An investigation into the effectiveness of extracts of three plants for the control of cucumber powdery mildew

Using plant natural compounds for the control of diseases has been subject to a host of research، due to their advantages on synthetic compounds. In this research، the effectiveness of leaf tissues extracts of radish، cabbage and celery was evaluated for preventive and curative control of cucumber powdery mildew in greenhouse tests. The acetonic، methanolic and water extracts of these plants at concentrations of 1 and 5% (w/v) were sprayed on the plants at either 1 day before or 1 day after the plant inoculation with spore suspension of pathogen. Then، disease severity was evaluated based on the number of disease spots per leaf 10 days after inoculation. The effectiveness of the extracts was also compared with Penconazole fungicide and Reynoutria sachalinensis (Rs) extracts، two commercial compounds for the control of disease. Results showed that the tested extracts reduced the disease severity on the cucumber leaves when applied at 1 day interval before or after the pathogen inoculation، but in varying degrees. In comparison with other extracts، acetonic extract of celery at the concentration of 5% (w/v) had the most preventive effect against disease، and its preventive efficacy was the same as Rs extract. Acetonic extract of celery and methanolic extract of cabbage at the concentration of 5% had the highest curative effect against disease، respectively، and their efficacy for disease cure was comparable to that of Penconazole. Our results showed that all extracts have potential for controlling cucumber powdery mildew.