Symptoms

• It usually occurs on foliage during the middle of the growing season.
• The disease starts as small, yellow spots which enlarge to form concentric rings on the upper leaf surfaces.
• Muskmelons are more susceptible than other cucurbits to Alternaria blight. Often muskmelon vines will be almost completely defoliated by this disease.
• The pathoegen also may cause fruit injury.
• Alternaria cucumerina may be carried in and on seed and can also overwinter in diseased plant debris or cucurbit weeds.
• Spores produced on infected foliage are spread by wind, rain, people, tools, etc.
• Plants weakened by lack of proper fertilizer or poor soils are more likely to be attacked than young, vigorously growing plants.
• Warm, wet weather favors development of Alternaria blight.

Management

• To control Alternaria blight, plant disease-free seed in fertile, well-drained soil, practice crop rotation with unrelated crops, destroy cucurbit weeds.
• Spray the crop with Mancozeb @ 2 g /lit.