Browsing by Author "Burch, Patrick L."

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    Effect of time from treatment to disturbance on woody plant control with triclopyr, picloram and/or 2,4-D
    Burch, Patrick L. (Virginia Polytechnic Institute and State University, 1985)
    Two studies were designed to test three herbicides and factors which influence their efficacy. In the first study four chemical combinations used for site preparation in southern pine, including triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid), trichloropicolinic acid), dichlorophenoxy)acetic acid] picloram (4-amino-3,5,6- and 2,4-D [(2,4- were screened for the most effective control of selected hardwoods. The chemical combinations were tested on Piedmont and Coastal Plain physiographic sites and were examined for the optimum amount of time for chemical activity between application and slash disposal (site disturbance). Efforts were also made to use target-plant and environmental data to predict chemical efficacy. A combination of triclopyr and picloram at 2 and 1 lb ai/ac, respectively, each gave the best overall control of hardwood brush. The amount of time required to obtain the optimum chemical control, presumably related to translocation, was found to be six to eight weeks after application to the foliage. Chestnut oak (Quercus prinus L.) control was successfully predicted on the bases of plant tissue and environmental data. In a second study the effect of temperature and time on the distribution of foliar-applied triclopyr, picloram, and 2,4-D were observed in red maple (Acer rubrum L.). Detection of the herbicides in the stems and roots using gas chromatography revealed that triclopyr was less affected by temperature differences; however, overall more herbicide reached the roots of red maple growing in a 21° C than those growing in a 29° C temperature. Triclopyr concentrations in the roots reached a peak much earlier than picloram or 2,4-D which did not peak until 42 days after application.
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    Evaluation of Screening Techniques for Woody Plant Herbicide Development
    Blair, Mitchell (Virginia Tech, 2004-02-02)
    Woody plant herbicide screening techniques were evaluated in an attempt to expedite the screening process and decrease amounts of herbicide active ingredient required. Rapid greenhouse screening of woody plant seedlings was performed in less than six months while rapid seed screening was performed in less than twenty days. A traditional field screen, requiring ten months, was performed for comparison purposes. Leaf area – biomass ratios were also examined for their influence on herbicide efficacy. Linear regressions were performed using traditional field screen data as the dependent variable and rapid screening technique data as the independent data. Rapid screens using triclopyr produced more statistically significant regressions compared to those involving imazapyr. Significant regressions were produced that could predict field response of several species using both herbicides and either rapid screening technique. This indicated that rapid screening techniques could determine herbicide efficacy and/or species spectrum of control in much less time with much less herbicide. Rapid seed screens could estimate species spectrum within five days after treatment. The rapid greenhouse screen and rapid seed screen techniques can provide woody plant herbicide developers initial efficacy and spectrum of control data in a cost- and time- effective manner. Testing showed that as woody plants mature from seedling to sapling, there is a decrease in the leaf area — total aboveground biomass ratio. The decrease in this ratio consistently decreased efficacy of both imazapyr and triclopyr at the lower active ingredient rates. Seedlings with the higher leaf area – biomass ratio had, on the average, higher efficacy response rates to herbicide treatments.
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    Methods for Rapid Screening in Woody Plant Herbicide Development
    Stanley, William Leonard (Virginia Tech, 2012-05-29)
    Methods for woody plant herbicide screening were assayed with the goal of reducing resources and time required to conduct screenings for new products. Past studies have demonstrated reductions in required screening resources (time, amount of herbicide active ingredient, and size of seedlings) can be achieved relative to field exclosure screenings. Rapid screening methods including, greenhouse seedling screening, germinal screening, and seed screening were performed using triclopyr and 8 experimental herbicides supplied by Dow AgroSciences (DAS). Five woody species were included in screenings: black locust, loblolly pine, red maple, sweetgum, and water oak. Two groups of seedlings were used in greenhouse screening: 1-year-old (1-0) and 2-year-old (2-0). Seedling age was not calendar years, but was the number of greenhouse growing seasons seedlings experienced prior to herbicide treatment. Height and mortality responses showed that 1-0 seedlings were more susceptible to herbicide injury than 2-0 seedlings. Significant linear regression models were produced correlating 1-0 seedling pre-dormancy with post dormancy responses, shortening the length of that screening to 11 weeks from treatment to results. Species and herbicide specific models were produced correlating 2-0 seedling responses to 1-0 seedling data, germinal responses to 1-0 seedling data, and seed responses to 1-0 seedling data. 1-0 seedling pre to post dormancy predictions were more successful than other models. Results suggest that rapid screening methods have some usefulness in early stages of product development to determine herbicide activity and spectrum of efficacy to guide planning of larger scale field trials, resulting in savings of time and resources.