Alternaria Leaf Spot
(click image to enlarge) Symptoms:
• Occurs first on older plants and leaves before spreading to younger plants and more immature plant parts
• Circular to irregular lesions (usually 2-10 mm diameter)
• Gray to dark brown to almost black middle and reddish margin
• Can be surrounded by a chlorotic area
Epidemiology:
• Cool temperatures (45-50° F)
• Favored by humid conditions
• Occurs on older leaves already weakened by senescence, poor nutritional status, or in combination with other pathogens
Control:
• Control overhead irrigation to minimize leaf wetness
• Irrigation management to avoid leaf wetness
• Increase air circulation by reducing stand