DECAY OF RED OAK: EFFECTS OF ANTAGONISTIC MICROFLORA ON WOOD DISCOLORATION AND THE EFFECT OF OXYGEN ON POLYPORUS COMPACTUS IN WOOD

The effects of branch stub microflora and reduced oxygen levels on wood decay by Polyporus compactus Overh. (Pc) were examined.;The effects of oxygen (O(,2)) tensions on wood decay incited by Pc were studied in controlled atmospheres. A method is described whereby red oak wood blocks were evaluated for dry weight losses at O(,2) tensions of 21%, 4.2%, and 1.0% over a 10 wk period at 24 C. Dry weight losses in inoculated blocks declined significantly as O(,2) tensions increased. Losses in inoculated and non-inoculated blocks were significantly different at O(,2) tensions of 21% and 4.2%, but not at 1.0%. The method compared to standard methods, is useful for determining amount of decay because volatile staling by-products are removed, fresh wood can be used, and soil is not used.;Microflora that colonized red oak branch stubs made in the autumn and spring were tested for antagonism to Pc and other decay fungi common to red oak. Surfaces of wood disks (cut into quarters) from stubs were printed on oak diffusate agar. Subsequent growth of microflora occurred, and antagonistic interactions with Pc were found. Eleven of 423 isolates tested on wood disks and sawdust substrates were antagonistic to decay fungi. Selected antagonists, Pc, and Xylobus frustulatus (Pers. ex Fr.) Boidin were introduced into drill wounds on branches of red oak during the spring and autumn. Branches with wounds were removed after one growth period, and the extent of wound closure and discolored wood column lengths (DWCL) were recorded for each treatment. Wound closure was reduced by three antagonists, and seasonal differences in wound closure were found. DWCL were increased significantly by spring inoculation with antagonists or decay fungi compared to autumn inoculations. In vitro colonization and decay of discolored wood from wounds by Pc was not influenced by inoculation with antagonists or decay fungi. However, differences in colonization and decay by Pc in sapwood, heartwood, and discolored wood were found. Colonization frequencies of discolored wood and heartwood were found. Colonization frequencies of discolored wood and heartwood appeared to be influenced by time of inoculation and the depth from which wood samples were taken. Biological control of decay was not achieved; however, the techniques used in these studies to isolate microbes from wood may be useful in the study of microbial ecology of woody substrates.