One of the difficulties in controlling soybean aphids with traditional insecticides is that populations have the ability to quickly rebound from insecticide applications. The goal of this three-year study was to determine the optimal timing for a single spray application of a broad-spectrum insecticide applied soybeans to control soybean aphids. Experiments were established at two planting dates (early and late) at the Arlington Agricultural Experiment Station at Arlington, WI. Treatments consisted of spray applications at different plant growth stages during the season, an unsprayed check, and a treatment which received multiple sprays at approximately 7 day intervals in attempt to keep it as free of aphids as possible. Yields were measured at harvest time to evaluate the efficacy of each spray treatment. In the early-planted experiments aphid numbers did not reach high enough populations to cause significant yield loss. Conversely, in the late-planted experiments higher aphid populations and significant yield reductions were prevalent. Results showed that spray applications made in the late vegetative to early reproductive stages were not effective in preventing yield losses, however, spray applications timed to coincide with the beginning of peak numbers (R2-R3 plant stage) were just as effective in preventing yield losses as multiple sprays.
Species 1: Homoptera Aphididae Aphis glycines (soybean aphid)
Keywords: spray timing
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