Hemp cannabinoids as natural pesticides - research, mechanisms, and agricultural perspectives 2026

Hemp has been producing cannabinoids for millions of years, and the question of why this costly metabolic investment exists has long remained unresolved. In 2023, a team from Cornell University published a study in Horticulture Research that combined field observation, tests on detached leaves, and the administration of pure cannabinoids in an artificial insect diet. The conclusions were more cautious than the popular narrative about a natural pesticide suggests, but they were based on measurement. This text breaks down that work, showing exactly what was measured, explaining why insects respond to cannabinoids despite the lack of CB1 and CB2 receptors, and describing the legal state that currently determines the possibility of any application in the European Union.

KEY INFORMATION
• The study by Stack et al. from Cornell University (Horticulture Research, 2023) showed an inverse relationship between cannabinoid concentration in leaves and damage from chewing insects.
• In an artificial diet, concentrations above 0.1% CBDA or CBGA significantly reduced the survival of Trichoplusia ni larvae; at 1% CBDA, none of the 45 larvae survived after three days.
• The study included CBDA and CBGA. THCA was not tested, and the experimental species was exclusively Trichoplusia ni, not Spodoptera frugiperda.
• Insects do not have CB1 or CB2 receptors. McPartland et al. (Journal of Comparative Neurology, 2001) found no binding of cannabinoid ligands in the five studied species.
• No cannabinoid preparation has authorization in the European Union as a plant protection product. Using an unregistered preparation on a crop is an offense in Poland.
• Polish law lists the production of natural plant protection products among the allowed purposes of hemp cultivation, which opens a research path, not a commercial one.

What did the Cornell University study really show?

The team led by Stack et al. from Cornell University tested the herbivore defense hypothesis on an F2 population derived from crossing the Carmagnola and USO-31 varieties (Horticulture Research, 2023, PMC10681003). The population splits into three chemotypes: CBDA-dominant plants, CBGA-dominant plants, and plants virtually devoid of cannabinoids. This arrangement allows for the comparison of genotypes of common ancestry that differ mainly in cannabinoid profiles.

The work consists of three independent experiments, not a single laboratory test. The first is a field observation of leaf damage by chewing insects. The second is a test on detached leaves with Trichoplusia ni larvae, conducted over six days. The third is the administration of purified cannabinoids in an emulsion to an artificial insect diet, in two variants: surface application and mixing into the food mass.

One result from the test on detached leaves deserves special attention because it concerns behavior, not mortality. Larvae feeding on genotypes devoid of cannabinoids spent significantly more time on the underside of the leaf than larvae on genotypes with CBDA dominance. The underside has a higher density of trichomes in hemp, so the insect's avoidance of it appears to be a response to a local dose of compounds, rather than general toxicity. This is an important clue because a deterrent effect can be more valuable in plant protection than killing: it spares the natural enemies of the pest.

Separating these levels is significant because only an artificial diet separates the cannabinoid itself from other plant traits. Genotypes devoid of cannabinoids had collapsed trichomes, so it is impossible to determine on the leaf whether the larvae are deterred by chemistry or surface morphology.

Why were acidic CBDA and CBGA studied instead of neutral CBD and THC?

In a living plant, cannabinoids are almost exclusively found in acidic forms. Neutral variants only form after decarboxylation, which occurs when the carboxyl group is removed under heat or prolonged storage. Therefore, a biting insect that encounters a fresh leaf comes into contact with CBDA and CBGA, not with CBD or THC. The choice of acidic forms in the Cornell experiment replicates what happens in the field, not what ends up in the consumer product.

It is worth clarifying a recurring misunderstanding. This study did not test THCA. The plants used in the experiment belonged to chemotypes dominated by CBDA or CBGA, as this is legal breeding material of industrial hemp. Claims attributing the measured insecticidal effectiveness to tetrahydrocannabinolic acid in this study are unfounded. More about the molecule itself and how it differs from the neutral form can be found in the text. THCA: what is it and how does it differ from THC.

