Alternaria Leaf-spot Diseases

Alternaria species are associated with several leaf-spot diseases of plants. Alternaric acid (8.10), produced by A. solani, which is the cause of early blight on potatoes and tomatoes, has a marked phytotoxic activity and may be responsible for many of the symptoms of the plant disease caused by the fungus. It also shows a specific anti-fungal activity. The branched chain structure is biosynthesized from nine acetate units and three Ci units derived from formate. The solanopyrones are another group of phytotoxic metabolites of A. solani. Solanopyrone A (8.11) induced necrotic lesions on the leaves of potatoes typical of this fungal infection. The structures of the solanopyrones were established by 

Another widespread species, A. tenuis, flourishes as a saprophyte on dead or weakened plants. This fungus can cause problems in paper manufacture because of its ability to discolour wood pulp. Examination of the mycelium of a strain of 

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Alternaria has been knovm for centuries to cause various plant diseases such as early blight of potato and various leaf spots and fruit rot. Species of this fungus are widely distributed in soil and on aerial plant parts. Because Alternaria requires high moisture levels (28-34%) for growth, infection of seeds occurs when the seed moisture is high, either in early stages of development or after wetting of crops from rain. 

Fruit with spots flesh may rot. Causes Angular leaf spot Alternaria blight black rot scab other fungal or bacterial diseases. See "Leaves with spots, blotches, or brown areas on page 85 for controls. 

Dark brown spots with concentric rings, usually appearing on older leaves first, are caused by Alternaria leaf blight. As the disease progresses, leaves curl down and eventually drop off. Fruit infected with this disease has brown, concentrically ringed, sunken spots. Prevent problems by planting resistant culti-vars such as Earligold , Pulsar , and Saticoy . 

Leaves with spots, blotches, or brown areas. Causes Powdery mildew angular leaf spot scab Alternaria leaf blight other fungal and bacterial diseases. Various diseases attack squash. Reduce problems by keeping foliage dry when watering and by not touching plants when wet. Spray infected plants with a dilute solution of copper spray to reduce the spread of the disease. 

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