Soybean yield was not influenced by foliar insecticide application at R3 and R5 stages

Due to low cost, farmers often combine foliar insecticide with a foliar fungicide application without assessing insect activity in their soybean [Glycine max (L.) Merr.] field. Therefore, this research was conducted to determine if prophylactic application of foliar insecticide improves soybean yield in Ohio. Objectives were to evaluate the effect of foliar insecticide applied at the R3 and R5 soybean stage on insect defoliation, insect pod and seed damage, and soybean grain yield. The experiment was conducted in 2022 and 2023 for a total of 10 site-years in Ohio. The experimental design was a randomized complete block with four replications of each treatment. Treatments included foliar insecticide applied at the R3 soybean stage (beginning pod), insecticide applied at the R5 soybean stage (beginning seed), and a non-treated control (no insecticide). Soybean leaf area affected by defoliation was evaluated the day of application and 2 weeks after application. At the R8 soybean stage (physiological maturity), soybean plants were collected and evaluated for insect pod damage and seed damage. The foliar insecticide application did not result in any significant change in soybean yield, likely explained by low insect defoliation and low pod damage. Prior to insecticide application, farmers should scout their fields and base decisions on integrated pest management strategies, considering threshold levels.