‘Perfect storm’ for mosquito invasion

By Jenny Neyman
Special to the Tribune

Photo Provided - The perfect weather conditions on the Kenai Peninsula have enabled a larger than normal mosquito infestation.

Photo Provided - The perfect weather conditions on the Kenai Peninsula have enabled a larger than normal mosquito infestation.

Only two things in life are certain, as the saying goes: Death and taxes. Alaska could add one more to that list — mosquitoes. And this spring, the inevitable swarm of the relentless bloodsuckers has hatched in such ferocity as to make the first two certainties seem not the worst of the list.
“It’s probably going to be a nice buggy year,” said Janice Chumley, integrated pest management specialist at the University of Alaska Fairbanks Cooperative Extension Service Office in Soldotna.
That’s putting it mildly. Kelly Keating-Griebel, of Soldotna, puts it less so:
“Never seen it like this before, and I’ve been here 42 years,” she said.
Southcentral Alaska is experiencing a perfect storm of conditions to produce a mass spring hatch of mosquitoes. Or rather, experiencing the consequences of storms last fall. Southcentral was deluged with rain last September and October, followed by temperatures plunging below freezing before an insulating layer of snow fell. That pushed frost deep into the ground, ensuring a slow thaw come spring. On top of that came a period of late snowfall in March. To pile on even further were cool, cloudy conditions persisting into April. It wasn’t until the end of April and into early May that the spring thaw really began in earnest.
But even as sunshine and warmer temperatures started making soggy work of the snow, the ground below was still frozen, leaving the excess water sitting in expanding melt pools on the surface.
That’s a perfect nursery for a certain type of mosquito.
“I think it’s just a late and heavy snowmelt,” said Matt Bowser, etymologist with the Kenai National Wildlife Refuge. “On my property and here at the refuge we had more and deeper pools that persisted later, so I think it was ideal conditions for this species of mosquito to really produce a lot.”
Mosquitoes have an aquatic component to their life cycles, living in water in their larval stage, so wet is good for the bugs. One local species in particular thrives in soggy spring snowmelt conditions. Bowser, though not an expert in mosquitoes, did study a few samples collected at refuge headquarters on Ski Hill Road.
“The ones that were the first couple that bit me. I took them into the lab and identified them,” he said.
Meaning, he didn’t just squash them?
“I do quite a bit of that, too, but it’s enough of a phenomenon this year I really wanted to look into it a little bit anyway,” he said.
They were of the genus Ochlerotatus, species communis. It’s a common type of mosquito widespread throughout cold climates of the Northern Hemisphere.
“They can be really abundant wherever there’s a lot of snowmelt. It’s a species that breeds in snowmelt pools, that’s where the larvae grow,” Bowser said.
The females feast on a blood meal in the summer or fall, then use that nourishment to produce eggs before they die. They lay their eggs on the ground, usually in a forested area, Bowser said. Come the spring thaw, pools of water form from the melting snow. When the eggs get covered in water and the temperature warms enough, the eggs hatch. The more water covering the ground as the temperature warms, the more Ochlerotatus communis eggs are likely to hatch. The emerging larvae feed voraciously, then pupate within about a week and turn into flying adults.
“This year there were just more, and more consistent, and bigger, pools than in most years, and it stayed on my property later than it has the last two years,” Bowser said.
To make matters worse, the snowmelt pool-hatching Ochlerotatus communis aren’t the only species of mosquito out and about these days. There’s also a species commonly called a snow mosquito, which overwinters as adults and emerges ready to feed in as little as one sunny day. Snow mosquitoes are larger and slower moving than the Ochlerotatus communis, but they’re just as hungry. The adults emerge from their pupa stage in late summer, then cozy up in piles of leaf litter or nooks and crannies in trees and stumps to wait out the winter. When the ambient temperature gets warm enough in the spring, or even in later winter, they’re ready to fly in search of a meal.
“They’re not frozen so they can respond quickly to the warming temperatures and be active even on a warm winter day,” Bowser said.
