Date of Graduation

12-2017

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Jason Norsworthy

Committee Member

Edward Gbur

Second Committee Member

Robert Scott

Third Committee Member

Richard Norman

Keywords

ACCase, Provisia, Quizalofop, Rice

Abstract

With the continued evolution of herbicide resistance, it is becoming more difficult to achieve adequate weed control in Arkansas rice production systems. Thus, new technologies are needed to combat these troublesome weeds. A new non-GMO, herbicide-resistant rice type is under development that is resistant to quizalofop, an acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide that will allow for selective grass weed control in rice. With the commercialization of this technology by 2018, research was conducted to determine the best fit for quizalofop-resistant rice in current production systems. Experiments included evaluation of off-target movement of quizalofop, determination of plant-back risk from quizalofop application, best rate structure of quizalofop, general efficacy on common grass weeds, and tank-mix interactions of quizalofop with common herbicides used in rice. Overall, the risk for off-target movement of quizalofop on Midsouth grass crops is minimal, with injury only observed under conditions that would be rare in the field. Plant-back risk after quizalofop or other ACCase-inhibiting herbicide applications is relatively low, with only grain sorghum and corn showing potential for injury if planted in quick succession after herbicide application. Quizalofop applications in quizalofop-resistant rice are effective for controlling barnyardgrass, broadleaf signalgrass, and red rice, with the best results from sequential applications of quizalofop at 120 g ai ha-1. A screening of barnyardgrass accessions from across the state of Arkansas proved quizalofop to be an effective graminicides, controlling all accessions evaluated. Tank-mix research for quizalofop and common rice herbicides prove that caution needs to be taken when tank-mixing quizalofop, especially with acetolactate synthase-inhibiting herbicides and auxinic herbicides due to the risk of antagonism. Overall, this research supports that quizalofop-resistant rice can be an effective tool for Arkansas rice producers.

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