They symptoms of a phoma blight infection are visible only on older leaves. Affected leaves display angular, yellow to brown irregular lesions scattered over the entire lamina. As the disease progresses the lesions grow and form larger patches that later turn into dull necrotic areas with grey centers and dark margins. In the final stage, the leaves start to wither and defoliation follows. Alternative host plants include common vine (Vitis vinifera) and Kentucky grass (Poa pratensis).
Phoma blight is a new disease, but now it is gaining economic importance in mango producing areas. The symptoms are caused by the fungus Peyronellaea glomerata, formerly known as phoma glomerata, thereby the common name of the disease. It is an ubiquitous and widespread fungus that survives in soil and on various dead or living plant material (seeds, fruits, vegetables), normally without causing symptoms. It can also be found indoors on wood, cement, oil painted surfaces and paper. The fungus is usually considered to be a secondary invader of diseased tissues. However, in some hosts, and under certain environmental conditions, (moist weather and elevated temperatures), it triggers disease. Optimal growth takes place at temperatures that range from 26 °C to below 37 °C.
The disease may be kept under control by spraying copper oxychloride (0.3%) just after the appearanceof the first symptoms and subsequent sprays at 20 day intervals. Treating fruits with neem leaf extracts in combination with cool storage completely inhibits the growth of a series of pathogens on fruits during storage.
Always consider an integrated approach with preventive measures together with biological treatments if available. Spraying fungicides containing benomyl (0.2%) after initial appearance, followed by 0.3% miltox at 20 day intervals works well to contain the fungus.
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