Blight

Blight is a fungal disease commonly affecting potato and tomato plants. A common telltale sign of blight is brown spots with concentric rings that can lead to defoliation and damage to fruit. Another sign is black or brown stem lesions and sunken brown spots on fruit.

For treatment remove all affected foliage to prevent spores from spreading to other plants. If possible, avoid overhead watering to prevent standing water on leaves, and check that the soil is not contaminated with mycelium. Finally, treat the plant with a fungicide concentrate mixed with water.