Mg. Cruickshank et al., INCIDENCE OF ARMILLARIA SPECIES IN PRECOMMERCIAL THINNING STUMPS AND SPREAD OF ARMILLARIA-OSTOYAE TO ADJACENT DOUGLAS-FIR TREES, Canadian journal of forest research, 27(4), 1997, pp. 481-490
The frequency of Armillaria species in precommercial thinning stumps a
nd the interaction at root contacts between Douglas-fir (Psendotsuga m
enziesii (Mirb.) France) crop trees and stumps colonized by Armillaria
ostoyae (Romagn.) Herink were investigated at sites in four biogeocli
matic zones along a transect from the coast through the southern inter
ior of British Columbia. The frequency of stumps colonized by A. ostoy
ae and Armillaria sinapina Berube & Dessureault varied among lower, mi
d, and upper slope transects. On coastal sites, A. sinapina dominated
fresh hygrotopes and A. ostoyae dominated slightly dry hygrotopes, and
the frequency of both fungi was low on moist hygrotopes. On interior
sites, A. ostoyae was found over all hygrotopes, but with lower freque
ncy on the driest sites. The distribution of the two Armillaria specie
s on sites is apparently determined by anoxia associated with periodic
soil saturation, by drying of the soil, and by host response limiting
spread of pathogenic species, At root contacts between colonized stum
p roots and crop tree roots, transfer and infection by A. ostoyae occu
rred more frequently in moist biogeoclimatic zones than dry ones. Lesi
on size on crop tree roots was related to inoculum volume at some site
s and to stump root diameter at others. The percentage of lesions on r
oots at which crop trees farmed callus was associated with tree bole v
olume. The results indicate that there will be crop tree mortality fol
lowing precommercial thinning, especially where inoculum levels are hi
gh in the Interior Cedar-Hemlock and Interior Douglas-fir biogeoclimat
ic zones.