Each of the more than two-dozen species of mosquito in Alaska has a slightly different life cycle. Some overwinter as adults, some as eggs. Some prefer lakes, ponds or streams for their larvae stage, while others take a chance on spring melt conditions. Some hatch in the spring, some later in the summer. Some need a blood meal as soon as they become adults, while others wait until they’re about to lay eggs. Some feed only once, while others gluttonously seek out more than one meal to lay more than one batch of eggs. All this variety boils down to one consistency — mosquitoes are an unavoidable part of summer.
Occasionally, as in this spring, conditions will favor a certain type of mosquito species’ life cycle, creating a massive hatch all at once. But the good news is that this unusually massive ravenous hoard will eventually die off into the more-usual dull roar. Because while mosquitoes are blessed in quantity, they fall short in longevity.
Snow mosquitoes, for instance, don’t often live very far into June. And the plague of Ochlerotatus communis this spring won’t be around for long, either.
“My expectation is that it will improve. The ones that are such a problem now are these early season breeders that are breeding in snowmelt, and those pools are drying. These adults will live for only so long, and then I think it will improve considerably by the middle of July,” Bowser said. “There’s only one generation per year, so that’s the good news,” Bowser said. “These females that are out feeding now, once they die then this species is done for the year.”
However, while Ochlerotatus communis ends, other species of mosquito emerge, not to mention — except that Bowser will — the other airborne biting pests yet to hatch this summer, such as black flies, white cocks, horseflies, no-see-ums and snipe flies.
So what’s an Alaskan to do, especially when warm sunny weather beckons to shed insect-repellant layers and get outside? Hope for a continuation of dry weather, for one thing.
“A lot of it really is weather dependent. If things are very dry it tends to suppress a lot of insects,” Chumley said.
But that’s merely a short-term avoidance, and one that causes other problems, including increasing wildfire danger. Mosquitoes are masters of the waiting game. They can wait out a dry spell and hatch when conditions do finally moisten up.
“The temperature plays into it, but a lot of it they can just be dormant for a while and wait until the optimum opportunity. If it stays super dry we won’t have as many bugs, but if it rains like it tends to do a little bit later on they’ll just hatch out then. With warmer temperatures and plenty of moisture, out they come,” Chumley said.
Some measures can be taken to reduce mosquitoes around the home. Remove snow in the spring, and don’t let water pool up and sit stagnant. Keep lawns mowed and remove leaves to cut down on places mosquitoes can lay their eggs. And consult the experts. For instance, the Cooperative Extension Service has resources available that advise ways to combat insect issues around the home and garden.
“The main strategy the Extension Service offers is to use integrated pest management, which combines a multitude of resources. And chemicals are one of them but it’s not the first choice. Depending on what the pest is and where the location is, there’s other things that people can do besides reaching for the can of chemicals,” Chumley said.
One bright side to this dark insect cloud is that mosquitoes in Alaska are not known to transmit yellow fever, West Nile virus or malaria, as they do in other parts of the world. For one thing, it’s too cold for those pathogens to survive year-round this far north. Even if one of these pathogens was carried north by, say, migrating waterfowl, it would take a mosquito having more than one blood meal to transmit the pathogen, and most Alaska mosquitoes only feed once.
If all else fails, try to remember that mosquitoes have a larger purpose than solely to harass those braving bare skin. Just as humans are an important food source for the mosquitoes, mosquitoes are an important link in the larger food chain, serving as sustenance to other creatures.
“Summertime in Alaska, we’re going to have bugs. But fish eat ’em, birds eat ’em — we have to figure that they’re just one of those annoying parts of the food chain,” Chumley said.
For more information on integrated pest management strategies, visit www.uaf.edu/ces.

Jenny Neyman is the publisher of the Redoubt Reporter.

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Posted by on Jun 19th, 2013 and filed under Headline News. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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