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dc.contributor.authorSmith, Adam N.en
dc.date.accessioned2015-10-17T06:00:51Zen
dc.date.available2015-10-17T06:00:51Zen
dc.date.issued2014-04-24en
dc.identifier.othervt_gsexam:2480en
dc.identifier.urihttp://hdl.handle.net/10919/56957en
dc.description.abstractSustainable weed control in managed agricultural systems requires the judicious use of multiple weed control tactics and prevents over-reliance on any one tactic. In this context, sustainable weed management plays a critical role in the mitigation of one of agriculture's most pressing problems- herbicide resistance. Research conducted in Virginia sought to explore the effects of integrating multiple weed management tactics in corn and cool-season turfgrass. Additionally, research was conducted to confirm nicosulfuron and glyphosate herbicide resistance in Virginia johnsongrass and elucidate the molecular mechanisms conferring those resistances. Rye and hairy vetch cover crop residues, combined with reduced rates of preemergence herbicide and postemergence glyphosate applications, were shown to provide sufficient weed control and corn yield. Cover crop type or residue level did not augment weed control in corn production systems, but the use of glyphosate was essential for late-season weed control. Rye and vetch biculture as a cover crop increased corn yield compared to rye cover crop alone. In cool-season turfgrass, the addition of reduced preemergence herbicide rates to corn gluten meal, an organic herbicide product, reduced crabgrass 25%. Moreover, control was dependent on herbicide choice. Herbicides applied at half of recommended labeled rates or less did not control crabgrass at a commercially-acceptable level, regardless of corn gluten meal addition. In field experiments, Virginia johnsongrass expressed resistance to nicosulfuron and glyphosate. Glyphosate at 0.88 kg ae ha-1 controlled johnsongrass 65%. Nicosulfuron at 0.14 kg ai ha-1 controlled the same population 10%. Greenhouse experiments confirmed differential sensitivity of putative herbicide-resistant johnsongrass seedlings to nicosulfuron and glyphosate when compared to a susceptible population. Herbicide resistance was not conferred via target-site mutation. Five ALS-gene site mutations were confirmed absent in Virginia johnsongrass, while three others were located in coding regions that could not be elucidated in johnsongrass. Further investigations showed glyphosate resistance was not conferred via reduction in herbicide absorption or translocation. The susceptible johnsongrass caused an increase in a polar metabolite at Rf = 0.17 with concomitant reduction in glyphosate over time. Although the mechanism is not clear, these data suggests that glyphosate resistance in johnsongrass may be associated with differential metabolism.en
dc.format.mediumETDen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectintegrated weed managementen
dc.subjectherbicide resistanceen
dc.subjectcornen
dc.subjectcool-season turfgrassen
dc.subjecttarget-site mutationen
dc.subjectherbicide absorption and translocationen
dc.subjectherbicide metabolismen
dc.titleReduced Chemical Weed Control Options in Virginia for Corn and Turfgrass and Characterization of Sorghum halepense Expressing Multiple Resistance to Nicosulfuron and Glyphosateen
dc.typeDissertationen
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen
dc.description.degreePh. D.en
thesis.degree.namePh. D.en
thesis.degree.leveldoctoralen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen
dc.contributor.committeechairHagood, Edward Scott Jr.en
dc.contributor.committeechairAskew, Shawn D.en
dc.contributor.committeememberMcCall, David S.en
dc.contributor.committeememberBarney, Jacoben
dc.contributor.committeememberThomason, Wade E.en


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