"Seed treatments are probably a better answer than sprays against carrot fly," Warwick HRI entomologist Rosemary Collier told delegates at the seminar.
"But seed treatments are inevitably limited by the amount (of the active chemical) that you can get onto the seed. For soil pests, granular formulations always provided good results so why have they virtually disappeared as a method of application?"
Where pyrethroid sprays are being used against carrot fly, early application is vital, she said: "Get them on before the eggs are laid because it only kills the flies, not the eggs. Good control of the second generation is particularly important as these damage the overwintered crop."
In the seed treatment trials, Force and some experimental insecticides performed well against carrot fly. Strategies such as late sowing and early harvesting help to reduce colonisation of crops and give insecticide treatments a better chance, said Collier. Physical barriers have also been tested in the HDC project and can help in certain circumstances.