27
May
Study Reviews Efficacy of Organic Compatible Bioherbicides
(Beyond Pesticides, May 27, 2026) In a perspective analysis published in Frontiers in Agronomy, researchers at the University of Nebraska and Serbia’s Maize Research Institute point out the growing availability of organic-compatible herbicide controls (referred to as bioherbicides) as an opportunity to “complement crop diversification and improve soil health, they may serve as a foundational component of agroecological cropping systems, driving a transition toward reduced external inputs and strengthening essential ecosystem services for long-term sustainability.â€
The researchers distinguish between biopesticides based on their mode of action, regulatory status, including whether they are compliant to federal organic standards as defined under Organic Food Production Act (OFPA), the National List of Allowed and Prohibited Substances, and guidance from the National Organic Program at the U.S. Department of Agriculture (USDA). The article references biopesticides listed by the Organic Materials Research Institute (OMRI), which undertakes its own review process contingent on three core factors, according to the authors:
- Must not be prohibited on the National List of Allowed and Prohibited Substances, as defined here;
- Manufacturing process does not include prohibited methods (genetic engineering, ionizing radiation, etc.); and
- All ingredients are compliant with organic standards and do not have any prohibited contaminants (contamination of crops, soil, and water with heavy metals or other toxins).
This distinction is critical given active attempts in Congress and federal agencies to enable greenwashing and undermine corporate accountability. For example, there is an ongoing effort to change/amend regulatory definitions of pesticide-related compounds in Section 10201 of the House-passed Farm Bill so that they are exempt from the standard registration review process under federal pesticide law, Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). (See Daily News here and action alert here for further information.)  Similarly, the organic community also staved off a multi-year effort to permit the use of synthetic materials (“compost feedstocksâ€) in the January 2026 National Organic Standards Board (NOSB) meeting. (See Daily News here.)
It should be noted that, under the NOP’s classification of materials guidance (NOP 5033, 2016), natural and synthetic are clearly defined as follows:
4.5 Materials Derived from Agricultural Products
Materials derived from agricultural products may be agricultural or nonagricultural, depending on the manufacturing and processing methods used.
The decision tree, NOP 5033-1, includes questions to differentiate between chemical reactions caused by naturally occurring biological processes, such as composting, fermentation, use of enzymes, and by heating or burning biological matter (e.g., cooking, baking, etc.).
Agricultural materials that are chemically changed due to allowed agricultural processing methods (e.g., cooking, baking, etc.) do not result in the classification of the processed agricultural product as synthetic.
4.6 Extraction of Nonorganic Materials
Some materials are produced using manufacturing processes that involve separation techniques, such as the steam distillation of oil from plant leaves. Separation and extraction methods may include, but are not limited to, distillation, solvent extraction, acid-base extraction, and physical or mechanical methods (e.g., filtration, crushing, centrifugation, or gravity separation).
For purposes of classification of a material as synthetic or nonsynthetic, a material may be classified as nonsynthetic (natural) if the extraction or separation technique results in a material that meets all of the following criteria:
- At the end of the extraction process, the material has not been transformed into a different substance via chemical change;
- The material has not been altered into a form that does not occur in nature; and
- Any synthetic materials used to separate, isolate, or extract the substance have been removed from the final substance (e.g., via evaporation, distillation, precipitation, or other means) such that they have no technical or functional effect in the final product.
4.7 Products of Naturally Occurring Biological Processes
Products of naturally occurring biological processes, such as fermentation and composting, are statutorily considered natural and nonsynthetic. Examples of nonsynthetic materials produced from naturally occurring biological processes include vinegar, citric acid, compost, gibberellic acid, and spinosad. Additional examples are provided in Table 1 of NOP 5033-1.
NOP has also published Guidance on Materials for Organic Crop Production (2016).
Background and Main Findings
The researchers in this article broadly define bioherbicides as “weed control agents derived from phytopathogenic microorganisms, plant- or synthetic-derived compounds (discussed later in this review), or their natural metabolites.†The main groups of bioherbicide classifications include microbial fungi, microbial bacteria, microbial viruses, essential oils, allelochemicals, natural products, and fatty acid-based substances. There are numerous challenges and features of biopesticides the authors refer to, including:
- Bioherbicides hold different modes of action based on the group. For example, essential oils “[r]apidly disrupts cell membrane integrity (burn-through)†or “inhibits respiration and reduces chlorophyll content†and fatty acid-based bioherbicides like pelargonic acid and ammonium nonanoate “disturb cell membranes.â€
- Some bioherbicides like pelargonic acid have been available on the market for over a decade, whereas others have limited data due to their relatively new status, which could slow adoption/prohibition into organic systems that could benefit from new inputs if they comply;
- Regulatory protocols for bioherbicide approval in the European Union and United States differ widely, with EU regulations for bioherbicides (and pesticides more broadly) adopting the precautionary approach, whereas the United States adopts a risk-based certification system based on permissible levels of exposure. (See EU regulations here for their approval criteria for active )
- Bioherbicides require a greater volume of product relative to synthetic inputs based on their inherently positive quality for not translocating across other plants or insects that are central to scrutiny for many EPA-registered pesticides, such as neonicotinoid insecticides.
