Browsing by Subject "herbicide"
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Item Evaluation of auxinic herbicides for broadleaf weed control, tolerance of forage bermudagrass hybrids [Cynodon dactylon (L.) Pers.], and absorption and translocation in common ragweed (Ambrosia artemisiifolia L.)(Texas A&M University, 2005-08-29) Moore, Frederick ThomasThese studies were conducted on several central Texas agricultural producers?? properties, the Stiles Farm Foundation, the Texas Agricultural Experiment Station, and the Texas A&M University campus. First, an experimental herbicide from Dow AgroSciences, GF-884, was evaluated for effectiveness in controlling three annual and three perennial weed species in production pasture lands and hay meadows. Several rates of GF-884 were examined and evaluated against three registered pasture products and one non-selective herbicide. Next, GF-884 was assessed for tolerance on two common bermudagrass hybrids (Cynodon dactylon (L.) Pers.) at three progressive rates with and without adjuvant. Finally, the herbicides, picloram and fluroxypyr, were applied to common ragweed (Ambrosia artemisiifolia L.) to characterize their individual absorption and translocation and assess any influence one might have on the other. GF-884 applied at rates of 0.91 and 1.14 kg a.e./ha provided >85% and >75% control of the annual and perennial weed species evaluated, respectively. These same rates of GF-884 consistently provided control that was equivalent or better than thatachieved with the registered products. No differences were observed among treatments when shoots from the perennial species were evaluated 12 months following treatment application. The tolerance experiments utilized GF-884 at rates twice that used to evaluate weed control efficacy. These elevated rates did not result in discernable influences on yield or forage quality for either hybrid forage grass when compared to untreated areas. The efficacy and tolerance observations suggest that GF-884 applied at the highest recommended weed control rate can effectively control several annual and perennial weed species without imparting detrimental effects to the hybrid bermudagrass being produced. Finally, in the presence of fluroxypyr, 14C picloram absorption was maintained throughout all sampling intervals. Picloram applied alone, maximized 14C absorption at 6 HAT then declined significantly. At the final sampling, 14C from picloram applied alone was in greater concentration in the treated leaf and the root. Picloram significantly decreased absorption of 14C fluroxypyr. Fluroxypyr alone maintained 14C absorption throughout all samplings, whereas the combination maximized at 12 HAT. Initially, picloram limited 14C translocation, however at 6, 12, and 24 HAT this was not evident.Item Fertility-Based Herbicide Injury Recovery from Clomazone in Hybrid Rice (Oryza sativa L.)(2012-10-16) McKnight, Benjamin 1985-Clomazone is a carotenoid biosynthesis inhibitor commonly used as a preemergence and postemergence herbicide in rice for the control of grass weeds. Rice injury can occur and symptoms are often associated with soil characteristics and environmental conditions. The objective of this research was to investigate how environmental conditions and planting density influence clomazone injury in rice plants. Also, different fertility treatments were assessed to determine if remediation from clomazone injury occurred. Field studies were conducted in 2008 and 2009 to determine the role of planting date, planting density and soil characteristics on clomazone injury in rice plants. Also, another field study was conducted in 2010 to assess any clomazone injury remediation benefits selected fertility treatments might have in rice cropping systems. In the 2008 and 2009 field studies, hybrid rice was seeded at three densities that comprised a range of slightly lower, slightly higher and commonly recommended planting rates. Two planting dates, March and April, were a test parameter to simulate early and optimal planting dates. Two locations with different soil characteristics, near Eagle Lake and Beaumont, TX, were the study sites. Clomazone herbicide treatments were applied at different rates and timings following planting. Visual injury ratings and yield data were collected during this two-year, two location study. Clomazone injury in rice was more severe in the coarse-textured soils planted at the early, March planting date near Eagle Lake. Visual injury ratings as high as 90% were observed in some plots. Injury was less severe in the April planting date near Eagle Lake, and at both planting timings near Beaumont. In both locations, clomazone injury did not translate into yield