‘Stock up on the bug spray’: Rain brings mosquitos out in force across Twin Cities area

This week’s copious rainfall was all that was needed to set the stage for the Twin Cities area’s mosquito population to explode, and the Metropolitan Mosquito Control District (MMCD) will spend the holiday weekend trying to beat them back.

For the next few days, the agency will send up to six helicopters airborne to drop tiny granular pellets on habitat where a “significant” batch of human-biting insects have already or are ready to hatch, said Alex Carlson, MMCD spokesman.

“They are going to start coming out,” he said. “Stock up on the bug spray.”

Pilots working 12-hour days will fly across all seven counties and more than 90 cities in the metro area, making two passes in attempts to kill off as many of the insects as possible, Carlson said.

The first round of flights will be to get ahead of cattail mosquitoes, a species that overwinters in the water as larvae and emerges around the beginning of July. An early projection calls for the species to reach a five-year high by the Fourth of July, according to the MMCD.

A second pass will tackle the more immediate threat. Floodwater mosquitoes, the most common of the 52 varieties found in Minnesota, need rain to emerge in the spring. This week’s soaker that dropped between 2 to 3 inches of rain set the stage for their arrival.

MMCD typically works only Mondays through Fridays, but with the timing of the rain, “we have to get the product in the water this weekend,” Carlson said. “If we wait, we’ll be swarmed by mosquitoes.”

The products called MetaLarv and Bti (Bacillus thuringiensis israelensis) can kill larvae on the spot, but they are not harmful to humans, pets or pollinators, Carlson said.

Helicopters will take off from several points across the metro, including airports in Crystal and Lake Elmo, the Hennepin County Fairgrounds in Corcoran and empty fields.

“If you are near a wetland, you will see them this weekend,” Carlson said. “But don’t be alarmed. Helicopters are not chasing fugitives.”

Carlson said mosquitoes are most active in the hours right after sunrise and right before sunset.

One sample collected by MMCD last week tested positive for West Nile virus, a disease typically not found in mosquitoes until later in the summer. Vector ecologist Jordan Mandli said the sample found in Ramsey County likely came from a Culex mosquito that had the virus at the end of last year, overwintered and re-emerged this year.

The finding comes with a warning to take precautions such as wearing bug spray and avoiding woodlands and areas with swamps or ponds during peak activity, Carlson said.

“They are not daytime feeders,” he said, so holiday picnics should not be too uncomfortable. Mosquitoes are also less active in cool conditions, which the forecast calls for. Highs through Monday will be in the upper 60s and low 70s with nighttime readings between 45 and 51 degrees, the National Weather Service said.

With dry conditions expected over the next few days along with treatment, Carlson is hopeful MMCD can get the upper hand on reducing mosquito numbers.

“Hopefully we won’t have quite as many and people can have a good summer,” he said.