ABSTRACT
A total of four field experiments were conducted during 2017, 2019 and 2020 in Ontario, Canada to determine if applying a fungicide 2 - 3 days after a herbicide, applied POST, reduces visible injury, increases crop vigour and increases yield of soybean. At 3 DAB (days after fungicide application), the POST application of glyphosate, fomesafen, bentazon, thifensulfuron-methyl, cloransulam-methyl and imazethapyr caused 0, 11%, 5%, 18%, 9% and 12% visible injury in soybean, respectively. The injury decreased over time with less than 5% injury at 8 WAB (weeks after fungicide application) in all treatments evaluated. The application of pyraclostrobin/fluxapyroxad after the application of herbicides evaluated did not reduce soybean injury. Soybean vigour with glyphosate, fomesafen, bentazon, thifensulfuron-methyl, cloransulam-methyl and imazethapyr applied POST without the fungicide application was 100%, 91%, 95%, 84%, 91% and 88%, respectively at 3 DAB. The soybean vigour increased over time to 95% - 100% at 8 WAB. The application of pyraclostrobin/fluxapyroxad after the herbicide application did not improve soybean vigour, except with thifensulfuron-methyl where soybean vigour was improved 6% when followed by pyraclostrobin/fluxapyroxad. There was no effect of herbicide and fungicide treatments on soybean yield except for thifensulfuron-methyl and imazethapyr without the fungicide treatments which reduced soybean relative yield 7% and 10%, respectively. The application of pyraclostrobin/fluxapyroxad after the application of imazethapyr increased soybean yield 3%. Based on these results, applying pyraclostrobin/fluxapyroxad fungicide 2 - 3 days after glyphosate, fomesafen, bentazon and cloransulam-methyl does not affect soybean injury, vigour or yield, but it can slightly enhance the vigour and yield of soybean when applied after thifensulfuron-methyl and imazethapyr.