Effect of Mid-Season Fungicide and Insecticide Application on Soybean Yield.

There are many factors that affect soybean yield, yet farmers are very concerned about the disease and insect factors that could cause potential yield loss. The objective of this study is to evaluate the effect of mid-season fungicide and insecticide application on soybean yield, alone or in combination. A six location on-farm field trial was conducted in 2015 and 2016 throughout Ohio in a randomized complete block design with four replications of treatments. Fungicide and insecticide treatments included: 1)control, 2)fungicide only, 3)insecticide only, 4)fungicide and insecticide (tank-mixed), 5)fungicide and insecticide (not tank-mixed), 6)fungicide and crop oil, 7)insecticide and crop oil, 8)fungicide, insecticide and crop oil (tank-mixed), were applied at R3 growth stage (initial pod development), and detailed measurement of disease and insect defoliation were carried out a week before application and two weeks and four weeks after application. Additionally, plants were evaluated for pod injury caused by bean leaf beetle. There was no significant difference in yield response between tank-mixed fungicide and insecticide applications and separate applications of both fungicide and insecticide. When fungicide was applied, soybean yield increased significantly at 3 of 6 sites by 8 to 15 bu/acre, but there was very little to no yield response associated with insecticide application due to limited insect population and defoliation in the field, below threshold level. The data indicated that fungicide application had a great influenced in soybean yield even though the amount of disease i.e. frogeye leaf spot were higher two weeks and four weeks after the application. Therefore, there is a high potential that fungicide application would improve soybean yield when diseases are found.