Browsing by Subject "weed control"
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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 Hybrid bermudagrass [Cynodon dactylon (L.) Pers.] tolerance and broadleaf weed control using tank mix combinations of diflufenzopyr(2009-05-15) Matocha, Matthew EdwardField studies were conducted during the 2003 and 2004 growing seasons to: 1) evaluate the control of silverleaf nightshade and western ragweed, and (2) assess the forage tolerance of Coastal and Tifton 85 bermudagrass hybrids using tank mix combinations of diflufenzopyr. Herbicides that were evaluated in each study included picloram, multiple rates of picloram with diflufenzopyr, triclopyr, triclopyr with diflufenzopyr, dicamba + diflufenzopyr, and diflufenzopyr alone. Visual ratings were taken on the weed control experiments approximately 30, 60 and 90 days after treatment. Phytotoxicity ratings were taken prior to each harvest of the Coastal and Tifton 85 varieties to determine influence of each herbicide treatment. Each bermudagrass variety was harvested twice during each growing season to determine dry matter yield and quality. Forage quality, including crude protein, acid detergent fiber, and neutral detergent fiber, was assessed using near infrared reflectance spectroscopy. Adding diflufenzopyr to triclopyr did not consistently increase control of silverleaf nightshade or western ragweed. In general, picloram + diflufenzopyr and picloram applied alone provided the greatest control of both species at the highest rate of picloram. Increased efficacy was more evident from the addition of diflufenzopyr to picloram in 2004 on western ragweed. By the final ratings in both experimental years, dicamba + diflufenzopyr provided no more than 76% control of either species. Both forage varieties showed significant variability in phytotoxicity between years. Although observed levels of growth reduction were relatively high at the first harvest in 2003, no treatment exceeded a 10% growth reduction by the second harvest for either forage variety. In addition, the only significant reduction in dry matter yield occurred at the first harvest of Coastal in 2003 from picloram + diflufenzopyr applied at the highest rate.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 Interference and control of sharppod morningglory (Ipomoea cordatotriloba dennstedt) in glyphosate-resistant cotton.(Texas A&M University, 2006-04-12) Steele, Gregory LeeSharppod morningglory is a perennial vine commonly found infesting croplands in Texas and the southeastern United States. Previous research regarding morningglory competition and control primarily focused on annual Ipomoea. Interference, control, and herbicide translocation of sharppod morningglory could differ from that of other morningglories because of differences in growth and resource allocation. Therefore, field and laboratory experiments were conducted from 2001 to 2004 to: 1) determine the effects of seed-propagated and root-sprouted sharppod morningglory on cotton economic value, yield, harvest efficiency, and fiber quality; 2) evaluate sharppod morningglory control with cotton herbicides, and determine the effect of diuron rates on glyphosate absorption and translocation; and 3) assess the impact of cotton herbicide program and cotton-corn rotation on weed species composition over three years. A relatively large proportion of sharppod morningglory biomass was accumulated belowground during the first 8 wk of growth in the greenhouse. Consequently, up to 6 plants 10-m row-1 did not significantly reduce cotton lint yield. Sharppod morningglory density impacted color grade more than any other classification parameter. Through combined effects on yield and quality, cotton lint value was reduced by approximately 85% in the presence of 8 sharppod morningglory 10 m-1. Glyphosate alone did not completely control sharppod morningglory. The use of glufosinate, bromoxynil, or a combination of glyphosate plus diuron provided acceptable control. Sharppod morningglory absorbed up to 75% of glyphosate when applied alone, but most glyphosate was retained in treated leaves and did not translocate well. Diuron decreased absorption, increased leaf retention, and inhibited glyphosate translocation to roots. Rotation to corn and the use of preemergence herbicides in cotton improved control of grass and broadleaf weeds during the year of treatment. In the season following the 3-yr rotation, there were no lasting effects of crop rotation on density or control of grasses and broadleaves. However, hand-hoed and herbicide treated plots resulted in weed densities 2- to 3-fold lower than the untreated. Preemergence herbicides and/or crop rotation can reduce weed density and improve weed control, but these strategies must be employed long-term to reduce density of problematic weeds through depletion of the soil seedbank.