Abstract
Methoxychlor residues, applied by helicopter to control Scolytus multislriatus (Marsham) were determined by gas-liguid chromatography from foliage, twig crotches, and soil beneath American elm, Ulmus americana L. , trees. Substantial residues were detected in twig crotches and soil beneath trees 1 year after they received mistblower sprays. Four methoxychlor formulations, one at a reduced rate and another containing a drift control chemical, were evaluated. All sprays produced measurable bark residues after 130 days, but xylene-based formulations gave longer-lasting deposits. Decagin added to 12½% sprays confined sprays within a 50-ft swath under winds of 2–4 mph yet did not deter twig-crotch deposition. Sprays applied without Dacagin drifted excessively and failed to maintain adequate swath coverage with a wind of 3 mph. The presence of foliage adversely affected twigcrotch deposits, but foliar residues declined drastically after 130 days. Water samples from a stream adjacent to treated trees indicated that most residues were in the top inch, were diluted by stream flow, and were undetectable after 24 hours. Samples taken at 2-week intervals from spring through fall showed methoxychlor present in 1 part per trillion in water and 1 part per billion in silt.
Published Version
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