Western grapeleaf skeletonizer
First through the early fourth instar larvae feed on the lower leaf surface, leaving only the veins and upper cuticle. This gives leaves a whitish paperlike appearance; eventually the entire leaf turns brown.The late fourth and all fifth stage larvae skeletonize the leaves, leaving only the larger veins. When abundant, larvae can defoliate vines by July. Western grape leaf skeletonizer does not occur in all grape-production areas because the moths are not long-distance fliers and this pest has been slow to spread in California since its first appearance in the 1940s. In areas where it does occur, granulosis virus (endemic to Southern CA and introduced in other counties) usually keeps populations below economically damaging levels. When the virus is insufficient, western grapeleaf skeletonizer is easily controlled with insecticides that are also effective on other caterpillars, leafhoppers, ..