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QoI Resistance in Sugar Beet Powdery Mildew (Erysiphe betae) in Scandinavia

T. M. Heick, A. L. Hansen, A. F. Justesen, and L. N. Jørgensen

July 2019


Powdery mildew caused by Erysiphe betae is one of the major fungal diseases in sugar beet in Denmark and Sweden. Frequent applications of fungicides mitigate the risk of powdery mildew epidemics and, consequently, reduce yield losses conferred by the disease. So far, mixtures of quinone outside inhibitors (QoIs) and triazoles have provided good efficacy against E. betae in field trials and common farming practice. However, development of fungicide resistance is a real risk, because only a limited number of active ingredients are available for the control of powdery mildew in sugar beet, and several other active ingredients are expected to be banned following reevaluation when the most recent European Union legislation is implemented. The G143A mutation associated with QoI resistance has been previously found in the United States. In this brief, its presence in Europe is reported for the first time. The current finding strongly encourages the adoption of anti-resistance strategies that minimize the spread of QoI resistance in sugar beet powdery mildew. Those strategies should be based on integrated pest management measures, including disease monitoring, the use of resistant cultivars, and the use of biological products. A sole reliance on QoI fungicides for sugar beet powdery mildew control should be avoided.


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