Weekly Update – July 1st – Are We at Peak Mosquitoes for 2025?
July 8, 2025
Weekly Update – July 15th – Mosquito Numbers Decline, West Nile Virus Activity Ramps Up
July 24, 2025
For the first time this year, mosquitoes are above the 10-year average
Adult mosquito numbers saw a huge increase last week and may be at their peak for 2025.
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.
Last week the average number of adult mosquitoes captured in CO2 traps shot up to over 700 mosquitoes per trap, which is well above the 10-year average for that week (about 330 per trap) and the highest total we've seen since this same week in 2020 (back then we captured 940 per trap in the second week of July). It seems we have officially moved past any lingering impacts from the drought years of 2021-2023 in terms of mosquito development.
Cattail mosquitoes continue to be active, especially in the northern parts of Washington and Anoka Counties. Aedes vexans, or "summer floodwater mosquitoes," are the most abundant species throughout the District. These are our most common summer mosquito and their numbers are heavily dependent on rain. They are doing well considering the multiple inch plus rainfall totals the Twin Cities have experienced in the last month.
However, the worst may be behind us. According to MMCD Entomologist, Dr. Scott Larson, "I do expect this last week to be the peak abundance for mosquitoes, so numbers should drop significantly in the next 2 weeks. Our 10-year average dips below 100 mosquitoes per trap by August, so the public should be comfortable soon enough." We will know that for sure after counting the totals in the traps that are being collected this week.
Below are maps showing all human-biting mosquitoes (left) and cattail mosquitoes (right) collected in CO2 traps on July 7th-8th:
West Nile virus activity is now present in all counties except Ramsey.
MMCD Vector Ecologist, Dr. Jordan Mandli, reported that last week eight more mosquito pools tested positive for West Nile virus and now activity has been detected in every county in the District except for Ramsey. Positive samples last week came from Anoka, Carver, Hennepin, Dakota, and Scott Counties. As Ramsey County is surrounded on all sides by counties with positive samples, it's probably safe for all Twin Cities residents to take precautions to avoid mosquito-borne disease.
According to Mandli, "Overall, we are currently trending slightly less than 2023, a year in which 21 cases of WNV were reported. While it’s still too early to make firm predictions, current trends suggest that 2025 could bring a higher-than-average WNV burden."
It is a good reminder that this is the time of year to take precautions like wearing insect repellent, emptying out standing water, and avoiding the outdoors during the peak mosquito feeding times of dawn and dusk.
MMCD Offers Group Presentations
MMCD offers presentations for school groups, kids camps, community events, clubs, and anyone else that may be interested! We've been active the past couple of weeks bringing live mosquito larvae and other hands-on educational tools. Reach out to our Public Affairs Manager Alex Carlson if you are interested in setting something up for your group!
