Mosquitoes are abundant in western Colorado this year. Know how to safely and effectively deal with the buzzing pests.

The near-historic snowfall this winter is still making itself known in early July, as all the snowmelt and ensuing moisture has brought on what feels like more mosquitoes to Colorado’s high country.

While there isn’t exact data to back it up (yet), there are likely many more mosquitoes in Colorado this year. 

“I haven’t heard reports of that happening, but it would make sense with our moisture this year,” said Melissa Schreiner, an entomologist for Colorado State University Extension in Grand Junction. “There’s more cockroaches, there’s more ticks, there’s more biting flies. It would make sense there would be more mosquitoes.”

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Areas in the western United States have seen an uptick in the insects because of the significant snowfall over the winter, according to Daniel Markowski, a technical adviser with the American Mosquito Control Association. Snowpack later leads to melt and flooding or an excess amount of water, which later dictates the amount of mosquitoes that appear.

Colorado has also seen a lot of rain this spring, which paired with temperature, also factor into the amount of mosquitoes in an area.

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Mosquitoes are most prevalent May through September, but their activity depends on the weather, Markowski said. The pests start making an appearance once temperatures are consistently above 50 degrees and love warm, humid weather. 

Not every type of mosquito will bite a human, and only female mosquitoes bite, as they need blood to produce eggs.

There are about 45 species of mosquito in Colorado, and despite what some may think, they can be found at nearly every elevation. Different mosquitoes will be active at certain elevations and times of year, according to Schreiner.

“They thrive in areas where water resources are available because they require those for their breeding and reproductive cycles,” Schreiner said. “In years of high precipitation, which this year has occurred for Colorado, with the insane moisture we’ve gotten, there tends to be an increase in standing water and stagnant pools, that’s capitalized on by those mosquito populations. These conditions produce ideal breeding grounds for mosquitoes.”

How to make your home less mosquito friendly

No one can control the weather, but it’s still possible to have an impact on how many mosquitoes hang out nearby. 

The biggest step one can take to prevent mosquitoes from multiplying is getting rid of standing water. Female mosquitoes lay their eggs on or near standing water, leaving the immature mosquitoes, or larvae to develop in the water, Markowski said. The larvae need leaves, soil, grass clippings or some other decaying organic matter to develop. Preventing such an environment can go a long way in preventing mosquitoes. 

Dump or drain water from wherever possible, such as gutters, old tires, wheelbarrows, tarps, birdbaths or other objects. Intercept the mosquito lifecycle by doing so about once a week. 

If there is water in a place that can’t be dumped, apply a larvicide. Products that contain bacillus thuringiensis israeliensis, or BTI, are environmentally friendly, according to Markowski. 

“BTI is made from bacteria that kills mosquito larvae,” Markowski said. “A small amount, in the form of compressed donuts, briquettes, or granules is usually effective for up to 30 days. Just read the label and they’ll tell you exactly how to apply the products and where to use them.”

There are also companies that will use a handheld sprayer or a truck to cover more ground and repel the bugs at a larger scale. 

Many truck-mounted or aerial mosquito spraying operations typically use adulticides to target mature mosquitoes. 

“There’s simply too many places mosquitoes can be produced,” Markowski said. “So some adult mosquitoes will invariably hatch off, especially when environmental conditions are favorable to their reproduction.”

The standard is to use an ultra-low volume (ULV) method that is approved by the U.S. Environmental Protection Agency. 

“When applied by a licensed vector control professional who follows label instructions, truck spraying poses minimal risk to people, pets, animals, and the environment,” states the Centers for Disease Control. 

Many communities, golf courses and parks in western Colorado have already sprayed for mosquitoes to limit the spread of West Nile and other viruses. 

Vector Disease Control International services 12 states including Colorado and keeps a master schedule that allows citizens to see what businesses or communities in their area have sprayed at VDCI.net/colorado-schedules.

How to repel mosquitoes

Turns out, citronella candles don’t cut it. But there are some other natural ways to keep mosquitoes out of your space. 

An insect repellant with DEET is going to be an effective way to keep the buzzing bugs away. The chemical compound is endorsed by the Centers for Disease Control, but some people can experience adverse reactions such as a rash. DEET comes in a variety of concentrations. The higher the number means the longer the effects will last, however, it’s widely recommended to not use DEET with a concentration greater than 30%. 

Picaridin is a similar and less irritating option, according to Markowski. 

Permethrin is an option as well, but it’s not a repellant. The chemical is an insecticide and should only be applied to clothing or other gear. 

More natural options include oil of lemon eucalyptus, which Markowski said can be an effective alternative to some of the harsher repellants. Other plant-based ingredients that could keep the critters away include citronella, lavender and peppermint, but they are less effective than synthetic versions or DEET.

Other options such as traps, bracelets and bug zappers are generally ineffective, according to Markowski. 

How to make yourself less attractive to mosquitoes

Everyone has heard the quip, “I must taste sweet, the mosquitoes are all over me!”

There is some science to that, believe it or not. 

“Mosquitoes, just like most other blood-feeding insects, use the carbon dioxide that we exhale out as a long-distance attractant to bring them close to their hosts,” Markowski said. “But once they actually get close to a host, they use a variety of other cues to finally hone in.”

According CSU Extension, mosquitoes can smell an exhale of carbon dioxide from up to 75 feet away. 

Wearing dark colors can provide a greater contrast that allows mosquitoes to see people better. Mosquitoes will also pick up on chemical cues as they get closer to a person or group of people. 

“These chemical cues include breath odors, microbiota byproducts on our skin, or other general human odors like octenol, ammonia, caproic acid, or lactic acid,” Markowski said. “We are all different and these different combinations are more or less attractive to different mosquito species.”

While some studies have shown that blood group “O” seems to be the most attractive for mosquitoes that bite humans, there isn’t a clear answer as to why. 

You’ve been bitten. Now what?

Even after all the work of preventing mosquitoes and repelling them, some still manage to mature and pester people on porches and patios. 

While most people don’t experience serious symptoms if they get a mosquito bite, there are serious dangers as well. 

Mosquitoes are vectors, meaning they can transmit diseases from one species to another. Mosquito-borne diseases include West Nile virus, Zika virus, Chikungunya virus, dengue, and malaria.

West Nile is of the biggest concern in Colorado, which was the state with the most cases in 2022, according to the CDC. Colorado has the second-most cases in the United States since 1999, with 6,063. Only California has recorded more. However, about half of those cases all occurred in 2003, just the second year West Nile was found in Colorado. 

Since then, the population has developed a bit of an immunity, Jennifer House, the deputy state epidemiologist and the state public health veterinarian at the Colorado Department of Public Health and Environment told the Colorado Sun last year. 

However, there are still plenty of people who need to build up an immunity, as indiciated by the rise in cases in the past two years. In 2022, Colorado saw the most hospitalizations from West Nile since 2003, according to the Colorado Department of Public Health and Environment.

The best way to prevent any symptoms is to protect yourself using a physical barrier of clothing or nets, or chemically protect yourself with natural oils or repellants.