Dispersal of the Adult Cabbage Maggot, Hylemya brassicae12

Abstract

Information on the dispersal of the adult cabbage maggot, Hylemya brassicae (Bouché), is scanty. Based on the relative amount of damage caused to crops located at various points from the source of infestation, Read (1958) concluded that the flies travelled short distances, mainly in the downwind direction. Mowat and Coaker (1968) assessed dispersal of a wild, dieldrin-resistant strain of the cabbage maggot from a large farm by determining the distribution of resistant flies in the surrounding areas over 3 years. They showed the fly had little innate tendency to disperse. Hawkes (1972) estimated that the rate of dispersal of 32 P-marked cabbage maggot adults released in a cabbage plot ranged from 8–20 m per day. The farthest point at which marked flies were recaptured was 58.2 m from the release point. Hawkes concluded that in the presence of the hedge and host crops, H. brassicae dispersed only through “trivial” movements and that wind direction did not affect the direction of dispersal. Reviewing the studies at the National Vegetable Research Station, Wellesbourne, England, Coaker and Finch (1971) suggested populations in brassica crops more than 800 m apart would be unlikely to intermix during the 2–3-week period of adult survival.