Mosquitoes are the animal that kills the most humans every year worldwide. Not with sharp fangs or claws, but through the multitude of diseases for which they can become a vector. A strategy that a group of Chinese researchers decided to turn against them, engineering a terrible pathogenic fungus (harmless to humans, obviously) to emit a floral scent that is irresistible to these insects, thus transforming it into a deadly trap capable of eliminating up to 100 percent of the mosquitoes reached by its scent.
An irresistible smell
The research began with the discovery that some species of entomopathogenic fungi (that infect insects), once they have killed their victims, begin to produce a compound known as longifolene which attracts other insects such as midges and mosquitoes, which are then infested by the spores of the fungus, dying in turn within a few days, and helping to further spread the infestation.
The compound in question is contained in the resin of various species of pine trees, and probably misleads insects into believing that it is produced by a flower rich in nectar, a fundamental food also in the mosquitoes’ diet, despite their passion for blood. Strengthened by this discovery, researchers from Zhejiang University, China, thought of transforming mushrooms into a lethal trap for mosquitoes.
A fragrant transgenic mushroom
The researchers genetically modified the spores of mushrooms of the Metarhizium pingshaense speciesto ensure that they produced a large quantity of longifolene. They then put them to the test, preparing containers full of transgenic spores, and testing their ability to attract and kill mosquitoes in the laboratory. The results were as hoped: the traps are capable of releasing longifolene for months, attracting mosquitoes even in the presence of humans and other odorous sources that compete for their attention. And they kill between 90 and 100 percent of the mosquitoes present, of both sexes.
According to its inventors, the trap based on genetically modified fungal spores seems to have all it takes to prove to be a winning solution in the fight against mosquitoes: it is cheap, harmless to humans, and it is almost impossible for insects to become resistant to it, as happens with relative ease when chemical insecticides are used. “If mosquitoes evolved the ability to avoid longifolene it would mean that they would also stop responding to the smell of flowers,” explains Raymond Leger, an entomologist at the University of Maryland who collaborated on the research. “But they need flowers to survive, and it would be interesting to see how they could escape the fungi while still being attracted to the smell of the flowers they need to survive. It’s an almost impossible challenge, and we can still further modify the fungus to produce other floral aromas, if they start specifically avoiding longifolene.”
Currently, the tests continue, with open-air experiments that will be used to collect data with which to submit the trap to the regulatory authorities. If everything goes as hoped, it could arrive on the market very quickly: a precious additional weapon in the war against the most dangerous insect in the world, particularly useful in these years in which climate warming and globalization continue to expand the areas in which many diseases transmitted by mosquitoes are endemic.