It is important to note that federal organic law sets strict evaluation criteria for allowed synthetic and prohibited natural materials, with a required holistic assessment to protect against adverse effects (related to material production, use, and disposal), ensure compatibility with organic systems, and determine material essentiality— distinguishing it from the federal pesticide law, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which focuses on narrow risk assessments associated with use only. Elements of review include:
- “The substance cannot be produced from a natural source and there are no organic substitutes;
- The substance’s manufacture, use, and disposal do not have adverse effects on the environment and are done in a manner compatible with organic handling;
- The nutritional quality of the food is maintained when the substance is used, and the substance, itself, or its breakdown products do not have an adverse effect on human health as defined by applicable Federal regulations;
- The substance’s primary use is not as a preservative or to recreate or improve flavors, colors, textures, or nutritive value lost during processing, except where the replacement of nutrients is required by law; and
- The substance is essential for the handling of organically produced agricultural products.
As the researchers state, and upon a closer analysis, there are a handful of organic-compliant bioherbicides with peer-reviewed literature identifying their efficacy data for weed-killing potential:
- Essential or horticultural oil-derived inputs have competitive reported efficacy data based on recent research, including a 50-90 percent efficacy rate of manuka oil on various weeds, including rigid ryegrass (Lolium rigidum), sterile coat (Avena sterilis), and crabgrass (Digitaria sanguinalis) (Travlos et al., 2020) and a 92-100 percent efficacy rate of cinnamon oil on common tumbleweed (Amaranthus retroflexus). (Campiglia et al., 2007).
- Ammonium nonanoate, a fatty acid-based input, had an 88-98 percent efficacy rate on spiny amaranth (Amaranthus spinosus), tumbleweed (Amaranthus albus), carpetweed (Mollugo verticillata), and Palmer’s pigweed (Palmer amaranth). (Parkash et al., 2022 ; Webber et al., 2010). However, it is annotated (or limited) to “use in farmstead maintenance (roadways, ditches, right of ways, building perimeters) and ornamental crops†(§ 205.601(b)(1) and “soaps, insecticidal†(§ 205.601(e)(8)).
Previous Coverage
While the green revolution is often heralded in conventional agriculture circles as the key agricultural innovation of the last century, recent research finds that biological controls likely had a bigger beneficial impact on world crop production. The study, Ecological Pest Control Fortifies Agricultural Growth in Asia–Pacific Economies, published in Nature Ecology and Evolution, makes the case that the introduction of predators to manage non-native pest species was just as important as the introduction of new cereal grain varieties. “Our work constitutes an empirical demonstration of how insect biological control helped solidify the agrarian foundation of several Asia-Pacific economies and, in doing so, places biological control on an equal footing with other biological innovations such as Green Revolution germplasm,†said study co-author Michael Furlong, PhD, of the University of Queensland, Australia. (See Daily News here.)
In a 2021 study published in Phytoparasitica, a promising new biocontrol agent for the tree of heaven (Ailanthus altissima)—considered an invasive species in the U.S. and Europe by some—was recently discovered by French-based scientists at USDA. The finding centers on a small mite of the Eriophyidae family, Aculus mosoniensis, which has been found to feed on tree of heaven. The finding is encouraging for the future management of this species in conjunction with balanced ecosystems. “In Europe, this Eriophyid mite is considered one of the most promising biological control agents of tree-of-heaven,†said Javid Kashefi, senior support scientist at the European Biological Control Laboratory (EBCL) in France. “This finding provides encouraging evidence that the geographic occurrence of this species is expanding in the continent.†(See Daily News here.)
Call to Action
The National Organic Standards Board (NOSB)—a stakeholder board created by Congress to advise the Secretary of Agriculture on organic standards under USDA and manage the list of allowed materials in organic production—met earlier this month. Join with Beyond Pesticides in advocating for continuously improving organic standards on issues such as:
- Microplastics should not be broadcast into organic crops and orchards. Pear ester is a chemical kairomone (chemical signals) synthesized to be structurally and functionally identical to a volatile substance emitted by mature and ripening pears and other fruits. It attracts codling moths and is used in various ways to control them. Pear ester should be added to the National List with an annotation that describes its use and prohibits use of a product microencapsulated in plastic: “use of pear ester is limited to passive traps/monitors and not for use in microencapsulated formulations.â€
- Chitosan is a material in search of a market in organic. It is a synthetic material that is not well characterized—and different forms have radically different uses. It is not necessary for organic production, and the NOSB has a Technical Review that summarizes many allowed substances for the petitioned use in wine made with organic grapes.
- Limits should be placed on the use of chlorine in livestock drinking water. Chlorinated drinking water is unavoidable for anyone using public water supplies, but many livestock producers supply drinking water from wells, cisterns, or ponds. The NOSB should propose guidance and/or instructions for certifiers regarding the application of this use in the various situations faced by livestock producers, including “shocking†wells with high concentrations of chlorine. The NOSB must perform a comprehensive review of cleaning, disinfecting, and sanitizing materials that can support annotations for these materials on the National List.
- E-Commerce must provide all information about organic products that is required by law. Probably every organic consumer who has shopped online has encountered product names, including the word “organic†or descriptions of products as “organic†or containing organic ingredients, and wondered whether that description is true. There is inconsistency between the requirements for a product offered for sale by a “brick and mortar†establishment and the requirements in eCommerce, and this inconsistency provides an opportunity for fraud. The requirements for eCommerce should be brought into line with those for physical establishments. The NOSB must immediately identify any obstacles to eliminating this loophole and propose a rule change that will address them.
For more information on organic, please see Beyond Pesticides’ organic program page. and Keeping Organic Strong page. For additional information on organic-compatible products, see Pesticide Products Compatible with Organic Landscape Management and Fertilizers Compatible with Organic Landscape Management.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Frontiers in Agronomy