Neutral CBD also has documented activity against insects, but it comes from other studies. Park et al. demonstrated in Scientific Reports that Manduca sexta larvae prefer tissue with lower CBD content, and those on a diet with high concentrations of this compound grow slower and die more often (Scientific Reports, 2019). To osobna linia dowodowa, prowadzona na innym gatunku i na innej formie chemicznej.

How do cannabinoids affect insects without CB1 and CB2 receptors?

Insects do not have an endocannabinoid system as known in mammals. McPartland et al. checked this directly: in the tissues of honeybees, fruit flies, navel orangeworms, Spodoptera frugiperda, and the beetle Zophobas atratus, they did not detect specific binding of synthetic cannabinoid ligands, and in the genome of the fruit fly, they did not find orthologs of CB1 and CB2 receptors or fatty acid amide hydrolase (Journal of Comparative Neurology, 2001). The authors hypothesized that the receptors disappeared due to a lack of ligands, as insects produce little arachidonic acid or do not produce it at all.

The absence of a receptor does not mean the absence of action. The measured effects indicate pathways independent of classical cannabinoid signaling, although none have been fully described yet. Below are the findings from the studies cited by the Cornell team.

• Change in electrical activity of the nervous system. In the electrophysiological recordings, the ganglia of Manduca sexta larvae treated with CBD responded to stimuli with a delay but much more strongly than the ganglia of control larvae (Scientific Reports, 2019).
• Disruption of feeding and growth. Larvae on a diet with a higher concentration of cannabinoid eat less and gain weight more slowly, as seen in both the Cornell study and in Park et al.'s work.
• Change in the activity of detoxifying and digestive enzymes. Abendroth et al. described a change in cytochrome P450 and beta-glucosidase activity in Spodoptera frugiperda after exposure to CBD (Arthropod-Plant Interactions, 2023).
• Disruption of molting. The thesis cited by the Cornell team describes a disruption in the structure of the cuticle in Manduca sexta leading to fatal molting errors. This is the weakest link in this list in terms of source ranking.

The Cornell team makes a caveat worth repeating. All previous mechanistic studies have been conducted on larvae of moths and beetles, which belong to one order of insects with one method of feeding. It is unknown whether the same mechanism operates in piercing-sucking insects, such as aphids, which do not consume leaf tissue but pierce vascular bundles and bypass the surface layer along with trichomes. If the action is based on contact with the leaf surface, this entire group may remain unaffected.

Popular descriptions add to this set TRP channels, octopamine receptors, uncoupling of mitochondrial respiration, and inhibition of cyclooxygenase in insects. In studies that actually measured the impact of cannabinoids on larvae, none of these pathways were confirmed. Treat them as hypotheses to be tested, not as descriptions of an established mechanism.

Which insects respond to cannabinoids, and which do not avoid them?

The answer depends on the species and can be the opposite of what is expected. Cannabinoids do not act like a broad-spectrum poison, but as a signal that some insects interpret as a warning, while others ignore or even prefer. This selectivity is scientifically more interesting than toxicity itself, as it speaks to the evolution of the plant-insect relationship.

Two things stand out. First, reliable data comes almost exclusively from caterpillars of moths and beetles, and from storage beetles. No one has properly studied aphids, spider mites, thrips, or harmful flies in field crops in this context. Second, the fruit fly behaves exactly the opposite of caterpillars, which in itself rules out the narrative of a universal repellent.

The most interesting result from this set is often overlooked because it does not fit the simple narrative of poison. In the same study, Park et al. investigated what happens to larvae poisoned with ethanol, which was used as a carrier for cannabinoids. It turned out that adding CBD increased the survival of poisoned larvae by forty percent and restored their ability to seek food. The same molecule that kills caterpillars at high concentrations saves them in a different experimental setup. The conclusion serves as a methodological warning: the effect of a cannabinoid depends on the dose, carrier, and state of the insect, so a single number taken out of context describes nothing.

Why does the hemp plant produce cannabinoids at all?

