Fruit and leaf spotting and russetting : New England Tree Fruit Management Guide : UMass Amherst

Russetting spotting on fruit and foliage of a gage plum.

Russetting on prune-type plums

Possible causes are phytoxic fungicides, particularly Captan. Russetted spots appear in early summer and can be more prevalent on the sun-exposed side of the fruit. Captan should not be applied from shuck split through early July, and chlorothalonil from shuck split through harvest.