Mountain Ash Disorder: Scab
Author(s) M.F. Heimann, G.R. Stanosz, G.L. Worf.
Mountain ash scab is not always a serious problem in Wisconsin, but in wet years it can reach near-epidemic levels, affecting not just mountain ash but apple and flowering crab trees.
This fact sheet details the signs and symptoms of this disorder, as well of effective means of controlling it (2 pages; Revised in 1997).