20
Mar
“Biopesticides” Critiqued as Poorly Defined and Regulated, Challenging Safety Assumptions and Use
(Beyond Pesticides, March 20, 2026) Biopesticides represent a kind of Utopian destination in the landscape of agricultural sustainability. If only they could ensure planetary harmony. A review of botanical biopesticides in the March 11 issue of Toxics raises important questions that require scrutiny and review under the pesticide registration process and when used in organic systems under the Organic Foods Production Act. The term biopesticide can be misleading, and any replacements for synthetic pesticides cannot be taken only on faith.
As Beyond Pesticides has noted previously, the U.S. Environmental Protection Agency’s (EPA) definition of biopesticides—“derived from such natural materials as animals, plants, bacteria, and certain minerals”—is broad, vague, and used differently by different interests. EPA regulates biopesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) in three categories:
- Substances that interfere with mating, such as insect sex pheromones, as well as various scented plant extracts that attract insect pests to traps;
- Microbial pesticides consisting of a microorganism (e.g., a bacterium, fungus, virus, or protozoan) as the active ingredient; and
- Plant-Incorporated-Protectants (PIPs), pesticidal substances that plants are genetically engineered to produce.
The review by Sandra Petrovic, PhD, and Andreja Leskovac, PhD, of the University of Belgrade, highlights the need not to rush from one solution—synthetic pesticides—to the next—biopesticides—without careful analysis of their modes of action and environmental fates, or ignoring the potential consequences.
Drs. Petrovic and Leskovac focus on botanicals out of the array of substances categorized as biopesticides. The EPA categories do not clearly address the ways botanical pesticides can be used, which are far wider than scented plant extracts in insect traps. Botanicals are plant-derived compounds such as phenols, flavonoids, resins, tannins, and terpenes. These are often in the form of essential oils from citrus plants, cloves, and mint. They may be applied to field crops, in greenhouses, and after harvest during storage and distribution.
Botanical biopesticides present serious challenges to any regulatory approval based on simplistic assumptions. Essential oils may contain more constituent compounds than commercial pesticides, and many, if not most, are unknown. The environmental fates of biopesticides are incompletely understood, although proponents tend to believe they break down rapidly and thus pose no risk beyond their intended use. But the downstream fate of biopesticides can lead to synergistic or additive toxic effects even when individual substances are present below allowed residue levels. Breakdown products can have very different chemical profiles and effects from their precursors, including in their “persistence, efficacy, and effects on non-target organisms,” the authors write.
Botanical pesticides are often quite volatile. This makes them less likely to remain as residues on crops, which is a plus compared to synthetic pesticides. However, evaporated and chemically complex essential oils “can emit measurable particulate matter” and each constituent can degrade into potentially more toxic compounds. They may also react with natural volatiles and form ozone. Particulate matter and ozone are potent health hazards—in fact, they are criteria pollutants regulated by EPA—and more commonly associated with vehicle and industrial emissions, but their potential generation by biopesticides must be considered.
Drs. Petrovic and Leskovac note that while using synthetic chemicals and biopesticides together is often touted as appropriate integrated pest management, “much less is known about their combined application, the interactions that may arise between them, and the potential agronomic or health implications of such mixed-use practices.” They cite research showing that essential oils can increase the toxicity of pyrethroids, organophosphates, neonicotinoids, and pyrroles.
All this indicates that just because a substance is “natural” does not mean it presents no hazard or risk. For example, rotenone, a plant-derived neurotoxicant, has been used for centuries to kill pests and in indigenous hunting. While it is still allowed by EPA for limited use in controlling invasive fish, it is not currently registered for food uses, and the Organic Foods Production Act’s National List of Allowed and Prohibited Substances includes a section that prohibits natural substances that are hazardous, including rotenone. Beyond Pesticides emphasizes that the review process leading to appropriate restrictions on rotenone must continue to be used for all “natural” pesticides.
In 2024, EPA proposed to streamline the registration review for several “low risk biopesticides,” including alpha methyl mannoside, a growth promoter, Duddingtonia flagrans, a fungus that inhibits predatory cattle nematodes, and Pepino mosaic virus, which protects greenhouse tomatoes from other viruses.
Last year, Beyond Pesticides called on EPA to ensure that this contemplated streamlining does not rely entirely on original or previous registration data, much of which is incomplete and otherwise inadequate and may have been based on “limited actual data, data waiver request rationales, and purported absence of new data or adverse incidents reported.” EPA rationalized its registration of alpha methyl mannoside based on just such flimsy evidence. Similarly, EPA approved Duddingtonia and Pepino mosaic virus by waiving numerous data requirements and using “scientific rationale”—a euphemism for broad assumptions made without empirical support—about the likelihood of harm to nontarget organisms and ecosystem stability.
Another serious concern regarding biopesticides is the category of Plant-Incorporated-Protectants (PIPs), promoted by the pesticide industry as environmentally benign companions to synthetic pesticides. PIPs include RNAi technologies, such as the genetic engineering of Roundup-ready seeds. The “i” stands for “interfering,” which should be an immediate red flag. This technology is derived from natural processes that silence certain genes in organismal development and is the basis for a number of pharmaceuticals. It starts with double-stranded RNA (dsRNA) that splits into RNAi when it encounters a particular enzyme called “dicer.” The RNAi molecules then act to silence genes.
