Early blight

Alternaria solani, Alternaria alternata

Symptoms

• Dark, sunken spots
• Characteristic wrinkled raised edge
• Infection is usually superficial with hard and dry tuber tissue
• Infection by harvesting of immature tubers in an infected crop

Infection and spread

• Survives as spores in the soil and on infested plant debris (as mycelium)
• Host plants of the nightshade family: black nightshade, woody nightshade, tomato, etc.
• Spread by wind and/or splashing water
• Infection occurs at temperatures between 10 - 35°C, with alternating dry and wet periods
• Lesions usually originate early in the season and grow later on into visible spots
• Strong lesion growth and sporulation around the flowering period
• A. alternata is a secondary parasite (infects weakened plants)