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Identification
Grey fly resembling a small housefly; white legless larvae found feeding on roots below soil level around brassica stems.
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Life Cycle
Adults emerge in spring to lay eggs at the base of plants; larvae feed on roots for several weeks; up to three generations per year.
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Damage Signs
Larvae tunnel into roots, causing wilting, stunted growth, and a blue-grey leaf tinge; seedlings often collapse and die.
healing
Treatment
Remove and destroy affected plants. There is no effective chemical rescue once larvae are established in roots.
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Prevention
Fit brassica collars around stems at planting and cover crops with fine mesh to prevent egg-laying.