BIOSTIMULANT PRODUCTS FOR THE CONTROL OF POWDERY MILDEW ON ZUCCHINI

Powdery mildew, caused by Podosphaera xanthii, is the most common disease of cucurbits and is mainly controlled by chemical fungicides. However, the most recent and effective fungicides can induce resistance in pathogen population thus losing their efficacy. Therefore, the knowledge of the effects of alternative substances against the disease is useful in order to manage an integrated disease control. The following biostimulant products were tested on zucchini cv. Consul in greenhouse: Alga Special, Algaton, Algavital, Biosaral and Chelal Alga (based on seaweed extracts, Ascophyllum nodosum mainly), Bioactive (blood meal), Fungiplan and Oidium (fertilizers), Vitaflow (borlande), Ekoprop (Trichoderma spp. Glomus sp., Pseudomonas sp.) and Salavida (P. trivialis). Quite all products were applied on leaves and in soil, in separate experiments, while Ekoprop and Salavida in soil only. The pathogen was artificially inoculated (50,000 conidia/ml) on cotiledonar leaves two days after each treatment and disease symptoms were evaluated as percentage of infected leaf area, eight days from inoculation. Among leaf treatments, the best effect against the disease was obtained with Bioactive, Biosaral, Fungiplan and Vitaflow which gave a control from 31% to 37% with respect to the inoculated control. Overall the products were more active when applied by soil irrigation; among them, Biosaral, Alga Special and Chelal Alga reduced the disease by more than 50% and Ekoprop and Salavida by 80%. We conclude that plenty of the tested products may be considered as partners of chemicals in integrated control systems. Further greenhouse and field experiments are in progress.