Upland variety will remain a persistant problem for the next several weeks
BY SOPHIA MCDERMOTT-HUGHES, VTDIGGER
A horde of bloodsuckers has descended upon the Lemon River Area, feasting on the inhabitants of Cornwall, Weybridge and Bridport.
Vampires? Not here. It’s a late-season surge of mosquitoes — and experts say this year’s weather patterns have created prime conditions for the irritating buzzers to abound.
“They’re relentless. They’re extremely aggressive,” said Craig Zondag, field coordinator for the Lemon Fair Insect Control District. “They’re just waiting for a blood meal.”
Mosquito season typically peaks in late June and early July after the June rains. But this year’s drought, combined with recent rains, pushed it back later and has led to an explosion in early August, Zondag said.
Typical mosquitoes seen in the area, aedes vexans, breed in the Lemon Fair River floodplains and Cornwall Swamp and can be treated with aerial larvicide. But the upland mosquitoes — ochlerotatus trivittatus and aedes cinereus species — lay their eggs in small woodland puddles and pools out of reach of the insect control district’s field staff.
Recent rains have provided the perfect conditions for the upland mosquitoes to flourish and attack the area’s residents en masse.
This summer’s outbreak follows a relatively mild mosquito season in 2020, when Zondag caught about 6,300 mosquitoes in his traps. He estimates the traps took in 6,000 mosquitoes on Monday alone.
Last year’s drought contributed to the low mosquito count and may have exacerbated this year’s boom. Mosquito eggs can stay viable for two to seven years, and many may have remained dormant until the right conditions for hatching presented themselves this year.
“It’s kind of like a seed bank out there of mosquito eggs just waiting for the perfect storm,” Zondag said.
Upland mosquitoes are multivoltine, meaning they can lay multiple rounds of eggs and can linger longer than their short-lived, univoltine brethren.
Multivoltine mosquitoes can also pose a disease problem due to their long lifespans. A shorter-lived mosquito seeks a small number of blood meals before laying her eggs and dying. Even if she — only female mosquitoes need blood — bites a bird carrying the West Nile Virus, for example, it is unlikely that she would have enough viral load to infect the next human she bites.
A multivoltine mosquito, however, needs more blood meals before she lays each round of eggs, and each meal provides more of an opportunity to build up a critical viral load to transmit to humans.
Zondag said that state testing has not found diseases in these species of mosquitoes in the past, but people should still be careful, especially as the season tapers out in the fall. Those last lingering mosquitoes can be particularly dangerous because they’ve had a higher number of blood meals — and therefore an opportunity to build up higher viral loads — throughout their longer lifespans.
“I’ll be sitting outside with some folks outside, and they’ll say, ‘Oh it’s only one mosquito,’” Zondag said. “I stop them right there and say, ‘No it’s not. That could be the one.’”
Relief is likely still far away for residents of the Addison County towns. Zondag hopes that the swarm will taper off in the next two weeks, but as unpredictable as this late mosquito season has already been, there’s no way of knowing when it will end.
For those suffering under the scourge, Zondag recommends wearing long sleeves and pants and using FDA-approved insect repellant on exposed skin. He also recommends directly spraying clothing and wearing a hat with mosquito netting.
Zondag encourages local landowners to walk their woods and treat deep-water pools with Bti products — a bacterium that directly targets mosquito and blackfly larvae. Landowners should pay special attention to the holes left behind by uprooted trees, a particularly fertile ground.
Residents can also use a barrier spray around the perimeters of their yards, focusing especially on the areas around doors where people frequent and mosquitoes like to rest.
While upland mosquitoes breed in the woods and out of reach of most residents, residents can target other types of mosquitoes to decrease overall numbers. Culex mosquitoes find fertile breeding grounds in any type of standing water. Residents should drain clogged gutters and rain barrels and check tires and tarps for pools of water. Abandoned dog dishes and infrequently cleaned birdbaths are other frequent culprits, Zondag said.