Student/presenter: Maxwell E. Smith, Master's student, Plant and Soil Science-Weed Science
Format: Oral presentation
Title: Crop Response and Control of Amaranthus palmeri in HPPD-tolerant Cotton using
Isoxaflutole
Maxwell E. Smith1, Peter A. Dotray1,2, and Adam Hixson3
1Texas Tech University, 2Texas A&M AgriLife Research and Extension, 3BASF
Amaranthus palmeri S Wats. (Palmer amaranth, pigweed, carelessweed) is one of the most troublesome weeds to cotton producers on the Texas High Plains. The development of glyphosate-resistance has complicated effective control of this weed species. Amaranthus palmeri has been shown to reduce cotton yield and creates harvest complications when escaped plants are left to compete with cotton. New HPPD-tolerant cotton from BASF allows for the use of a mode of action that has not previously been used in cotton. The objective of this study was to evaluate the crop response and control of Amaranthus palmeri in HPPD-tolerant cotton using the HPPD herbicide isoxaflutole. In 2021, a field study was conducted at the Texas Tech University New Deal Research Farm. In this study, cotton response and weed control were evaluated following preemergence and early postemergence applications of different herbicide programs, many of which included isoxaflutole. Crop response (injury) 21 days after the preemergence application was <12%. Average Amaranthus palmeri control 29 days after the preemergence application was >92% for all treatments that included isoxaflutole in the preemergence application and was ≤89% for all treatments that did not include isoxaflutole in the preemergence application. Amaranthus palmeri control was >80% for all treatments 14 days after the early postemergence application. Amaranthus palmeri control was >71% for all treatments 28 days after the early postemergence application. Cotton lint yields were >1,470 kilograms per hectare for all treatments, excluding the nontreated control. This study suggests that isoxaflutole is effective at controlling Amaranthus palmeri and will give cotton producers in the Texas High Plains another mode of action to use against glyphosate resistant weeds.