Herbicide response of tropical spiderwort (Commelina benghalensis) as affected by CO2 and soil moisture levels

Authors: AHLERSMEYER, ANDREW - Auburn University; Prior, Stephen; Price, Andrew; MAITY, ANIRUDDHA - Auburn University

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2025
Publication Date: 2/24/2025
Citation: Ahlersmeyer, A., Prior, S.A., Price, A.J., Maity, A. 2025. Herbicide response of tropical spiderwort (Commelina benghalensis) as affected by CO2 and soil moisture levels [abstract]. Southern Weed Science Society, Charleston, SC January 26-29 2025.

Interpretive Summary:

Technical Abstract: Tropical spiderwort (Commelina benghalensis L.) is a federally noxious weed that has become increasingly problematic for Southeastern U.S. farmers, especially peanut growers in Alabama, Georgia, and Florida. It is a unique perennial species as it produces both above- and below-ground flowers, and is one of the few monocotyledonous broadleaf weeds. Due to its natural tolerance to glyphosate, along with limited herbicide options for management in peanuts, tropical spiderwort is a serious threat to optimal peanut production. Additionally, variations in environmental factors like soil moisture and CO2 may influence its growth and sensitivity to commonly used peanut herbicides. This study aimed to evaluate the effects of reduced soil moisture and elevated CO2 on the growth, physiology, and herbicide sensitivity of tropical spiderwort. A free air CO2 enrichment (FACE) experiment was conducted during the late summer of 2024 at the USDA National Soil Dynamics Laboratory in Auburn, AL. Tropical spiderwort plants from a suspected resistant population from Northwest Florida were transplanted into pots with field soil and subject to different irrigation levels (low, medium, and high) and CO2 levels (ambient and elevated). Treatments of glyphosate, MSMA, and flumioxazin were applied at 0.5x rates, and various measurements (visual injury, flower, branch, and leaf number, and branch length) were recorded weekly up to four weeks after application. At physiological maturity, dry biomass and lengths of roots and shoots were documented. Initial results demonstrated that all herbicides provided some level of tropical spiderwort growth suppression at all moisture levels, with MSMA providing near 100% control. However, under low moisture conditions, tropical spiderwort showed higher tolerance to both glyphosate and flumioxazin. Elevated CO2 appeared to have no impact on tropical spiderwort herbicide tolerance. Further replications of these methods will provide improved understanding of the interactive effect of soil moisture and CO2 on tropical spiderwort management.