Digital Commons Network^™

Establishing And Optimization Of Tissue Culture Work With Erigeron Canadensis, Robert Petursson

Masters Theses

Glyphosate resistance among weed species has been an increasing problem in crop production over the past two decades. Glyphosate resistant Erigeron canadensis (horseweed) has been found on multiple continents and 20 U.S. states. It appears that the resistance is of non-target type, with mechanisms of action that have yet to be elucidated at the gene level. For the first portion of the study, I focused on reproducing the original indirect organogenesis protocol but discovered biotype variability can influence regeneration success. An improved indirect organogenesis method was then developed using the previously published methods that could be used across biotypes. A …

A Bioassay To Determine Poa Annua Responses To Indaziflam, Benjamin D. Pritchard

Masters Theses

Herbicide resistance within Poa annua is widespread in managed turfgrass systems. In 2020, a P. annua collection from a golf course in the southeastern United States was reported to be resistant to indaziflam as well as six other mode-of-action groups. Considering P. annua is the most troublesome weed in turfgrass, a bioassay to screen other collections with putative indaziflam resistance is needed. A dose-response experiment was conducted with ten concentrations of indaziflam (0, 250, 500, 750, 1000, 1250, 1500, 2000, 4500, and 9000 pM) in Gelrite® culture during 2021 and 2022. An herbicide-susceptible (S1) collection of P. annua, a …

Relative Soybean Response To Aminocyclopyrachlor, 2,4-D, Dicamba, And Aminopyralid, Trey I. Clark

Masters Theses

This research compared the visual symptomology of four auxin herbicides applied at three rates to simulate tank contamination on non-auxin tolerant soybeans. The herbicides examined were aminocyclopyrachlor (ACP), 2,4-D, dicamba, and aminopyralid. The standard labeled rates (SLR) used to base the application rates were 0.12 kg ae ha^-1 for ACP and aminopyralid while dicamba and 2,4-D used 1.12 kg ae ha^-1. These four herbicides exhibit similar symptoms on soybeans which is problematic when diagnosing soybean response. One goal of this project was to obtain high-quality images of the four herbicide’s effect on soybeans, with the hope of …

Modeling Emergence Of Annual Bluegrass (Poa Annua L.) In Hybrid Bermudagrass [C. Dactylon (L.) Pers. X C. Transvaalensis Burtt-Davy], Dallas Rose Taylor

Masters Theses

Annual bluegrass (Poa annua L.; ABG) is a troublesome weed of turfgrass systems. A model to predict ABG emergence patterns could aid in timing measures to control ABG. Field research was initiated in January 2019 at the East Tennessee AgResearch & Education Center (ETREC) (Knoxville, TN) to better understand environmental conditions associated with ABG emergence. Plots (1 m²) included both hybrid bermudagrass [C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, cv. ‘Tifway’, at a 1.5 cm cutting height] and bare soil. Emerged ABG inside a 1000 cm² area in the center of each plot was …

Confirming Resistance To Prodiamine And Glyphosate In A Single Annual Bluegrass (Poa Annua L.) Biotype From Tennessee, Shane Matthew Breeden

Masters Theses

Annual bluegrass (Poa annua L.; POAAN) is a cool-season weed that commonly infests warm-season turfgrasses during winter dormancy. In spring 2012, poor POAAN control (<50%) was reported on golf course roughs in Alcoa, TN (35.75 °N, -83.88 °W) following treatment with a tank mixture of prodiamine (1120 g ha^-1[hectare]) and glyphosate (840 g ae ha^-1) during bermudagrass dormancy. The objective of this research was to determine if this POAAN biotype was resistant to prodiamine and glyphosate.

Using mature plants from the field, 81 of the 100 selections were not controlled by glyphosate and prodiamine; 96 of the 100 selections were not controlled by glyphosate, while 84 were unaffected by prodiamine. Only a single plant sampled was susceptible to both herbicides. …

Potential Interaction Between Pre- And Post-Emergence Herbicides And The Efficacy Of Insecticide And Fungicide Seed Treatments In Cotton, Cory Joseph Vineyard

Masters Theses

An apparent reduction in the performance of neonicotinoid seed treatments in controlling thrips, especially in cotton, has been observed, which has coincided with the increased use of both pre- and post-emergence herbicides to control glyphosate-resistant weeds. The objective of this research was to evaluate the potential interactions of both pre- and post-emergence herbicides on the efficacy of insecticide and fungicide seed treatments in cotton

Aldicarb along with imidacloprid and thiamethoxam seed treatments reduced thrips numbers compared with non-treated seed. However, thiamethoxam did not provide effective control. Some pre-emergence herbicide treatments reduced plant health. While there was evidence that thrips injury …

Aminocyclopyrachlor Efficacy For Non-Cropland Weed Control, José Javier Vargas Almodóvar

Masters Theses

The production of chemicals for crop protection purposes evolved after World War II with the commercialization of the auxin herbicides 2,4-D and MCPA. Their utility and effectiveness created an interest for North American and European companies to develop and research thousands of agrochemicals available today.

Recently discovered and introduced to the market by DuPont Crop Protection, aminocyclopyrachlor is the first broad spectrum synthetic auxin herbicide in this chemical class, and is structurally similar to the auxin herbicides: aminopyralid, clopyralid and picloram. Aminocyclopyrachlor has activity on broadleaf weed species with limited activity on monocot species. Aminocyclopyrachlor is absorbed via plant roots …