Do backyard mosquito sprayers also kill good bugs, like bees? CuriousNC finds out.

Not-so-hot take: mosquitoes are the worst.

They kill more than a million people worldwide each year (by spreading denge fever, yellow fever, zika virus, West Nile Virus, malaria and more), they infect our dogs and cats with heartworms, and they drive us from our yards and make us miserable every summer.

So it’s no surprise that more and more people are turning to mosquito control companies that offer services — including spraying — to wipe out those blood-sucking monsters.

But do the services that rid our yards of mosquitoes also kill the good insects we need, like bees and butterflies?

CuriousNC consulted some experts and learned that the unfortunate answer is yes — but that “yes” doesn’t mean pollinators are wiped out by sprays. In fact, the scientists we talked to emphasize that there are practices mosquito control companies follow that will minimize the loss of pollinators.

Michael Reiskind, associate professor of entomology at N.C. State University, explains that mosquito control companies spray an insecticide — almost always a pyrethroid — to vegetation outside your house.

“That vegetation is where mosquitoes like to rest, so it kills them when they go in there. But it will kill other insects that go in there to rest. We call that a non-target effect.”

But insecticide labels, which by law, must be followed, prohibit the spraying of flowering or blooming plants, or spraying where mist can drift onto flowering or blooming plants, or anywhere the sprayer sees bees “foraging” a plant.

The Asian tiger mosquito (Aedes albopictus) is “the most prevalent species across the state, particularly in large urban areas,” according to Michael Waldvogel of N.C. State. Mel Nathanson News & Observer

The label on the product Bifen 7.9 (containing the chemical bifenthrin), widely used by mosquito companies, states: “This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops if bees are foraging the treatment area.”

The chemicals should likewise never be sprayed on or close to edible plants, including fruit-bearing trees and vegetable and herb gardens.

Structures like houses and swingsets also should not be sprayed, but Reiskind says rules are murky about structures such as fences.

Do your homework

Reiskind’s colleague, Michael Waldvogel, says avoiding bees entirely is difficult, but the most important thing consumers can do before hiring a mosquito treatment company is to find out what chemical the company uses and read the label ahead of time.

“The basic thing we drum into everybody, whether they’re a professional pesticide applicator or the public, is always read the label before you do anything,” he said.

Waldvogel, an associate professor of entomology at N.C. State, says spraying very early in the morning before pollinators are out can also mean there is less impact on them. But that isn’t always practical.

“If you’re very adamant about that, don’t spray in the middle of the day,” he said. “But somebody has to get treated later in the day. You have to look at: do you have a lot of flowering plants, do you have a lot of pollinators? You want to think long and hard about what kind of chemical they’re going to use. You pick one that is going to have the minimum impact on pollinators.”

Bumble Bee
Pyrethroid insecticides used to kill mosquitoes will kill any insect that encounter it, including bees and butterflies.. DEAN FOSDICK ASSOCIATED PRESS

But the reality is, there’s no way to entirely avoid hurting pollinators if you’re spraying for mosquitoes.

“If you really want to look at protecting pollinators, that’s your major goal, maybe you need to rethink whether you treat your property at all with a spray that goes on foliage,” Waldvogel said.

There are some products with garlic that have a repellent effect, Waldvogel says, but durability is a question. (Reiskind also points out that “natural” products can be equally lethal to pollinators and are essentially unregulated.)

Joey Osbourne, founder of the North Carolina-based mosquito control company Mosquito Authority, says his company follows all rules for applying products targeting adult mosquitoes in a way that minimizes impact, including avoiding blooming or flowering plants.

Osbourne, who has been a beekeeper himself for six years, says he has two honey bee hives on the same property that is sprayed for mosquitoes every 21 days, and his hives are thriving and producing honey.

Look over the fence

If you do decide to go with a spray service, Waldvogel stresses that the “drift” of the insecticide sprayed be considered, both in your own yard and in your neighbor’s yard.

