Chondostereum purpureum (Pers.:Fr.) Pouzar
Silvering of the foliage is the characteristic symptom (A). At first, silvering may be associated with only one or two major branches, but eventually the entire tree becomes silvery in appearance. When infection is severe the leaves may curl upward. On apple, symptoms are usually evident shortly after petal fall. The symptoms progress over several seasons and trees slowly decline before dying. In some instances, affected limbs may recover and produce no symptoms in following years. The heartwood of affected trees is typically stained brown. In autumn, the fruiting bodies of the fungus (basidiocarps) appear on the surface of dead or severely infected limbs or the trunk (B).
Widespread; the fungus affects many hosts.
The silvering of the foliage is a unique symptom of this disease.
Pruning cuts are susceptible to infection from spores released from basidiocarps during periods of rainy weather. The wounds are susceptible for about a week. Trees under stress are prone to attack; therefore, adequate drainage and fertilization help to reduce the incidence of disease. Infected trees should be rogued prior to the production of basidiocarps to reduce inoculum pressure. There are no practical chemical control measures to prevent infection.
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