Control of the Cabbage Looper with a Nuclear Polyhedrosis Virus Disease

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Abstract
A nuclear polyhedrosis virus disease was found to be effective in controlling the cabbage looper (Trichoplusia ni (Hbn.)) on cabbage, cauliflower, and lettuce in southern California. A virus concentrate of 5.5 billion polyhedral per milliliter was used in 1957 at rates of 1, 5, and 10 ml. per gallon. In April the time required from exposure of hatching larvae until most of them died was 20 days. In September cabbage loopers were not successfully controlled nor was leaf damage prevented after two applications of virus were made to half-grown cauliflower when loopers had become large enough to cause some leaf damage before dying. However virus applications on small plants soon after thinning, when loopers were small or in the egg stage, gave much better control. Three applications protected a cauliflower field from plant thinning until harvest time.

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