Weekly Update – May 22nd – Adult Mosquitoes Surge, Annoyance Reports Pour In
June 1, 2023
Weekly Update – June 12th – Dry Weather Lowers Mosquito Numbers in Some Areas
June 20, 2023
Mosquitoes in 2023 have been well above the 10-year average, but pacing behind the same time in 2020.
For the second week in a row adult mosquitoes are trending above average, although the total is flattening.
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.
For the second week in a row adult mosquitoes captured in CO2 traps were well above the 10-year average, although there wasn't a significant increase from May 29th to June 5th. The dry weather we've experienced in the Twin Cities over the last several weeks is likely a reason for the lack of a District-wide increase, though there does appear to be several areas of significantly high mosquito activity.
According to MMCD assistant entomologist Dr. Scott Larson, "despite the lack of rain in many parts of the District many of the CO2 traps are pulling in lots of mosquitoes; 19 of our CO2 traps had over 1000 human-biting mosquitoes last week." Some of the high activity areas include western Hennepin County, northern Anoka and Washington Counties, and Carver County.
Cattail mosquitoes (Coquillettidia perturbans) are also beginning to emerge throughout the District. This is a unique species that overwinters as larvae and emerges once per year around the beginning of July. According to Larson, there is not a huge emergence right now, but we are seeing them earlier than other seasons.
Here are the mosquito trap counts from last Monday, June 5th:
First West Nile Virus positive mosquito has been found.
Each year MMCD Vector Ecologist Kirk Johnson tests mosquitoes for the presence of West Nile virus, the most common mosquito-borne disease in Minnesota. To date, 51 mosquito samples have been tested and the first positive result came from a sample collected June 1st in Anoka County.
According to Johnson, "West Nile virus is always present in mosquitoes at this time of year as it overwinters in adult mosquitoes. We’ve had positive results from the first week of June in the past, still this is much earlier than the average first date of WNV detection locally (July 10) and the median first date (July 6)."
Culex mosquitoes are more active in warm weather, so we are bound to see more as the temperatures continue to rise.
Ensure you are protecting yourself from mosquito-borne disease by using bug spray, wearing long, light, and loose clothing, and avoiding the peak feeding times of dawn and dusk.