loss at any seeding rate or planting timing. In 2010, field studies were conducted near Eagle Lake and Ganado, TX to assess fertility-based clomazone injury remediation. In one experiment, hybrid rice plots were subject to linearly increasing rates of clomazone herbicide to produce a standard curve of clomazone injury. In the second experiment, a uniform, label rate of clomazone was applied to induce injury for the assessment of the effect of fertility amendments on clomazone-injured rice. Fertility treatments consisted of nitrogen-based fertilizers and foliar-applied iron sulfate and magnesium sulfate. Visual injury ratings, plant height, and yield were collected during the study. Also, tissue samples were collected three times for laboratory analysis of chlorophyll content. In the standard curve experiment, herbicide injury increased with increasingly higher rates of clomazone applied. The highest visual injury was observed in plots receiving the highest rates of clomazone. In the remediation experiment, fertility treatments had a significant effect in only one tissue-sampling event at Eagle Lake as determined by laboratory analysis for chlorophyll content. Fertility amendments did not have a significant effect on visual injury ratings at either location at any assessment event. Specific fertility treatments significantly increased plant height in three measurement events, and yield at the Ganado locations. Plots receiving treatments containing nitrogen fertilizers produced taller plants at both locations, and increased yield at the Ganado location.Item Impact of Herbicides on Winter Canola (Brassica napus L.) Production and Fatty Acid Composition in South Texas(2013-01-16) Cogdill, Todd JosephCanola is a cool-season, oilseed crop grown throughout Europe, Canada, and the Northern Great Plains region of the United States. The expansion of canola production into new growing regions, such as the Southern Plains region, has resulted in new production challenges. The Southern Plains region cultivates canola as a winter annual compared to a spring annual for the Northern Great Plains and Canada. Given the difference in climate and weed spectrum, region-specific weed management systems need to be developed. Agronomic practices can affect seed oil content, protein content, and fatty acid composition, however the effect of herbicides on these and other characteristic of canola are unknown. Therefore, experiments were conducted in 2010 and 2011 to evaluate a broad spectrum of herbicides for potential use in South Texas canola production with respect to crop injury, effects on canola seed oil content, fatty acid composition, weed control, biomass yield, and forage quality. Visual crop injury at 42 DAE was unacceptable for saflufenacil at both 0.12 and 0.06 kg ai ha-1 and ethalfluralin at 1.05 kg ai ha-1. Trifluralin at 1.12 and 0.56 kg ai ha-1, S-metolachlor at 2.14 and 1.07 kg ai ha-1, pyroxasulfone at 0.24 and 0.12 kg ai ha-1, and pendimethalin at 0.8 kg ai ha-1 had lowest visual injury of all treatments. Fluroxypyr applied EPOST caused severe injury at both 0.21 and 0.11 kg ae ha-1. All other EPOST treatments did not cause any visible injury. Seed oil content was not affected by the herbicides evaluated. Fatty acid composition, specifically stearic acid, oleic acid, linolenic acid, and oleic to linolenic acid ratio, was affected by herbicide treatments. This research found that protoporphyrinogen oxidase (PPG oxidase) inhibitor herbicides, such as carfentrazone-ethyl and saflufenacil, negatively affect canola oil quality. Biomass yield was improved for all herbicide treatments except pendimethalin PRE when compared to the untreated plots. Crude protein content of canola forage was not affected by herbicide treatment. Digestible dry matter appeared to be reduced by treatments that included an EPOST application of sethoxydim. The research shows that pendimethalin and S-metolachlor may be suitable for canola production in South Texas based on low crop injury and effective weed control. Neither pendimethalin nor S-metolachlor is currently labeled for use in canola. The herbicides trifluralin, ethalfluralin, quizalofop P-ethyl, ethametsulfuron-methyl, sethoxydim, glyphosate, clethodim, and clopyralid are currently labeled for use in canola and were confirmed suitable for canola production in South Texas. Carfentrazone-ethyl is currently labeled for use in canola but the effects on oil quality should be considered.Item Spray carrier stability, plant mobility, and runoff potential of trifloxysulfuron(2009-06-02) Matocha, Mark AndrewTriflxysulfuron is a sulfonylurea herbicide developed for postemergence weed control in cotton, sugarcane, and turf. Greenhouse