A Lexington ZIP code was sprayed for mosquitoes. What does the city use to kill them?

Lexington’s 40502 ZIP code is being so strongly swarmed by mosquitoes, the health department sprayed the area with an insecticide early Tuesday to cut the population.

Nathan Powell, senior environmental health specialist with the Lexington-Fayette County Health Department, said the agency’s program is treating the Henry Clay area after trapping 238 mosquitoes in 12 hours.

“It seemed like it was a little bit excessive,” Powell told the Herald-Leader in a phone interview Monday. “If it’s above 75, then we’ll go out … and try to treat to reduce the number of biting mosquitoes.”

Climate change is expected to be a boon for mosquitoes by prolonging their breeding season and expanding their natural range. In May, an outlook from the nation’s Climate Prediction Center projected above-normal temperatures and precipitation throughout the summer.

LFCHD spokesperson Kevin Hall told the Herald-Leader in an email that the treatment was scheduled to take place between 3 and 6 a.m. Tuesday.

The insecticide is called Duet. According to information posted on the health department’s website, the U.S. Environmental Protection Agency-registered mosquito control kills more of the pests by stimulating them to fly up and come into contact with the insecticide.

Here’s what this means for Lexington residents, plus tips you can use to keep mosquitoes out of your own yard.

What does Lexington use to spray for mosquitoes?

Often used in public health contexts, Duet is an insecticide used to control disease-spreading mosquitoes.

According to health products and services company Clarke, which developed Duet, it contains two active ingredients: sumithrin and prallethrin.

Both are pyrethroids, a group of synthetic insecticides designed to mimic a natural counterpart: pyrethrins. It turns out the plant chrysanthemums don’t like mosquitoes either. The powerful and natural mosquito repellent found in the plant’s flowers has been used by humans for thousands of years since its discovery in ancient Persia.

Duet works somewhat similarly as its natural counterpart, although it has one additional function that makes it even more deadly to mosquitoes. Called “benign agitation,” the active ingredients in Duet stimulate mosquitoes, stirring them to flight. Once airborne, they come into contact with the insecticide and are killed in greater numbers.

Duet is designed to be used in ultra-low volume applications , meaning very small amounts of the pesticide are distributed in fine droplets that break down quickly in the environment.

Are there exposure risks with mosquito spraying?

According to Clarke, people and pets can be outdoors during application.

There are no re-entry restrictions or limitations. If it’s applied at night, when mosquitoes are active and butterflies and bees are not, it should not harm beneficial pollinating insects, according to Clarke.

Duet is considered to be toxic to fish . To minimize harm, residents can cover their fish ponds during an application. However, because Duet is applied in low volumes and breaks down quickly, exposure risk should be low.

How do I keep mosquitoes away from my yard?

The best thing you can do to make sure your backyard isn’t a breeding ground for mosquitoes is to eliminate any sources of stagnant water.

“Pet water bowls, potted plants, tarps, boats, garbage cans, anything that can collect water that will sit over a period of time can create a mosquito harborage,” Powell told the Herald-Leader.

Breeding grounds can be water sources you don’t normally think about, like clogged gutters and dripping outdoor faucets. Any type of container that can hold at least a teaspoon’s worth of water a quarter of an inch deep can become a harbor for mosquitoes.

If you have a bird or bee bath in your backyard and don’t want to get rid of it, buy mosquito dunks at the hardware store to prevent it from becoming a breeding ground.

Look for dunks that primarily contain the bacteria bacillus thuringiensis israelensis, often abbreviated as BTI. BTI bacteria produce toxins that target the larvae of mosquitoes and black flies, according to the EPA. BTI mosquito dunks do not affect other types of beneficial insects, like honeybees.

They also have the benefit of being cheap, can cover a wide area of standing water (one dunk covers 100 feet) and each individual dunk is good for about a month. Once applied, mosquitoes will continue to lay eggs in the standing water, but their larvae will not survive, effectively ending their life cycle.

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