Efficacy of copper oxychloride brands in the control of cucumber downy mildew

 Downy mildew is one of the most important diseases of cucumber. The use of multi-site fungicides in disease control programs is recommended to ensure adequate crop protection and to delay the potential resistance of high-risk groups of single-site fungicides. The efficacy of 15 different copper oxychloride (WP 35%) brands of Iranian formulators with a concentration of 2 g/L, in control of cucumber downy mildew were assayed. Other treatments were two registered fungicides flopicolide + propamocarb hydrochloride SC 68.75% (Infinito) 2 ml/L and cyazofamid SC 400 (Ranman®) 0.5 ml/L with control treatment. Trials were performed in Tehran (Varamin) and Mazandaran (Amol) provinces with 16 treatments and southern Kerman province (Jiroft) with 17 treatments in a randomized complete block design with four replications. The experiments were carried out in greenhouse production systems (Varamin and Jiroft) and open field (Amol). Foliar spray began with the appearance of first symptoms of the disease and was repeated at intervals of 5 to 7 days. In Jiroft, Tehran and Mazandaran experiments, 2, 3 and 4 sprays were performed with experimental treatments, respectively. Experimental plots were evaluated at the stage of disease severity with a grade of 9 in the scoring index in control plots. Analysis of variance showed significant differences in all experiments between treatments and control. Comparison of the mean of the experiments showed that the brands of copper oxychloride had not the same effect and were divided into several statistical groups. Their efficiency was 65.9-72% in greenhouse conditions and 29-43% in open field conditions.