Biological Control of Powdery Mildews

Powdery mildew fungi are important obligate parasites of plants. They produce white cover on aerial parts of host plants, which then turn to yellow. The diseased plant becomes yellow and then wilted result in reducing quality as well as quantity of products in field and vegetable crops and also fruit trees. Among all of the control measures against powdery mildew, the most common method is application of the chemical fungicides, after disease incidence. Regarding to the hazards of agrochemicals and also considering the probability of incidence of resistant races of the pathogen, the biological control is considered as a safe and useful method for controlling the disease. The fungi Ampelomyces quisqualis, Pseudozyma flocculosa and Lecanicillium longisporum; the bacterium Bacillus subtilis; the mite Tydeus lambi and twenty-spotted lady beetle Psyllobora vigintimaculata, have been used effectively against the powdery mildew of cucumber, squash, tomato, pepper, grape and rose. Some of these biological agents have been introduced to the market, commercially.