Killing Mosquitoes With the Smell of Flowers

As the fight against malaria and other mosquito-borne diseases continues, it is imperative that we introduce novel solutions to control mosquito populations. Inspired by mosquitoes’ attraction to flowers for finding nectar, scientists have engineered fungi to release a floral scent, leading the unsuspecting mosquitoes to their eventual demise. 

Despite the introduction of the malaria vaccines RTS,S in 2021 and R21 in 2023, malaria cases continue to rise, reaching approximately 282 million cases in 2024 – an increase of 9 million cases from the previous year. The WHO World Malaria Report highlights antimalarial drug and insecticide resistance as major barriers to eliminating malaria, emphasising the need for novel interventions. With current mosquito control methods facing growing limitations, what are the alternatives?

In a study published in Nature, an international research team spanning China, Burkina Faso, and the US engineered the mosquito-killing fungi as a promising answer to this question.

Co-author and Professor of Entomology at the University of Maryland, Raymond St. Leger, explained that “after observing that some types of fungi could trick mosquitoes into thinking they were flowers, we realized we could turbo-charge the attraction by engineering fungi to produce more longifolene, a sweet-smelling compound that’s already very common in nature. Before this study, longifolene wasn’t known to attract mosquitoes. We’re letting nature give us a hint to tell us what works against mosquitoes.” 

Metarhizium fungi were used thanks to their mosquitocidal spores and limited off-target effects.

Longifolene-laced fungi present a more environmentally friendly alternative, with the chemical having a long safety record for its use in perfume. St. Leger said, “We've also designed the fungus and its containers to target mosquitoes specifically rather than any other insects and longifolene breaks down naturally in the environment”.

The specificity of the fungus is a major advantage, as conventional insecticides used to control mosquito populations are toxic towards the environment, wildlife, and human health. 

Unlike insecticides, resistance to the killer fungi is less likely to arise as it builds upon an evolutionary necessary mechanism. “It'll be very difficult for them to overcome that hurdle, and we have the option of engineering the fungus to produce additional floral odors if they evolve to specifically avoid longifolene” St. Leger explained.

These killer fungi are particularly exciting as they are easily cultivated using common scraps from harvesting, like rice husks. This presents a more sustainable solution for less economically developed countries in the global south, where malaria is most prominent. 

However, rising global temperatures threaten to spread mosquito growth to countries outside of tropical regions, carrying malaria and other mosquito-borne diseases with them. “Mosquitoes love many of the ways we are changing our world,” St. Leger said. “Right now, we’re hoping to use these approaches in Africa, Asia and South America. But one day, we may need them for ourselves.”

Although laboratory and computer-based findings show promise, more research must be done to establish success in real mosquito environments. The international team, including St. Leger, are currently facilitating larger outdoor trials with the hope of approval from regulatory bodies.