Forest Pests: Insects, Diseases & Other Damage Agents

Butt Rots

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. - Decay of the butt log in living trees is the most serious cause of cull loss for logging because it affects the highest valued log and weakens the tree. The incidence of butt rot in green ash is less than the 40-percent average for other southern hardwoods. The extent of decay in the stem increases with wound size and age.

Identifying the Diseases. - Hollows, abnormal swellings, butt bulge, old basal wounds, or fruiting bodies indicate butt rot. Decayed wood may be soft or brittle and brown to white. The decay column may extend vertically for several meters. Affected trunks are weakened and subject to breakage.

Identifying the Fungi. - Numerous fungi cause butt rot in ashes. The most common are Ganoderma lucidum (Curtis:Fr.) P. Karst., Laetiporus sulphureus (Bull.: Fr.) Murrill, Lentinus tigrinus (Bull.: Fr. ) Fr., Phellinus igniarius (L.: Fr.) Quel., Pleurotus ostreatus (Jacq.: Fr.) P. Kumm., Postia tephroleuca (Fr.: Fr.) Julich, Rigidoporus lineatus (Pres.) Ryvarden, and R. ulmarius (Sowerby.:Fr.) Imazeki in Ito. Fruiting bodies form less frequently on ashes in the South than in northern regions, usually requiring isolation from the wood for identification.

Biology. - Exposed wounds are sites of entry of decay fungi. Spores from fruiting bodies are wind disseminated to wounds where they germinate, producing hyphae that penetrate the tree. The rate of decay varies with the fungus, wound size, host vigor, and environmental conditions.

Control. - Wound prevention is essential because most infections occur through injuries including mechanical wounds, fire scars, and frost cracks extending into the wood. Tree should be harvested before pathological rotation age to minimize degrade. Severely decayed trees should be cut and removed.

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