Abstract
Powdery mildew caused by Oidium mangiferae, is the most important disease of mango. Field surveys of five cultivars in five Governorates, revealed that incidence of infection was higher on cvs. Alphonso and Seddek than on Zebda, Hendi Besenara and Ewise. The highest disease incidence was recorded in El-Behera Governorate. The various environmentally friendly natural compounds as the biological control agents (BCAs) (Verticillium lecanii, Bacillus subtilis and Tilletiopsis minor); mineral salt (phosphate solutions, KH sub(2)PO sub(4)); antitranspirant (kaolin) and antioxidant (ascorbic acid) applied independently or in mixtures as alternatives to chemical fungicides were evaluated for their efficacy in controlling mango powdery mildew in an integrated management system. Application of BCAs, kaolin alone and/or in combination with KH sub(2)PO sub(4) in vitro to mango leaf disks before inoculation with O. mangiferae markedly decreased conidial germination and leaf infection. The largest decrease was obtained with combined treatments. In field trials during 2003 and 2004 in El-Noubaria using cvs. Alphonso and Seddek naturally infected by powdery mildew, each treatment, applied at 15 d intervals effectively controlled O. mangiferae on blossom clusters and fruit set. BCAs and kaolin treatments were superior in reducing powdery mildew infection. Blossom clusters and fruit set infection were inhibited by using a mixture of BCAs with kaolin and/or KH sub(2)PO sub(4). Other tested compounds, such as ascorbic acid as a single treatment or in combination with other compounds showed some effectiveness in reducing disease severity. Mixtures of all four natural compounds were more effective in significantly reducing powdery mildew severity and conidia counts on blossom clusters and fruit set and increasing fruit set and yields on trees of both cultivars than mixtures of two or three or single applications. BCAs, mineral salts, antitranspirant and antioxidant in combinations could be used in an integrated management system to control powdery mildew in mango trees.