Date of Graduation

12-2021

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

Tom Barber

Second Committee Member

Ed Gbur

Third Committee Member

Trent Roberts

Fourth Committee Member

Thomas R. Butts

Keywords

Deep Tillage, Integrated Weed Management, Pesticide Application Technology, Resistance Management, Roller Wiper, Zero-Tolerance

Abstract

Management of Palmer amaranth [Amaranthus palmeri (S.) Wats.] in the Midsouth in soybean [Glycine max (L.)] and cotton (Gossypium hirsutum L.) production systems has become increasingly troublesome due to resistance to many of the commonly utilized herbicides in these systems. Developments have been made to utilize new chemistries as well as incorporate integrated weed management strategies to control Palmer amaranth, but questions have risen given the economic feasibility or effectiveness of these new strategies. Additionally, regulation has limited producers’ abilities to utilize some herbicide chemistries. As a result, experiments were conducted to 1) understand the utility of isoxaflutole in isoxaflutole-tolerant cotton systems, 2) investigate the potential for roller wiper-based applications of dicamba in dicamba-tolerant soybean systems, and 3) optimize the use of various integrated weed management practices for dicamba-tolerant cotton production systems. The addition of isoxaflutole to cotton weed management programs garnered comparable Palmer amaranth control with minimal crop injury and no yield reductions while adding an additional site of action for weed control previously not utilized in cotton. Roller wiper applications of dicamba were generally not as efficacious for Palmer amaranth control compared to broadcast applications, limiting their potential as a substitution for over-the-top applications of dicamba. The use of integrated weed management practices showed great potential for weed population reductions, primarily with the use of one-time deep tillage and dicamba-based herbicide programs. Economically, the use of hand-weeding as part of a zero-tolerance strategy for weed management was inhibitive as the cost appeared to outweigh the benefits provided in the short term, not including the price of herbicide resistance evolving. However, weed populations were numerically reduced when hand-weed was utilized. Findings for this research will better enable producers to make informed management decisions when looking to adopt new technologies and strategies in their production systems aimed at combating Palmer amaranth among other weeds.

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