Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2009
Publication Date: 7/15/2009
Citation: Bolton, M.D., Khan, M.F. 2009. Management of Rhizoctonia Root Rot of Sugarbeet - Fungicide Efficacy and Identification of Environmental Parameters for Disease Development [abstract]. Phytopathology. 99(6)(Supplement):S14. Interpretive Summary:
Technical Abstract: Rhizoctonia solani AG 2-2 is the causal agent of Rhizoctonia root and crown rot in sugarbeet. This disease has recently been increasing in occurrence and severity in sugarbeet production areas in the Red River Valley of Minnesota and North Dakota. Since the intraspecific groups AG 2-2 IIIB and AG 2-2 IV both cause Rhizoctonia root and crown rot and are both prevalent in the Red River Valley, our objectives were to compare disease development of these intraspecific groups at four different soil temperatures under controlled climate conditions. A second objective was to determine the minimum amount of soil moisture required for disease to occur. Finally, a third objective was to determine the efficacy of several fungicides at the temperature and moisture levels determined to be optimal for disease development. Trials were conducted using growth chambers set at four temperature regimes (day time high temperatures of 10, 15.6, 21.1 and 26.7°C). No disease development occurred at 10°C. No above-ground symptoms were seen in plants grown at 15.6°C. Both AG 2-2 IIIB and AG 2-2 IV showed significant disease development at 21.1 and 26.7°C during the two-week post inoculation evaluation period. Efficacy of several classes of fungicides was tested at 26.7°C since this was the temperature most conducive to disease development. Application of azoxystrobin and prothioconazole controlled the disease but difenoconazole was not effective at controlling Rhizoctonia root rot.