The diffusion and toxicity of the fumigant chloropicrin injected in sugar maple and white birch tree

Abstract

Twenty sugar maple (Acersaccharum Marsh.) and 20 white birch trees (Betulapapyrifera Marsh.), all containing columns of decayed or discolored wood, were bored and injected with one of three dosages of chloropicrin or were left untreated. One year after treatment, four trees of each species were felled and dissected. The wood was then analyzed for fumigant concentration and assayed for the presence of fungi. All remaining trees were inspected yearly for adverse response to treatment. Three years after treatment, dieback and leaf discoloration were apparent in birch trees treated with moderate to high dosages of chloropicrin. No adverse response to treatment was apparent in any maple tree or in birch trees treated with low dosages of chloropicrin. In the dissected trees, chloropicrin vapors were generally detected in the interior of the trees at sites 0.5 m above and 0.5 m below the treatment site. In the higher dosage birch trees, chloropicrin was detected more frequently and in higher concentrations from outer sapwood. Control of the causal decay fungi in the trees was not ascertained in this study; however, in the birch trees, growth of opportunistic decay fungi was inhibited in sections from treated but not untreated trees.