Observations: potential long-term environmental impact of tebuthiuron and its metabolites in Utah juniper trees.

Abstract

The concentrations, distribution, and longevity of tebuthiuron [N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N'-dimethylurea] and its metabolites in Utah junipers [Juniperus osteosperma (Torr.) Little] killed by tebuthiuron are not known, causing concern about potential residues and their release into the environment from decaying plants or burning wood. Utah juniper trees killed by tebuthiuron at 3 north-central Arizona locations were assayed for tebuthiuron and its metabolites by gas chromatography with flame photometric detection. Foliage, twigs, stems, and litter from recently killed trees averaged 13.3 +/- 0.4, 0.4 +/- 0.1, 0.4 +/- 0.1, and 4.0 +/- 6.6 mg/kg of tebuthiuron plus its metabolites, respectively. Dead stems averaged 0.5 +/- 0.4 mg/kg in sapwood, 0.1 +/- 0.1 mg/kg in heartwood, and 0.4 +/- 0.7 mg/kg in bark, 3 to 9 years after application. Root bark averaged 1.1 +/- 1.9 mg/kg, and root wood averaged 0.5 +/- 1.4 mg/kg. Although long lived, these small tebuthiuron residues should have little potential environmental harm if treated Utah juniper wood is used as firewood or fence posts.