Stem Damages
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Blue Stain of Sapwood p.37 |
Several Ceratocystis- and Leptographium- type species.
Hosts.-- All conifers are susceptible if they have been attacked by bark beetles.
Distribution.-- Throughout the range of hosts.
Damage.-- Blue stains are weakly pathogenic fungi that are introduced into the cambium of trees by attacking beetles. The fungi often aid significantly in the killing of trees, thereby making beetle attacks more successful. The stain spreads quickly, especially via the wood rays, to the extent of the sapwood. The lumber defect is largely cosmetic although heavy staining may indicate the presence of wood decay fungi which also are carried into trees by beetles. Blue stain can occur in sapwood of roots and branches as well as the stem.
Identification-- The apparent staining is actually the color of the fungal hyphae. The staining pattern marks the location of the fungi. After inoculation by beetles, they grow out in all directions from the beetle galleries or bore holes. Blue, black, brown, green and even red-tinted stain begins in the outermost sapwood and radiates toward the heart (fig. 19). The stain often is wedge or fan-shaped in pattern. It stops abruptly at the heartwood-sapwood interface.
Similar damages.-- Atropellis canker causes distinct blue-black staining which tends to occur in crescents, following the annual rings more than radiating. A distinct canker is formed in Atropellis infections. Bark beetle gallery patterns are found under bark adjacent to blue stain. Blackstain root disease staining originates in the roots but can extend several feet upward in the stem. Like Atropellis piniphila, staining from blackstain root disease follows annual rings to form crescents of stain in cross- section.
Stem Damages
