Weekly Update – July 11th – Mosquito Numbers Approach 2021 Levels, More West Nile Found
July 19, 2022
Weekly Update – July 25th – Looking Like 2021 All Over Again
August 2, 2022
Mid-July is often an active time of year for mosquitoes, but thanks to dry conditions and several other factors the numbers are down quite a bit again this year.
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.
As of last week most of the District had received below average rainfall and much of the seven counties were either in moderate drought or abnormally dry according to the U.S. Drought Monitor. Lack of rain means lack of mosquitoes and for the second year in a row the overall number of mosquitoes collected in CO2 traps are way below average.
According to MMCD assistant entomologist, Dr. Scott Larson, in the Twin Cities "this week was the first time we collected fewer mosquitoes (on average) than in 2021. In fact, only 13 (out of 139) CO2 traps captured more than 130 human-biting mosquitoes." Larson also explained that in the few traps that collected a high number, over 95% of those collected were cattail mosquitoes.
Here are the mosquito trap counts from last Monday, July 18th:
Mosquitoes test positive for West Nile virus in Dakota County.
Warm, dry weather is ideal for container-breeding mosquitoes that are less dependent on rain than floodwater mosquitoes. Species that breed in permanent water or in containers are often more likely to carry diseases like West Nile virus and La Crosse encephalitis.
MMCD Vector Ecologist reported that a sample of mosquitoes collected in Dakota County have tested positive for West Nile virus. This makes four positive tests for the year in four different counties - Hennepin, Ramsey, Anoka, and now Dakota. Positive samples from four different counties indicates that the virus is already widespread this year. Residents are advised to continue to take precautions by using insect repellent, wearing long sleeves and pants, and avoiding peak feeding times of dawn and dusk.
For the latest updates on mosquito control, disease activity, and planned treatments, follow MMCD on Twitter or Facebook.
