Investigation
CBD is a powerful biological insecticide against mosquito larvae, study reveals
A study from Ohio State University reveals that mosquito larvae, both resistant and susceptible strains of insecticides, are killed by an extract of hemp leaves up to 48 hours after exposure. The research, led by Erick Martinez Rodriguez and Peter Piermarini and published in the journal 'Insect', concluded that CBD (cannabidiol) present in the hemp extract was the main active compound responsible for killing the larvae. This discovery is particularly important because it suggests a new, more effective and biological way to kill mosquitoes that can be potential transmitters of diseases.
Mosquitoes can carry pathogens responsible for diseases such as malaria, dengue fever and Zika, and the problem is that some are becoming resistant to the insecticides used against them. But researchers at Ohio State University may have a solution to this problem.
The study, published in July 2024 in the journal 'Insect' and part of the special issue 'Natural Metabolites as Biocontrol Agents of Insect Pests', suggests that hemp extracts and CBD are valuable sources for the development of biopesticides for mosquito control. It was shown that insects die when exposed to cannabidiol (CBD) - a chemical compound produced by cannabis plants. Furthermore, the extract was lethal even in mosquitoes that had genetic resistance to conventional pesticides.
“To mitigate pyrethroid resistance in mosquito vectors of emerging and re-emerging human pathogens, there is an urgent need to discover insecticides with novel modes of action. Natural alternatives, such as plant-derived extracts, could serve as replacements for traditional synthetic insecticides if they prove to be sustainable, cost-effective and safe for non-target organisms,” the researchers explain.
Hemp (Cannabis sativa) is a sustainable plant known to produce several secondary metabolites with insecticidal properties, including terpenoids and flavonoids. The aim of the study was to evaluate the larvicidal activity of hemp leaf extract on mosquito larvae of strains of Aedes aegypti to pyrethroid-susceptible (PS) and pyrethroid-resistant (PR).
Concentration-response curves for the 48-h larvicidal activity of methanol (black) and hexane (purple) partitions of hemp leaf extract (orange) against pyrethroid-susceptible Ae. aegypti. Values are means ± SEM based on 12 replicates of 6 larvae per concentration (1,2, 3,7, 11, 33, and 100 ppm).
Another objective was to identify which components of the extract were responsible for any observed larvicidal activity. “We found that a methanolic extract of hemp leaves induced similar concentration-dependent larvicidal activity against PS (LC50: 4.4 ppm) and PR (LC50: 4.3 ppm) strains within 48 hours. Partitioning of the leaf extract between the methanol and hexane fractions revealed that total larvicidal activity was restricted to the methanol fraction. Analysis of this fraction by gas chromatography-mass spectrometry and nuclear magnetic resonance showed that it was dominated by cannabidiol (CBD),” the study states.
The researchers only examined the properties of one strain of hemp, but suggest that many others may hold promise for biopesticide production.
Larvicidal trials using authentic CBD confirmed that this compound was primarily responsible for the toxicity of the hemp leaf extract against both strains. “We conclude that hemp leaf extracts and CBD have the potential to serve as viable sources for the development of novel mosquito larvicides,” they state.
“Overall, our study provides additional evidence supporting the notion that hemp is a valuable potential resource for the development of novel insecticides to control mosquitoes. The promising results of the present study motivate future studies to further evaluate hemp extracts and CBD as potential larvicides, as well as to determine the potential non-target and environmental impacts of using hemp extracts and CBD as larvicides. Furthermore, future studies should evaluate the economic viability of using hemp leaves as an insecticide source. Notably, hemp is an emerging and easily cultivated crop in the U.S. and its leaves are often discarded. Thus, the availability of raw materials does not appear to be a limiting factor as it may be for other biopesticide sources.”
The researchers also note that they only examined one strain of hemp in the current study. “Numerous strains of hemp varieties with highly diverse secondary metabolite profiles are available. Future studies should examine multiple hemp strains to identify additional active ingredients beyond CBD and determine which strains would be most efficient for hemp cultivation for biopesticide production,” they conclude.
Read the study in full here:
insects-15-00517
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[Disclaimer: Please note that this text was originally written in Portuguese and is translated into English and other languages using an automatic translator. Some words may differ from the original and typos or errors may occur in other languages.]____________________________________________________________________________________________________
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With a degree in Journalism from the University of Coimbra, Laura Ramos has a postgraduate degree in Photography and has been a Journalist since 1998. Winner of the Business of Cannabis Awards in the category "Journalist of the Year 2024", Laura was a correspondent for Jornal de Notícias in Rome, Italy, and Press Officer in the Office of the Minister of Education of the 21st Portuguese Government. She has an international certification in Permaculture (PDC) and created the street-art photography archive “Say What? Lisbon” @saywhatlisbon. Co-founder and Editor of CannaReporter® and coordinator of PTMC - Portugal Medical Cannabis, Laura directed the documentary “Pacientes” and was part of the steering group of the first Postgraduate Course in GxP's for Medicinal Cannabis in Portugal, in partnership with the Military Laboratory and the Faculty of Pharmacy of the University of Lisbon.
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