Date of Graduation

5-2020

Document Type

Thesis

Degree Name

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

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Norsworthy, Jason K.

Committee Member

Scott, Robert C.

Second Committee Member

Gbur, Edward E. Jr.

Third Committee Member

Norman, Richard J.

Fourth Committee Member

Hardke, Jarrod T.

Keywords

Rice tolerance; furrow-irrigated rice; rice levees; herbicide options; cultivar

Abstract

Florpyrauxifen-benzyl is a synthetic auxin herbicide which was commercially released in 2018 to combat troublesome grass, broadleaf, and sedge weed species in rice. Many factors may influence cultivar response to a new herbicide; hence, it is important to understand factors contributing to crop sensitivity to an herbicide in order to make appropriate recommendations. Prior to the onset of this study, research had been conducted on florpyrauxifen-benzyl in a flooded environment; however, none had been executed in a non-flooded environment. Experiments were conducted to evaluate the response of a long-grain variety ‘CL111’, a medium-grain variety ‘CL272’, and a long-grain hybrid ‘CLXL745’ to florpyrauxifen-benzyl as influenced by herbicide rate, environmental conditions, growth stage, days between sequential applications, and applications with an acetolactate (ALS)-inhibiting herbicide and a cytochrome P450-inhibiting insecticide. Additionally, weed control experiments were conducted to evaluate florpyrauxifen-benzyl as part of a full-season herbicide program in furrow-irrigated rice and in mixtures with other herbicides on rice levees. Generally, florpyrauxifen-benzyl at the field rate of 30 g ae ha-1 did not cause excessive injury or yield loss. However, the hybrid CLXL745 was most sensitive to florpyrauxifen-benzyl, especially sequential applications made at the labeled rate, resulting in yield loss. Data from these tolerance studies indicate the long-grain variety CL111 is most tolerant to florpyrauxifen-benzyl, while CLXL745 is most sensitive, thus caution should be exercised when applying florpyrauxifen-benzyl to this cultivar. Florpyrauxifen-benzyl applied at mid-season provided 96 to 98% control of Palmer amaranth in a furrow-irrigated rice system. Comparable levels of Palmer amaranth control were observed between florpyrauxifen-benzyl and a standard treatment of 2,4-D, offering another herbicide to control weeds on rice levees in areas where 2,4-D use is restricted. Results from these experiments indicate florpyrauxifen-benzyl will provide a valuable weed management tool for rice farmers.

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