کدوییان

Damping-off disease caused by Phytophthora melonis is the most common disease of cucumber seedlings Cucumis sativus L.. To study the efficacy of 8-hydroxy quinoline sulfate (Beltanol®) in control of cucumber damping-off disease, glasshouse experiments were carried out with six treatments at research stations in Tehran, Alborz, and Semnan provinces in Iran. Treatments included 0.3, 0.4, and 0.5 ml∙l-1 of Beltanol as the experimental fungicide, metalaxyl+mancozeb (Rosalaxyl® WP 72%; FRAC code 3 + M03) at 2 g∙l-1 as the standard fungicide along with inoculated and untreated and non-inoculated (healthy) controls. Cucumbers were cultivated from seed in trays, and treatments were applied twice. Once after seed sowing and second time at the 2-leaf stage. Disease incidence was recorded at the 4-leaf stage. Beltanol at 0.3 ml∙l-1 had the least effect among fungicides, with nearly 50% of treated plants showing signs of disease. Application of Beltanol at 0.4 and 0.5 ml∙l-1 decreased disease incidence by 59.55 and 64.47% compared to the inoculated control, respectively. Rosalaxyl® performed better than Beltanol and reduced disease by 83.55%. However, to provide alternatives for proper fungicide rotations, Beltanol at the rate of 0.4 ml∙l-1 may manage damping-off disease in cucumber.

The use of a multi-site fungicide in cucumber downy mildew protection programs are recommended to ensure crops are adequately protected and delay a possible resistance development of high-risk groups of single-site fungicides. Commercially available dicopper chloride trihydroxide (also known as copper oxychloride) based fungicides (M FRAC Group) were assessed for their efficacy against cucumber downy mildew in comparison to a commonly used phosphonate (Fosphite® 53 WSL, P7 FRAC Group) and untreated control. Foliar treatments started with the onset of disease symptoms and were repeated weekly. Disease severity was calculated twice during crop development. Significant differences between the treatments were detected. Fosphite® was the most effective among other treatments, with a reduction in disease severity of 82.6%. Among the copper oxychloride-based fungicides, statistically significant differences were detected. Copertox® and Oksavit® were significantly effective than the other products at the first disease assessment, and Copertox® being the most efficient fungicide at the second disease assessment. Significant differences were also detected among control plots. The efficiency of commercial brands of copper oxychloride in control of cucumber downy mildew was 53-67%. This efficiency is acceptable in normal disease conditions but not desirable in an epidemic situation. If the conditions are favorable for a severe disease epidemic, it is necessary to combine them with more effective fungicides such as Fosphite.

In this study, 41 isolates of the genus Trichoderma including six species of Trichoderma arundinaceum, T. asperellum, T. atroviride, T. harzianum, T. longibrachiatum and T. virens were isolated from soils of cucumber fields in Kermanshah province, and their efficacy to control Phytophthora drechsleri, the causal agent of cucumber damping off, was investigated in laboratory and greenhouse conditions. In direct confrontation between Trichoderma isolates and the pathogen, all isolates were able to promote, establish, and sporulate on pathogen mycelia. Through dual culture test, the most inhibitory effect on pathogen growth (62.89%) was recorded for T. harzianum (isolate T1). Volatile compounds of T. harzianum (isolate T7) had the greatest mycelial growth inhibition (46.59%) compared with control. Complete growth inhibition of the pathogen was recorded when the growth medium was supplemented with culture filtrate of Trichoderma isolates at concentration of 15% and 30%. At the concentrations of 15% and 30%, 18 isolates and 22 isolates completely inhibited the pathogen expansion respectively. In the greenhouse, the results of data analysis on the survival percent of plants in various treatments showed significant differences between the isolates of Trichoderma in terms of preventing cucumber damping off. In conclusion, T. asperellum showed the highest ability to control Phytophthora damping off and promoting cucumber growth which is a new record for Iran. This species can be an appropriate choice for biological control of the disease caused by P. drechsleri in cucumber.