[In the News] Will Frigid Temperatures Mean Fewer Insects?

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What strategies do insects use to survive the cold?

March 24, 2014
June Van Klaveren

Insects have had about 400 million years to figure out how to survive cold weather and so far they’ve done pretty well. But this year’s “polar vortex” may send many pests into survival mode.

Surviving Winter.

Insects are cold blooded and rely on external sources to provide heat. Thus, they must tolerate freezing or rely on other mechanisms to avoid it. They are amazingly well equipped to deal with cold temperatures by being either freeze tolerant or freeze avoidant.

Freeze avoidance happens when insects preserve the liquid state of their bodily fluids at low temperatures. They use certain compounds called cryoprotectants (similar to ethylene glycol found in your car’s antifreeze) to lower the temperature at which freezing occurs in their bodies.

Freeze tolerance is the conversion of 50 percent or more of an animal’s total body water into extracellular ice.

While it’s true that extremely cold temperatures for prolonged periods of time can decrease insect populations, other factors are at play as well. Dr. Roger Gold, Texas A&M University, contends that sudden temperature changes have the biggest bearing on insects. “Temperatures could go well below freezing without a problem to insects if they have time to adjust. It is actually rapid freeze-thaw cycles that affect pests because these changes expand and rupture cells. The more times this occurs, the greater the likelihood of severe damage or death.”

Structural pests rely on other strategies to avoid the cold such as migrating, entering houses and other structures or burrowing below the freezing depth.

Dr. Brent Sinclair, Western University in London, Ontario, Canada, studies the mechanisms of cold tolerance in insects. “The most common strategy for pest species is to avoid the cold altogether — for example by sheltering in the envelope of a house or underground,” he said.

According to Professor Greg Henderson, LSU, some varieties of insects (like paper wasps) hibernate under the bark of trees and will see high mortality due to the cold. “Social insects like ants and termites should not be significantly affected,” he said.

Fire ants, most experts agree, have moved north and may not be fully adjusted to the cold. With time, however, they will adapt to changing conditions.

In regards to the polar vortex, Sinclair says, “It’s important to remember that the numbers associated with the polar vortex are often wind-chill numbers, which don’t matter to cold-blooded insects, and are especially irrelevant to pests in soil or wood. Having said that, the wind chill does remove heat very fast from the outside of buildings, so areas within the envelope that might normally be quite warm may be colder as a result of the wind chill. So insects that depend on that warmth might be hit harder than usual.”

PEest Control in 2014?

The impact the polar vortex will have on the pest control industry in certain parts of the country is up for debate. However, some of the best researchers in the United States and Canada say it will have minimal long-term economic impact on the pest control industry.

What is a Polar Vortex?

“Polar vortex” is the new buzzword of 2014 for Americans learning about its role in producing record cold temperatures across the country. The polar vortex is a high altitude low-pressure system that hovers over the Arctic in winter. In early January, the polar vortex weakened and broke down, allowing fragments of cold air to “head shouth” into mid-latitudes. Source: Climate.gov

Dr. Phil Koehler, University of Florida, points out, “Because of cold temperatures, there may be a delay in things happening — like termite swarming because ground temps may be cooler longer but I don’t see more winter mortality than usual.”

“The weather will give insects a temporary setback, but as soon as the weather warms up, they will take off again,” said Jan Nyrop, a professor of entomology and senior associate dean of Cornell University’s College of Agriculture and Life Sciences.

The consensus of those interviewed by PCT seems to be that cold temperatures may delay emergence of certain species but the economic impact should be minimal. “Insects have the miraculous ability to survive climatic shifts. Overall, there has been no impact over time and populations will be able to build back up from those that survive. Environments are changing. Insects are changing but with their high reproductive rates, pests will be able to adapt,” Gold said.

As for 2014, you could see delays in the emergence of termites but other than that, pest management businesses should feel minimal impact. “We are not going to win the war against insects no matter the temperature,” Gold said.

The author is a contributing writer to PCT and can be contacted at jvanklaveren@giemedia.com.