Studies on the dispersal of dieldrin-resistant cabbage root fly.
Abstract
The following is virtually the authors' summary. The dispersal of a population of Hylemya (Erioischia) brassicae (Bch.) was studied in Oxfordshire over a three-year period, their resistance to dieldrin [cf. RAE A 52 530] being employed as a means of recognising the flies. In order to assess the extent of their dispersal into surrounding susceptible populations, the genetical determination of deldrin resistance in this species was studied; it was found to be controlled by a single autosomal, semi-dominant gene. Laboratory comparison of the reproductive capacity of resistant and susceptible strains showed no difference between the two, apart from a reduction in egg viability in the resistant strain that may have been due to the previous exposure of larvae to dieldrin. The considerable dispersal found in the first year of the study was probably attributable to the abormally dense population and habitat destruction at the central site in the previous spring, following the failure of insecticidal control measures. Comparatively small changes in the distribution of resistance flies in subsequent years suggested that the fly has little innate tendency to disperse.