Investigation on the Efficacy of the Fungicide potassium phosphate (WSL 53%) against Downy Mildew on Greenhouse Cucumber, Pseudoperonospora cubensis Rostovzev

Downy mildew caused by Pseudoperonosprora cubensis is one of the most important foliar diseases of greenhouse cultivated cucumber which causes significant economic damages in Iran annually. For theassessment of the effect of potassium phosphate (Fosphite ® WSL 53%) on the control of the disease, two areas (Yazd and Varamin) with precedent infection were selected and experiment was performed in a completely randomized block design with 5 treatments and four replications during 2012. Treatments included Fosphite at the rates of 3, 4 and 5 ml/l, famoxadone cymoxanil (Equation ® pro 52.5% WDG) at the rate of 0.3 g/l and control without spraying. Spraying was carried out twice immediately after the appearance of the disease symptoms within 7-10 days. The disease severity was assessed by measurement of disease caused spots on the surface of leaves and sporangium formation 7 days after the second spraying. Data collected were analyzed by SAS software and Duncan's multiple range tests for mean comparison. Results indicate that fungicide application caused significant decrease in the disease severity compared with the control treatment. There is a significant difference between Fosphite 5 ml/l and Equation pro treatment but no significant differences are observed among 3, 4 and 5 ml/l treatments (P£0.05). Minimum disease severity occurred in Fosphite 3, 4 and 5 ml/l followed by Equation pro 0.3 g/l application in the control of downy mildew.