Incidence of Infection and Decay Caused by Heterobasidion annosum in Managed Noble Fir on the Warm Springs Indian Reservation, Oregon

Abstract

Abstract On the Warm Springs Indian Reservation in north-central Oregon, a 70- to 80-yr-old noble fir stand that was thinned 26 yr prior to sampling exhibited 72% incidence of H. annosum infection for wounded trees and 83% for unwounded trees. Decay volume averaged 6% in wounded trees and 1% in unwounded trees. In a similar stand that was thinned 7 yr prior to sampling, incidence of infection was 94% for wounded trees and 80% for unwounded trees. Decay volume averaged 3% in wounded trees and 0% in unwounded trees. Trunk wounds and stumps created from thinning both appeared to be effective infection courts. We developed a regression model that demonstrates increasing decay volume with increasing wound age and thinning stump diameter. Only the S-type intersterility group H. annosum was detected in our isolates using isozyme analyses. Vegetative compatibility (VC) tests in one stand revealed an average of 2.7 VC groups/tree. Multiple VC groups in individual trees suggest that wound infection by H. annosum spores is significant in managed noble fir. Our results support the common recommendations to treat stumps with boron-containing products and avoid trunk wounding during harvest to minimize subsequent spore infections by H. annosum. West. J. Appl. For. 16(3):106–113