ABSTRACT
Under field conditions cabbage root fly activity is influenced considerably by a) the times the flies emerge from the overwintering puparia, b) by factors inducing aestivation and, c) by the influence of day-length on the induction of diapause. By making detailed studies of these factors, we are now able to forecast more acurately both seasonal and local variations in the timing of cabbage root fly infestations.
Despite such forecasts, however, certain populations are still difficult to control, mainly as a result of 1) having to apply insecticide to established crops during mid-summer, 2) from certain farmers growing brassica crops in inappropriate areas, and 3) from a second species, the turnip fly (Delia floralis), also damaging plants in certain localities. The influence of these factors on the current strategies for pest control are discussed.
