Research at NMSU examines the effectiveness of mosquito repellents

Mosquitoes can carry many deadly diseases, including Zika, West Nile virus and dengue fever. Last year, there were 33 cases of West Nile virus in New Mexico. At New Mexico State University, research is underway to better understand the life cycle of the insect in order to disrupt the process of disease transmission.

Dr. Immo Hansen works at the Hansen Laboratory on campus as a principal investigator, studying disease-transmitting arthropods, including mosquitoes.

Recently, the lab tested resistance to insecticides in mosquitoes and the effectiveness of various repellents. What they discovered is that chemical repellents are the most effective at repelling mosquitoes for hours on end.

NMSU’s Hansen Lab tests the effectiveness of insect repellents

Dr. Hansen says that compared to a control, Deet reduced mosquito attraction by about 40%. According to Hansen, some essential oils repel mosquitoes at a similar rate, but the effectiveness is short-lived. Unlike insecticides, chemical repellents offer the user long-lasting protection without harming the ecosystem.

“Especially now that mosquito season is peaking, these repellents are flying off the shelves, and some work better than others, so it’s really important to know which ones are good and which ones are not so good,” said Hansen.

Dr. Hansen and his team use a wind tunnel to conduct research that helps determine the effectiveness of repellents.

“When you test mosquito repellent in the field, you have the problem that the wind is unpredictable, it can change direction and blow away your repellents. In order to solve this problem, we use the small blower here in order to achieve a constant airflow,” said Hansen.

The wind tunnel provides a stable environment for testing repellents. Using a cage filled with a predetermined number of mosquitoes and a voluntary bait in the wind, the team is able to calculate the effectiveness of a given repellent.

Dr. Hansen says that when looking for an effective repellent, you should look for one of the following active ingredients: deet, picaridin, ir3535, and lemon eucalyptus oil. These repellents have all proven protective for hours. But for Dr. Hansen, the best solution to keep mosquitoes away is to keep them away from your living space.

“Check your window screens, make sure there are some and make sure they don’t have holes, keep them outside your house,” Hansen said.

Screenshot by Jonny Coker

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Dr. Immo Hansen conducts research at the NMSU wind tunnel.

The second thing is to get rid of standing water in your garden. This is a breeding habitat for mosquitoes, and simply getting rid of this habitat will reduce the number of mosquitoes in your area. Dr. Hansen says homes that have areas of standing water, like a pond, mosquito fish are very effective at controlling mosquito populations and one of his favorite mosquito control methods.

“I have a swimming pool in my garden and I have a whole swarm of mosquito fish in there… You don’t even have to feed them, they live on insects that fall into the water, and they will take care of the mosquitoes, they just eat all the larvae,” Hansen said.

As for insecticides, Dr. Hansen sees them as a temporary solution. Insecticides are effective in killing mosquitoes, but they disrupt the surrounding ecosystem and can be harmful to pollinators. In addition, mosquitoes acquire resistance to insecticides over time if they are used too frequently:

“It’s an effective method, but doing all of these other things — reducing breeding habitats, using fish, and screening your home is probably the most effective long-term solution,” Hansen said.

According to Hansen, being prepared and protected is your best chance of preventing vector-borne diseases.

Sara H. Byrd