Biosynthesis of cannabinoids requires specialized enzymes and separate secretory tissue, so it must be beneficial for the plant. Three hypotheses have been considered: protection against herbivores, protection against ultraviolet radiation, and action against pathogens. The Cornell team's work strengthens the first of these, as it provides the missing experimental link.

The argument from distribution is straightforward. Cannabinoids are produced in glandular trichomes on the outer surface of leaves and female inflorescences, precisely where the plant interacts with the insect. The density of trichomes is highest in reproductive tissues, which have the greatest value for the survival of the genetic line. The authors of the study also note that the difference in cannabinoid concentration between male and female inflorescences may be a clue in the question of the evolution of dioecy in cannabis.

The study itself formulates an important caveat to this argument. Since the trait of lacking cannabinoids is associated with the collapse of trichomes, in the experiment on the whole leaf, it is impossible to separate the influence of chemistry from the influence of a physical barrier on the surface. Only the administration of purified compounds in an artificial diet showed that the cannabinoid itself alters the growth and survival of larvae independently of the leaf structure. This is the proper content of the conclusion, not a vague statement about millions of years of evolution.

Does the hypothesis of protection against UV-B radiation hold up?

This hypothesis has a longer history than the evidence. Pate proposed in the 1980s that cannabinoids could absorb ultraviolet radiation and protect reproductive tissues, and early work by Lydon et al. in 1987 noted an increase in THC content in plants exposed to UV-B. This is the basis for dozens of popular texts, usually without mentioning what later measurements revealed.

More recent data goes in the opposite direction. Rodriguez-Morrison et al. exposed two cannabis strains to controlled doses of radiation at a wavelength of 287 nm for nine weeks of flowering and found no increase in flower yield or cannabinoid concentration (Frontiers in Plant Science, 2021). In one strain, the total concentrations of THC and CBD actually decreased with the dose, terpene content decreased in both, and the plants showed damage: reduced leaf blade area, deformities, and decreased photosynthetic efficiency.

The practical conclusion is twofold. For science, this means that the ultraviolet hypothesis has no support in controlled experiments today and should not be presented as an established fact. For the grower, it means something even more direct: supplementing with ultraviolet radiation is not a tool for increasing cannabinoid content, and at higher doses, it harms the plant.

Do cannabinoids also affect fungi and bacteria?

Insects are not the only direction. Appendino et al. studied five major cannabinoids, namely CBD, CBC, CBG, THC, and CBN, against clinically significant strains of methicillin-resistant Staphylococcus aureus and found strong activity from all five (Journal of Natural Products, 2008). The study was an analysis of the relationship between structure and activity, so it also showed which modifications of the molecule destroy this activity.

The very structure of that study says something valuable about the molecule. Antibacterial activity proved to be little sensitive to the structure of the prenyl chain and its position, and even to the presence of a carboxyl group, meaning it persisted in acidic forms. However, it was destroyed by methylation and acetylation of hydroxyl groups and esterification of the carboxyl group. The authors interpreted this as meaning that the carrier of activity is the olivetolic core, while the prenyl chain only regulates affinity for lipids. For a potential preparation, this has practical consequences: modifications that facilitate formulation may inadvertently disable the activity.

However, it must be said honestly where the translatability of this result ends. Activity against pathogenic bacteria in laboratory conditions says nothing about effectiveness against plant pathogens in the field. Research on the ability of cannabinoids to inhibit plant disease agents is scarce, and an older observation by McPartland about the fungistatic action of cannabinoids against a pathogen affecting cannabis dates back to 1984 and has not been properly followed up.

In practice, this means that we know less about cannabinoids as fungicides today than about cannabinoids as insecticides, and even there, we know little. The concentration values circulating on the internet that inhibit the growth of gray mold or fusarium, given with precision to units, have no equivalent in the peer-reviewed literature that can be pointed to. The issue of testing residues and the purity of the raw material is, by the way, a separate topic that we expand upon in the text about what an independent laboratory tests in CBD products. what an independent laboratory tests in CBD products.

