Date of Graduation

5-2015

Document Type

Thesis

Degree Name

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

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Jason K. Norsworthy

Committee Member

Tom Barber

Second Committee Member

Trenton Roberts

Third Committee Member

Edward Gbur

Abstract

Since 2006, glyphosate-resistant Palmer amaranth has been considered the most problematic weed in agronomic crops across the Midsouth. As a result of glyphosate resistance, producers began to again utilize a diverse herbicide program for management of this weed, which consists of several soil-residual herbicides most notably diuron, fluometuron, fomesafen, and metolachlor. Fluridone inhibits phytoene desaturase in plants, and is unique in that its mechanism of action (MOA) is not currently registered for use in cotton. Studies were conducted to determine the length of residual that fluridone provides in controlling Palmer amaranth in Arkansas glyphosate- and glufosinate-resistant cotton programs and along field margins in comparison to other soil-residual herbicides. Furthermore, studies were conducted to assess the persistence of fluridone in Arkansas soils and the risk for injury to crops subsequently planted following fluridone use in cotton. Regardless of the cotton program, fluridone failed to provide season-long control of Palmer amaranth; hence, reducing the number of postemergence applications will not be recommended when applying fluridone at cotton planting. Additionally, fluridone failed to provide season-long control of Palmer amaranth along ditchbanks over that of other labeled soil-residual herbicides; however, when applied under favorable conditions fluridone applied preplant incorporated provided extended control of Palmer amaranth with or without a sequential application. Injury to wheat as a rotational crop from an application of fluridone to cotton was greater than that of other crops commonly rotated with cotton; albeit, injury was not severe enough to result in wheat yield reductions. Although fluridone did not provide season-long control of Palmer amaranth, introducing a herbicide with a unique MOA into current cotton would be beneficial for reducing the risk of resistance to herbicides that are currently used in cotton.

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