The adult flies are black and glossy, around 5-8mm long, with a thin body, shiny wings and yellow legs. They lay their eggs close to the roots of the host plant in spring. Once hatched, the larvae make their way down into the soil to eat the roots, which causes damage to the crop.
Damaged plants show a dark, ‘rusty’ discolouration around the areas which have been eaten. Other symptoms include stunted growth, forking or bulbus growths. If younger plants are affected, they may wilt or the crop may fail. In many cases, damaged plants become inedible.
