Soybean Yield Response to Pyraclostrobin and Drainage Water Management

Although pyraclostrobin {carbamic acid, [2,[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy] methyl] phenyl]methoxy-,methyl ester} has been used to protect soybean [Glycine max (L.) Merr.] from foliar diseases, its interaction with drainage water management (DWM) systems was unknown. Field research during two wet years (95 to 97 mm greater than the past decade) evaluated the effects of pyraclostrobin application timing (R3, R5, R3+R5, and R3+R5+lambda-cyhalothrin) and DWM system (nondrained and drainage only [DO] or drainage plus subirrigation [DSI] at 6.1 and 12.2 m drain tile spacings) on soybean yield, grain quality, and severity of Septoria brown spot (SBS) (Septoria glycines) and frogeye leaf spot (FLS) (Cercospora sojina). Grain yields increased 18 to 22% with DO or DSI at 6.1 and 12.2 m spacings compared to a nonfungicide treated, nondrained control. In the absence of drainage, pyraclostrobin with or without lambda-cyhalothrin increased yields 20 to 27% compared to the nondrained, nonfungicide treated control. The combination of DWM and pyraclostrobin increased grain yields up to 36%. Pyraclostrobin plus lambda-cyhalothrin at R3+R5 increased yield 8 to 12% except with DO at 12.2 m compared to similar nonfungicide-treated DWM systems. A DWM and pyraclostrobin interaction was detected for grain oil and protein concentration, but differences were minimal. Pyraclostrobin with or without lambda-cyhalothrin reduced severity of SBS and FLS 2 to 8% depending on the year, but DWM did not affect severity of these diseases. The greatest synergistic yield increase on a claypan soil occurred when foliar disease management and DWM systems were used together in years with higher than normal rainfall.