Does Tennessee Have Mosquitoes and When Are They Worst?

Tennessee has a thriving mosquito population, with researchers documenting at least 23 species across the eastern part of the state alone. The worst stretch runs from late June through September, when heat and humidity create ideal breeding conditions, though activity can begin as early as April and linger into October depending on the region and weather patterns. The state’s mix of river valleys, forests, and humid subtropical climate makes it hospitable to both native species and aggressive invaders that have reshaped the mosquito landscape over the past few decades.

Which Mosquitoes Dominate the State

The single most abundant mosquito in Tennessee is the Asian tiger mosquito (Aedes albopictus), an invasive species that arrived in the United States in the mid-1980s and has since become the dominant biter in much of the Southeast. A multi-year trapping study across eastern Tennessee collected over 4,200 female mosquitoes representing 23 species, and Aedes albopictus outnumbered its closest relative, the native eastern treehole mosquito (Aedes triseriatus), by a widening margin each year, growing from roughly a two-to-one ratio to nearly five-to-one over three consecutive seasons.¹ That trend matters because the Asian tiger mosquito is an aggressive daytime biter that thrives in suburban yards, flower pots, discarded tires, and any container holding even a small amount of standing water.

Beyond the Aedes group, members of the genus Culex are the other major players. In the Memphis area and surrounding Shelby County, Culex pipiens complex mosquitoes and Culex restuans were among the most frequently collected species, feeding primarily on birds but also taking blood meals from mammals, including humans.² These night-biting Culex species are less noticeable to most people than the tiger mosquito, but they carry their own disease risks.

When Mosquito Season Peaks

Mosquito activity in Tennessee is tied directly to temperature, rainfall, and how quickly the weather warms in spring. Researchers modeling Asian tiger mosquito populations in eastern Tennessee found that the species’ peak egg-laying activity kicks in once temperatures climb above about 79°F (26°C), and that both the amount of rain and the rate of temperature change influence how fast populations grow.³ In practical terms, here is what that looks like across the calendar:

• April through May: Overwintering eggs begin hatching as temperatures warm. You’ll notice a few mosquitoes, but populations are still building. This is the window when standing water from spring rains fills containers and tree holes, seeding the next generation.
• June through August: The worst stretch. Sustained heat and afternoon thunderstorms create a cycle of new breeding water and rapid larval development. July and August are typically the peak months, when Asian tiger mosquitoes and Culex species are at their highest numbers.
• September: Still active, sometimes intensely so. Late-summer rains from tropical moisture can trigger another surge. Populations remain high until nighttime temperatures consistently drop below the mid-60s.
• October and beyond: Activity tapers off. Hard frosts kill adult mosquitoes, though Aedes species leave behind drought-resistant eggs that survive the winter in soil and debris, waiting for the following spring.

A wet, warm June accelerates the whole timeline. A dry spell in July can temporarily knock numbers down, but the first soaking rain afterward brings them roaring back because all those drought-tolerant eggs hatch at once. This boom-and-bust pattern driven by rainfall is one reason Tennessee residents sometimes feel blindsided by mosquitoes that seem to appear overnight.

When They Actually Bite

If you have heard that Asian tiger mosquitoes only bite during the day, the reality is more complicated. A study tracking Aedes albopictus activity across urban and suburban sites found that while the species is most active around midday and the early afternoon, it also bites at sunrise, sunset, and even at night during peak season.⁴ That means in midsummer Tennessee, there is essentially no safe window to be outside without protection. Culex species, by contrast, are primarily crepuscular and nocturnal, so evenings on the patio carry a double threat from both groups.

The eastern Tennessee trapping data echoed this, showing two clear landing-activity peaks for Asian tiger mosquitoes: one in the early morning and another in the late afternoon or early evening.¹ If you plan outdoor activities in summer, midmorning and early afternoon tend to be the lowest-risk windows, though even then you are not guaranteed relief.

Diseases Mosquitoes Carry in Tennessee

Tennessee’s mosquitoes are not just a nuisance. Several pathogens circulate through the state’s mosquito populations each year, and understanding which diseases are realistic concerns helps you decide how seriously to take prevention.

