr om plots where infected fourth instar larvae had been introduced had h igher inoculum density than those from plots with second instars. (C) 1996 Academic Press, Inc.