Apple scab

Apple scab

Venturia inaequalis (Cooke) G. Wint.


On leaves, young lesions are velvety brown to olive green with indistinct margins, and will often not be readily noticeable until after petal fall in commercial orchards (A). The number of lesions can vary from few to several hundred per leaf, depending on the season and varietal susceptibility. Older leaf lesions are typically raised, with a corresponding cupping on the underside of the leaf, and dark green to gray to brown in color, with distinct margins (B, C). Leaves that are heavily infected tend to curl, shrivel, and fall from the tree. On the fruit, young lesions appear similar to those on leaves (D). Although the entire surface of the fruit is susceptible to infection, lesions often cluster around the calyx end of the fruit. As lesions get older, they become brown and corky and take on a "scabby" appearance (E).

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