Pathogenicity to Sitka spruce of Ceratocystis rufipenni and Leptographium abietinum, blue-stain fungi associated with the spruce beetle
1997
Solheim, H. | Safranyik, L.
The pathogenicity of the blue-stain fungi Ceratocystis rufipenni Wingfield, Harrington & Solheim and Leptographium abietinum (Peck) Wingf., associated with the spruce beetle (Dendroctonus rufipennis (Kirby)), was evaluated after inoculation of 35 Sitka spruce (Picea sitchensis (Bong.) Carriere) trees at densities of 200, 400, and 800 inoculation points/m2 in a 60-cm band at breast height. Trees were felled 5 months after inoculation to assess fungal infection and pathogenicity. Ten trees inoculated with C. rufipenni at the two highest densities were rated as dead at the time of harvesting whereas all trees inoculated with L. abietinum were rated as surviving or survival uncertain. Inoculation with C. rufipenni produced significantly longer lesions in the phloem and killed significantly more phloem than did L. abietinum. For both fungi, the percentage of dead phloem increased with increasing inoculation density. The percentage of occluded sapwood increased with increasing inoculation density of C. rufipenni, and all sapwood was occluded at 800 inoculations/m2. Inoculation with L. abietinum resulted in approximately 25 percent occluded sapwood and the occlusion was not affected by inoculation density. Ceratocystis rufipenni may contribute considerably to overwhelm spruce trees infested by D. rufipennis.
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