Fruit and leaf spotting and russetting

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.