West Nile Virus

West Nile virus has been present in Tennessee since at least 2002, when it was first detected in mosquito pools collected from wildlife management areas in the northwestern part of the state near Kentucky Lake. That initial detection turned up the virus in both Asian tiger mosquitoes and Culex erraticus, with further positive pools found over subsequent weeks.⁵ In the Memphis area, blood-meal analysis pointed to the American robin and common grackle as the most important bird reservoirs keeping the virus cycling through Culex mosquito populations.² Most human infections cause no symptoms or a mild flu-like illness, but a small percentage of cases develop serious neurological complications.

La Crosse Encephalitis

La Crosse encephalitis is the mosquito-borne disease most distinctive to Tennessee and the broader Appalachian region. The virus emerged in the state in 1997 and has caused pediatric illness in East Tennessee every year since, making it an ongoing concern for families with young children.⁶ The virus is transmitted primarily by Aedes triseriatus, but field research in Tennessee demonstrated that the Asian tiger mosquito and the Japanese rock pool mosquito (Aedes japonicus) also carry and transmit it, with infection rates in the Asian tiger mosquito actually slightly higher than in the native vector.⁷ All three species showed evidence of passing the virus to their offspring through their eggs, which means the virus persists in the environment even through winter.

Eastern Equine Encephalitis

Eastern equine encephalitis is rarer but far more dangerous when it does occur. Tennessee had no recorded cases in horses until 2002, after which outbreaks hit multiple times in the western part of the state. In 2008, an outbreak affecting several horses in West Tennessee produced the state’s first laboratory isolate of the virus. No human cases have been reported in Tennessee, but the virus was detected in Culex erraticus mosquitoes, which were collected in far higher numbers than the traditional swamp-associated vector.⁸ Horse owners in the state should keep equine vaccinations current.

Canine Heartworm

Tennessee mosquitoes also transmit Dirofilaria immitis, the parasite responsible for canine heartworm. Researchers screening mosquito pools at two Tennessee sites found heartworm DNA in roughly 1 to 8 percent of pools, depending on the location, with most positives coming from Culex pipiens collected later in the season.⁹ If you have a dog in Tennessee, year-round heartworm prevention is not optional. The mosquito season is long enough and warm enough that even a brief lapse in monthly preventive medication can leave your pet exposed.

Differences Across the State

Tennessee stretches over 400 miles from the Great Smoky Mountains to the Mississippi River, and mosquito conditions vary meaningfully from one end to the other. East Tennessee’s forested valleys and moderate elevations favor container-breeding Aedes species and, as described above, make the region a hotspot for La Crosse encephalitis. The cooler mountain elevations provide some relief, but the valleys and residential areas at lower elevations can be intensely buggy.

Middle Tennessee, including the Nashville metro area, has a mix of suburban habitats and agricultural land. Standing water in construction sites, stormwater ponds, and backyard containers supports both Aedes and Culex species. West Tennessee, with its flatter terrain, floodplain forests, and proximity to the Mississippi River, tends to produce larger Culex populations. The Memphis metro area has been a particular focus of West Nile virus surveillance, with researchers mapping environmental characteristics associated with infected mosquito locations to help target control efforts.¹⁰

Why Your Yard Matters More Than You Think

The Asian tiger mosquito does not fly far. Its typical range from a breeding site is only a few hundred feet, which means the mosquitoes biting you in your backyard almost certainly hatched in your backyard, or your neighbor’s. Unlike floodwater mosquitoes that can travel miles on the wind, tiger mosquitoes are homebodies that exploit tiny pockets of standing water: plant saucers, clogged gutters, toys left outside, bird baths, the crumpled tarp in the corner of the garage.

A community-driven program in East Tennessee tested whether reducing this kind of yard litter could actually dent mosquito numbers. After organized neighborhood cleanup events, researchers found a significant decline in Aedes egg counts at cleaned-up sites compared to control locations.¹¹ The catch is that this effect was measured in egg abundance; the number of adults that emerged from remaining eggs did not differ as clearly. That suggests cleanup helps, but it has to be thorough and sustained. Missing even a few hidden containers can keep the cycle going.

Practical steps that make a real difference: dump and scrub any container holding water at least once a week (scrubbing matters because tiger mosquito eggs stick to container walls above the waterline). Drill drainage holes in tire swings. Keep gutters clear. Change bird bath water every few days. Treat ornamental ponds with larvicide dunks. And because your neighbor’s yard contributes to your mosquito problem, this is genuinely a situation where a neighborly conversation or a community cleanup day pays off.

