Perenniporia Stem Rot
Perenniporia fraxinophila (Peck) Ryvarden
[Syn. Fomes fraxinophilus (Peck) Sacc.]
Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, R.L.; Thompson, L.C.; McCracken, F.I. 1993. Ash pests: A guide to major insects, diseases, air pollution injury and chemical injury. Gen. Tech. Rep. SO-96. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 45 p.
Importance. - Perenniporia stem rot causes a white, mottled heartrot of all major species of ashes from Tennessee westward to Arizona and northward into Canada. It is a major contributor to the decay of green ash stems in the shelterbelts of the Great Plains.
Identifying the Disease. - Heartwood decayed by this fungus is straw yellow to yellowish white, soft, and crumbly. Trees in advanced stages of decay are susceptible to breakage and windthrow, especially in the shelterbelts of the Great Plains.
Identifying the Fungus. - Perennial, bracket-shaped basidiocarps usually form on the bole and major branches near branch stubs. Basidiocarps are initially dirty white on the upper surface, but darken and become cracked with age. The lower surface is white and porous. They may grow to over 25 cm in diameter.
Biology. - Basidiospores released from basidiocarps during wet periods germinate to produce hyphae that infect trees mainly through branch stubs and grow down the branch trace to the heartwood to initiate decay. Fruiting bodies may develop and accumulate on the bole for many years as the decay column expands. The incidence of basidiocarps on ashes is often directly proportional to trunk diameter.
Control. - Infection can be reduced by preventing wounds and trimming branch stubs to allow callus to cover the wounds, particularly in older, less vigorous landscape trees. Precautions should be taken to protect healthy crop trees during thinning and harvesting operations in forest stands.
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