The impact of a fungicide and an insecticide on soybean growth, yield, and profitability

A growing number of soybean producers have begun to incorporate below threshold fungicide and insecticide treatments into their management programs in attempts to increase yield. The objective of this study was to determine the influence of a fungicide and insecticide on soybean yield and growth when disease and insect pressure is minimal. Soybean was planted at three locations across Indiana, USA, in 2009 and 2010 and treated with various combinations of glyphosate, pyraclostrobin, and lambda-cyhalothrin. Yield was increased by 100 kg ha⁻¹ and 150 kg ha⁻¹ by a R4 application of pyraclostrobin alone and by lambda-cyhalothrin alone, respectively. Seed mass was increased 3% by pyraclostrobin, while seed number m⁻² was increased 5% by lambda-cyhalothrin. No other yield component was influenced by the fungicide or insecticide. Economic analysis using Simulation and Econometrics to Analyze Risk (SIMETAR) demonstrated a single, post application of glyphosate to be the most efficient treatment option across a range of risk attitudes. This study indicates that yield increases are possible using below threshold applications of fungicides and insecticides. However, growers may not benefit from such applications if input costs are higher than the economic returns of the increased yield.