BIOLOGY OF THE CRUCIFER FLEA BEETLE, PHYLLOTRETA CRUCIFERAE (COLEOPTERA: CHRYSOMELIDAE), IN SOUTHWESTERN ONTARIO

Abstract The biology of the crucifer flea beetle, Phyllotreta cruciferae (Goeze), was studied in the laboratory, and under field conditions in southwestern Ontario. Field-collected adults, held in a state of induced hibernation were used for some laboratory studies. A rearing procedure was developed and a culture maintained for eight generations provided additional adults for laboratory work. Development and behaviour of the various crucifer flea beetle stages at different temperatures were studied. The mean preoviposition period ranged from 3.8 (32°C) to 22 (20°C) days. Time required for development from egg to adult varied from 24 (30°C) to 54 (20°C) days. For oviposition capability and egg to adult development, developmental thresholds were ca. 17° and 11°C, respectively, and 61 and 456 degree days were required. Crucifer flea beetle adults overwintered in leaf litter and the top 2.5 cm of soil, in windbreaks, fencerows, and cultivated areas. Adults appeared in early spring. Peak adult movement occurred at this time, primarily within 2 m of the ground, and oriented toward crucifer plots. Using heat unit summations calculated from soil temperatures, adult emergence in the field from eggs set out at various times was predicted with an accuracy of ± 3.7 days. Population studies and heat unit accumulations indicated that there was a single generation of crucifer flea beetle in 1974, and two generations in 1975. Adults were restricted primarily to cruciferous crops, with rutabaga and Chinese cabbage being the preferred hosts, among those varieties tested.