Mosquito Season in the Twin Cities: What the District Treats and What You Do

What does the Metropolitan Mosquito Control District do?

It is a public agency serving Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington counties. Its main approach is larval control: crews survey wetlands and catch basins and treat water where larvae are found. Adult control supplements this in places such as parks and for events, and the district is funded through property taxes.

According to the district's own pages, larval work is the core of the program. Staff apply a natural soil bacterium and a growth regulator to water where larvae are found, by hand to small sites and by helicopter or drone to larger wetlands. Field crews also check catch basins, the storm-drain pits under street grates, where water can sit.

Adult control is used after sampling shows numbers above a threshold, mostly in high-use park areas, for public events or in response to resident reports. The district also treats black flies in rivers under a state permit. It does not control ticks; it monitors them.

What this means for a homeowner is that the public wetlands and storm systems in your area are being worked on by professionals. What it does not mean is that every puddle on your property is covered, and the district says so itself: its guidance for residents is mostly about removing the water that mosquitoes need.

When does the season start and end?

Field work begins in spring when snowmelt, rain and temperatures allow. One year crews started on April 13, and the district reported about 200 seasonal staff working daily until about October. Mosquito numbers build through May and June and peak in the summer. A fall resurgence can follow heavy rain with warm weather.

There is no single start date. The district says the start depends on snowmelt, rain and air temperatures, and recent years show dates in mid-April. We do not state weather normals for the Twin Cities because sources disagree, and the district's own start date varies by year.

The table gives a rough shape of the season. It is built from the district's reports and news coverage plus general seasonal reasoning, and it does not promise dates.

What can you do on your own lot?

Remove standing water. The district's guidance names bird baths, gutters, rain barrels, tarps, low spots, tree holes and old tires. Refresh bird baths weekly, clear gutters several times a year, cover or screen rain barrels, fill low spots that stay wet for more than three days and store tools and tarps so they do not hold water.

These steps come from the district's resident guidance. They sound minor, but a single clogged gutter or a saucer under a flowerpot can produce a steady stream of mosquitoes. The district asks residents to contact it before treating a wetland on their own, because not every wetland produces mosquitoes and treating one small site does not help if others nearby are untreated.

The effect of draining adds up across a block. If you and your neighbors all dump water weekly in June, the district's work reaches further. It is also the one step with no cost and no product.

• Bird baths: change the water at least once a week
• Gutters: clear clogs several times a year so water does not sit
• Rain barrels: cover or screen them with mesh small enough to stop mosquitoes, and empty them a couple of times each season
• Low spots: water that stands more than three days can produce mosquitoes, so fill and level the area
• Tarps, wheelbarrows and buckets: store them so they cannot collect rain
• Tree holes: fill with sand or foam, or ask an arborist
• Old tires: remove them; they are among the best breeding containers

When is a private yard treatment worth considering?

When draining has been done and the yard is still unusable, or for a specific event or heavily used area. A treatment reduces adult mosquitoes around the yard for a period, but it cannot keep up with water that keeps refilling. It is a supplement to draining, not a replacement.

A technician doing mosquito control starts with a look at the yard: the low spots, the gutters, the shaded places where adults rest. The plan is explained before anything is applied, and the price is confirmed on site.

Properties near water have more to deal with. Houses near lakes, creeks and ponds, such as those in Minnetonka, Eden Prairie or Savage, sit close to public wetlands that the district treats, and also close to private margins that it does not. In those yards, draining and a seasonal plan often work together.

Treatments near water have label restrictions, so tell the dispatcher how close the shoreline or wetland is. The district's own guidance notes that its adult-control materials are toxic to fish and bees, which is a reminder that products are not casual.

Why does mosquito trouble differ between a lakeside yard and a city lot?

Because the breeding water differs. Near lakes, creeks and wetlands, public water is the main source, and the district treats it. On a city lot, small containers and clogged gutters are the main source, and only the owner can fix those. The district's weekly updates note when container-breeding mosquitoes become active in June.

A house beside a pond or a creek corridor gets mosquitoes from water the owner does not control and cannot see to the end of. The district's larval work targets such sites, which is why the owner of a lakeside house depends on it. Even so, the owner's own containers and gutters add to the total, and the district asks residents to deal with them.

A lot in a dense neighborhood has less natural water but plenty of artificial: a gutter on a flat roof, a neighbor's tarp, a catch basin at the curb, an old tire behind a garage. Container-breeding mosquitoes become active in early summer, according to the district's weekly update for one June, and they breed in just such places. In older parts of Minneapolis and Saint Paul with alleys and small yards, a few minutes of walking the lot and the alley can turn up several sources.

Neither case is solved by a product alone. For lakeside yards, a technician may recommend a seasonal treatment alongside draining. For city lots, draining and a talk with neighbors do most of the work. See our area pages for Navarre and Hopkins for how the two settings differ.

Finally, remember that people's tolerance varies. A few bites at dusk are different from a cloud at noon. Tell the dispatcher what you experience, when and where, so the plan can fit the actual problem.

What should you tell the district, and what should you tell a technician?

Tell the district about large, persistent breeding water you cannot fix, such as a wetland or a neglected pool, and about heavy mosquito numbers in a public place. Tell a technician about your yard, the gutters, the shade and the events you want covered. Each handles a different part of the same problem.

The district's pages invite residents to contact it with concerns about wetlands and mosquito activity. We do not print its phone number, since numbers change; use the contact details on its website.

For a technician, useful details include: where you notice the bites and at what time of day, whether there is standing water you cannot drain, whether you have a pond, a fountain or a creek, and any pets or fish that products must avoid. The technician then explains what will be used and where, and the price is confirmed on site before work starts.

Why is a wet year different, and what about the fall?

Heavy rain fills ponds, ditches and containers, producing more breeding sites. News coverage described 2025 as expected to be heavy after a wet year, and a fall resurgence has followed heavy rain combined with warm weather. So bites in September are plausible. The district's crews wind down around October.

A wet spring and summer give mosquitoes more places to lay eggs,. We do not give counts, and the district's weekly updates are the place for current conditions. What the news coverage does support is that the pattern of rain followed by warmth can bring a late surge.

Do not stop checking in September. Containers that were empty in August can fill after a September storm, and a warm week can bring a hatch. The sensible habit is to keep dumping and clearing until the first hard frosts end the season outdoors.

The contrast with warm-climate cities is stark. In Minnesota the season has an end, and it is a real end. That is why a mosquito plan here is a summer plan, not a twelve-month one.

How does this fit with other seasonal pests?

Mosquitoes are the summer thread in a calendar that runs through spring ants and carpenter ants, summer wasps, the October move indoors of mice and insects, and the dormant winter. Planning around that calendar is more useful than thinking about each pest alone.

The calendar is covered in our monthly pest calendar. In short: spring is the thaw and the first mosquito crews, summer is mosquitoes and wasps, autumn is the entry window for mice and insects, and winter is the indoor season. Mosquitoes occupy only part of the year, so a plan that charges for them in January is not following the weather.