The onion maggot, Hylemya antiqua (Meigen), is the most important insect pest of onions in Canada and in the northeastern and northcentral United States. This pest first reached North America from Europe in 1841, and since that time it has frequently devastated onion crops. It is particularly severe in New York where crops can be destroyed completely if no steps are taken to protect them. The insect can develop resistance to insecticides very quickly; many compounds recommended in the past had to be abandoned because they ceased to be effective against the pest. Also, there is evidence that the onion maggot is beginning to develop low but significant levels of resistance to several of the currently used insecticides. The insect's ability to develop resistance to insecticides threatens the production of onions grown commercially in New York and other states. Since very few new compounds are becoming available, there is an urgent need to use every possible practice that might help to alleviate the problem and to develop alternative control measures which can be integrated with the still effective chemicals.