Efficacy and safety of generic azoxystrobin at controlling Rhizoctonia solani in sugar beet

Rhizoctonia solani Kühn is a major soil-borne pathogen limiting sugar beet (Beta vulgaris L.) production in the United States and other countries worldwide. There is no commercial cultivar which is immune from infection by R. solani and highly resistant cultivars typically have a yield penalty. Growers use cultivars with some levels of resistance and rely on the timely application of fungicides to control R. solani. Azoxystrobin (Quadris®) has been the most widely used fungicide for control of R. solani on sugar beet since its registration in the United States in 1997. In 2015, growers wanted to know whether generic azoxystrobin, which became available on the market and at a lower price than Quadris®, would provide effective control of R. solani. The objectives of this greenhouse study were to evaluate the efficacy and safety of generic azoxystrobins at controlling R. solani on sugar beet compared to the industry's standard Quadris. Three generic azoxystrobins - Satori®, Aframe™ and Equation™ - and two application methods - in-furrow at planting and band applications to 4-leaf stage sugar beet - were evaluated. Inoculation with R. solani AG 2-2IIIB was done after fungicide applications. To check for phytotoxicity, fungicides were applied but with mock inoculation. Plant survivors, plant height, root weight and disease severity were evaluated. Results indicated that the generic azoxystrobins were safe to use on sugar beet seeds and plants and provided similar disease control of R. solani as the industry's standard Quadris treatment. This study demonstrated under greenhouse conditions that Satori®, Aframe™ and Equation™ have the potential to be used by growers for disease management in sugar beet fields with a history of R. solani.