Cattail Season – How MMCD Monitors and Controls the Unique Species of Mosquito
September 18, 2023
Metropolitan Mosquito Control District 2023 Season Highlights
November 17, 2023
The last week of adult mosquito surveillance for 2023 ends with another below average week.
MMCD has conducted the last week of District-wide adult mosquito surveillance and the season ends below 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.
The mosquito story of 2023 has been very similar to that of 2022 and 2021 - a dry summer meant fewer mosquitoes for most of the year and cooler temperatures in September brought the season to an early conclusion. Staff conducted the final week of District-wide mosquito surveillance on the evening of September 11th and recorded some of the lowest mosquito totals of the year.
According to MMCD assistant entomologist Dr. Scott Larson, "We’ve collected an average of fewer than 50 mosquitoes per trap since mid-July which I don’t really need to explain is not many mosquitoes. We actually never had a District-wide large emergence of Aedes vexans in 2023. Some of the other summer Aedes were relatively more common."
The only major difference from 2023 to the two preceding years was that significant snowfall during the winter of 2022-23 led to and early peak that brought mosquito numbers well above average. Larson says that we could be in for something similar in the spring of 2024 if we get another snowy winter: "Be warned that the huge number of spring Aedes we saw this year likely led to huge numbers of eggs laid, which could easily result in a large number of spring Aedes again next season."
Here are the mosquito trap counts from last Monday, September 11th:
Despite lack of floodwater mosquitoes, container breeding mosquito (Culex) numbers were high and WNV samples were abundant.
Cooler weather has slowed the risk of West Nile virus transmission somewhat, but mosquito pools continue to test positive for the disease. Last week 11 of 78 pools of mosquitoes tested positive for West Nile virus from samples that had been collected over the last three weeks. The positive samples came from Hennepin, Ramsey, and Washington Counties.
MMCD Vector Ecologist Kirk Johnson sums up the season: "This brings the season total to 128 [West Nile virus] positive mosquito samples, four shy of the District record set in 2018. The WNV infection rate in mosquitoes tested has fallen dramatically over the past four weeks. With two weeks of gravid trap sampling remaining and considering the weather this week has been cool, that 2018 record could persist."
Below is a graph that reflects the Culex infection rate throughout 2023:
The Culex infection rate peaked in mid-August of 2023.
Most field work will wrap up over the next few weeks.
Field staff continue to work on cattail mosquito surveillance and treatments, tire pickups, Culex surveillance, map updates, and a few other items as we we wind down 2023. The next step will be to organize all of the data collected and begin to assemble the 2023 Technical Advisory Board report. Check back for updates and any new information as we wrap up 2023 and prepare for 2024.
Also, an important note that the last day for new tire pickup calls is Friday, September 29th. View our Tire Recycling page for more details.
