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Borax: Its Toxicity to Fomes annosus in Wood and its Diffusion, Persistence, and Concentration in Treated Stumps of Southern Pines. J. W. Koenigs, Principal Plant Pathologist, Southeastern Forest Experiment Station, USDA Forest Service, Forestry Sciences Laboratory, Research Triangle Park, North Carolina 27709; Phytopathology 61:269-274. Accepted for publication 10 September 1970. DOI: 10.1094/Phyto-61-269.

Growth of Fomes annosus was prevented in wood of loblolly pine by 660 ppm of total anhydrous borax in oven-dry wood (300 ppm in wet wood). In freshly cut stumps, this concentration of borax diffused to its maximum depth more rapidly than the fungus would germinate and grow from the point of application. Borax diffused at toxic concentrations to a depth of only 2.1-5.1 cm. Thus, logging scars at the base of stumps should be treated with borax to afford complete protection. The chemical persisted uniformly at a toxic concentration 5.1 cm below the stump surface for at least 8 weeks. Twenty-six months after treatment, borax had leached to subtoxic levels throughout the upper 0.3 cm of stumps, but at a depth of 1.2 cm, 38% of the cross-sectional area still contained toxic amounts. Borax raised the pH of wood from 4.8 to 7.6-8.1; this effect is not important in preventing colonization of the stump surface by F. annosus since a supratoxic concentration of borax was required to achieve it.