Maggots Attacking Michigan Onions1

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Abstract
A 4-year study of maggots infesting onions grown on peat soil revealed the following: 52 spp. of flies were taken in onion fields. Only 20 taken as maggots in growing onions, and of these 20, just 6 or 7 were of any importance. The multiplicity of spp. present in a field may confuse growers unfamiliar with technical identification. H. antiqua (Mg.), the onion maggot caused most of the damage to Michigan grown onions. H. cilicrura (Rond.) caused a significant part of all maggot damage to onions during May and June. The earlier collections had a higher proportion of H. cilicrura than later collections. The attack of germinating onions by this pest may alter the timing of recommended spray and dusting control measures. Maggots of lesser bulb flies. E. strigatus (Fall.) and E. tuberculatus (Rond.) were collected in great numbers from growing onions in late July and August. Although these spp. are not usually primary invaders of healthy bulbs, at least 1 case of primary infestation of set onions was observed. H. antiqua. although found in fresh cull piles, was not taken there after the emergence of the 1st generation of flies in the spring. This re-emphasizes the necessity of immediate destruction of cull onions after harvest to prevent the development of maggots. The Diptera reared from old onion cull piles were scavenger or predator spp. 7. The 52 Diptera spp. are listed by family.

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