Mint and Lemon Eucalyptus Oils' Effects on Mosquitoes and Other Bugs

Jim Crocker
25th February, 2024

Mint and Lemon Eucalyptus Oils' Effects on Mosquitoes and Other Bugs

Southern House Mosquito (Culex quinquefasciatus)

Photo adapted from: Julia Kasper / CC BY (Source)
Vector-borne diseases, spread by insects like mosquitoes, pose a significant and growing threat to public health globally[2]. Traditional control methods often rely on synthetic chemical insecticides, but these can have detrimental effects on the environment and non-target organisms. This has driven research into alternative, more eco-friendly solutions. Recent work from researchers at Manonmaniam Sundaranar University[1] investigates the potential of essential oils from Spearmint (Mentha spicata) and Citriodora (Eucalyptus citriodora) as a means of controlling the Culex quinquefasciatus mosquito, a major vector of diseases like filariasis and West Nile virus. The study focused on assessing the toxicity of these oils, not just to the target mosquito, but also to other aquatic life and beneficial insects like honeybees. The researchers used gas chromatography-mass spectrometry (GC-MS) to identify the specific chemical compounds present in each oil. This revealed that carvone was the most abundant compound in Citriodora oil (70.44%), while isopulegol was dominant in Spearmint oil (30.4%). Testing showed both oils were effective at killing mosquito larvae. At a concentration of 100 parts per million (ppm), Spearmint oil achieved 100% mortality of fourth-instar (late-stage larval) Culex quinquefasciatus after 48 hours, while Citriodora oil resulted in 76.4% mortality (P≤0.001). Importantly, microscopic examination of the larvae revealed physical damage to the head and gut tissues following exposure to both oils, and histological analysis confirmed severe damage to the cells lining the gut. This suggests the oils aren’t simply poisoning the mosquitoes, but actively disrupting their physiology. Beyond killing larvae, the study also examined the oils’ ability to repel adult mosquitoes. Both oils demonstrated significant repellency at a concentration of 150 ppm, lasting for at least 210 minutes. This is a crucial aspect of vector control, as preventing bites is a key strategy in reducing disease transmission. A key concern with many insecticides is their impact on non-target species. The researchers assessed the toxicity of the essential oils to an aquatic predator species, finding that both Spearmint (17.2% mortality at 200 ppm) and Citriodora (15.2% mortality at 200 ppm) were considerably less toxic than the commonly used insecticide temephos (75.4% mortality at just 1 ppm). Furthermore, using computer modelling (in silico screening) with a tool called BeeTox, they predicted that the individual chemical compounds within the oils posed no contact toxicity risk to honeybees. This research builds on a growing body of evidence demonstrating the potential of natural compounds for pest control. Previous studies have shown that various environmental contaminants, even at low doses, can stimulate or disrupt insect physiology and behaviour[3][4]. While those studies focused on the unintended consequences of pollutants, this research actively seeks to harness natural compounds for beneficial effects. Similar work has highlighted the potential of Eucalyptus essential oils as natural pesticides, demonstrating their antioxidant, antimicrobial, and phytotoxic properties[5]. The current study expands on this by specifically focusing on mosquito control and rigorously assessing non-target effects. The findings suggest that Spearmint and Citriodora essential oils represent a promising alternative to synthetic insecticides for controlling Culex quinquefasciatus mosquitoes, offering a potentially safer and more sustainable approach to vector management.

EnvironmentBiochemSpices

References

Main Study

1) Chemical composition and toxicity of commercial Mentha spicata and Eucalyptus citriodora essential oils on Culex quinquefasciatus and non-target insects.

Published 23rd February, 2024

https://doi.org/10.1007/s11356-024-32249-6

Related Studies

2) Managing mosquitoes and ticks in a rapidly changing world - Facts and trends.

https://doi.org/10.1016/j.sjbs.2018.06.007

3) Stimulation of insect vectors of pathogens by sublethal environmental contaminants: A hidden threat to human and environmental health?

https://doi.org/10.1016/j.envpol.2023.122422

4) Sublethal chemical stimulation of arthropod parasitoids and parasites of agricultural and environmental importance.

https://doi.org/10.1016/j.envres.2023.116876

5) Essential Oils and Biological Activities of Eucalyptus falcata, E. sideroxylon and E. citriodora Growing in Tunisia.

https://doi.org/10.3390/plants12040816


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