Party time for ‘aggressive, biting’ mosquitoes in Mass.

Expert says rains triggered big hatch of two annoying species

WEYMOUTH, Mass. — Fourteen years ago, Kurt Upham founded ohDEER, which offered homeowners a natural way to repel deer from chomping on perennials and other landscape plants.

While that’s still part of the company’s business, most of its fleet is now dedicated to tick and mosquito control -- and it’s calls about the latter pest that have really shot up lately, Upham said.

“As the rain continues, as it has been, we get busier and busier,” Upham said. “Because more people are getting inundated with mosquitoes and friends are telling friends.”

On an average day, ohDEER technicians make about 80 applications of the company’s cedar oil-based solution to lawns and shrubbery. Upham said that adds up to about 3,500 gallons a day. Upham’s main issue this season is pandemic-related: too much work and too few employees willing to commit to the job.

And problem is, things just may get busier for ohDEER and other mosquito control companies in the coming weeks -- because of all that rain.

Kaitlyn O’Donnell, staff entomologist at the Norfolk County Mosquito Control District in Walpole, said the persistently wet conditions triggered the hatching-out of two species of ‘flood plain’ mosquitoes, Aedes vexans and Psorophora ferox.

“We’re going to see a big increase in those two species and they’ll probably stick around for a few weeks,” O’Donnell said. She added that both species are known as aggressive, human biters.

In addition, at least in Norfolk County, large numbers of another aggressive, human biter have been found: Coquillettidia perturbans. That species usually peaks in July, but certainly can be a pest through August.

Of course, mosquitoes can be more than just pests.

Culex pipiens is the primary vector for the West Nile Virus. O’Donnell said the number of these mosquitoes has been fluctuating in recent weeks.

“We had a pretty high week just two weeks ago, but last week’s numbers were low again,” she said. “They really thrive in hotter, drier years and they’re more of an urban species so we don’t get as many of them in more rural areas.”

Culiseta melanura is a key vector for Triple E or Eastern Equine Encephalitis, and O’Donnell said the numbers for that mosquito have been low this year -- especially compared with 2019 and 2020, years in which outbreaks of the disease occurred.

However, other mosquitoes carry the EEE virus to humans, including C. perturbans -- and there are, again, plenty of those mosquitoes around. Those mosquitoes are known as ‘bridge vectors,’ O’Donnell said, because they bridge the gap for the virus between birds and humans.

As for why we usually see cases of EEE and West Nile in late summer and fall?

“It takes time for the mosquito population to build and for the virus to build in the bird population which is where the cycle takes place,” O’Donnell explained.  “Birds are the reservoir hosts. The virus cycles in the bird population and builds and builds. The mosquitoes are biting the birds and passing the virus from bird to bird. So it’s building in the bird population.”

Then it takes a bridge vector -- essentially a mosquito with indiscriminate tastebuds -- to first bite an infected bird, then bite a human -- thus passing along the virus to a body in which it can replicate.

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