As Philadelphia residents spend the summer in green spaces like Wissahickon Valley Park and Fairmount Park, city and state experts are warning the public to be mindful of increasing tick activity.

June marked the start of peak season for tickborne illnesses, the Philadelphia Health Department said in a June advisory, and high activity typically lasts through the summer and into October.

Although the parasite is especially prolific during warmer months, the 2025 season has been especially tick-y. The Pennsylvania Tick Research Lab, based at East Stroudsburg University, recorded more than double the number of ticks in May across the state compared to the same time last year. The country as a whole, especially the northeast, is seeing the highest number of emergency room visits for tick bites since 2019, according to the Centers for Disease Control and Prevention (CDC).

Ticks prefer shady, humid environments and tend to be found in wooded areas, tall grass, leaf litter, ground-cover plants, as well as around stone walls and woodpiles, according to the Pennsylvania Department of Environmental Protection.

Tick numbers fluctuate every year, but researchers say the insects — and the diseases they carry — are continuously spreading in the U.S. because of factors such as land use, development, and climate change, which creates longer tick seasons.

In Philadelphia, the health department is warning residents of increasing tickborne illnesses, in addition to the multiple infections typically reported each year. The Powassan virus is a rare but serious disease first reported in Pennsylvania in 2011. Borrelia miyamotoi has caused Hard Tick Relapsing Fever in fewer than 35 people in Pennsylvania. Both diseases are transmitted by Blacklegged ticks, the department said in its June advisory.

Asian longhorned ticks — an invasive species first found in Pennsylvania in 2018, now in 29 counties — are capable of carrying Rocky Mountain spotted fever, Heartland virus and Powassan virus, but there is not yet evidence that they’ve transmitted these to humans. The Lone Star tick species, which can transmit a meat allergy, and Gulf Coast ticks infected with the bacterium Rickettsia parkeri, have been discovered in Philadelphia in recent years.

Philadelphia’s ticks are especially pervasive compared to the rest of the country, according to a new report by the global pest management company Terminix. Philadelphia ranks among the top five U.S. cities with the highest tick activity, with Pennsylvania home to the fourth-largest tick population across all states, the company’s 2024 service data shows.

The state leads the country in reported Lyme disease cases, according to 2023 CDC data.

Tom Dobrinska, a technical service manager at Terminix, said Philadelphia’s large population leads to more tick reports and the city is home to multiple hosts, such as deer, mice, and raccoons. Plus, the city’s humid weather conditions, wide park systems, and neighboring woodlands serve as ideal habitats for the arachnids.

“You have urban sprawl; you still continue to have people building and going into areas where the ticks were in the first place, especially those areas that are forested and heavily wooded. Philadelphia has a ton of beautiful parks and landscapes. If you have that, then you also have a huge ecosystem that’s related to that as well,” Dobrinska said.

As a commercial hub, Philadelphia lends itself to the importation of an array of tick species, Neil Shader, a spokesperson for the state’s Department of Environmental Protection, said in an email. Philadelphia has one of the most diverse tick populations in the state.

The city’s health department advises people to see a doctor if they develop a rash or flulike symptoms. But not every tick bite is infectious; just half of blacklegged ticks sampled in Philadelphia over the past decade tested positive for Lyme disease.

Other bug-related news Philadelphians should watch out for

West Nile virus mosquitoes

The West Nile virus was detected in mosquitoes in Philadelphia for the first time this season, city health officials announced in July. The mosquitoes were collected on June 18 near Pennypack Park in Northeast Philadelphia.

No human cases have been reported in the city since June, Jim Kyle, a spokesperson for the city’s health department, said in an email. The department, which conducts West Nile virus surveillance alongside the state’s Department of Environmental Protection, has detected a few more positive mosquitoes, but the virus is not considered a significant threat and the department currently doesn’t need additional state funding to mitigate the spread, Kyle said.

City health officials also advised medical providers to look out for symptoms of the virus and to test patients when necessary from now through October, or when the first frost occurs.

Most people who get infected with the West Nile Virus don’t experience symptoms, which include fever, headache, body aches, vomiting, or a rash, according to the CDC. People over 60 and those with weakened immune systems are more likely to become severely sick.

In 2024, nine people in Philadelphia were diagnosed with West Nile virus.

Residents can see tips on how to reduce the risk of catching a tick-borne illness or West Nile virus on the Philadelphia Department of Public Health and the state’s Department of Environmental Protection websites.

Stephanie Bruneau, assistant director of adult education at Morris Arboretum & Gardens of the University of Pennsylvania, encourages homeowners to try pest management methods that avoid harming other pollinators. She uses mosquito dunks in her Mt. Airy backyard and is able to sit outdoors without being bothered by the insects.

“Pesticides that folks use to control mosquitoes kill a lot of beneficial insects too, and then the whole cycle is out of whack in a way that doesn’t actually benefit the homeowner in terms of mosquito prevention,” she said. “When it’s not a healthy, functioning ecosystem, then things can get out of control.”

Spotted lanternflies

The “If You See It, Stomp It” campaign continues.

The majority of Pennsylvania’s counties, including Philadelphia, are under quarantine for the spotted lanternfly, meaning they have to comply with regulations that aim to stop the spread of the polka-dotted insect.. The invasive species was first spotted in the state in 2014. It poses a significant threat to Pennsylvania’s vineyards, plant nurseries, and timber industries, and leaves behind a sticky “honeydew” that attracts bees and wasps, according to the Pennsylvania Department of Environmental Protection.

Four more counties were put under quarantine this year.

Julie Urban, an entomologist at Penn State, has been studying the lanternfly since it arrived in Berks County a decade ago. She said there’s a resurgence in the area, because the insect’s food sources are rebounding from its damage several years back. The rainy weather this year may be a factor as well, she said. Luckily, Berks County growers are prepared, having received training from the USDA and various research institutions.

Up north, lanternflies are treading closer to Erie County, Urban said. That’s concerning for grape growers because insecticides and upkeep costs are expensive. And Erie County’s grapes are mainly used for juice and jelly, which have a lower profit margin. Their automated farming techniques may also create fewer opportunities for lanternfly removal, she said.

“That’s something that we’re researching to try to figure out what that risk is and how to best provide recommendations to keep the lanternfly out of any potential harvest,” Urban said.

Scientists are researching potential natural predators, such as the parasitic wasp, to control the lanternfly population and reduce dependency on pesticides. In July, congressional representatives from Pennsylvania and New York introduced a bipartisan bill to curb the insect’s spread.

As for Philadelphia residents, she recommends sticking to the state’s “Stomp It!” campaign to help mitigate the spread of the insect. She also suggests going to Penn State’s Management Guide for tips.

“The longer we can keep it from getting (to Erie), the more time we have for these other solutions, like the parasitoid wasp,” Urban said. “We have a lot of irons in the fire. It buys us more time for the research to come up with better solutions.”

Abby Weiss is an environmental reporter for the Local and a Report for America corps member. She can be reached at Abby@chestnuthilllocal.com.