“I always tell people who do these kinds of treatments, you better look over the fence,” he said. “Does that person have a dog outside during the daytime and the chemical is drifting to his dog, to the dog’s water bowl? To the neighbor’s 5-year-old out there playing in the yard? Do they keep bees in their backyard? ... When houses are close together, talk to your neighbor.”

Spraying when the winds are under 10 mph will help with drift, he said.

Before spraying, Waldvogel says to remove outdoor pet water bowls and children’s toys and cover your grill so that they’re not exposed to chemicals. Bird baths should be flushed and the water replaced.

Waldvogel strongly suggests walking your property with the mosquito sprayer ahead of time to pinpoint areas that should be avoided.

Clean up your yard

The most important thing you can do to reduce mosquitoes in your yard is to take away their habitat.

And mosquito control companies, Waldvogel says, should also be advising you on how to do that.

“You’re paying the professional to tell you do something about that tarp covering your boat with the water puddle that mosquitoes are breeding in,” he said. “They’ll tell you what you should correct in your yard that will help reduce the population — and get neighbors to do the same thing.”

Obourne says his company’s services include eliminating breeding habitats before one drop of chemical is even sprayed, estimating that perhaps 50 percent of mosquitoes are eliminated by the “tip and toss” practice of ridding an environment of standing water, which is the breeding ground for mosquitoes.

“In controlling a pest, you do the least environmentally impactful things first, then progress to the point of using chemicals,” Osbourne said. “Mosquito Authority is very conscientious when it comes to protecting and preserving beneficial insects.”

For areas where water can’t be completely eliminated, like in a bird bath or fountain, Osbourne says an all-natural larvicide is used in the water, which kills the mosquito larvae but doesn’t harm other wildlife. This can wipe out another chunk of a yard’s mosquito population.

Waldvogel points out that keeping your own yard clear of standing water may not be enough. You need to get your neighbors onboard.

“Mosquitoes are a neighborhood-scale problem,” Waldvogel says. “They don’t want to fly too far, they want to live near their food source. The more people in your neighborhood that participate in what we call source reduction — which means ‘clean up your yard’ — the better. If you have standing water somewhere, get it un-standing.”

Studies look to reduce chemical use

Reiskind also pushes the “tip and toss” practice to rid your yard of standing water. It’s simply the best first step to controlling mosquitoes.

Reiskind manages mosquito control studies at N.C. State, in conjunction with the N.C. Department of Health and Human Services, designed to determine how to best reduce the risk of the transmission of diseases, such as the Zika virus. For his studies, Reiskind also often works with Mosquito Authority, which has an entomologist on staff.

Last year’s mosquito study looked at the effectiveness of spraying and whether neighbors benefit from spraying at a “target house” (they do).

This year’s study looks at alternative approaches to mosquito control, in conjunction with conventional approaches, such as spraying. The study involves the use of traps that attract and kill the egg-laying female Tiger Mosquito, the most common mosquito here.

“The goal of the study is to use less and less of that (spraying) approach,” Reiskind says. “This year’s test is specific to that mosquito and unlikely to effect any other insects or animals.”

Osbourne is excited about the studies that help reduce the amount of chemicals needed to control mosquitoes, but stresses that mosquitoes must be controlled.

“Mosquitoes kill people and make people sick and something has to be done,” Osbourne said. “Whether it’s a company like us or the public taking action.”


Get more information on reducing mosquito populations at N.C. State (entomology.ces.ncsu.edu).

John Allran, a toxicologist at the N.C. Department of Agriculture, can answer questions about specific chemicals. 919-733-3556.

The DriftWatch website — nc.driftwatch.org — is a great resource that lets beekeepers and organic farmers register their sites and communicate with pesticide applicators when it comes to large-scale spraying after natural disasters.


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Brooke Cain is a North Carolina native who has worked at The News & Observer for more than 20 years. She writes about TV and local media for the Happiness is a Warm TV blog, and answers CuriousNC questions for readers.