The first signs of apple scab often are not noticed by the homeowner. These signs include twisted and puckered leaves that have black, circular scabby spots on the underside. On the upper surface the spots look velvety and have an olive green appearance. The spots may fuse and cover the whole leaf. As the disease progresses the leaves yellow and drop.
Fruit develop scabby spots that are tan and sunken.
Apple scab may be confused with cedar-apple rust, also a fungal disease. Cedar-apple rust can also cause yellowing leaves but the spots are bright yellow with a dark center of black fruiting bodies. Life Cycle Fungal spores overwinter on infected fallen leaves. Spring wind and rains carry the spores on to the young leaves. Cool, moist springs favor infection.