Toxic and repellent effects of hemp leaf extracts and cannabidiol against adult female yellow fever mosquitoes, Aedes aegypti.

Martínez Rodríguez E.; Phelan P.; Canas L.; Acosta N.; Feliciano P.; Tubbs J.; Loperena E.; Rakotondraibe H.; Piermarini P. · PloS one · 2026

**Background & Methods** This experimental study evaluated the toxic and repellent properties of hemp leaf extract and cannabidiol (CBD) against adult female Aedes aegypti mosquitoes. Three complementary assays were employed: acute topical toxicity testing (500 nL application to thorax with 24-hour mortality assessment), a no-choice membrane blood-feeding assay to measure feeding deterrence, and a mosquito airborne repellency test (MART) to assess spatial repellency effects. **Key Findings** - Hemp leaf extract demonstrated dose-dependent adulticidal activity with an LD50 of 22.13 μg/mosquito at 24 hours post-topical application; however, purified CBD isolate at equivalent doses caused significantly lower mortality than the whole extract, indicating other bioactive compounds contribute to toxicity. - In the membrane blood-feeding assay, hemp leaf extract produced dose-dependent repellency effects, whereas CBD isolate showed substantially weaker repellent activity even at higher equivalent concentrations. - The MART assay revealed that hemp extract did not elicit spatial repellency, suggesting low volatility of the repellent compounds and indicating that repellent mechanisms operate primarily through direct contact rather than airborne exposure. **Dosage & Administration** Topical application of 500 nL per mosquito; specific extract concentrations and CBD equivalent doses tested were not quantitatively specified in the abstract. LD50 for hemp leaf extract: 22.13 μg/mosquito. **Safety & Adverse Effects** Not reported. The study focused on mosquito lethality and repellency without addressing human or environmental safety parameters. **Evidence Quality** This is a controlled experimental study with appropriate negative and dose-response controls. However, the evidence is limited to laboratory conditions using adult female mosquitoes only; field efficacy, environmental persistence, and applicability to other disease vectors remain unknown. A significant limitation is that the abstract does not specify the complete chemical composition of the hemp extract or the relative concentrations of CBD versus other potentially active compounds, limiting mechanistic understanding. The study provides moderate-quality evidence for the proof-of-concept that hemp-derived products possess mosquitocidal properties, but further research is needed to identify synergistic compounds, optimize formulations, and evaluate real-world effectiveness and safety.

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