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Trilobites

In experiments, researchers showed that the disease-spreading insects couldn’t resist the sweet smell of a fungus that infected and killed them.

A mosquito infected by two species of Metarhizium fungi — one that glows green under the microscope, and one that glows red.Credit...Huiyu Sheng

Nov. 1, 2025, 5:02 a.m. ET

Watch your back, DEET. There’s a new form of mosquito control in town — one that involves olfactory trickery, genetic engineering and a deadly infectious fungus.

Researchers reported last week in the journal Nature Microbiology that Metarhizium — a fungus already used to control pests — can be genetically engineered to produce so much of a sweet-smelling substance that it is virtually irresistible to mosquitoes. When they laced traps with those fungi, 90 percent to 100 percent of mosquitoes were killed in lab experiments. The scientists say this may provide an affordable, scalable and more ecologically friendly way to quell the bloodsucking insects.

“This work is cool in that it puts together a classic biological control idea with a more modern high-tech approach,” said Noah Rose, a biologist who studies mosquito-borne disease transmission at the University of California San Diego, who wasn’t involved in the study. “They show that this kind of idea might have legs.”

Mosquitoes are by some measures the most deadly animals on Earth. They spread malaria, dengue and other diseases, which collectively infect up to 700 million people and kill one million each year.

Public health professionals fumigate communities and manufacture pesticide-laced bed nets to cull mosquito numbers. But many insect populations have evolved resistance to chemical interventions.

Emerging techniques counter the pests through clever biology — for example, preventing disease growth by infecting the insects with Wolbachia bacteria, or sterilizing them with radiation. The latest study provides another tool: a fungus that lures mosquitoes to their death.

Metarhizium* *attracts a wide range of insect hosts by emitting longifolene, a woodsy-smelling compound used by perfumers. The fungus essentially masquerades as a delicious flower. Mosquitoes are drawn to the scent, and the spores produced by the fungus kill the insects by overtaking their insides and consuming them for nutrients. But in nature, Metarhizium only produces longifolene after it has already killed an insect.

In the study, the researchers genetically engineered a strain of Metarhizium that constantly manufactures longifolene at extremely high levels. This involved inserting the gene responsible for synthesizing the compound from pine trees into the fungi. They grew the engineered strains on a cheap material made of wheat and rice and then configured them in square traps, each slightly smaller than a magazine.

Within about five days, the traps killed half the mosquitoes used in lab experiments, which were conducted in a large room about half the size of a pickleball court; nearly all the mosquitoes died days later. The devices even worked when scientists placed competing scents in the room — including those from human volunteers who slept in the experimental chamber under a bug net.

Raymond St. Leger, a mycologist and entomologist at the University of Maryland who was an author of the study, said the team developed a patented trap design that features openings through which only mosquitoes can fit. That could assuage concerns that the traps may accidentally harm endangered or beneficial insects. The team plans to test those prototypes in outdoor environments soon.

Dr. St. Leger doesn’t see this as a replacement for other forms of mosquito control. He and his collaborators are researching how Metarhizium can be used in combination with other techniques.

Still, one appeal of this approach over others is that the fungus is easy to produce in a variety of settings. Dr. St. Leger’s colleagues in China already built a factory to produce Metarhizium by the ton, while rural communities around the globe can grow it on rice and chicken feces.

Dr. Rose said he sees the appeal of the fungal approach, especially if mosquitoes are unlikely to be able “to evolve resistance to it.”

Because mosquitoes keep evading human interventions, Dr. Rose also sees value in letting millions of years of fungal and insect evolution do the hard work.

“I like the idea that you don’t have to eliminate them,” he said. “They come to you, and their natural enemy does the eliminating for you.”

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