Impact of acetic acid concentration, application volume, and adjuvants on weed control efficacy

Authors: Webber Iii, Charles; White, Paul; SHREFLER, JAMES - Oklahoma State University; Spaunhorst, Douglas

Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2018
Publication Date: 7/15/2018
Citation: Webber III, C.L., White Jr, P.M., Shrefler, J.W., Spaunhorst, D.J. 2018. Impact of acetic acid concentration, application volume, and adjuvants on weed control efficacy. Journal of Agricultural Science. 10(8):1-6. https://doi.org/10.5539/jas.v10n8p1.
DOI: https://doi.org/10.5539/jas.v10n8p1

Interpretive Summary: Weeds compete for natural resources such as water, light, and nutrients, and as a result in increase production costs and reduced yields. There is an increasing interest in the use of natural herbicides for the production of organic crop production. Vinegar has been identified as a potential organic herbicide, yet additional information is needed to determine the influence of acetic acid concentration, application volume, and adjuvants on weed control. Acetic acid is a contact herbicide, injuring and killing plants by first destroying the cell membranes, which results in the desiccation of the plant tissues. Household vinegar typically contains 5% acetic acid, while greater acetic acid concentrations are available commercially. Field research was conducted in southeast Oklahoma (Lane, OK) to determine the effect of acetic acid concentrations, application volumes, and adjuvants on weed control efficacy. The factorial experimental design included vinegar at three acetic acid concentrations (0, 5 and 20 %), two sprayer application volumes (187 and 935 L/ha), three adjuvants (none, orange oil, and canola oil), and one weedy-check. The experiment was repeated twice. Visual weed cover and control ratings were collected 4 days after treatment. The experiment had very high weed densities with multiple grass and broadleaf weed species. The weedy check average weed cover percentages were as follows: 98% total weeds; 53% grass; 44% broadleaf; 52% large crabgrass (Digitaria sanguinalis (L.); 25% carpetweed (Mollugo verticillata L.); and 14% cutleaf evening primrose (Oenothera laciniata Hill). Total weed control ranged from 0% control when no vinegar was used to 74% control when 20% acetic acid was applied at 935 L/ha with canola oil. Vinegar was more effective in controlling broadleafs than in controlling grasses. Optimum total grass and crabgrass weed control occurred with 20% acetic acid applied at 935 L/ha, resulting in weed control that ranged from 44 to 63%. Broadleaf control was 84% or greater for plots receiving either 10% acetic acid applied at 935 L/ha or 20% acetic acid applied at 187 or 935 L/ha. Also, 5% percent acetic acid applied at 187 L/ha provided good cutleaf evening primrose control (77 to 90%). When averaged across application volumes (187 and 935 L/ha) and adjuvants (none, orange oil, and canola oil), weed control increased for all species as acetic acid concentrations increased from 5 to 20%. When averaged across acetic acid concentrations and adjuvants, weed control increased as application volumes increased from 187 to 935 L/ha. Individual comparisons among adjuvants within acetic acid concentrations and application volumes showed little or no advantage to adding either orange oil or canola oil to vinegar spray solutions.

Technical Abstract: Vinegar has been identified as a potential organic herbicide, yet additional information is needed to determine the influence of acetic acid concentration, application volume, and adjuvants on weed control. Acetic acid is a contact herbicide, injuring and killing plants by first destroying the cell membranes, which results in the desiccation of the plant tissues. Household vinegar typically contains 5% acetic acid, while greater acetic acid concentrations are available commercially. Field research was conducted in southeast Oklahoma (Lane, OK) to determine the effect of acetic acid concentrations, application volumes, and adjuvants on weed control efficacy. The factorial experimental design included vinegar at three acetic acid concentrations (0, 5 and 20 %), two sprayer application volumes (187 and 935 L/ha), three adjuvants (none, orange oil, and canola oil), and one weedy-check. The experiment was repeated twice. Visual weed cover and control ratings were collected 4 days after treatment. The experiment had very high weed densities with multiple grass and broadleaf weed species. The weedy check average weed cover percentages were as follows: 98% total weeds; 53% grass; 44% broadleaf; 52% large crabgrass (Digitaria sanguinalis (L.); 25% carpetweed (Mollugo verticillata L.); and 14% cutleaf evening primrose (Oenothera laciniata Hill). Total weed control ranged from 0% control when no vinegar was used to 74% control when 20% acetic acid was applied at 935 L/ha with canola oil. Vinegar was more effective in controlling broadleafs than in controlling grasses. Optimum total grass and crabgrass weed control occurred with 20% acetic acid applied at 935 L/ha, resulting in weed control that ranged from 44 to 63%. Broadleaf control was 84% or greater for plots receiving either 10% acetic acid applied at 935 L/ha or 20% acetic acid applied at 187 or 935 L/ha. Also, 5% percent acetic acid applied at 187 L/ha provided good cutleaf evening primrose control (77 to 90%). When averaged across application volumes (187 and 935 L/ha) and adjuvants (none, orange oil, and canola oil), weed control increased for all species as acetic acid concentrations increased from 5 to 20%. When averaged across acetic acid concentrations and adjuvants, weed control increased as application volumes increased from 187 to 935 L/ha. Individual comparisons among adjuvants within acetic acid concentrations and application volumes showed little or no advantage to adding either orange oil or canola oil to vinegar spray solutions.