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Organic Herbicides

Updated March 05, 2019
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Gared Shaffer

SDSU Extension Weeds Field Specialist

Many gardeners across the state of South Dakota desire to have weed-free gardens, yards and flowerbeds. Many homeowners do not want to use inorganic herbicides due to their potential health effects. There may be a need for safer options for weed control in areas where children and pets play. It is often thought that because herbicides are organic they are safe. This is mostly true due to the natural quick breakdown of organic herbicides in the environment compared with some inorganic herbicides which have a short or long residual life in the soil or a plant. High concentrations of some organic herbicides may potentially pose an acute risk but not a chronic risk. Every organic herbicide would fall under the title as non-selective, meaning it will kill or suppress all plant growth that it comes in contact with. Organic herbicides can be a useful tool when combined with other means of weed control.

Active Ingredients

Organic herbicides use one or more of the following active ingredients:

  • Acetic Acid
  • Citric Acid
  • d-limonene (Citrus Oil)
  • Clove Oil or Clove Leaf Oil
  • Cinnamon Oil
  • Lemon grass Oil
  • Eugenol
  • 2-Phenethyl Propionate
  • Sodium Lauryl Sulfate
  • Ammonium Nonanoate
  • Pelargonic Acid+Fatty Acids

On every label, you will also find ingredients under the title of inert ingredients, surfactants and adjuvants. These ingredients in organic herbicides are always organically based.

Active Ingredient (AI) Product Name
Acetic Acid Vinagreen, Weed Pharm, EcoSharpTM Weed & Grass Killer
Acetic Acid+Citric Acid All Down®, Brush-Weeds & Grass Herbicide
Citric Acid Blackberry & Brush Block
Citric Acid+Clove Oil Burnout®
Clove Oil (d-limonene) Avenger
Clove Oil + Cinnamon Oil Weed Zap®
Clove Leaf Oil Matran® EC
Eugenol Weed SlayerTM
Eugenol+2-Phenethyl Propionate+Sodium Lauryl Sulfate EcoSmart®
Lemon grass Oil GreenMatch® EX
Ammonium Nonanoate AXXE®
Pelargonic Acid+Fatty Acids Scythe®

 

Application

To improve the effects of organic herbicides, consider performing a thorough spray coverage even to the point of running off plant leaf surface. Other considerations would be to use the highest label rate allowed of surfactant/adjuvant, and treat weeds when they are 4 inches or less in height or reach in growth stages between 2 to 4 leaves. University research has found that when applying organic herbicides, “lower concentrations at high spray volumes (i.e. 10% concentration in 70 gallons per acre) appear to be more effective than high concentrations at low spray volumes (i.e.20% concentration in 35 gallons per acre)”1.

Reference:

  1. VINEGAR: AN ALTERNATIVE TO GLYPHOSATE? Accessed 1-18-19