Insect Update – Week of June 28th – Low mosquito numbers for the 4th of July
July 7, 2021
Insect Update – Week of July 12th – Still trending below average
July 19, 2021
Results from the July 6th Monday night surveillance show cattail mosquitoes far below normal
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.
Cattail mosquitoes (Coquillettidia perturbans) typically peak around the beginning of July, which means that we are likely experiencing a much lower than average year for this one generation species. This is partially due to the dry weather and also the fact that MMCD treated over 31,000 acres this spring and 1,800 acres last fall for cattail mosquito larvae. In the entomology lab, Scott Larson says "if this was the peak of perturbans captures (and we adequately sampled it), then we had a very low population this year." He also explained that last Monday's conditions were not ideal for collecting mosquitoes with low temperatures and rain in some parts of the district. This week's collections may give a more accurate glimpse at the cattail mosquito population in Minnesota with better conditions for tonight's traps.
When you compare the first week of July capture of cattail mosquitoes in CO2 traps between 2021 and 2020, you can see a stark difference:
All mosquito species are lower than normal and black flies have mostly gone away.
Not only are cattail mosquito numbers low, but all species of human biting mosquitoes are down for this time of year. Even Culex mosquitoes, which don't rely on rain as much and prefer standing water in containers, are lower this week than previous weeks. This is a good sign for potential West Nile virus transmission as Culex mosquitoes are the primary vector in this part of the country.
Here are this week's graphs:
VECTOR UPDATE: No mosquito samples test positive for West Nile virus
We are nearing the time of year when we typically find our first mosquitoes that are carrying West Nile virus. According to MMCD Vector Ecologist Kirk Johnson, "the median date for our first WNV positive mosquito pool is July 6th and the mean date of the first WNV positive mosquito is July 11th." In 2019 and 2020 we did not find our first WNC positive mosquito pool until August.
Learn how MMCD conducts RAMP tests for West Nile virus.
Check Out Our Updates Resident's Guide!
We have updated our Resident's Guide webpage and created a new video with some great tips for reducing mosquitoes in your backyard. Also, be sure to visit our booths at upcoming County Fairs and next month at the Minnesota State Fair to get more tips and ask us any questions you may have about mosquitoes, ticks, or black flies!
For the latest updates on mosquito control, disease activity, and planned treatments, follow MMCD on Twitter or Facebook.
