Blue-stain Fungi Associated with Roots of Southern Pine Trees Attacked by the Southern Pine Beetle, Dendroctonus frontalis.

Forty paired plots were established from eastern Texas to Alabama to study root-infecting, blue-stain fungi in southern pine stands undergoing southern pine beetle (SPB) attack. Woody roots were sampled in plots undergoing recent or current attack by the SPB. Comparisons were made between occurrence of Leptographium spp. and related fungi and data on various characteristics of natural stands and plantations studied. Three fungal species, L. terebrantis, L. procerum, and Ophiostoma ips, along with unidentified Leptographium and Graphium species, were isolated from sampled roots. L. terebrantis was isolated more frequently from SPB-attacked plots (P < 0.001) than was either L. procerum or O. ips. More blue-stain fungal species and related genera were isolated from SPB-attacked plots than from control plots (P < 0.001). This also was true for combined isolation percentages of L. terebrantis, L. procerum, and O. ips (P = 0.03). Presence of blue-stain fungi also was associated with higher stand basal area in the control plots (P = 0.045). Isolation frequencies of O. ips and L. procerum, along with the combination of these fungal species with L. terebrantis, were logistically related to increasing stand basal area in the control plots (P = 0.02, 0.02, and 0.01, respectively). No logistic relationship was found for frequency of any of the three blue-stain species with respect to basal area in SPB-attacked plots. These results suggest blue stain fungi are important in the dynamics of susceptibility of southern pines to SPB attack.