But RNAi technology has serious flaws. It does not always silence only the target gene, but can affect other parts of a genome in the target organism or in other, nontarget species. As one recent critical review put it, “There is no shared understanding of dsRNA sequences that trigger off-targeting.” And another, more enthusiastic review of RNAi technologies even points out that “the rapid evolution of resistance in target insect species now poses a serious threat to the durability and field efficacy of this technology.”
The same review details other downsides to the use of RNAis: dsRNA “may still affect microbial communities essential for nutrient cycling and plant health” despite its rapid degradation in the environment, and it “is not always fully degraded by microbes.” In addition, dsRNA can bind to soil minerals and possibly transfer through food webs, including among predator species like ladybugs and parasitic wasps that ingest dsRNA in treated prey. Further, pesticide researchers are exploring the delivery of RNAi via nanotechnology, which adds a new and vast degree of uncertainty to pesticide technologies’ effects on human health and the biosphere.
As Beyond Pesticides noted in its 2021 critique of EPA’s broad definition of biopesticides, “There is something counterintuitive in labeling something a ‘bio’ product (which connotes something ‘natural’) when in fact it involves genetic engineering—an entirely synthetic process.” Genetic engineering is not allowed under the USDA Certified Organic brand and label.
The regulatory systems of both the U.S. and the E.U. were developed for synthetic pesticides, and, as Drs. Petrovic and Leskovac observe, the “properties, modes of action, and environmental fate differ significantly” between synthetics and biopesticides. However, they add, this does not mean biopesticides should be given a pass toxicologically. “Instead, they should be regulated as complex chemical mixtures that require robust compositional characterization, standardized toxicological assessment, and realistic exposure evaluation, comparable in scientific rigor to that applied to synthetic pesticides.”
Continuing research suggests that careful development of biopesticides can result in much improvement over synthetics. See the Daily News regarding rose essential oil as a stimulator of tomato plants’ defenses against pests. The reported study used very low concentrations of essential oil and found that higher concentrations might be harmful. Beyond Pesticides also analyzed research on a biofungicide produced by orange peel and distilled without solvents, which can be very effective against numerous fungi infecting fruit and vegetables. These studies reflect the understanding that agricultural product protection must be holistic, taking into account both production methods and downstream effects.
Beyond Pesticides stresses that the current system is in a perpetual “chase” for the next pest “fix,” whether chemical or biological. The only way to foster stability amongst competing organisms is through balance, not total annihilation. This is what organic regenerative agriculture is founded on. Soil health and enhancing biodiversity are essential for “plant health, resilience, and prevention of disease and infestations….Organic advocates maintain that without a holistic approach, land managers remain on a pesticide treadmill and undercut ecological balance necessary in organic systems.”
Thus, in the search for food security based on sustainable relationships between humans and non-human consumers of desirable resources, there are two aspects of reality that no pest control system can escape: pest resistance and nontarget effects. Using “natural” tactics with the same old strategy will not work, because that strategy is based on the fantasy that technology can always triumph over nature, and that unintended consequences can be externalized. The pesticide industry has used this fantasy to its own financial advantage for a century. But technology’s triumph is always temporary, and cannot beat nature at her own game.
See Beyond Pesticides’ Organic Agriculture page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Biopesticides and Human Health Risks: A Critical Review
Petrović and Leskovac
Toxics 2026
https://www.mdpi.com/2305-6304/14/3/246
Beyond Pesticides Calls on EPA To Ensure Comprehensive Review of “Biopesticides”
Beyond Pesticides, January 28, 2025
https://beyondpesticides.org/dailynewsblog/2025/01/beyond-pesticides-calls-on-epa-to-ensure-comprehensive-review-of-biopesticides/
“Biopesticides,” with Broad Definition, Challenged as Unsustainable
Beyond Pesticides, August 13, 2021
https://beyondpesticides.org/dailynewsblog/2021/08/biopesticides-with-broad-definition-challenged-as-unsustainable/
Biofungicides Show Promise in Agriculture and Land Management, Study Finds
Beyond Pesticides, September 6, 2024
https://beyondpesticides.org/dailynewsblog/2024/09/review-of-biofungicides-highlights-feasibility-of-alternatives-to-hazardous-pesticides-in-organic-agriculture-and-land-management/
Study Bolsters the Case for Essential Oils (EO) in Organic Pest Management for Tomato Production
Beyond Pesticides, April 3rd, 2024
https://beyondpesticides.org/dailynewsblog/2024/04/study-bolsters-the-case-for-essential-oils-eo-in-organic-pest-management-for-tomato-production/
Minimum Risk Pesticide: Definition and Product Confirmation
Environmental Protection Agency
https://www.epa.gov/minimum-risk-pesticides/minimum-risk-pesticide-definition-and-product-confirmation#confirmunder
205.602 Nonsynthetic substances prohibited for use in organic crop production.
The National List of Allowed and Prohibited Substances
U.S. Code
Title 7 Subtitle B Chapter I Subchapter M Part 205 Subpart G The National List of Allowed and Prohibited Substances
https://www.ecfr.gov/current/title-7/subtitle-B/chapter-I/subchapter-M/part-205/subpart-G/subject-group-ECFR0ebc5d139b750cd/section-205.602
(see https://www.epa.gov/pesticides/epa-proposes-streamlined-registration-review-process-several-low-risk-biopesticidesfrom) “minimum risk” pesticides (see
https://www.epa.gov/minimum-risk-pesticides/minimum-risk-pesticide-definition-and-product-confirmation#confirmunder) section 25b of FIFRA.
