How to prevent early blight in tomatoes

Humidity and excess moisture create the ideal conditions for the development of this fungal disease. It usually starts in patches on the land and thereafter spreads throughout the crop

- Bill Kerr

Early blight (Alternaria solani) is a very common fungal disease of tomatoes and potatoes, and can infect a number of other crops as well.

A. solani is often referred to as ‘target spot’ because the infection lesion resembles the concentric-circle pattern of a target. Each lesion is about 1cm in diameter and all parts of the plant are vulnerable. Lesions on the fruit are more likely to begin near the stem end.

A. solani is a ‘necrotrophic pathogen’: it kills the host tissue using enzymes that eat into the cell wall, and feeds on the dead plant cells.

The disease can hamper production in rainy, humid regions. It is rarely a problem in crops under plastic, but it can cause great damage to seedlings grown under shade netting and in humid conditions. The problem is that seedlings have to be irrigated frequently, and when dew and humidity are added, conditions are ideal for