Cabbage root fly
Pest Maggots that eat the roots of brassicas and kill young plants.
What to look for
Young plants wilt on sunny days, leaves turn blue-grey and growth stops. The roots are tunnelled by small white maggots, and radish and turnip are bored through.
When: Flies are active from April to June and again in August and September.
How to prevent it
- Fit a collar (a 15 cm square of carpet underlay or cardboard) around the stem of each plant at planting.
- Cover the crop with fine mesh from planting, with the edges buried.
- Plant larger, stronger transplants, which tolerate attack better.
How to deal with it
- There is no cure, so lift and bin affected plants and do not compost them.
- Earth up around stems to encourage extra roots on tall plants.
- Rotate brassicas to a new bed each year.
Crops it affects
If you choose to use any treatment, use only products approved for UK home gardens, follow the label and avoid spraying open flowers. See all pests and diseases.