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The onion maggot is one of the most damaging pests of onions in the northern growing region of Ontario. It also attacks garlic, leek, and shallot. The maggots are small, translucent white, legless and oblong-shaped with a pointed anterior. Adults are small grey-black flies. Infestation from maggots causes wilting of plants. Three generations of onion maggots occur each year in Ontario. Damage from the first generation is usually seen mid-to-late June as wilted onion seedlings. Second generation damage occurs in July, when the onions have begun to form bulbs and feeding by larvae does not kill the plants.

Onion Maggot Adult
Source: Pest and Diseases Image Library, Bugwood.org

Onion Maggot Pupae
Source: Pest and Diseases Image Library, Bugwood.org

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