Weekly Update – July 5th – Cattail Mosquitoes Responsible for Surge in Some Areas
July 13, 2022
Weekly Update – July 18th – Drought Conditions Continue and Mosquitoes Numbers Stay Low
July 26, 2022
Mosquito numbers usually begin to decline as we head into the latter part of July, but this year they are well below the 10-year average.
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.
With most of the state in moderate to severe drought throughout the summer of 2021, we saw remarkably low mosquito numbers. We aren't in quite the same drought conditions this year, but a general lack of consistent precipitation has led the amount of mosquitoes collected in traps to approach 2021 levels.
According to MMCD assistant entomologist, Dr. Scott Larson, in the Twin Cities "mosquito population levels are flattening and we’re approaching levels seen last year. Other parts of the US are apparently seeing record numbers of mosquitoes right now." Cattail mosquitoes are responsible for most of the areas that are seeing high mosquito numbers with this species accounting for the majority collected in northeastern Carver County and northern Anoka County.
Here are the mosquito trap counts from last Tuesday, July 11th:
Mosquitoes test positive for West Nile virus in two more counties.
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 two more samples of mosquitoes have tested positive for West Nile virus one from Ramsey County and another from Anoka County. These two add to the first positive sample collected in June in Hennepin County making three counties with confirmed West Nile samples in counties that encompass over two thirds of the District population. 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.
In 2021 there were more human cases of West Nile virus in Minnesota than in 2020 despite there being far fewer mosquitoes in 2021. One of the factors that could contribute to West Nile transmission is a lack preparedness - when people don't notice an abundance of nuisance mosquitoes, they may be less apt to take precautions like wearing bug spray. Please encourage family and friends to protect themselves against mosquito bites as we head into the more active part of the summer for disease transmission.
For the latest updates on mosquito control, disease activity, and planned treatments, follow MMCD on Twitter or Facebook.
