Biological control of western grape leaf skeletonizer (Harrisina brillians B. and McD.) in California

The western grape leaf skeletonizer, native to the southwestern states and northern Mexico, was first found in San Diego County in 1941 and very soon thereafter demonstrated a capacity to cause serious crop losses in the vineyards of that county. A biological control program was started in 1950 as a part of a comprehensive plan to control existing infestations and to prevent their spread to the more important commercial grape-growing areas to the north. Exploration for natural enemies was conducted during 1950 to 1952 and covered the known area of distribution of the pest in the Southwest and Mexico, as well as that of related species in the Atlantic Coast States from New York to Florida. Two insect parasites of the larvae and a virus disease were established in San Diego County as a result of importations from Arizona. These have been highly effective in reducing existing infestations to a low level, with only occasional short-lived outbreaks in semicommercial and back-yard plantings. They have also aided in preventing spread of the pest.