Field Identification
A hump-backed anthomyiid fly whose maggots liquefy onion, shallot, and leek bases—the underground equivalent of a bad roommate eating the rent money. Wilting seedlings and soft necks often mean larvae are already tunneling.
Adults resemble small houseflies; white maggots bore into bulbs and roots leaving slimy rot and secondary pathogens. Damage clusters where alliums are repeated year after year without rotation.
How to Deal With It
Organic Control Methods
Spinosad or neem directed at the base of plants during egg-laying windows; insecticidal soap has limited reach—focus on soil line and repeat after heavy rain per label.
Encourage rove beetles, ground beetles, and parasitic wasps (e.g., Aphaereta species) that attack fly pupae in soil; Steinernema feltiae nematodes against larvae in moist soil.
Rotate alliums on at least a three-year cycle; delay planting until soils warm slightly to shorten vulnerable seedling stage; interplant carrots or other masking crops; destroy culls and bolting onions that attract flies.
Floating row cover sealed at edges excludes egg-laying females; fine mesh over seedbeds until plants size up.
Avoid fresh manure before allium beds; use clean sets and transplants; scout for eggs at soil cracks near plants.
Let Nature Handle It
Natural Enemies
- Parasitic Wasps (Braconidae)
- Rove Beetles (Staphylinidae)
- Ground Beetles (Carabidae)
- Entomopathogenic Nematodes
Threat Map