Cabbage root fly

Abstract

Delia brassicae (Wied.) is a destructive pest of cruciferous crops throughout Europe and North America. In Britain, it is most injurious to cauliflowers and cabbage, particularly summer and autumn cauliflowers and summer cabbage, but it also damages brussels sprouts, calabrese, radishes, swedes, turnips, garden stocks and wallflowers. The pest can also live on many common cruciferous weeds. Plants can be attacked at all stages of growth, but the most serious damage usually occurs on young plants, which can be killed if severely attacked in the seedbed or shortly after transplanting. Heaviest attacks resulting from eggs laid by the first generation of flies occur during late April and May. Brassica plant beds and transplants may be attacked in July by larvae of the second generation. Winter cauliflower and spring cabbage rarely suffer economic damage in the field, but attacks to the buttons of brussels sprouts in autumn may lead to rejection by processors. D. floralis (Fall.), a closely related species, occurs in some years in the north of England and in Scotland. It causes damage within the bulbs of turnips and swedes from late September onwards. This revised leaflet on D. brassicae contains sections on the nature of its damage, its morphology and life-history, natural enemies, control on the farm, and control in gardens and allotments. The natural enemies mentioned include Bembidion lampros (Hbst.), Trechus quadristriatus (Schr.) and Aleochara sp. Reference is also made to another crucifer pest, Phytomyza rufipes Mg.