How do cannabinoids compare to neem, Bt, and pyrethrins?

The comparison today clearly favors the alternatives to cannabinoids, but not due to weaker action. The reason is different and much simpler: azadirachtin, Bacillus thuringiensis, natural pyrethrins, and spinosad have a complete registration pathway, years of field data, and established doses and application timings. Cannabinoids have none of these.

Acheuk et al. described the state of plant biopesticides in Europe and the Mediterranean region, highlighting the paradox of this field: there are many substances with promising activity, but only a handful of products have been brought to registration (Biomolecules, 2022). The bottleneck is not chemistry, but the cost and time of the dossier and the lack of ecotoxicological data of the quality required by the registering authority.

There is one direct comparison of both worlds in the same protocol. Mantzoukas et al. compared CBD oil with neem oil against fourth-instar larvae of three storage pests on wheat, rice, and corn. Both oils showed clear insecticidal activity, causing significant mortality at higher doses, and both experimental groups produced less offspring than the control. The effect was dose-dependent in both cases. This is the closest match we have today, and it results in a tie, but it concerns storage insects, not field ones.

A reliable answer to the question of competitiveness is therefore: today cannabinoids do not compete with anything because they are not approved for use. The question of their place in plant protection will only become meaningful when data that currently does not exist is generated.

Are cannabinoids safe for bees and beneficial insects?

This question determines the fate of every new insecticide, and the answer in the case of cannabinoids is minimal. There are two premises available, and both must be read cautiously, as neither is a toxicity study in the sense required for registration.

The first comes from the work of McPartland et al., in which the honey bee was one of five species without detectable cannabinoid ligand binding. The second is the hive experiment by Skowronek and Strachecka: workers receiving oil with 30% CBD content in syrup or on strips of fabric had higher antioxidant enzyme activity than the control group, as well as higher concentrations of calcium, magnesium, and phosphorus in the hemolymph (Antioxidants, 2023). The authors conclude about the supportive action, not about the lack of harm.

The difference is significant and easy to overlook. The study on the antioxidant system did not measure mortality, the impact on larval development, or flight behaviors, so it does not replace an ecotoxicological study. There is no data in this context regarding predators and parasites used in biological control, such as beneficial insects, lacewings, or parasitic wasps. Until such data appears, the claim of a mild cannabinoid profile for beneficial insects remains an assumption.

What does the law of the European Union and Poland say about such use?

The rule is simple and leaves no room for interpretation. A plant protection product may only be placed on the market and used after obtaining permission, as stated in Regulation (EC) No. 1107/2009, which is directly referenced by the Polish Act of March 8, 2013, on plant protection products (Dz.U. 2013 poz. 455). No cannabinoid substance has such permission in the European Union.

The practical consequence applies to everyone, not just the commodity producer. The law provides for fines for violations in this area, and adjudication occurs under the provisions on offenses. A specific range of amounts allegedly written in this law is circulating; however, such an amount does not exist in its text, as the amount of the fine results from general provisions on offenses, not from the law on plant protection products.

The second layer concerns the raw material itself. Industrial hemp, according to Polish law, refers to plants of the species Cannabis sativa L., in which the sum of delta-9-THC and THCA in flowering or fruiting tops does not exceed 0.3% when calculated on a dry weight basis. It is the sum of both compounds that counts, not just delta-9-THC, which changes the result of laboratory testing and can be a source of costly misunderstandings; we describe them in the text about why farmers destroy legal hemp due to a fraction of a percent. Why farmers destroy legal hemp due to a fraction of a percent.. The basis is Article 4 point 5 of the Act on Counteracting Drug Addiction as amended by the Act of March 24, 2022 (Dz.U. 2022 poz. 763). The national threshold corresponds to the EU threshold, but it does not imply that they are the same: these are two separate regulations with the same numerical value.

There is one surprising detail in all of this. Cultivating industrial hemp requires registration in the producers' register maintained by the director of the regional branch of KOWR, and the law lists the purposes for which such cultivation may be conducted. Among them is the production of natural plant protection products. Thus, the Polish legislator has allowed this direction as a cultivation goal, although a ready product still cannot be used without permission for the product itself.

