Why Garlic Repels Mosquitoes and Keeps Them From Breeding - WIRED

A group of scientists from Yale University conducted a phytochemical analysis of 43 fruits and vegetables to identify natural compounds capable of interfering with the reproductive behavior of flying pest insects. To do so, the team used fruit flies, a species that often mates on food, as a model organism. Based on this behavior, the researchers hypothesized that some fruits and vegetables might contain substances capable of altering the reproductive processes of these insects. After exposing different specimens to the mashed food included in the experiment, they observed that none of the products had a significant aphrodisiac effect. However, they found that garlic completely blocked mating and egg laying. After this initial finding, the researchers sought to determine the source of the effect and focused their attention on the influence of garlic on the flies’ senses of taste and smell. To this end, they conducted two experiments. In the first, they placed the garlic puree in such a way that the insects could only smell it; in the second, they allowed them to taste it as well. The results showed that the taste was the factor that actually inhibited reproductive behaviors. The team then conducted a chemical analysis of the garlic to identify the compound responsible for the effect. They determined that diallyl disulfide was the element that caused the inhibition. In practice, this substance acts on a sensory receptor present in the fly's taste organs, known as TrpA1. The TrpA1 receptor functions as a sensor that triggers immediate rejection responses when it detects potentially noxious tastes. According to an article published in the journal Cell, garlic specifically activates a group of bitter taste-sensitive neurons containing this receptor. This activation not only provokes a physical avoidance reaction but also changes at the molecular level by modifying the expression of various genes. Among the alterations identified, that of a gene closely related to the sensation of satiety stands out, suggesting that contact with garlic compounds directly interferes with the biological processes that regulate appetite and feeding in these insects. The authors posit that increased satiety appears to drive behaviors that limit mating and reproduction, primarily in females. A Natural Repellent for Many Species In addition to fruit flies, the experiments were replicated in other flying insects, including two species of mosquitoes that transmit diseases such as yellow fever, dengue, and Zika virus, as well as tsetse flies. In all cases, the tests showed that garlic can act as an effective remedy to discourage reproduction. The researchers’ findings suggest that this plant, Allium sativum, could be used as a tool to control various insect pests harmful to both human health and agriculture. “It’s inexpensive and grown all over the world,” said John Carlson, a Yale professor and coauthor of the study. “The idea of using it to ward off hematophagous creatures was proposed in 1897 by Bram Stoker in his novel Dracula, and perhaps he was right.” This story originally appeared on WIRED en Español and has been translated from Spanish.