Researchers behind a novel study have pinpointed why flying insects strongly dislike garlic: it contains an organic compound that inhibits both mating and egg-laying processes. Furthermore, the repellent effect on flies and mosquitoes is due not to the aroma, but to the taste of garlic, as this particular substance specifically interacts with taste receptors.
Garlic (Allium sativum), one of the oldest cultivated plants on Earth, was employed not only in cooking or for sacred purposes in Ancient Egypt, but also as a medicinal substance, predominantly to combat infections and parasites. Garlic saw extensive use in the medicine of Ancient China, Ancient Rome, and Ancient Greece. During the European Middle Ages, it was utilized to ward off evil spirits, vampires, and the plague, while also treating wounds and infections.
In more recent times, it has been discovered that garlic harbors organic compounds exhibiting antiseptic, antifungal, and insecticidal properties. For instance, people have observed that garlic can function as a natural repellent, deterring flying insects. Moreover, amateur gardeners have utilized garlic infusions and decoctions for years to control plant pests and diseases.
A team of biologists from Yale University (USA), whose findings were published in the journal Cell, elucidated the reason behind the winged insects’ aversion to garlic. The scientists determined that one of the compounds present in garlic acts as a sort of birth control agent on mosquitoes and flies.
This discovery was almost accidental; the scientists were examining receptors and neural circuits governing insect reproductive behavior as part of a different project. Fruit flies (Drosophila) were used as the model organism.
Given that Drosophila typically mate on fruit, the researchers hypothesized that something within fruits or vegetables might function as an aphrodisiac, stimulating their mating activities. Therefore, the scientists prepared purees from 43 different fruits and vegetables, setting up a sort of buffet for the fruit flies.
Contrary to expectations, none of the dishes offered to the Drosophila increased their mating activity, but the experiments revealed something else entirely. Garlic puree produced the exact opposite result: the Drosophila that consumed this puree completely ceased mating and stopped laying eggs.
In subsequent experiments, researchers rigorously re-verified this reaction in fruit flies. It turned out that garlic entirely blocks reproduction not only in Drosophila, but also in tsetse flies, as well as Aedes mosquitoes—vectors for yellow fever, dengue fever, and the Zika virus.
The scientists established that the repulsive factor for winged insects is the taste, not the smell, of garlic—specifically, the presence of diallyl disulfide within it. This chemical substance suppresses both behaviors—mating and oviposition—and primarily affects the females.
The sensory receptor responsible for detecting diallyl disulfide is TrpA1, situated in the insects’ taste organs. In response to this substance, TrpA1 initiates a cascade of neural and genetic reactions that ultimately lead to behavioral changes in the insects, such as avoiding garlic and, crucially, halting reproduction.
Interestingly, wasps proved entirely indifferent to garlic. This initially puzzled the scientists until it was discovered that wasps lack the TrpA1 receptors.
Diallyl disulfide is utilized as an ingredient in various food supplements; this specific compound is what imparts the characteristic garlic aroma to products. The scientists proposed that this substance could also be widely employed as an environmentally safe, accessible, and inexpensive method for controlling disease vectors and agricultural pests.
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