Clean seed is imperative. Deep plough the sclerotia and remove weedy grasses from around field. Apple Scab - Venturia inaequalis Occurs wherever apples are grown. Favored by cool moist conditions particularly in the spring. It is the most important disease of apples.
Early symptoms begin young leaves or sepals as light colored irregular spots.
The disease then become velvet black and finally shiny black and almost circular in outline. The scab can affect leaves causing curling and defoliation and can affect fruit which is very serious because of zero tolerance. Severe disease results in low yield and no fruit. Fungus overwinters as perithecia in dead leaves on the ground. They actually develop in the winter and wet weather in spring rehydrates them to exude ascospores.