Weekly Update – August 6th – Cool Weather Brings Mosquito Numbers Down
August 13, 2024
Weekly Update – August 20th – Rainy Month Brings Another Slight Increase in Mosquito Numbers
August 26, 2024
The number of mosquitoes increased slightly last week, but remains low.
Heavy rain in early August led to a slight uptick in mosquitoes last week, but numbers are low overall.
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 our entomology lab predicted in last week's update, there was a slight increase in mosquitoes collected last week due to heavy rain the week prior. Human-biting mosquitoes are back close to the 10-year average for the first time since June 11th. As is typical for mid-August, there aren't a lot of adult mosquitoes around except for a few species like Culex and Anopheles.
According to MMCD Entomologist Dr. Scott Larson, "Interestingly, there were over 400 Anopheles mosquitoes also collected in [a] trap last Monday and that is a lot of Anopheles to capture in one night and a complete outlier, really. Those Anopheles mosquitoes have been having a good year." In other parts of the world, Anopheles are a concern because they are the primary vector of malaria, but malaria is not a threat in Minnesota.
Below are the maps from Monday-Tuesday, August 12th-13th:
Mosquitoes have tested positive for West Nile virus in all seven metro counties
With the abundance of Culex mosquitoes this year it's not terribly surprising that West Nile virus activity is increasing. As of this week we now have collected mosquitoes that tested positive for West Nile virus in all seven counties, after a positive sample was collected in Scott County last week.
Most of the species collected are Culex pipiens or Culex restuans, which rarely bite humans, but some of the positive samples are Culex tarsalis which are more opportunistic and will bite humans in addition to birds. There have been two human cases reported to CDC in Minnesota this year, neither of which were in the District.
It's always important this time of year to take precautions to reduce mosquito bites including wearing bug spray and removing standing water.
Come See MMCD at the Minnesota State Fair!
Come see our booth in the Dairy Building at the Minnesota State Fair which starts this Thursday and runs through Labor Day! Our interactive booth features a lot of fun elements, including:
- Live mosquito larvae
- Microscopes to view specimens
- Coloring pages, temporary tattoos, and other fun stuff for kids
- Information about mosquitoes, ticks, and black flies
- Handouts about protecting yourself from mosquitoes
...and much more! We hope you stop by and see us!