and laboratory studies were conducted at the Texas A&M University campus and at the USDA-ARS research facility in Stoneville, MS to: 1) quantify the dissipation of trifloxysulfuron in a spray tank at 0, 1, 3, 7, 14, and 21 d after mixing as influenced by pH of the spray carrier and evaluate the resulting effects on efficacy on Palmer amaranth (Amaranthus palmeri S. Wats); 2) determine the effect of spray carrier pH on absorption and translocation of radiolabeled trifloxysulfuron in Palmer amaranth and Texasweed (Caperonia palustris (L.) St. Hil.); 3) determine average edge-of-field concentrations, total mass losses, and fractional losses of trifloxysulfuron applied to cotton at the 5-leaf stage and to bare soil as influenced by simulated rainfall. The dissipation of trifloxysulfuron followed first-order kinetics. Calculated half-life values indicated that hydrolysis occurred more rapidly with the more acidic spray carriers with little or no difference between neutral and alkaline pH levels. Bioassay on Palmer amaranth showed no differences in plant dry weights due to pH level or dissipation time. The absorption of 14C-trifloxysulfuron was greater for Palmer amaranth than for Texasweed when averaged over time and pH. Altering pH did not affect the translocation of trifloxysulfuron in Palmer amaranth. In contrast, translocation of 14C-trifloxysulfuron in Texasweed increased in the order of pH 5 < pH 7 = pH 9. Cumulative trifloxysulfuron losses in runoff from cotton plots were 0.21 g ha-1 while losses from bare plots were 0.13 g ha-1. These values corresponded to fractional losses of 2.7% for cotton plots and 1.7% for bare plots of the total amount applied. These studies provide important information regarding the stability, plant uptake, and runoff potential of a commonly used sulfonylurea herbicide.Item The Interaction of Propanil+Thiobencarb with Imazethapyr and Imazamox for Enhanced Red Rice (Oryza spp.) Control in Imidazolinone-Tolerant Rice (Oryza sativa L.)(2014-04-28) Jones, Trevor NelsonRecent observations from field systems suggest that RiceBeaux? may enhance efficacy of imidazolinone herbicides for control of red rice. Therefore, this research was undertaken to evaluate the herbicidal interactions of RiceBeaux? with Newpath? and Beyond?. Field experiments were conducted in 2012 and 2013 at the David R. Wintermann Rice Research Station in Eagle Lake, TX. In both years, imazethapyr alone and imazethapyr+RiceBeaux? treatments, were evaluated for control of XL723, which was used to simulate red rice in the field. In 2012, imazethapyr alone treatments provided 60 to 85% control of XL723 14 DAT and 87 to 100% control 21 DAT. Imazethapyr+RiceBeaux? combinations provided 51 to 91% control of XL723 14 DAT and 87 to 100% control 21 DAT. During both years, all treatments provided greater than 98% control of XL723 28 and 35 DAT. In 2013, treatments that did not include a tank-mix with RiceBeaux? provided 60 to 77% control of XL723 14 DAT and 80 to 94% control 21 DAT. Imazethapyr+RiceBeaux? combinations provided 60 to 85% control of XL723 14 DAT and 81 to 99% control 21 DAT. These data indicated that for both years, Imazethapyr+RiceBeaux? combinations provided no additional control of XL723 compared to imazethapyr alone. In 2013, experiments were conducted to evaluate the interaction of RiceBeaux? on imazamox in the field. Imazamox alone provided 62 to 75% and 87 to 94% control of XL723 14 and 21 DAT, respectively. Imazamox+RiceBeaux? treatments provided 57 to 85% control 14 DAT and 86 to 100% control 21 DAT. All treatments provided excellent control 28 and 35 DAT. Based on these data, imazamox+RiceBeaux? combinations provided no additional control of XL723 compared to imazamox alone. Laboratory experiments were also conducted to characterize the interaction of RiceBeaux? on translocation and absorption of imazamox using ^(14)C-imazamox. TX-4 red rice plants were treated with ^(14)C-imazamox, with plants subsequently harvested at 8 separate timings. At each harvest timing, six samples were harvested from each plant and analyzed using Liquid Scintillation Spectrometry to quantify radioactivity. Significantly more ^(14)C-imazamox was recovered from the cuticle when imazamox was applied alone, resulting in lower amounts of imazamox absorption. In contrast, imazamox+RiceBeaux? resulted in significantly higher absorption of ^(14)C-imazamox at 24, 48, and 96 hr after treatment. Results indicated RiceBeaux? may allow more imazamox to cross the lipophilic cuticle to reach the sites of action, which may result in enhanced red rice control. This interaction may explain the enhanced red rice control observed in field studies when RiceBeaux? tank-mixes were applied.