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Field guide to exotic pests and diseases: Black stain root disease
Ophiostoma wageneri (Goheen & Cobb) Harrington
Cross section of black stain that develops follows annual rings
Source: D. Morrison, Canadian Forest Service
In contrast, most sap stains are wedge-like and blue.
Source: E. Allen, Canadian Forest Service
Distribution: southwestern/western USA, western Canada.
Hosts: Douglas fir, hemlock, pine, spruce, fir.
Signs: reduced leader and branch tip growth followed by leaf discolouration and crown thinning: these symptoms usually accompanied by characteristic purple-brown to black stain in main lateral roots, root collar and lower bole (where it is usually limited to long, tapered streaks). Cross-sections of infected boles show narrow bands of stain following annual rings (in contrast, most sap stains are wedge-shaped, blue). There are three varieties distinguished by both host preference and morphological characteristics.
Likely pathway: bark, lumber, wood packaging material including dunnage and insects.
Potential impact: hinders water conduction, causes vascular wilt and mortality in Douglas fir and pines.