Use of crop inputs, including prophylactic application of insecticides, has increased in soybean production. A liquid fertilizer-ready formulation of the insecticide bifenthrin was recently labeled for in-furrow use with a starter fertilizer on soybean. An experiment was conducted at six sites (three in Minnesota and three in Ohio) in 2013 and two sites (Minnesota) in 2014 to evaluate effects on soybean of prophylactic in-furrow applications of a liquid fertilizer-ready insecticide (bifenthrin) and a 2-6- 16 (N-P-K) liquid starter fertilizer alone and in combination. Across three site-years in Minnesota where insect injury was recorded, the insecticide decreased the percentage of plants with seedcorn maggot injury (P = 0.0291). However, across all site-years, insecticide and fertilizer had no effect (P > 0.05) on plant population, plant height, or grain yield. Prophylactic use of these additional inputs under typical soybean-growing conditions in this region may not provide a return on investment.
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