How to Manage Pests
Pests in Gardens and Landscapes
Granulosis virus disease
The most effective biological control agent of western grapeleaf skeletonizer is a granulosis virus.
This host-specific virus kills eggs, larvae, and pupae. The virus attacks the gut of the larvae, which
results in dark diarrhetic blotches on the leaves. Healthy larvae can become infected by virus particles
in the excrement. Other insects distribute the virus when they walk through the diarrhetic blotches.
There are four typical symptoms of infection in adults and larvae: 1) eggs are scattered and the number
of eggs is reduced, 2) eggs fail to hatch, 3) larvae consume tiny patches of tissue rather than consuming
entire areas of the leaf, and 4) larval growth and coloration change and larvae shrink and eventually
Infected larvae are disoriented