Cannabinoids Help Hemp Resist Chewing Insects, Study Finds

Cannabinoids may serve as part of hemp’s natural defense system against chewing insects, according to a 2023 study published in Horticulture Research. The research does not show that cannabinoid-based pesticides are ready for agricultural use, but it offers evidence that these compounds can reduce herbivore damage and may help breeders develop more pest-resistant hemp varieties.

Researchers at Cornell AgriTech compared hemp plants with different cannabinoid profiles in field and laboratory experiments. In field trials conducted in New York, plants with higher concentrations of foliar cannabinoids generally sustained less damage from chewing herbivores. Cannabinoid-free plants were particularly vulnerable, with some being heavily or completely defoliated soon after transplanting.

The team also studied larvae of the cabbage looper, Trichoplusia ni, a generalist chewing insect. Larvae consumed less tissue and grew less when fed detached leaves from cannabinoid-producing plants than when fed leaves from cannabinoid-free plants. In separate feeding trials, researchers added the acidic cannabinoids CBDA and CBGA directly to an artificial insect diet. Increasing concentrations were associated with lower larval growth and survival.

Those controlled diet experiments are important because they provide evidence that cannabinoids themselves can affect insect performance, rather than merely being associated with another plant trait. Still, the study does not establish that cannabinoids are equally effective against all pests. The researchers did not test sap-sucking insects such as aphids and mites, and insects that specialize on cannabis may have evolved ways to tolerate or avoid its chemical defenses.

The findings also help explain why hemp produces more than 100 identified phytocannabinoids. Although cannabinoids are widely studied for their effects in humans and other vertebrates, their biological role in the plant has been less clear. The researchers propose that cannabinoid production may have evolved partly as a defense against herbivores, potentially alongside other functions such as protection from pathogens or ultraviolet radiation.

Most cannabinoids in living hemp tissue occur in acidic forms. Heat can convert CBDA, THCA and CBGA into CBD, THC and CBG through decarboxylation. The Cornell study examined CBDA and CBGA but not THCA, in part because of federal restrictions related to THC-producing hemp research.

In practical terms, the research points first toward plant breeding rather than a ready-made spray. Developing hemp cultivars that remain compliant with legal THC limits while retaining stronger natural defenses could reduce insect damage in some production systems. Using isolated cannabinoids as pesticides would require additional testing to determine effective doses, target pests, environmental effects, effects on beneficial insects and risks associated with residues.

Any commercial pesticide based on these compounds would also face regulatory review. The U.S. Environmental Protection Agency’s biopesticide framework covers certain pest-control products derived from natural materials, but a product must meet applicable safety, efficacy, labeling and environmental requirements before it can be marketed. Food-crop uses would raise additional questions because cannabinoid residues can have pharmacological activity.

For now, the Cornell work is best understood as evidence of a natural plant–insect interaction—not proof that hemp cannabinoids can immediately replace conventional pesticides. Further studies across locations, growing conditions and pest species will be needed to determine how useful this defense could be in sustainable crop protection.