Symptoms
Dark-brown, spreading spots on the leaves (often with a lighter margin and a whitish coating on the underside in humid conditions), brown streaks on the stems, and hard, brown rots on tomato fruit. In wet, warm summers it develops with lightning speed and can destroy a crop in a few days.
Treatment
Immediately remove infected leaves and fruit; in organic growing the options are limited — prevention is key. Under high disease pressure, copper-based or fungicidal preparations are applied preventively.
Prevention
Airy planting spacing, watering at the base (not onto the leaves), growing tomatoes under cover (a roof protects against rain), crop rotation, resistant varieties, and avoiding the proximity of potatoes.
Sources
- Atlas of vegetable diseases
