Alternaria Blight
Alternaria spp. (A. dauci, A. brassicicola, A. alternata, A. solani)
Fungus
Leaves
Stems
Fruit
Overview
A fungal disease causing dark brown to black lesions with concentric rings on leaves, stems, and fruit of various crops. Particularly damaging to carrots, brassicas, and solanaceous crops.
Symptoms
Dark brown to black spots with concentric rings (target spots) on leaves. Lesions may girdle stems. Damping off in seedlings. Dark, sunken lesions on fruit. Premature defoliation and reduced yield.
Environmental Conditions
Humid
Prevention
Use disease-free seed. Rotate crops on a 3-year cycle. Ensure good air circulation. Remove crop debris. Hot water seed treatment.
Management
Apply copper or chlorothalonil fungicides. Remove infected plant parts. Improve drainage and air circulation. Avoid overhead irrigation.