Development of Resistance to Insecticides by the Onion Maggot, Hylemya antiqua, in Minnesota1

Abstract

The onion maggot, Hylemya antiqua (Meigen), has developed a high degree of resistance to the chlorinated hydrocarbon insecticides in the Minneapolis area. Under conditions of a severe maggot infestation at Fridley, Minn., applications of V-C 13 Nemacide® ( O -2,4 diehlorophenyl O,O -diethyl phosphorothioate), ethion, and diazinon at 1 lb. actual toxicant per acre and carbophenothion at 2 lbs. actual per acre in the seed furrow gave excellent control, but plots treated with heptachlor, dieldrin, aldrin, and endrin were indistinguishable in appearance from the untreated checks. Experiments at Castle Rock, Minn., during 1960, 1961, and 1962 indicated that aldrin, dieldrin, endrin, and heptachlor are still effective in controlling the onion maggot in this area. Onion maggot, damping off, smut ( Urocystis cepulae Frost.), and pink root ( Pyrenochaeta terrestris (Hansen) Gorenz, J. C. Walker, and Larson) aII contributed to a loss of stand in these plots. Two granular formulations, one containing 5% V-C 13 Nemacide +5% thiram (bis(dimethylthiocarbamoyl)disulfide) and the other containing 5% ethion+5% thiram, gave excellent control of maggots and good control of smut and pink root when applied at 2 lbs. actual toxicant per acre in the seed furrow. Onion growers at Hollandale, Minn., appeared to be controlling the onion maggot satisfactorily in 1961 by using a mixture of 2 oz. 75% dieldrin and 1 oz. 75% thiram per pound of seed in the planter box; however, experimental evidence indicated that maggots were becoming resistant to dieldrin and heptachlor in this locality in 1962.