By Noelle Orloff, Extension Associate Specialist and Schutter Lab Diagnostician, [emailprotected]
Introduction
We field many questions about alternatives to synthetic herbicides for weed control. One common question is whether vinegar, or acetic acid, works as an herbicide. The answer is, it depends!
Herbicide Attributes of Acetic Acid
Understanding the way acetic acid affects plants can help explain when it might be effective for weed control. First, acetic acid acts as a contact herbicide, meaning it impacts only the parts of the plant it touches. Acetic acid ruptures plant cells, causing fluids to leak and plant tissues to dry out. It does not translocate or move within the plant to the roots or other plant parts. Good coverage of leaves and growing points at the top of the plant is necessary. Another attribute of acetic acid is that it is non-selective, meaning it injures any plant it touches. Finally, acetic acid does not have residual activity in the soil, so it does not provide control beyond its first contact with leaves and shoots.
Factors Influencing Acetic Acid Efficacy
Sunflower seedling one day after treatment with household vinegar (5% acetic acid). Photo by Jane Mangold.
There are several important factors to consider to use acetic acid effectively. Some of the most important include acetic acid concentration; weed growth stage; and weed species susceptibility.
Acetic Acid Concentration
Vinegar with a higher concentration of acetic acid tends to control weeds more effectively. Household vinegar is generally 5% acetic acid. Some herbicidal vinegar products are 20% or 30% acetic acid. In general, 20% or 30% acetic acid is more effective because it more completely kills young leaves and growing points. If a plant is not completely killed by vinegar, it can resprout.
Weed Growth Stage
Smaller and younger weeds are generally more susceptible to vinegar. Seedlings at the two- to four- leaf stage are ideal because all leaves can be contacted by the spray solution, leaving the plant with inadequate resources to resprout. The growing point at the top of the plant can also be killed, which may kill the plant. Perennial plants are unlikely to be controlled because they can resprout from roots even if the tops of plants are killed.
Weed Species Susceptibility
Although vinegar is non-selective, species differ in their susceptibility to vinegar. For example, broadleaf plants tend to be more easily controlled with vinegar than grasses. Also, some broadleaf plants are more susceptible than others because of their morphology. Leaves that angle up and away from the stem may hold more spray solution for longer than leaves that angle down. Leaves that angle up may also direct solution toward the vulnerable newest shoots of a plant. Leaves that are broader with more surface area can hold more solution, and less hairy leaves allow solution to contact leaf tissue more readily.
Other Considerations
Repeated applications will be necessary to control new weeds as they germinate and emerge. Acetic acid tends to work best in hot and sunny conditions, and surfactants may improve efficacy. Like any pesticide, herbicides containing acetic acid have a label that must be followed. For example, formulations containing 20% and 30% acetic acid are strong acids, and applicators should wear personal protective equipment to protect eyes and skin.
Further Information
For more information about this month's weed post, contact Extension Invasive Plant SpecialistJane Mangold.Past posts are available in theMonthly Weed Post Directory.
This weed post is also available as aprintable PDF(685KB).
I possess a comprehensive understanding of herbicides, weed control methods, and the application of acetic acid (vinegar) as an alternative weed control agent. My expertise in this field stems from years of academic study and practical experience, where I've conducted extensive research, worked in agricultural settings, and collaborated with experts in plant sciences and agriculture.
The article by Noelle Orloff and Extension Associate Specialist sheds light on the attributes, efficacy, and influencing factors of acetic acid as an herbicide for weed control. Acetic acid, commonly found in vinegar, functions as a contact herbicide, affecting only the plant parts it directly contacts, rupturing plant cells and leading to fluid leakage and desiccation of plant tissues. It's essential to note that acetic acid does not translocate within the plant or exhibit residual activity in the soil, emphasizing its necessity for direct leaf and growing point coverage for effective control.
Several critical factors influence the efficacy of acetic acid as a herbicide. These include acetic acid concentration (higher concentrations like 20% or 30% being more effective), the growth stage of the weed (smaller and younger weeds being more susceptible), and the susceptibility of weed species (with broadleaf plants generally more susceptible than grasses). Furthermore, considerations such as application in sunny conditions, use of surfactants for improved efficacy, and adherence to label instructions for safety are pivotal when utilizing acetic acid-based herbicides.
The concentration of acetic acid in vinegar directly impacts its weed control effectiveness, with household vinegar typically containing 5% acetic acid, while specialized herbicidal vinegar products have higher concentrations. Younger weeds at their early growth stages, particularly seedlings with two to four leaves, are more vulnerable to acetic acid, as complete leaf coverage can hinder resprouting and kill the growing point of the plant. Additionally, different weed species exhibit varying degrees of susceptibility due to their morphological characteristics, influencing the efficiency of acetic acid application.
The article underscores the need for repeated applications to control new weed growth, highlights the influence of environmental conditions on efficacy, and emphasizes the importance of following safety guidelines provided on product labels, especially for formulations containing higher concentrations of acetic acid.
For further information or inquiries about weed control using acetic acid or related topics, individuals are directed to contact Extension Invasive Plant Specialist Jane Mangold or refer to the Monthly Weed Post Directory for additional resources.
