Controlling biological deterioration of wood with volatile chemicals. Final report

Abstract

Volatile fungicides placed in holes in pressure-treated Douglas-fir transmission poles with internal decay diffuse as vapors for about 2.4 m above and below the groundline to control decay for at least 10 y. The presence of fungitoxic vapors of chloropicrin (trichloronitromethane) in these poles suggests added years of control. Vapam (sodium N-methyldithiocarbamate) was less effective, but both of these chemicals are used nationwide. Methylisotiocyanate (MS), which appears especially promising in both laboratory wood-block screening tests and in poles 2 years after treatment, may prove outstanding as a control for internal decay of poles. Successfully formulated as a solid, MS could increase the safety and versatility of fumigant use. A comparison of devices for inspecting Douglas-fir poles for decay emphasized the importance of having well-trained inspectors who know the limitations of the tools and methods they use. A manual for the maintenance of Douglas-fir and western redcedar poles was published to aid inspectors and managers of wood pole systems. Fumigants varied in their residual protection against invasion by decay fungi with chloropicrin having the highest residual fungitoxicity. Fumigants had no adverse effect on vegetation around poles, nor on the strength properties of wood. Of the 8 decay fungi isolated from overmore » 15,600 pressure-treated Douglas-fir poles, Poria carbonica and Poria placenta were by far the most prevalent. Of the five most prevalent nondecay fungi isolated from these poles, a Scytalidium species can produce an environment unsuitable for reinvasion of the wood by decay fungi. The resistance of the Scytalidium species to chloropicrin raises the possibility of a combined chemical-biological control of internal decay.« less