First Weekly Update – May 13 – Mosquitoes Low, Black Flies High to Start 2025
May 20, 2025
MMCD will be at Grand Old Day and several other events this coming weekend!
Rain during surveillance has made collecting mosquitoes difficult, and current numbers appear to be low.
Every Monday night starting in mid-May through September, the Metropolitan Mosquito Control District sets out a variety of mosquito and black fly traps throughout the district and employs a network of sweep net collections done by employees and volunteers. Any insects collected are brought back to our lab on Tuesday to be identified throughout the week with maps published to show current mosquito and black fly activity.
Staff at the Metropolitan Mosquito Control District have multiple methods to collect adult mosquitoes to provide vector-borne disease surveillance and get an overall glimpse at the mosquito populations in different areas. These methods include CO2 traps, gravid traps, sweep net collections, and more and each of these take place weekly during summer months. While these are proven methods that can provide an accurate count of mosquito and black fly activity, there are a number of factors that can impact their collections. The last two weeks the main factor has been excessive rainfall.
Last week (May 19-20) sweep net collections had to be canceled and CO2 traps were operating during heavy rainfall all through the night. This week (May 27-28) sweep net collections took place during light rain for most of the District and CO2 traps operated during light overnight rains. These factors may have caused fewer mosquitoes to be active and end up caught in MMCD traps or nets. The overall number of mosquitoes active may be slightly higher than the maps below indicate, though other data including resident calls to report annoyance and larval mosquito surveillance indicate that numbers are not that high yet this season.
Below are maps showing mosquitoes collected in CO2 traps over the past two weeks (click to enlarge):
Helicopters have been busy! Over 40,000 acres treated in the past two weeks.
Due to a combination of heavy rainfall causing a mosquito brood and the timing for cattail mosquito treatments, MMCD helicopters have been very busy over the past two weeks. Last week staff completed over 30,000 acres of treatment from Thursday through the Sunday of Memorial Day weekend. This week crews finished up with another 10,000 acres of treatment that was completed Thursday.
Most of the acres treated were to target cattail mosquitoes - a unique species that overwinters under the ice as larvae and emerges from the water once per year around the beginning of July. Late May is typically the best time to treat wetlands that hold cattail mosquito larvae because they begin to surface and prepare to emerge from their breeding sites. This year our entomology lab is projecting a 4x increase in cattail mosquitoes based on precipitation and surveillance data from last year. To reduce the nuisance caused by these mosquitoes, MMCD staff treated 26,885 acres of cattail mosquito habitat, which is up from only around 8,000 in 2024.
Helicopters will now likely not be active until the next significant rainfall.
Summer event season kicks off this weekend!
We are past Memorial Day and schools are starting to let out throughout the Twin Cities, which means summer is here! MMCD staff will be participating in events during the next several months to engage with District residents and provide education about mosquitoes, ticks, black flies, and more!
MMCD Mosquito Tattoo
Check us out during the coming days at the following events:
- Lake Phalen WaterFest - Saturday, May 31st
- Tater Daze Parade - Saturday, May 31st
- Grand Old Day - Sunday, June 1st
- Family Nature Day at Sunfish Lake Park - Saturday, June 7th
- Take a Kid Fishing, Dakota County (West St. Paul) - Sunday, June 8th
We will have giveaways like tattoos and pencils and most events will feature live mosquito larvae to interact with and learn about!
MMCD's Helicopter Activity in the News
With all of the busy activity happening over the last week, we had a visit from KSTP News to provide an updated. Check out their story below:
