Symptoms
Maggots feed inside bulbs causing yellowing and collapse. Rotting bulbs with foul odour. Seedling death in young plants. Adults lay eggs at soil level near plant base.
Prevention
Use fine mesh covers to exclude adults from seedbeds. Practice crop rotation with non-allium crops for at least 3 years. Remove and destroy infected plants. Apply diatomaceous earth around plant base.
Treatment
Organic
Apply entomopathogenic nematodes to soil to target larvae. Use diatomaceous earth as a physical barrier. Remove and destroy affected plants to prevent spread.
Chemical (last resort)
Apply chlorpyrifos or diazinon to soil at planting. Treat soil drench at first sign of infestation. Chemical control is most effective targeting eggs and early instar larvae.
Affects 1 crop
Sources
MARDI Vegetable Pest Guide; DOA Extension Bulletin