Onion maggot (Delia platura, incorrectly known as bean root maggot fly) rarely affects young lupin and pea crops sown into green decomposing organic matter.
What to look for
Plant
Stunted and dying seedlings with a brown mushy root/hypocotyl in paddocks with large amounts of plant stubble or other organic matter.
Seedlings growing in windrows are more likely to be affected.
Insect Larvae
Cream maggots up to 7mm long with dark jaws visible have tunnelled into affected parts.
Adult flies are about 5mm long, similar to the bushfly but more slender, hairy and the wings are more grey.
Where did it come from?
Contaminated stubble
Contaminated soil
In years when damage has been seen, crops were sown into green decomposing organic matter, weather conditions were warm, and fungal infection was also seen in crop roots.
Adult flies are attracted to soils rich in organic matter and lay eggs in the soil.
Larvae usually feed on decaying organic matter but will burrow into germinating plants and begin to feed.
Depending on temperature, larvae pupate after 3-6 weeks and emerge as adult flies two weeks later.
Management strategies
If re-sowing is required seed at a higher rate and use seed dressings.
