Insect Update – Week of August 23rd – Mosquitoes begin to increase, more West Nile found
August 30, 2021
Insect Update – Week of September 7th – Mosquitoes Still Out as Season Begins to Wrap-Up
September 16, 2021
After being briefly above average on August 23rd, overall mosquito numbers are back to below average this week.
Results from the August 30th surveillance show that mosquito numbers remain low in the days immediately following several inches of rain, but they may tick up next week.
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.
After a brief uptick last week where the mosquitoes in 2021 were above the 10-year average for the first time, overall mosquitoes caught in CO2 traps are back to below average based on collections on August 30th. Any mosquitoes that may have hatched from the heavy rain that fell during the last week of August may not have hatched by Monday the 30th and they may be more reflective in next week's trap totals.
According to MMCD assistant entomologist Scott Larson, "Culex mosquitoes captured in the gravid trap network were down quite a bit." Larson suspects that the rain may have helped flush out some larvae from roadside catch basins.
Despite the lower numbers of Culex mosquitoes caught, West Nile virus still remains a threat to residents of the District at this point in the year, however. MMCD vector ecologist Kirk Johnson has tested mosquitoes that were found to be carrying the virus in almost every county in the metro this year and we remain in the peak time of year for West Nile virus transmission. The Minnesota Department of Health reported the first human case of West Nile virus to the CDC from a resident in Hennepin County. Residents are advised to lower their risk of mosquito-borne disease by wearing insect repellent and avoiding peak feeding times of dusk and dawn.
Here are the mosquito trap counts from last Monday, August 30th:
Fall is coming, but mosquito-borne disease threat is still present.
As the temperatures begin to decline, mosquito populations tend to decrease as well and we are likely to see fewer mosquitoes over the next several weeks. However, the mosquito-borne disease threat remains high with increased risk for West Nile virus along with reports of other mosquito-borne disease in the area. We mentioned above and have frequently pointed out through the past couple of weeks that we are in the peak time of year for West Nile virus transmission. Recently, the Minnesota Board of Animal Health reported that a horse in Itasca County tested positive for the mosquito-borne disease Eastern Equine Encephalitis (EEE).
Please help us out by reducing mosquito habitat on your property - check your yard after the weekend rain to see if there is any standing water and eliminate it promptly.
For the latest updates on mosquito control, disease activity, and planned treatments, follow MMCD on Twitter or Facebook.
