The Potential for secondary Cercosopora leaf spot suppression with foliar fungicide applications made for Rhizoctonia solani management in Sugar Beets

摘要

In Wyoming's southeastern irrigated sugar beet production region, field experiments were conducted in the years 2011- 2013 to determine if fungicide applications made for Rhizoctonia root and crown rot disease (RRCR) management would have cross over effect on the later occurring Cercospora leaf spot (CLS) disease development in sugar beet and conversely if later CLS fungicide treatments on their own would have an effect on RRCR development. Secondary goals were to determine if fungicide active ingredient or method of RRCR fungicide application had a differential impact on RRCR and subsequent CLS disease. In 2011, most RRCR-targeted treatments significantly reduced overall CLS disease as measured by AUDPC on average 54% compared to the non-treated check. However, in 2012 and 2013 there was no effect of the early RRCR-targeted treatments on AUDPC for CLS disease. CLS-targeted treatments reduced CLS disease up to 95% but had no effect on RRCR disease. For RRCR, banded fungicide treatments were more effective than broadcast treatments, with no differences in activity between prothioconazole and azoxystrobin. These results provide evidence that fungicide applied for RRCR control can provide some benefit in managing CLS; however, benefits were minor and growers would still be required to use timely fungicide applications to realize economic yields.