Observations on the cabbage stem flea beetle, Psylliodes chrysocephala, on winter oil‐seed rape in Cambridgeshire

SUMMARY The biology of the cabbage stem flea beetle, Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), on winter oil‐seed rape crops was studied in Cambridgeshire from 1974 to 1978, with particular reference to autumn and winter activity. The timing of adult invasion of crops in the autumn and subsequent attack on plants by larvae showed considerable variation from year to year, being influenced mainly by temperature. Also, early‐germinating crops tended to be invaded earlier than later‐germinating ones. Egg development, which was closely correlated with temperature, required an accumulated sum of 240 day o C above 3.2 o C (calculated from daily mean temperatures). Monitoring adult activity, and consideration of temperature data, allowed dates of egg hatch to be predicted. The usefulness of this information for accurately timing chemical sprays against the pest is discussed.