Exploratory Tests to Increase Preservative Penetration in Spruce and Aspen By Mold Infection

Exploratory tests were made of the effect of mold infection on absorption and penetration of an oil preservative in black spruce and aspen of fence-post size. Freshly cut black spruce and aspen trees were sawed into pieces of l-l/3 to 2 feet (40 to 60 centimeters) in length, and 2-l/2 to 5 inches (6 to 12 centimeters) in diameter. Immediately after sawing, the bark was completely removed and the pieces dipped for 20 seconds in one of several chemical solutions containing fluoride or arsenic. Solutions containing sodium pentachlorophenate were used to prevent mold infection and thereby to serve as controls in assaying the importance of infection. In tests employing both soaking and pressure treatments, absorption and penetration of an oil preservative solution usually were 3 to 5 times greater in heavily mold-infected than in mold-free or slightly mold-infected wood. These exploratory tests indicated clearly that heavy mold infection can be induced on spruce and aspen and that such infection increases the permeability of the wood. However, the data were too meager to determine whether the fluorine- or arsenic-containing solution was more effective in encouraging mold infection. On aspen at least, the arsenic acid solution led to the development of a wider variety of molds and the greatest absorption of oil preservative. The fluorine-containing solutions especially favored heavy growth of the common green Trichoderma mold. The increased permeability of wood with profuse Trichoderma infection was reportedly associated with a partial or complete breakdown of the ray and other parenchyma cells.

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