Onion Thrips Control, 1987

Onions were planted at the M.S.U. Muck Research Farm, Bath, Mich. Plots were single rows (17 inches between rows) 20 ft long, arranged in a completely randomized design with 4 replicates. Two border rows were left unsprayed between each plot. Treatments were applied with a single nozzle (D4) hand-held CO2 sprayer at 40 psi. Sprays were applied 25 and 30 Jul. The day before the first spray, 10 plants were randomly selected and marked within each plot, and the thrips on each plant counted in the field; the plants were disturbed as little as possible. The thrips were counted on the same plants on 27 and 31 Jul. The total numbers of thrips per 10 plants were calculated for the first prespray sample and the last postspray sample. The total change per plot between the first and last sample date was converted to a percentage of the initial count and this number was used to determine differences among treatments.