Effect of Pyraclostrobin Fungicide on Disease Pressure, Plant Health, and Soybean Grain Yield.

Soybean [Glycine max (L.) Merr] is one of the world’s most important crops, supplying approximately half of the global demand for vegetable oil and protein. Soybean is the most commonly grown crop in Ohio, accounting for over 1.8 million ha, and the Ohio soybean industry is valued at over 2.7 billion dollars. Further grain yield increases are critical to meet food and bio-based product demands. Strobilurin fungicides may help increase soybean yield through the control of plant pathogens. Pyraclostrobin, a type of strobilurin fungicide, has received increased attention due to claims of positive yield effects. Reports of physiological changes from pyraclostrobin include increased leaf greenness, chlorophyll content, and photosynthetic rates. To determine the effect of pyraclostrobin on soybean yield, a trial was performed at three Ohio locations in 2013 and 2014. The objective of the study was to evaluate the effect of pyraclostrobin on soybean plant health, disease suppression, and soybean grain yield in high-input and traditional (reduced input) production systems. Pyraclostrobin was applied to soybeans at the R3 growth stage (initial pod development). Plant health was assessed at 2 and 4 weeks after fungicide application by measuring chlorophyll content and by analyzing chlorophyll fluorescence. Foliar diseases were evaluated as percent leaf area affected. Statistical analysis was performed using SAS software, and ANOVA was calculated. Preliminary results from 2013 indicate pyraclostrobin increased soybean grain yield at two out of three locations in the high-input production system. However, there was no effect of pyraclostrobin in the traditional production system. Pyraclostrobin had limited benefits on plant health, but reduced foliar disease 42% of the time. Yield increase benefits due to pyraclostrobin application are likely attributed to reduction in foliar disease and most likely to occur in systems with a high yield potential.