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Full-Text Articles in Life Sciences
Assessing Multiple-Herbicide Resistance In A 2,4-D Resistant Waterhemp (Amaranthus Tuberculatus) Biotype From Nebraska – Student Research, Roberto Crespo
Assessing Multiple-Herbicide Resistance In A 2,4-D Resistant Waterhemp (Amaranthus Tuberculatus) Biotype From Nebraska – Student Research, Roberto Crespo
Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research
A waterhemp biotype was recently reported resistant to 2,4-D in Nebraska. In addition to the repeated use of 2,4-D, atrazine and imazathapyr were reported to be frequently used to control broadleaf weeds. Greenhouse experiments were conducted to confirm 2,4-D resistance and test for resistance to growth regulator herbicides and other herbicide modes-of-action (MoA). A single dose-response experiment showed reduced sensitivity in all three waterhemp biotypes to atrazine, imazethapyr and lactofen; therefore, they were generally considered resistant to those three herbicide MoA. None of the biotypes contained the Ser264 target-site mutation. Since the ametryn dose-response experiment resulted in all susceptible biotypes, …
Herbicide-Resistant Risk Assessment: Response Of Common Nebraska Weeds To Dicamba Dose, Roberto J. Crespo
Herbicide-Resistant Risk Assessment: Response Of Common Nebraska Weeds To Dicamba Dose, Roberto J. Crespo
Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research
Dicamba-resistant soybeans are being developed to provide an additional herbicide mechanism of action that can be used in soybean, and to provide a tool to help manage or mitigate the evolution of other herbicide-resistant weed populations. The objectives of this thesis were to assess the risk of common Nebraska weeds developing resistance to dicamba, quantify baseline dose-response to dicamba of high-risk weed species, and survey the variability in dicamba dose-response among populations of those species. Twenty-five weed scientists were asked to estimate the risk likelihood of ten weed species evolving resistance to dicamba following the commercialization of dicamba-resistant soybean. Palmer …
Weed Control In Maize (Zea Mays L.) With Effective Minimum Rates Of Foramsulfuron, Kami̇l Kir, M. Nedi̇m Doğan
Weed Control In Maize (Zea Mays L.) With Effective Minimum Rates Of Foramsulfuron, Kami̇l Kir, M. Nedi̇m Doğan
Turkish Journal of Agriculture and Forestry
Dose-response experiments were conducted under controlled conditions to determine the effective minimum rates (ED_{90}) of foramsulfuron for 11 weed species that occur in maize growing areas in Turkey. Annual weeds were collected from maize fields in the cotyledon stage and transferred to pots containing a mixture of soil-turf (1:1 ratio). Perennial weeds were grown from rhizome pieces collected from infested fields. Weeds were then treated with different rates of foramsulfuron to determine the effective minimum rate (ED_{90}) for each weed species via dose-response experiments. Results showed that ED_{90} rates were lower than the recommended herbicide rate for most weed species. …
Dose-Response Modeling With Marginal Information On A Missing Categorical Covariate, John R. Stevens, David I. Schlipalius
Dose-Response Modeling With Marginal Information On A Missing Categorical Covariate, John R. Stevens, David I. Schlipalius
Conference on Applied Statistics in Agriculture
When the relationship between a dosage-type variable and a binary outcome depends on a categorical variable, a common analysis would employ a dose-response model with the categorical variable as a covariate. When the level of the categorical variable is not known for all subjects, however, the standard dose-response model alone cannot provide useful inference. We present an EM-based approach to account for the missing covariate in a dose-response model setting when additional knowledge about the marginal distribution of the covariate is available. This approach is motivated by a study of the beetle Rhyzopertha dominica, a pest of stored grain in …
The Effect Of Design And Dose Level Choice On Estimatlng The Optimal Dose In A Quantitative Dose-Response Experiment, Henry R. Rolka, George A. Milliken, James R. Schwenke, Marta Remmenga
The Effect Of Design And Dose Level Choice On Estimatlng The Optimal Dose In A Quantitative Dose-Response Experiment, Henry R. Rolka, George A. Milliken, James R. Schwenke, Marta Remmenga
Conference on Applied Statistics in Agriculture
D-optimality is a commonly used criterion to evaluate a design with respect to parameter estimation. The variance of the optimal dose estimate is another criterion for evaluating a design. The quantitative dose-response experiment involves fitting a model to data and estimating an optimal dose. Two techniques for estimating an optimal dose and three models are used to compare the variances of optimal dose estimates over nine equally spaced balanced designs and five fixed unequally spaced six-point designs. The results show that a design which is more D-optimal than another design does not necessarily produce optimal dose estimates with less variance.