Bay County residents are swatting away a surge of mosquitoes following heavy rainstorms in late June that caused flooding across the region.
Rebecca Brandt, manager of Bay County Mosquito Control, said the rain created ideal conditions for mosquito eggs to hatch in ditches, woodlots and floodplains, especially near the Kawkawlin River.
“We saw an increase of our nuisance mosquitoes, which are our floodwater mosquitoes, in early July,” Brandt said. “That is a result of when we get heavy rain events… where that water will sit for about a week or so.”
That stagnant water was just enough time for eggs on the ground to hatch and develop into biting adults. Mosquito crews immediately began larval control, checking flooded areas and applying biological treatments, but some mosquitoes still managed to emerge, especially ahead of the July Fourth holiday.
Most of the increased mosquito activity has been concentrated in Williams and Monitor townships. Brandt said adult mosquitoes from that emergence are still present, but they’re nearing the end of their lifespan.
“Since these mosquitoes will live for about two to three weeks, we're still seeing those adult mosquitoes in those areas,” she said.
Crews have responded by ramping up nighttime fogging operations in areas with high trap counts or resident complaints. But controlling flying mosquitoes poses challenges.
Brandt said while their fogging products are effective that some of the mosquitoes hide in wooded areas or down by the river where their trucks can't get.
That’s why it often takes multiple passes to reduce adult mosquito numbers. She said recent efforts are working.
“We’re seeing our trap numbers going down in those areas,” Brandt said.
Bay County has more than 30 mosquito species that breed throughout the summer. While floodwater mosquitoes are currently the focus, crews are also monitoring shoreline marshes and cattail habitats where other species thrive.
Although activity is expected to decline soon, the season is far from over.
“We’ve been seeing our mosquito season extend into about early October the past few years,” Brandt said. “It’s important that we do remember that mosquitoes are still active.”
The department also monitors for mosquito-borne viruses. This year, Bay County has recorded one positive sample of West Nile virus and two for Jamestown Canyon virus, typical for this point in the season. West Nile has been present locally since around 2002.
“Mosquitoes can spread viruses,” Brandt said. “In particular, West Nile virus is a virus that we will see in the Saginaw Valley region each year.”
To limit exposure, she recommends wearing long sleeves and pants when outdoors, and using repellents with DEET, picaridin or oil of lemon-eucalyptus.
Residents can also help by dumping standing water from backyard items like toys, bird baths, buckets, tarps and rain barrels. Those with water that lingers after a rain can call Mosquito Control to request an inspection.
“If you know of an area that has standing water… certainly call our office,” she said. “That is what our day shift does… so that we can prevent that larvae from emerging adult mosquitoes.”
Homeowners reported an uptick in mosquito complaints in the days leading up to July 4, especially in flood-prone neighborhoods.
“We certainly did notice those phone calls up here in the Monitor to Williams Township corridor,” Brandt said. “And that in turn helped us get some traps out in those areas.”
Brandt said they’ll continue fogging in high-activity areas, and will remain on alert in case more storms roll in.
“It’s just kind of a wait and see game,” she said. “If we get some flooding events… that means for the week after that, we’ll focus on controlling the mosquito.”
