Beetroots combat mosquitoes

Researchers from Sweden and the USA have discovered a substance in beetroot peel that is highly effective in combatting mosquitoes. The substance, geosmin, is extremely expensive and difficult to get hold of. The new discovery changes all that.

The researchers have discovered that a substance in beetroot peels attract mosquitoes and can be used to trap them. Photo: Marcus Stensmyr

The researchers have discovered that a substance in beetroot peels attract mosquitoes and can be used to trap them. Photo: Marcus Stensmyr

Marcus Stensmyr and Nadia Melo at Lund University in Sweden, together with colleagues at the University of Washington and Florida International University, identified the odorant geosmin, which only attracts female mosquitoes. In the hunt for a damp place to lay eggs, the females associate geosmin with certain microorganisms that the aquatic mosquito larvae eat. By prepping ponds with geosmin, it is possible to separate females and males, and prevent mosquitoes from propagating.

“Using this method, it’s possible to combat mosquitoes without affecting other insects. Traps can be set that only capture mosquitoes – water containers scented with geosmin are irresistible for the females”, says Marcus Stensmyr.

One problem is that synthetic geosmin costs SEK one million per gramme. However, the researchers discovered that geosmin occurs naturally in juice from beetroot peel.

Can save many lives

The researchers conducted field studies in Florida, USA, and in Brazil. In Florida, synthetic geosmin was used with very good results. In Brazil, the beetroot traps were used – with equally good results.

Globally, mosquito-borne diseases infect about 200 million people every year and cause over 700 000 deaths. Climate change has led to a further increase in mosquito-borne diseases and their spread to previously unaffected areas. It is often poor people who are affected, as they cannot afford protection and do not know what action to take.

“Our discovery can actually help a lot of people. Beetroot, of course, can be grown almost anywhere”, says Marcus Stensmyr.

Cheap and natural

Using the juice from beetroot peel is an inexpensive, natural and environmentally sustainable way to combat mosquitoes. No other organisms are adversely affected. Initially, the researchers want to spread this knowledge among poor population groups in Africa, South America and Asia. They also anticipate that there will probably be demand for traps of this type in mosquito-intensive cities such as Miami and Singapore.

“We utilise an inborn preference among mosquitoes and it’s therefore unlikely that mosquitoes will eventually develop resistance, which is a problem with many chemical methods”, says Marcus Stensmyr.

The results were published in an article in the journal Current Biology.

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