Laminated Root Rot

Phellinus weirii (Murr.) Gilb.

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 and grand fir are most susceptible. Western hemlock and subalpine fir are less susceptible and other conifers in northern Idaho and Montana are tolerant or resistant.

Distribution. – The range of Douglas-fir or true firs in northern Idaho and northwestern Montana.

Damage. – Mortality or windthrow. Decays roots and kills cambium of roots and root collar. Mortality occurs in large disease centers and small groups. Infected trees are often attacked by bark beetles as well.

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Figure 66 - Cream to cinnamon-colored mycelium on the outer bark of roots with Laminated Root Rot.	Figure 67 - Brown stain is sometimes seen in the sapwood or outer heartwood of trees with Laminated Root Rot.
Identification. – Infected trees have typical root disease crown symptoms. Most diagnostic is the thin layer of cream-colored mycelium coating the outside bark of infected roots (fig. 66). Fuzzy, cinnamon-colored mycelium is often found in bark cracks with the cream-colored mycelium. Infected trees occasionally have some basal resinosus. Freshly cut stumps often have brown stains visible in patches on the surface associated with the early stages of decay (fig. 67). Decayed wood separates easily along the annual rings and is extensively pitted with small white or cinnamon-colored pockets (fig. 68)' The disease may develop as a butt rot in some trees long before the trees are finally killed. Similar damages. – Armillaria root rot also causes basal resinosus but white mycelium is present under the bark in the cambial region rather than on the exterior of roots.
	Figure 68 - Laminated Root Rot separates easily at the annual rings and is pitted with tiny holes. Cinammon brown mycelium and tiny hair-like hyphae are often found in the decay.

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.

Childs, T. W. and E. E. Nelson. 1971. Laminated root rot of Douglas-fir.  USDA For. Serv., For. Pest Leaflet 48, 7 p.

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

Nelson, E. E., N. E. Martin, and R. E. Williams. 1981. Laminated root rot of western conifers. USDA For. Serv., For. Ins. & Dis. Leaflet 159, 6 p.

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