EVALUATION OF ALTERNATIVE FUNGICIDES TO AZOXYSTROBIN FOR MANAGING RHIZOCTONIA ROOT AND CROWN ROT IN NEBRASKA

摘要

In Nebraska, Rhizoctonia root and crown rot, caused by Rhizoctonia solani, is generally considered to be the most commonly occurring and damaging sugar beet disease in Nebraska. Previous studies have demonstrated that applications of azoxystrobin based on soil temperatures exceeding 65°F will effectively reduce disease and improve yield parameters. However, the almost exclusive use of Quadris (azoxystrobin) for more than a decade raises concern for resistance development by the pathogen to this fungicide and other members of the strobilurin class. We then began a study in 2012 to evaluate the performance of alternative fungicides currently registered for Rhizoctonia root rot in sugar beets (Priaxor, Proline, and Headline) and compare their performance to Quadris utilizing both in-furrow treatments at planting and foliar applications based on soil temperatures. The study consisted of 9 treatments and data collected included multiple disease counts during the season, and sucrose and root yield determinations at harvest. The treatments consisted of 1) untreated control, 2-5) applications of each fungicide applied in-furrow at planting, 6-9) applications of each fungicide made using both in-furrow and foliar applications after 4 inch soil temperatures averaged 65° F for three consecutive days. Our results indicated that Quadris, Priaxor, and Proline all performed similarly, significantly reducing disease incidence and increasing sugar yields compared with untreated inoculated controls. Headline wasnot effective in improving yields or reducing disease compared to the untreated inoculated controls. We further determined that better results were obtained with the combination of in-furrow and foliar applications later in the season than the in-furrow alone.