Powdery mildew of Mangoes
Oidium mangiferae attacks the young tissue of all parts of the inflorescence, leaves and fruit. Infection shows initially as small patches of white powdery mycelium, which may later coalesce to cover large areas. On older leaves and fruit, infected tissue has a purplish-brown cast as the white growth weathers away.
Leaves: Young infected leaves may become distorted. Grey necrotic lesions appear on the upper side of the leaf, and leaves tend to curl downwards. Leaves may become brown and dry, and drop from the plant if disease is severe.
Fruits: As infected newly set fruit develop, the epidermis of the infected area cracks and corky tissue is formed. The entire fruit may become covered by mildew. It is also reported that infected fruit may become yellow and misshapen. Initial infection with O. mangiferae is promoted by warm temperatures and moderate relative humidity, although development of the disease is favoured by cool, dry conditions. The disease is spread by wind-borne conidia from other mango trees or from within an infected tree’s canopy. Oidium mangiferae survives from one season to the next as mycelium in dormant buds and as haustoria on old infected leaves.