QuestionsHow to growVegetable GrowingSummer cabbageCabbage root fly on established plants 0 Vote Up Vote Down Lucy Mc Enery asked 14 years ago I have cabbage plants that are well established and have now the cabbage root fly symptoms. At this stage, what can I do?? Any sprays?? or alternative cure. 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 7 years ago You could try drenching with a fruit and veg insecticide. Apply about 100mls slowly down the stem at ground level. There will be a short withdrawal period on the insecticide.