Semester of Graduation

Summer 2024

Degree

Master of Agriculture (MAgr)

Department

School of Plant Environmental and Soil Sciences

Document Type

Thesis

Abstract

Studies were conducted in 2021 through 2023 at the LSU AgCenter Dean Lee Research and Extension Center near Alexandria, LA to determine the sensitivity of 2,4-D- or dicamba- tolerant cotton (Gossypium hirsutum L.) to an early season application of a Group 15 and foliar-only herbicides. Both studies were randomized complete block designs with a two-factorial arrangement of treatments with four replications. In the dicamba-tolerant cotton study, Factor A consisted of no foliar-herbicide, dicamba alone, glyphosate alone, or dicamba plus glyphosate. Factor B consisted of either no Group 15 residual herbicide, acetochlor, or S-metolachlor. In the 2,4-D- tolerant cotton study, Factor A consisted of either no foliar-herbicide, 2,4-D choline alone, glyphosate alone, glufosinate alone, premix of 2,4-D choline:glyphosate, or 2,4-D choline plus glufosinate. Factor B was identical to the dicamba-tolerant study. In both studies, treatments were applied to one-leaf cotton. Data recorded in both studies were visible crop injury ratings, heights, node numbers, and lint yield.

Visible cotton injury was greater following treatments with S-metolachlor at 3 DAT compared to no Group 15 and acetochlor. No differences in cotton height or node number were indicated to be significant following any treatments. Lint yield differed in the dicamba-tolerant cotton study when following dicamba-alone and dicamba plus glyphosate. Due to recovery in visible injury, differences in lint yield were more due to in-field variability.

In the 2,4-D-tolerant cotton, visible injury following any foliar herbicide plus acetochlor or S-metolachlor injured cotton greater than the nontreated. Treatments following acetochlor or S-metolachlor injured cotton more than their absence at 3 or 7 DAT, but by 28 DAT no difference was observed. Heights following the main effect of Group 15 herbicides was significant in the 2,4-D-tolerant cotton. However, neither cotton node numbers nor lint yield were found to be affected.

In both studies, visible injury dissipated by 28 DAT, indicating that the initial injury following the treatments is only temporary and the cotton will recover in the following weeks. The recovery from visible injury and lack of negative effect on growth or lint yield, indicates that the evaluated treatments can safely be applied to 1-leaf cotton.

Date

5-1-2024

Committee Chair

Stephenson IV, Daniel O.

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