How to Manage Pests
Pests in Gardens and Landscapes
Onion maggot—Delia antigua
Adult maggots are small gray flies that are somewhat smaller than houseflies. When at rest, they keep
their wings folded one over the other. Larvae are creamy white, legless maggots about 10 mm long.
Onion maggot flies lay eggs in the soil near the germinating plants. Larvae feed on the developing seedling and on the expanding bulb. Mature larvae pupate in the soil. There are several generations per year. Maggots prefer soils heavy in organic matter where they can survive and move to seeds. Onion maggots are generally restricted to cooler coastal climates.
Onion maggots can attack germinating seedlings, feeding on the developing roots and epicotyl. They can
continue to feed on the expanding bulb during later stages of growth, creating tunnels and cavities in
the bulb and underground stem. Plants may die or become wilted and yellow. Maggots generally do not cause
economic damage to garlic; they are primarily pests of onions.
Prevention is the best management strategy. Avoid overfertilization with manure; maggots prefer to lay
eggs in rich soil. Disc weeds at least 2 weeks before planting. Plant transplants or pregerminated seeds.
Cover seedbeds with protective
cloth or cover
individual plants to prevent adults from laying eggs near
maggot feeding in onion bulb
maggot feeding in onion seedling