Influence of fungicidal seed treatments and soil type on severity of root disease caused by Rhizoctonia solani AG-8 on wheat

Rhizoctonia solani anastomosis group (AG) 8 is the main cause of cereal root disease in Australia and elsewhere and there is strong interest in deploying more effective fungicide treatments than those utilized historically. Investigations compared the efficacies of a new versus the current recommended fungicide at different application rates, and the influence of soil type, on their efficacy against R. solani AG-8 attacking wheat. The potential for vastly improved control and management of root disease on wheat and other cereals caused by R. solani AG-8 from utilizing a new seed treatment fungicide, Rancona Dimension (ipconazole + metalaxyl + N-Methyl-2-pyrrolidone) was confirmed. Greatest reduction in disease severity from R. solani AG-8 followed application of seed treatment with Rancona Dimension at a high rate (640 mL/100 kg of seed) followed by the low rate (320 mL/100 kg of seed), with both rates significantly better than the currently registered treatment, Dividend® (difenoconazole + metalaxyl-M) that performed poorly in comparison and offered little disease remediation at either a high or a low rate (260 or 130 mL/100 kg of seed, respectively). Reductions in disease severity from seed treatment with Rancona Dimension were reflected in smaller reductions of dry shoot and root weights and shoot and root lengths. Rancona Dimension offers farmers significantly improved control on wheat affected by Rhizoctonia root disease than current treatment of seed with Dividend®. That Rancona Dimension® remained effective even when applied at a low rate allows a farmer to make the more cost-effective decisions in future in terms of fungicide application in dealing with particular threat levels from R. solani AG-8 in their individual situations. Rancona Dimension was efficacious on plants growing in sand or a loam soil, indicating that this fungicide will be commercially effective across different soil types.