There may be a new way to kill disease-carrying mosquitoes. The insects die when they are exposed to cannabidiol (CBD) – a chemical produced by cannabis plants. What’s more, the chemical is lethal even in mosquitoes that have genetic resistance to standard pesticides.
Mosquitoes can carry pathogens responsible for diseases including malaria, dengue fever and zika. Some of the insects are also becoming . But and at the Ohio State University and their colleagues may have a solution.
They found the mosquito larvae that cause yellow fever die within two days of consuming an extract taken from the leaves of hemp – a type of cannabis. Even mosquitoes resistant to commercial insecticides succumbed to the hemp extract.
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The researchers found CBD was highly abundant in the leaf extracts, so they tested the effects of pure CBD against the larvae. It had a similar effect as the hemp extracts, leading the team to conclude that CBD is toxic to the larvae.
“One of the advantages of hemp is that it is an emerging crop and in high demand,” says Martinez Rodriguez. “There will likely be an abundance of raw material to generate a hemp-based insecticide, especially if parts of the plant that are typically discarded [like the leaves] can be exploited.”
Rodriguez and Piermarini now want to further explore exactly how CBD kills the mosquito larvae, and test whether it can be used to kill adult female mosquitoes as well, since it is adult females that bite people and transmit disease.
“These compounds are already present in nature; through technology, we must now figure out how to produce them on a large scale, in a cost-effective manner,” says  at the Federal University of Viçosa, Brazil, who was not involved in the study.
What is still unclear, however, is whether CBD kills mosquitoes exclusively or whether it is lethal to insects more broadly. at Mahindra Summit Agriscience Limited in India, suspects it may not have broad effects because it is a plant-derived chemical. “Biological [compounds] come from nature, so they should generally not harm it,” he says.
But both he and Martins stress the need to test more for the effects of CBD. “Just because a compound is natural, it doesn’t necessarily mean it is safer,” says Martins. “We should remember that nature can be ruthless.”
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