Schweinitzii Root and Butt Rot

Phaeolus schweinitzii (Fr.) Pat.

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Douglas-fir is by far the most common host. All conifers are susceptible, especially to butt rot.

Distribution. – Range of hosts in Idaho and Montana.

Damage. – Decays inner wood of roots, causes root galling, and decays butt heartwood. Windthrow frequently results from uprooting or butt breakage. Douglas-fir beetles and Armillaria often attack P. schweinitzii-infected Douglas-firs.

Identification. – Trees infected with P. schweinitzii alone seldom have distinct root disease crown symptoms. Crowns of extensively infected Douglas-firs are sometimes thin and show poor shoot growth and some branch dieback. Conks are occasionally produced on the ground near infected trees or stumps. Less frequently, they develop directly on infected trees or stumps. They are annual, spongy conks with large pores on the undersurface. Caps are brown and velvety (fig. 73); undersides are green when fresh becoming brown with age. Caps are usually 5-10 inches in diameter with short stems. Large clusters often form. Small roots which are infected have dark red-brown, resinous centers (fig. 74). Decay is dry and yellow at first, becoming brown and cubically cracked in advanced stages (fig 75). Thin, resinous felts are often present in cracks of advanced decay.	Image Unavailable
	Figure 73 - Conk of Phaeolus Schweinitzii has a velvety brown or yellow-brown cap, a stem (stipe) and a pored, green to brown lower surface.
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Figure 74 - Small-diameter root with dark red resinous heart indicating Schweinitzii Root Rot.	Figure 75 - Schweinitzii Root and Butt Rot causes a brown cubical rot of the root and stem heartwood.

Similar damages. – The decay caused by Fomes pinicola is also brown and cubically cracked. However, F. pinicola decays dead trees and decays both sapwood and heartwood. Mycelium felts in F. pinicola decay are thick and not resinous, and F. pinicola conks are frequently found in association with the decay.

Link to Table 1 – Comparison of Common Heartrots in Species Other Than Western Redcedar

Link to Table 2 – Comparison of Common Root Diseases

Link to Images in Forestry Images

References.

Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv.,Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.

Bega, R. V. 1978. Diseases of Pacific Coast conifers. USDA For. Serv. Ag. Hndbk. No. 521, 206 p.

Boyce, J. S. 1961. Forest Pathology. McGraw-Hill Book Co., New York, NY. 572 p.

Hepting, G. E. 1971. Diseases of forest and shade trees of the United States. USDA For.
Serv. Ag. Hndbk. No. 386, 658 p.

Kimmey, J. W. 1964. Heartrots of western hemlock.  USDA For. Serv., For. Pest Leaflet 90, 7 p.

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