Insecticide Resistance in Tennessee Mosquitoes

If your first instinct is to reach for a spray, know that the chemicals communities rely on most heavily are losing their edge. A study of Culex pipiens and Culex quinquefasciatus mosquitoes in Shelby County (Memphis) found partial resistance to four commonly used insecticides, including permethrin, deltamethrin, chlorpyrifos, and bendiocarb. Permethrin, which is the active ingredient in many retail bug sprays and yard treatments, performed the worst of the four.¹² This does not mean permethrin is useless, but it does mean that relying on it as your sole strategy is increasingly unreliable, and it underscores why source reduction (eliminating breeding water) remains the foundation of effective mosquito control.

Municipal mosquito abatement programs typically use truck-mounted ultra-low-volume spraying to knock down adult mosquitoes during outbreaks. These applications can reduce adult numbers in the short term, but they do not reach the larvae developing in hidden containers and do not prevent re-colonization from untreated areas. If you live in a Tennessee city that sprays, think of it as one layer in a system, not a solution by itself.

Natural Predators and Their Limits

Tennessee’s ecosystems include several natural mosquito predators. The treehole predator Toxorhynchites rutilus, a large mosquito whose larvae eat the larvae of other mosquito species, has been studied for its potential to control container-breeding pests. In experimental settings, this predator significantly reduced populations of the Japanese rock pool mosquito but had no measurable effect on the native treehole mosquito, which has co-evolved with it and is better at avoiding predation.¹³ That kind of mixed result is typical of biological control: it can shift species composition, but it rarely eliminates the problem.

Fish that eat mosquito larvae, especially Gambusia (mosquitofish), are sometimes stocked in ponds and ditches. Dragonflies, bats, and purple martins also consume adult mosquitoes. All of these help, but none of them will make a noticeable dent in a suburban yard where dozens of small water-holding containers are producing hundreds of new mosquitoes every week. The breeding sites are simply too small and too numerous for predators to keep up.

What Tennesseans Often Get Wrong About Mosquito Risk

Public perception research reveals some persistent gaps between what people think about mosquito-borne disease and what the evidence shows. In a survey of 1,200 adults about West Nile virus, a third of respondents incorrectly believed that at least a quarter of people bitten by an infected mosquito would get sick, when in fact the vast majority of infections produce no symptoms at all. About 14 percent thought the virus could spread through coughing or sneezing. And while nearly half said insect repellent was the best prevention strategy, only 13 percent had actually changed their repellent habits in the previous year.¹⁴

The overestimation of illness risk combined with the failure to actually use repellent is a revealing disconnect. People worry about the wrong thing (a single bite making them severely ill) while neglecting the simple step that most reduces their exposure. For Tennessee specifically, the bigger blind spot is La Crosse encephalitis: it is the state’s most locally distinctive mosquito-borne disease, disproportionately affects children, and yet receives far less public attention than West Nile or Zika ever did.

Repellents That Work in Tennessee Conditions

DEET remains the most broadly effective mosquito repellent against both Aedes and Culex species. Products containing 20 to 30 percent DEET provide several hours of protection. Picaridin at similar concentrations performs comparably and has a lighter feel on the skin. Oil of lemon eucalyptus (the refined version, not the raw essential oil) is the plant-derived option with the strongest supporting evidence, though it should not be used on children under three.

For the Asian tiger mosquito specifically, repellent matters more than it does for some other species because this mosquito bites during the day and in shaded areas where you might not expect trouble. If you are gardening, walking a trail, or eating lunch on a patio between May and September in Tennessee, you are in tiger mosquito territory. Clothing treated with permethrin adds another layer: despite the resistance issues seen in Culex, permethrin-treated fabric still deters and kills mosquitoes on contact at the individual level. Combining a skin-applied repellent with treated clothing is the most effective personal strategy available.

Citronella candles, ultrasonic devices, and wristband repellents do not hold up well under controlled testing. They might reduce bites marginally in a small area, but they are not reliable protection in a Tennessee summer when mosquito pressure is high. Fans are a surprisingly effective low-tech option for porches and patios: most mosquitoes are weak fliers, and a steady breeze disrupts their ability to land on you and to follow the carbon dioxide plume they use to locate hosts.