Prevalence of Viral Diseases of the Fruittree Leafroller, Archips argyrospila (Walker) (Lepidoptera: Tortricidae), in Louisiana

Abstract

A nucleopolyhedrovirus (NPV) and a granulovirus (GV) were found infecting field populations of fruittree leafroller, Archips argyrospila (Walker), larvae in Louisiana. Both viruses were recovered from infected larvae at 7 of 8 widely separated sampling sites. Additionally, a small proportion (<5%) of the larvae (maximum 10.2%) had double infections. Overall, infection rates ranged from 0 to 24.4 percent and were statistically correlated with defoliation and host population levels in a positive, density-dependent manner. It appears that though high populations and warm temperatures favor development of a widespread epizootic, the leaf rolls (shelters) protect larvae from contamination at low to moderate population levels. At outbreak larval densities, the rates of viral prevalence approached 25 percent, and the viruses, coupled with other natural control factors may, in time, become effective in population control.