Alternaria triticina Prasada & Prabhu

1. Symptoms: Small, chlorotic, oval- or elliptical shaped lesions appear and, as they enlarge, these lesions become irregular in shape. The chlorotic borders of the lesions may become diffuse and turn light to dark brown in color (See picture). Lesions are difficult to distinguish from those caused by spot blotch. Infection usually starts on the lower leaves, but symptoms can be found on all plant parts.
2. Development: The fungus survives as conidia on seed or as mycelia within seed. Sporulation on lower leaves provides inoculum that can be dispersed by wind, leading to secondary spread of the disease. Seed-borne inoculum often results in spike infections late in the crop cycle. High humidity or irrigation, as well as warmer temperatures (20 to 25ºC) favor infection and disease development.
3. Hosts/Distribution: Bread wheat and durum wheat, as well as several related grasses, are the primary hosts. The disease is common in the eastern and central areas of the Asian Subcontinent.
4. Importance: Alternaria leaf blight can be very severe if environmental conditions are favorable for disease development; major losses can result when susceptible cultivars are grown.