On cherry and plum the gum oozing from Cytospora leucostoma infection is more crystalline. In Colorado at least one-third of the producing peach trees have cankers on trunks, scaffold limbs, or in the fruiting wood. Within a couple of seasons these infections can cause dieback and eventual death of the tree. In highly susceptible peach varieties, the canker can weaken an entire orchard in three or four years. Apples also can become infected, but without the gumming associated with the disease on stone fruit.
Recent studies show that canker development can take place throughout the year.
However, the greatest canker growth occurs in the spring as temperatures warm up and before tree activity resumes. The fungus causing this problem is known by all of the names provided above. Leucostoma persoonii Hohn. Valsa leucostoma was used in the past as a synonym of Leucostoma persoonii but is no longer considered correct. The confusion stems from 1917 when von Hohnel split the genus Valsa into the two genera Valsa and Leucostoma .