What does the path to permission look like in the European Union?

It is important to understand that there is not one decision, but two separate ones at two different levels. First, the active substance must be approved at the EU level. Only then does a specific product containing that substance receive permission to be placed on the market, issued by the member state. The Polish Act on Plant Protection Products does not define these terms independently: it directly refers to the definitions from Article 3 of Regulation (EC) No. 1107/2009, including the definition of the permission itself from point ten of that article.

For cannabinoids, this means that there is not even the first step. No form, neither acidic nor neutral, has been submitted and approved as an active substance, so the question of national permission is moot. In regulatory terms, CBDA and CBD are actually two different substances, not two forms of the same, so each would require its own documentation.

The law does provide for expedited pathways, but none of them bypasses assessment. Article 53 of Regulation 1107/2009 allows a product to be permitted for a limited time in case of danger; in Poland, such permission is granted by the minister responsible for agriculture upon request, after consulting with the minister of health and the minister of the environment. A separate pathway concerns small-scale applications, i.e., crops that are too niche to justify full registration. However, both pathways assume that the active substance is already approved.

This arrangement explains why promising laboratory results so rarely lead to a product. The bottleneck is not demonstrating that something kills a larva, but compiling data on the behavior of the product in the environment, on residues in agricultural produce, and on the impact on non-target organisms. Cannabinoids currently have none of these data sets.

Is it allowed to spray roses with CBD oil from the store?

No, and it is worth breaking this down into three separate reasons, as each is sufficient on its own. The question comes up regularly, usually in the version about aphids on roses or spider mites on tomatoes in a home greenhouse, so it deserves a specific answer, not a vague generalization.

The legal reason is the simplest: a food or cosmetic product used for plant protection becomes a plant protection product, and no consumer oil has such permission. The size of the cultivation or the fact that it is grown in a pot on a balcony does not change this.

The second reason is chemical. The concentrations at which the Cornell study observed effects on larvae pertained to an emulsion applied to the insect's food under experimental conditions, not to spraying plants. Consumer oil is a suspension in a carrier oil, with additives that no one has studied for contact with the leaf blade. The third reason follows from the second: plant oil applied to a leaf in the sun can burn it, and the side effect of a home experiment can be more severe than the aphids themselves.

For aphids, there are approved and inexpensive solutions: potassium soap, paraffin oils, azadirachtin-based products with current permissions, and the introduction of predators. The current list of approved products is maintained by the State Plant Health and Seed Inspection, and it is this body, not a popular science article, that is the appropriate source when choosing a product.

What else do we not know about cannabinoids as biopesticides?

The Cornell study is the beginning of a research line, not its summary. The authors themselves state that they are far from a complete picture and point out specific gaps. Collecting them in one place is fairer than listing alleged advantages, as it shows how much work separates the current state of knowledge from anything that could be applied.

There is another risk in this puzzle that is rarely discussed because it requires a shift in perspective. Since fruit flies have shown a preference for food with added phytocannabinoids, a product based on these compounds may not only repel some insects but also attract others. In risk assessment, it is not just the toxicity that matters, but the overall balance of interactions with the insect community in the crop, including economically neutral and beneficial species. Without such a balance, it is impossible to predict whether the treatment will reduce pest pressure or merely shuffle its composition. This question is routinely asked today for every new active substance, and in the case of cannabinoids, it still remains unanswered.

To this list, we add the question of chemical form. Experiments were conducted on acidic forms and neutral CBD, but no one has systematically compared the entire family of compounds in one protocol, while cannabis produces many more. Standardization of methods is a prerequisite here, as results from different centers vary in extraction methods, purity assessment, and larval rearing.

What does this mean for the farmer, scientist, and reader?

For the farmer, the conclusion is clear and practical. Cannabinoids should not be used today for crop protection in any form, and if you are running a hemp plantation and observe less pest pressure than in neighboring fields, consider it a biological curiosity, not an agronomic tool. Choose treatment agents from the current register maintained by PIORiN.

