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 s tudy root-infecting, blue-stain fungi in southern pine stands undergoi ng southern pine beetle (SPB) attack. Woody roots were sampled in plot s undergoing recent or current attack by the SPB. Comparisons were mad e 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 isol ated from sampled roots. L. terebrantis was isolated more frequently f rom SPB-attacked plots (P < 0.001) than was either L. procerum or O. i ps. More blue-stain fungal species and related genera were isolated fr om SPB-attacked plots than from control plots (P < 0.001). This also w as true for combined isolation percentages of L. terebrantis, L. proce rum, and O. ips (P = 0.03). Presence of blue-stain fungi also was asso ciated with higher stand basal area in the control plots (P = 0.045). Isolation frequencies of O. ips and L. procerum, along with the combin ation of these fungal species with L. terebrantis, were logistically r elated 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 ar e important in the dynamics of susceptibility of southern pines to SPB attack.