Black Spot or Apple scab is caused by the fungus Venturia inaequalis. It infects leaves, shoots, buds, blossoms and fruit. It occurs almost everywhere apples are grown and is the most serious and widespread disease of this crop, especially important in regions with high rainfall and relative humidity during the growing season. The first symptoms usually appear as small spots on the underside of young leaves or as spots on either surface of older leaves. The spots (or lesions) are brown or olive-green and have an indefinite margin at first. The lesions on older leaves are more definite in outline, and become velvety-grey to sooty black. Sometimes the tissue below individual lesions becomes raised, giving such leaves a blistered, scabby appearance. The lesions merge to cover most of the leaf surface if infection is severe. Infected leaves are often twisted, distorted and stunted and tend to fall prematurely.