Control of Onion Maggot, 1986

Abstract

Abstract The objective of this study was to compare granular and wettable powder formulations of an insect growth regulator (Trigard) and to compare application methods for control of the onion maggot. Onions ('Downing Yellow Globe') were planted 28 Apr in a commercial onion field at the Krummery Farm, Stockbridge, Mich. Plots were single rows, 20 ft long, with an untreated buffer row between each plot. Treatments were arranged in a randomized complete block design with 4 replications per treatment. Granular in furrow treatments were applied with the seed with a V-belt seeder with a 1-inch planting shoe. Band treatments were applied to the soil surface in a 3-inch band and shallowly incorporated prior to seeding. Diazinon drench treatments were applied with a hand sprayer at 50 gal/acre in a 3- to 4-inch band over the row, beginning as soon as first egg laying was observed, and repeated weekly (23 and 30 May and 6, 13, and 20 Jun). Trigard drench treatments were applied biweekly (23 May and 6 and 20 Jun). Weekly foliar insecticide sprays of parathion or diazinon were applied to the entire field by helicopter, but had no apparent effect on the onion maggot. A 100-plant section of row in each plot was marked with stakes prior to the first injury and sampled weekly from 30 May through 27 Jun and on 10 Jul for observable onion maggot injury and stand remaining. Yield of marketable onions, number of onions, and number of bulbs damaged by onion maggot were evaluated from 10 row-ft in the center of each plot on 21 Aug.