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Quantitation and impact of particle drift from auxin-like herbicides
xiii, 133 leaves : illustrations ; 28 cm.
These studies were conducted at the Texas A&M Field Laboratory, the Texas A&M University campus, and at the campus of New Mexico State in Las Cruces, NM. First, the effects of quinclorac on cotton (Gossypium hirsutum L.) and tomato (Lycopersicon esculentum var pyriforme 'Roma') were evaluated to create an injury-evaluation procedure that could be used to quantify quinclorac drift rates based on plant injury. Next, spray droplet size spectra produced by quinclorac and the liquid, dry, and emulsion formulations of 2,4-D during application with various nozzle sizes were evaluated using a Malvern laser spectrometer. Quinclorac and 2,4-D formulations were also sprayed through different nozzles in a drift chamber to assess spray deposition at different wind speeds. Finally, the effects of reduced rates of 2,4-D on cotton growth, development, and yield were observed. These data were used in conjunction with previous research to predict yield loss from early-season drift injury. Evaluation scales for quinclorac injury on cotton and tomato were successfully constructed from previous scales. This suggests that such scales can be used with different species and herbicides, but changes may be necessary for some auxin-like herbicides or plant species. Data from the Malvern laser spectrometer suggested that formulations of 2,4-D affected droplet size, particularly when the SS8001 flat-fan nozzle was used. Quinclorac had little influence on droplet sizes when compared to water alone. Drift-chamber studies revealed that more liquid-formulated 2,4-D than emulsion was deposited downwind from the spray nozzle under 15 km/h wind conditions. Finally, 2,4-D applied to field cotton had little influence on cotton nodes and boll weights, but decreased the number of reproductive bolls. Strong correlations were recorded for cotton injury and yield loss, particularly during 2002 and 2003 (R² = 0.82 and 0.80, respectively). These studies are valuable because they provide information regarding quantifying auxin-like herbicide injury on different species, understanding downwind concentration and deposition of spray-droplets from different sources, and the ability to predict cotton yield loss from early-season auxin-like herbicide injury.
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Includes bibliographical references (leaves 91-97).