Warm Winter Usually Has Little Effect On Overall Insect Numbers

Common beliefs don't stand up to the facts, according to WVDA experts.

Published on: May 2, 2012

Most people believe a warm winter means there will more insects in the spring. But, as the old song says, "It Ain't Necessarily So."

Experts at the West Virginia Department of Agriculture say cold temperatures are barely a factor in the numbers of bugs that we see when spring arrives. It is true, they say, that warm weather may predict that bugs will emerge earlier in the year. Also, bugs may be active for a longer portion of the year when the winter is warm. Overall, numbers though, may not be increased at all in a year when the cold season is warmer than is typical.

"Perhaps one of the greatest factors when considering insect populations is our own perception," says WV Agriculture Commissioner Gus R. Douglass. "Most insects live, breed and die with little notice from the human race. We only pay attention to the numbers of the ones that really 'bug' us."

DOESNT ADD UP: The common idea that a warm winter increases bug numbers doesnt stand up to scrutiny. An entomologist at WVDA says there are many factors in bug numbers but whether we experience a warm winter or a cold winter is not likely to be one of them. Bugs in the photo are green stink bugs.
DOESN'T ADD UP: The common idea that a warm winter increases bug numbers doesn't stand up to scrutiny. An entomologist at WVDA says there are many factors in bug numbers but whether we experience a warm winter or a cold winter is not likely to be one of them. Bugs in the photo are green stink bugs.

"You'd think that the mild winter would cause greater survival of insects," says WVDA entomologist Berry Crutchfield. "But you've got to remember that less than 3% of insects are considered pests. Plus, if there's more of a particular insect because of a warm winter that probably means that there's going to be a greater number of insects that prey on them."

Many insects are adaptable to cold weather. Some overwinter as eggs, others actually produce compounds similar to antifreeze before they enter dormant phases in winter. Honeybees warm their hives by beating their wings to generate body heat.

Sudden early freezes can knock down populations before winter actually arrives. Late freezes following unseasonably warm weather can kill prematurely-emerged insects. Also, heavy rains can drown soil-dwelling insects or promote the growth of fungal diseases that affect populations. All these events can color our perception.

"I just hope that whatever factors are involved that we don't get a greater number of brown marmorated stinkbugs in the eastern panhandle," says Douglass. "This is a pest of major concern to our fruit growers, some of whom have already been hit by late freezes, and other farmers who also have suffered terrible stinkbug losses in recent years."