Effect of Pyraclostrobin on Growth, Yield and Diseases of Soybean.

Abstract

The effects of pyraclostrobin, a strobilurin fungicide, applied at different times and concentrations on the growth, yield, and diseases of soybean were examined. In 2006, treatment with pyraclostrobin [150 g active ingredient (a.i.) ha^-1] at the end of flowering delayed maturation and increased 100-seed weight more than treatment with iminoctadine albesilate (400 g a.i. ha^-1). This effect was not observed when pyraclostrobin was sprayed at the beginning of flowering. In 2007, seed weight and the proportion of large seeds were increased by the treatment with pyraclostrobin at either 133, 67, or 40 g a.i. ha^-1; the fungicide was more effective at a higher concentration. At either time or concentration examined, pyraclostrobin reduced the occurrence of seeds with purple stain more effectively than iminoctadine albesilate or no fungicide spraying. There was no difference in diseased leaf area (bacterial pustules, rust, and brown spot) among the fungicide treatments. These results indicated that pyraclostrobin spraying reduced the occurrence of seeds with purple stain and increased seed size.