Expect more of these pests this summer in Illinois (+ how to stay protected)
Rainy summer weather conditions in Illinois will likely increase populations for at least four types of pests, according to a recent outlook from the National Pest Management Association.
The NPMA’s Spring & Summer 2026 Bug Barometer forecast summer heat will bring increased fly and tick populations, while rainy conditions will bring a spike in ants and cockroaches in Illinois homes.
“They are two pests Illinois homeowners should definitely be on the lookout for,” Jim Fredericks, board-certified entomologist and senior vice president of public affairs at NPMA, wrote in an email to the News-Democrat.
Mosquitoes are another concern in Illinois, and the biting insects tend to thrive in warm weather. Mosquitoes can pose a public health risk, and infected Culex mosquitoes can spread West Nile virus.
People who contract West Nile virus can be asymptomatic, but others may experience fever, headaches and nausea, and in rare cases the virus can cause serious illness and death. Illinois had the sixth-greatest number of West Nile cases reported in the U.S. over the last 25 years.
Officials with the Illinois Department of Public Health encourage residents to take precautions against biting pests and animals that can pose a risk.
“Spring and summer provide so many opportunities for outdoor fun all across Illinois,” IDPH Director Dr. Sameer Vohra said in a May 14 press release. “It is important to remember that some common biting pests and animals may be carrying disease that can cause serious human illnesses. Illinois residents should take precautions like wearing bug repellent and vaccinating their pets against rabies, among other measures, to keep themselves and their communities healthy and safe.”
Here’s what to know about other potential pests in Illinois this summer.
What about rodents?
Illinois health officials recently reported a possible case of hantavirus originating from contact with rodent droppings. The suspected Illinois case is unrelated to the recent MV Hondius cruise ship outbreak and is thought to be a North American strain, which is not transmissible person-to-person.
Still, hantaviruses can cause serious illness and death. To mitigate contact with rodents that can be disease vectors, pest management experts recommend sealing any holes in your home, keeping your food in airtight containers and keeping your space tidy and free of clutter.
“If you see a rodent in your home, it’s usually because it is seeking food and shelter,” Fredericks said. “It’s not hard for rodents to find a way in: mice can fit through holes and cracks as small as a dime, and rats through openings the size of a quarter.”
How to protect yourself from pest problems in Illinois
Mosquitoes only need a small amount of water to lay their eggs, so it’s a best practice to remove any standing water in your yard.
“Prevention is paramount,” Fredericks said.
Other tips include using an EPA-registered insect repellent, wearing long pants and long-sleeved shirts when possible and replacing birdbath water regularly.
When you come inside, Fredericks said you should do a tick check on yourself and any family members or pets.
“The sooner you find an attached tick, the easier it is to remove,” Fredericks said.
When removing a tick, use fine-tipped tweezers and avoid grabbing the tick’s body to mitigate additional fluid transmission. You should clean the affected area and watch out for any fever, rash or flu-like symptoms, Fredericks said.
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