Rise in 'floodwater mosquitoes' expected in wake of historic Ida deluge

Aedes vexans 'floodwater mosquito.' Photo credit: Alain Hogue, photographer: www.photonature.ca

As millions of people try to recover after Tropical Rainstorm Ida tore through the Northeast last week causing historic flooding, experts have warned about the rise of "floodwater mosquitoes."

Most mosquitoes in urban areas, like the common house mosquito, are from a species that breeds in standing water that collects in puddles, buckets, birdbaths, tarps and neglected or abandoned swimming pools. Floodwater mosquitoes, such as the Inland Floodwater Mosquito, Aedes vexans, lay eggs in dry locations where there is a high probability of flooding.

And there was extreme flooding last week across a wide portion of the mid-Atlantic and Northeast, including in and around the New York City and Philadelphia metro areas after Ida tore through.

"It's important to understand that different mosquito species have different life cycles," Dr. Jim Fredericks, chief entomologist and vice president of technical and regulatory affairs with The National Pest Management Association (NPMA), said. "Also, different mosquito species have different capacity for transmitting disease."

Fredericks told AccuWeather that floodwater mosquitoes lay eggs in moist environments or in places just above the natural waterline. After a short period of drying, the eggs must then be flooded with water to hatch. During periods of drought, eggs can remain dormant but viable for many years, waiting for the water to rise. "When rains come and those depressions or seasonal pools flood, that's when those eggs will hatch, and so they're often most commonly found and experienced directly after extreme rains," Fredericks said.

Floodwater mosquitoes are most abundant around the edges of moist pastures, irrigation furrows, swales, ditches and similar habitats. Rainfall pushes the groundwater upward and creates puddles, small ponds and flooded meadows and fields. If the temperature is right, a newly-hatched mosquito can develop into an adult in less than a week during the spring and summer. Plus, larvae can hatch in masses.

In addition to rainfall, temperature plays a huge role in the life cycle of a mosquito, Fredericks explained. Mosquitoes will grow faster when temperatures are higher. The lower the temperature, the longer it takes mosquitoes to develop from larvae into adults.

Cars and trucks are stranded by high water Thursday, Sept 2, 2021, on the Major Deegan Expressway in Bronx borough of New York as high water left behind by Hurricane Ida still stands on the highway hours later. (AP Photo/Craig Ruttle)

"If it's warm, lots of rain," Fredericks said, "you're going to have lots of mosquitoes because the populations are going to be able to turn over more quickly. You'll have more adult mosquitoes sooner, and those adult mosquitoes are going to continue to lay eggs." Although floodwater mosquitoes are known for biting and can be annoying, experts don't consider them vectors for diseases like Zika or West Nile viruses."

"All mosquitoes need water to complete their life cycles, which is why people experience an increase in mosquito activity after an intense rain event like a tropical system. "The timeline that happens, typically after large flooding events like we're seeing just from all this all the rain and the hurricane and tropical depression is that you'll have many areas like in woodland areas that just become flooded," Fredericks said. "That's going to be prime breeding ground for one of the important floodwater mosquitoes: Aedes vexans."

Although not a vector of diseases, Aedes vexans is an aggressive biter and is active at night as well as during the day. Fredericks explained that those areas that experienced historic flooding during Ida will start seeing those floodwater mosquito populations peak within one week. Common house mosquitoes will develop after a couple of weeks, he said.

And mosquitoes are pestering people beyond the Northeast.

Aedes vexans 'floodwater mosquito.' Photo credit: Alain Hogue, photographer: www.photonature.ca

Andrew Ratka with the Mosquito Squad of Northeastern Wisconsin told WBAY that areas in the Midwest are also experiencing a rise in floodwater mosquitoes. "We're out in the field every day. And what we're seeing I'd say is a massive hatch that has recently happened I'd say within the last week or so," Ratka said.

If mosquitoes are abundant in your area, you can hire pest control experts to help you learn how to be aware of and eliminate potential mosquito breeding habitats on your property. Also, it's worth paying a visit to AccuWeather's pest preparedness hub for strategies on neutralizing mosquitoes and other types of bugs.

But, most experts agree, removing standing water left by typical rainfall or flooding can significantly decrease mosquito breeding and go a long way toward controlling the mosquito population on your property. Additionally, wearing EPA-approved repellents, such as products with DEET, and long-sleeve clothing while outdoors can mitigate the bites.

Fredericks said the mosquito population is expected to remain high for at least a couple more weeks in most areas until the temperature drops to the 50s or 60s F. "You're typically going to see mosquito season lasts until daytime temperatures are 50 degrees or so. Most insects are unable to fly when temperatures are less than 50 degrees," he said.

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