Occurrence of Fungicide Resistance and Chemical Control of Cucumber Downy Mildew

Downy mildew caused by Pseudoperonospora cubensis is a destructive disease on cucumber,which mainly relies on chemical control.It could effectively decreased by implementing the integrated prevent strategy with chemical control,prediction and forecast,greenhouse ventilation,resistant varieties and biological control and preventive application of fungicides.The main fungicides consisting of contact fungicides and systemic fungicides should be applied alternatively or mixed with other fungicides of different action mechanism to delay the development of fungicide resistance.P.cubensis resistant to phenylamide fungicides occurred world widely,and strains resistant to QoI fungicides were detected in Japan.The risk of resistance to novel fungicides should be assessed,and the strategies of management of resistance to high-risk fungicides should be implemented to prolong the application years of fungicides.