HURON – Nuisance mosquitoes are just that. But those known as Culex Tarsalis are a different story, because they are the ones that sicken people with the West Nile Virus.
City Parks and Recreation employees spent time Thursday learning how to identify the different species of mosquitoes that find their way into traps located throughout Huron.
“That does make a huge impact on how we work to control the mosquitoes,” said Geoffrey Vincent, a Ph.D candidate in the Department of Biology and Microbiology at South Dakota State University.
He conducts a training session for parks workers each year in Huron.
“What I do, what I specialize in, is I study anthropods that can transmit diseases,” Vincent said.
He used to work with ticks and the Lyme Disease and Rocky Mountain Spotted Fever that they carry. Now he concentrates his time on mosquitoes and the West Nile Virus.
The virus has not shown up in Beadle County yet this year.
But it’s only a matter of time.
“We have seen (mosquito) numbers dramatically increase,” Vincent said. “But that’s going to be a combination of both rain and temperature.”
Nuisance and Culex Tarsalis mosquitoes are extremely different in their lifestyle and habitat choices, he said. Nuisance mosquitoes lay their eggs on dry ground. The eggs have to dry out, and when water comes up and gets them wet they will hatch.
“Culex Tarsalis, on the other hand, has to find water,” he said. “It lays its eggs right on top of the water, so the water has to be existing for them to actually lay their eggs.”
It means that when the city is placing larvacide in standing water there’s a good chance mosquito eggs are present.
“When you’re out and you know you need to larvacide, you need to know what type of habitat to look for, you need to understand that particular vector mosquito,” Vincent said.
“Otherwise, you’re just going to be going off dropping larvacide in places it doesn’t matter,” he said.
There are about 40 other species of mosquitoes in South Dakota.
“But we don’t see them all, all the time,” he said. “And they usually have low numbers.”
Experts know that the Culex Tarsalis and Culex Pipiens are vectors, or carriers, of West Nile Virus.
Culex Pipiens mosquitoes tend to be more toward the eastern portion of the state. “As we move west through the state, we see less and less of those,” he said.
Culex Pipiens also require a different type of breeding habitat.
“They have the same type of breeding strategy, but there is something – and we don’t necessarily have the answer for it – that makes Tarsalis a stronger survivor in South Dakota as we move west,” Vincent said.
Eastern seaboard states deal with Culex Pipiens, but have no Culex Tarsalis mosquitoes. The opposite is true in states like Colorado and westward to the Pacific, where it’s all Tarsalis.
Unfortunately, while mosquito numbers drop off when colder weather arrives in the fall, they do survive winter, in different ways.
Nuisance mosquitoes lay eggs that will survive. “All the adults die off, but their eggs remain, waiting for the rain to come,” he said.
“Tarsalis over winters as an adult, so it will burrow some place – we don’t know where yet, we’ve got some suspicions – it will burrow into the ground and when it warms up enough it will come out and go about its business,” Vincent said.
