Single and mixed inoculations of ponderosa pine with fungal associates of Dendroctonus spp

Small ponderosa pines (10-25 cm in diameter at breast height) were inoculated with single and paired isolates of Leptographium terebrantis and Ceratocystis ips from Dendroctonus valens and single and paired isolates of C. minor and C. nigrocarpa from D. brevicomis. The radial depth of sapwood occlusion at sites of inoculation was assayed by standing 25- to 35-cm-long stem sections in solutions of Fast Green dye and observing patterns of nonconduction after 24 hr. The average radial depths of radial sapwood occlusion resulting from inoculation with either isolate of L. terebrantis alone were significantly greater than depths obtained when these isolates were coinoculated with isolates of C. ips. The amount of sapwood occlusion varied within and among treatments and, in the case of fungi carried by D. valens, was reduced in trees inoculated with isolates of L. terebrantis and C. ips together. Sapwood occlusion preceded blue staining and provided an early assay of sapwood colonization and dysfunction