Cabbage root fly, a ± 6 mm long grey insect and it looks very similar to the common housefly.
Also known as:
Cabbage root fly (Delia radicum) is a ± 6 mm long grey insect and looks very similar to the common housefly. Cabbage root flies are found on crucifers. The eggs are laid at the base and sometimes in leaf axils of brassicas. The maggots, known as cabbage maggots, bore their way through the stem just above ground level. Slowed growth, followed by wilting of the leaves turning bluish, means that cabbage fly maggots are active. The maggots attack the stem, disrupting the transport of water and nutrients. The affected parts rot and the plant dies.
Check for eggs around the base of the plant and in the leaf axils of leaves. Remove found eggs with a brush or a hard jet of water.