Seasonal Abundance of the Cabbage Looper as Related to Light Trap Collections, Precipitation, Temperature and the Incidence of a Nuclear Polyhedrosis Virus 1

Abstract

The seasonal abundance of the cabbage looper, Trichoplusia ni (Hubner) was studied at Painter, Virginia for the period 1958–60. The incidence of a nuclear polyhedrosis virus was the most important factor influencing abundance of cabbage loopers. Optimum conditions for the spread of the virus were associated with the development of heavy looper infestations followed by excessive rainfall. Reinfestations of loopers developed on new plant growth after almost complete elimination of the previous infestation by polyhedrosis. Three distinct looper outbreaks and subsequent control by polyhedrosis occurred in a single season.