Cabbage Root Fly Delia radicum
The Root-maggot Flies often have a smaller body than the House Flies. But in most other respects they really do look alike. One of the most notorious Root-maggot Flies is Delia radicum, the Cabbage Root Fly. The larvae live in the roots and the lower parts of a number of cultivated plants, especially cabbage, radish, cauliflower and turnip. It is a real pest, for after some time the plant looses contacts with the roots and dies or simply collapses.
The puppa overwinters and delivers a new fly by the end of April or beginning of May. The adult flies are 7 to 10 millimeter in length. A female deposits up to 100 eegs on ground level near the stem of a Brassica-species. The eggs hatch after only 6 days. The larvae will feed on the plant for the next 20 days. Then they pupate in the ground for just 21 days. In this way up to 3 generations are produced annually in southern Britain. In northern parts only two generations are seen and further north there may be just one generation.
The Cabbage Root Fly has various other names, including Cabbage Fly, Root Fly, Turnip Fly, Cabbage Maggot, Root Maggot and Root Maggot Fly.