Verticillium wilt
A soil-borne fungal disease that blocks the water-conducting tissue, causing leaves to yellow and wilt, often on one side of the plant.
Also known as: Verticillium
Symptoms and identification
Lower leaves yellow and wilt, often starting on one side or one branch, with V-shaped yellow areas on tomato leaves. Cutting the stem shows brown streaks in the wood. Trees such as maples and olives may lose whole branches.
Causes
The fungus survives in soil for many years and enters through roots. It is favoured by cool, moist soil followed by warm weather.
Organic treatment
Remove and destroy badly affected plants. Prune out dead branches on trees and keep them watered and fed. Soil solarisation reduces the fungus in beds.
Prevention
Grow resistant varieties (marked V on tomato labels), rotate crops, and avoid planting susceptible plants where the disease has occurred.
Chemical treatment (use with care)
There is no effective chemical cure in gardens.