Scab

Scab disease:-
1. Common scab:- 
> Common scab of potatoes is a soil-borne disease caused by the bacteria-like organism Streptomyces scabies. 
> The disease occurs throughout the potato growing regions of the world, including Africa.
2. Fungal scab:- 
> Scab diseases of trees and shrubs are caused by a group of closely related fungi, mainly of the genera Venturia, Fusicladium and Fusicladosporium. 
> They are favoured by wet weather in spring and summer.
> Apple scab is a disease caused by the fungus, Venturia inaequalis, which spreads by airborne spores and survives the winter on fallen leaves. Expect scab marks to appear on leaves from mid-spring until leaf fall in autumn.