Rising temperatures could make insect repellents less effective

A recent research discovery suggests that, as environmental temperatures increase, the effectiveness of natural insect repellents against mosquitoes could decline.

Mosquitoes have a pain receptor called TRPA1, which acts like a fire alarm, detecting noxious heat and harmful chemicals to protect the insect.

This receptor also plays a crucial role in determining which hosts these insects find attractive, especially if they’re unprotected by repellents.

Study co-author Peter Piermarini is a professor of entomology at The Ohio State University. 

“What we found was that the chemicals were not able to activate the mosquito wasabi receptor as effectively when temperatures exceeded the heat activation threshold,” explained Piermarini.

Temperature weakens natural repellents

Essentially, insect repellents work as chemical barriers, keeping away pesky mosquitoes from their potential targets. But, in warmer temperatures, the TRPA1 receptors of mosquitos become less sensitive.

This means that natural repellents, such as citronella and catnip oil, may lose some of their buzz. As a result, products containing these ingredients might not work as well in extreme heat conditions.

This, in combination with longer breeding periods caused by a warming climate, could potentially exacerbate the spread of mosquito-borne diseases considerably.

The experimental testing

Professor Piermarini and graduate student Yeaeun Park set out to investigate the role of temperature in repellent sensitivity in mosquitos.

The researchers removed TRPA1 mosquito receptors and injected them into frog egg cells. They then tested how these receptors responded to citronella and catnip oil under normal and elevated temperatures.

The experts found that these receptors were still activated, but were less sensitive to those substances in hotter temperatures. “It was very close to what we predicted.” said Piermarini.

The second experiment involved observing how adult female mosquitoes reacted to these repellents at varying temperatures.

Once temperatures exceeded 32 degrees Celsius, mosquitoes showed less avoidance to these substances, implying a similar behavior might be observed in real-world scenarios.

Synthetic vs. natural repellents

However, not all repellents are created equal in the face of rising temperatures. A synthetic mosquito repellent, DEET, was also tested in the study.

Unlike natural counterparts, DEET doesn’t interact with the wasabi receptor to deter mosquitos, and its efficiency remained unaffected by higher temperatures.

“This suggests that during the hottest days of the year you’d probably want to stick with a more conventional synthetic repellent and avoid using a natural product with citronella or catnip oil,” noted Piermarini.

In-depth understanding can save lives

Now that we have this information, where do we go from here? The next step for the Ohio State team is to unearth the specific mechanisms behind temperature-induced desensitization of the TRPA1 receptor.

The researchers plan to study this phenomenon extensively, possibly by recruiting human participants.

“The more we learn about the mechanisms by which these natural products work, it can help us determine which ones might be better to use under certain conditions,” said Piermarini. “Understanding these limitations can potentially save lives.”

When it comes to battling the bugs, our defenses should remain robust, regardless of the weather. So, as the world gets warmer, it is time we adapt our arsenals.

Adapting mosquito control strategies

With rising temperatures reducing the effectiveness of natural repellents, researchers and public health officials are exploring alternative strategies to keep mosquito populations in check.

Innovations in mosquito control, such as genetically modified mosquitoes, habitat disruption, and novel synthetic repellents, are gaining attention as potential solutions.

One promising approach involves the use of spatial repellents – substances that create a protective barrier in an area rather than relying on direct application to the skin.

Scientists are also investigating plant-derived compounds that remain effective in high temperatures, ensuring that natural alternatives continue to play a role in mosquito defense.

As climate change extends mosquito breeding seasons and shifts their geographic range, adapting repellent strategies will be crucial for reducing the risk of mosquito-borne diseases.

Future research will focus on developing heat-resistant formulations and integrated pest management techniques that can withstand the warming climate.

The full study was published in the journal Pesticide Biochemistry and Physiology.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–