Hope that the winter has reduced the populations of mosquitoes, ticks and other pests are just that, hope.
Experts agree that the mosquito population has taken a hit but that they’ll be at full strength by early summer.
However, one group of insects appears to have suffered a major setback, said Gerardo Camilo, associate professor of biology at St. Louis University: the exotic mosquitoes that were heading north from the Gulf region.
“Exotic mosquitoes” have slowly been migrating north from the Gulf and Caribbean, he said. But, “Those species of mosquitoes could not survive this sort of winter.”
For example, the hot, humid Southeast has been attractive to the Asian tiger mosquito and its relatives. They can carry Chikungunya disease and dengue fever and have had health officials in the United States on edge for years, Camilo said.
“It’s on the radar,” said Drew Hane, operations manager of vector control at the St. Louis County Department of Health.
But the cold that permeated so much of the Southeast would have been deadly for the invaders, Camilo said.
Locally, mosquitoes appear to have had a rough time with the series of cold snaps with below-freezing temperatures.
Camilo recalls that last year mosquito swarms emerged as early as late February. They haven’t done so this year, he said. The below-freezing and single-digit periods froze mosquito eggs in ponds, and those hiding in sewers and drainage tunnels, Camilo said, places that weren’t affected much in recent warmer winters.
Camilo estimated the temperatures this year killed half the wintering mosquitoes.
Still, if there’s any relief, it will be short lived, Hane says. Midwest mosquitoes have withstood worse conditions than this year, Hane said. “It might be an easier spring,” he said, but by July, their populations will rebound.
Urban-dwelling mosquitoes, those most responsible for carrying West Nile virus, are another variable for the local population, said Mike Arduser, natural history biologist with the Missouri Department of Conservation. In the cities, “they need containers, wet places, water.” That would mean near homes, discarded tires and other shelters with heat sources. So there’s no way to tell how well they fared, he said.
Meanwhile, ticks and chiggers more than likely weathered the winter with little effect on their numbers, Arduser said.
While chiggers are an itchy nuisance, ticks remain the most dangerous pests, experts say. They carry Rocky Mountain spotted fever, Ehrlichiosis, tularemia, Q-fever, Lyme or a Lyme-like diseases and the southern tick-associated rash illness. A new virus, called Heartland disease, was recently identified in western Missouri. None have reached alarming numbers in the St. Louis region.
Hane said the first blast of below-zero temperatures this season may have taken a toll on ticks. But after the snow covered the ground, they were insulated from harsher conditions.
The tick population has been robust over the last couple of years because of friendly winters and an abundant food supply of wild animals, mainly deer, rabbits, mice and other fur-bearing animals, experts said.
Eldon Cole, an extension specialist stationed in Mount Vernon, Mo., said nothing this winter has indicated a drop in tick populations statewide.
Historically, pest numbers have been knocked down by late-season cold snaps more than by harsh winters, experts said.
If the weather gets mild and grass looks like it’s turning green and bugs start emerging, a below-freezing period would damage the mosquito and tick population.
But then, Arduser said, a cold snap would damage other things that emerge in the spring, such as trees, other weather-sensitive plants and useful bugs.
“We’d like to think the winter would reduce them,” he said. “They have a way of surviving winters, and they can survive some pretty cold weather. One bad year isn’t going to make a difference.
“Don’t throw away your mosquito repellent.”