A recent study suggests that hemp leaf extract containing cannabidiol (CBD) might serve as an effective natural insecticide, particularly against the larvae of mosquitoes that spread yellow fever. The research, published in the journal Insects, demonstrated that hemp extract with a sufficient concentration of CBD killed Aedes aegypti mosquito larvae within two days. These mosquitoes transmit diseases like dengue, Zika, and yellow fever. Notably, the study showed that CBD was effective against both pyrethroid-susceptible (PS) and pyrethroid-resistant (PR) mosquitoes, highlighting its potential as a biopesticide, especially where conventional insecticides have failed.

The study, led by Erick Martínez Rodríguez, a graduate student in entomology at Ohio State University, was inspired by earlier findings that a plant native to Madagascar could also serve as a natural insecticide. Rodríguez emphasized the importance of controlling mosquitoes in their early stages, as they are most vulnerable at the larval stage. While the exact mechanism of how CBD kills mosquito larvae remains unclear, the researchers pointed out that CBD likely affects multiple biochemical targets in the insects. Interestingly, insects lack the cannabinoid receptors typically found in mammals, adding to the mystery of how CBD exerts its larvicidal effects.

Despite the uncertainty about its mode of action, the research demonstrated that only a small amount of hemp extract was needed to kill a significant percentage of the mosquito population. When compared to synthetic insecticides, the required amount of CBD was relatively high. However, compared to other natural insecticides, the quantity of CBD needed was relatively low, making it an appealing option. This finding is consistent with previous studies that have observed CBD's ability to kill other mosquito species and insect pests such as the tobacco hornworm and corn earworm.

The hemp extract was produced by drying the leaves of hemp plants and using methanol for extraction, which was then evaporated to leave behind the extract. This process has the potential to be scaled up for larger production if proven effective and safe. Co-author Peter Piermarini noted that more research is necessary to determine the safety of CBD for non-target species like honey bees and other pollinators, as CBD appears to be safe for humans and companion animals but is toxic to insects.

Overall, this research highlights the potential of hemp leaf extract, specifically CBD, as a natural and sustainable alternative to synthetic insecticides. The study’s findings contribute to growing evidence that CBD has toxic properties against various insect species, making it a promising candidate for controlling mosquito populations and, by extension, the spread of deadly diseases. However, further research is needed to explore its broader ecological impacts and its safety for non-target organisms.