For scientists and agronomy students, this field is open and exceptionally well-defined. The gaps in knowledge are explicitly stated by the authors of the Cornell study, and Polish centers have a natural advantage in this area: a tradition of hemp cultivation, access to plant material, and analytical support. We describe the context of low-input agriculture more broadly in the text about konopiach w rolnictwie ekologicznym.

For the reader purchasing cannabis products, the distinction is simple. CBD oil is a consumer product, not a plant protection agent, and the studies described here say nothing about its application. The value of cannabis extends far beyond supplements and includes fiber, food, and building materials, but each of these applications has its own regulations and documentation. Mixing them together results in either a loss of money or a fine.

Finally, a note on reading reports in this field. The Cornell study is solid and states exactly what it measured: two acidic cannabinoids limit feeding and growth of one species of caterpillar, and in the field, higher concentrations of cannabinoids in leaves are associated with less damage. Everything that goes beyond this statement in popular discussions should be verified in the source before being repeated.

Frequently Asked Questions

Do cannabinoids actually act on insects like pesticides?

They do, but under experimental conditions and against a narrow group of species. In the study by Stack et al. from Cornell University, concentrations above 0.1% CBDA or CBGA in an artificial diet reduced the survival of Trichoplusia ni larvae, and at 1% CBDA, none of the 45 larvae survived after three days. This does not create a product for use in crops.

Which cannabinoids were studied in this context?

In the work from Cornell, acidic CBDA and CBGA were tested, as these forms occur in the living plant. THCA was not included in this study. Neutral CBD has separate documentation: Park et al. demonstrated in Scientific Reports poorer growth and higher mortality of Manduca sexta larvae on a diet with a high concentration of this compound.

Is it allowed to use cannabinoids for crop protection in Poland?

No. Plant protection products require authorization according to Regulation (EC) No 1107/2009, which is referenced by the Act of March 8, 2013, on plant protection products. No cannabinoid preparation has such authorization in the European Union, and using a product without authorization is subject to a fine imposed under the provisions on offenses.

Why does the hemp plant produce cannabinoids?

The best-documented response is defense against herbivores. Cannabinoids are produced in glandular trichomes on the outer surface of leaves and female flower clusters, and a study from Cornell showed that purified CBDA and CBGA limit the growth and survival of larvae even when administered bypassing the plant.

How do cannabinoids affect insects without CB1 and CB2 receptors?

This has not yet been fully established. McPartland et al. demonstrated in 2001 the lack of binding of cannabinoid ligands in five insect species. Measured effects include altered electrical responses in nerve ganglia, reduced feeding, and changes in detoxification enzyme activity, but a coherent mechanism is still lacking.

Can cannabinoids replace chemical plant protection products?

Not in the foreseeable future. There is a lack of field data on the durability of the preparation, studies on economically significant pests other than caterpillars, and risk assessments for non-target organisms. Without these three elements, no registration dossier will be created, and without registration, there can be no application.

Will hemp seed oil or CBD oil work on pests?

Not in a useful way and not legally. Seed oil practically contains no cannabinoids. CBD oil is a suspension in carrier oil with additives not intended for contact with leaves, and using a consumer product for plant protection makes it an unregistered plant protection product.

What does this mean for hemp cultivation in Poland?

For now, it means research potential. Cultivation requires registration in the producer registry maintained by the director of the KOWR regional branch, and the law lists the production of natural plant protection products among the allowed purposes of cultivation. The preparation itself would still require a separate authorization as a plant protection product.

If you are looking for cannabis intended for consumption rather than for agricultural treatments, check the section hemp food.

The article is for informational and educational purposes and does not constitute legal advice. The legal status described in the article is valid as of the publication date: regulations regarding hemp may change. Before making a decision, consult a lawyer or current legal acts.

Author: Michał Waluk · Opublikowano: 2026-05-04 · Aktualizacja: 2026-08-10