Alternaria spp.
Common fungal disease causing target-like spots on leaves of many crops. Related to early blight of tomatoes.
Dark brown to black spots with concentric rings (target pattern). Yellow halos around spots. Spots may merge. Leaf drop. Fruit lesions.
Fungal pathogens that overwinter on infected debris and seed. Many species affect different crops.
Wind-borne spores. Splashing water. Contaminated seed. Spreads rapidly in warm, humid conditions.
Warm temperatures (75-85°F). Extended leaf wetness. Alternating wet and dry periods. Stressed plants.
Use disease-free seed. Rotate crops 2-3 years. Avoid overhead irrigation. Remove crop debris. Maintain plant vigor.