Powdery mildew (Leveillula taurica)
Symptoms appear as yellowish spots on the leaves. On the lower surface of affected leaves the spots are covered by a whitish growth constituting spores of the fungus. Affected leaves eventually dry up but do not fall off. The fungus is endophytic (grows within the leaf contrary to other powdery mildew fungi that are grow on surface of the leaves). It has a wide host range. It is not seed-borne but it survives on herbaceous weeds and other susceptible hosts. Temperatures slightly above 20 degC, dry conditions and fairly high relative humidity favour disease infection. However, fungal dispersal takes place mainly at low humidity.
- Use of resistant varieties, if available.
- Use overhead irrigation.
- Use sulphur sprays.