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Winter's cold and rain does not bother bugs
MISSISSIPPI STATE – Many Mississippians don’t mind unusually cold and wet winters because they think the weather is killing insects, but that is rarely what actually happens.
The state’s moderate climate is ideal for growing crops and multiplying insects, and the insects that live in Mississippi are suited to weather fluctuations. An insect’s ability to survive the winter is called overwintering, and it determines how quickly their numbers increase in the spring.
Charles Wax, state climatologist and professor of geosciences at Mississippi State University, said Mississippi averages 42 degrees and gets approximately 15.6 inches of rain each winter. This winter, temperatures got colder as the winter progressed.
“It was 4, 6 and 8 degrees colder than average in December, January and February respectively,” Wax said. “In December, teens were common at many locations across the state, and in January, the coldest recorded temperature was 5 degrees, recorded twice at Holly Springs.”
Rainfall was close to normal. December saw 3.07 inches of rain more than normal, but January’s and February’s rainfalls were .41 inches and 1.06 inches below average, respectively. December’s biggest rains were in the south central and southeastern parts of the state; Columbia got 12 inches of rain and Hattiesburg had 17 inches of rain.
Blake Layton, entomologist with the MSU Extension Service, said cold winters are not usually harmful to insect populations.
“Our native insect pests are well equipped to survive the winter,” Layton said. “Whether or not an insect survives depends on its particular species, but in general, cold and wet is more detrimental than cold and dry.”
Different species survive winter in different ways. Insects such as stink bugs and boll weevils overwinter as adults. Others, such as tomato fruitworm or corn earworm, overwinter as pupae in the soil where they are insulated from winter temperatures.
Some cutworms overwinter as partly grown larvae and some, including the Eastern tent caterpillar, overwinter as eggs. Other species survive subfreezing temperatures because they have “antifreeze” in their blood.
“Some species may experience higher winter mortality, but it may not be enough to have a notable impact,” Layton said.
The Southern green stink bug is one native pest affected by severe winters.
“Their numbers are predictably higher following mild winters and lower following colder winters,” Layton said. “However, other stink bug species, such as green stink bugs and brown stink bugs, are less affected by the cold.”
Cold weather hurts non-native pests from tropical or subtropical environments most. Back in the days when boll weevils pressured cotton, farmers saw significant cost control savings after hard winters. Entomologists and row-crop producers this year will be closely watching the red-banded stink bug, a relatively new invasive species from farther south that became a major concern in less than five years.
“It may be affected by this winter’s temperatures, but we will have to wait and see,” Layton said.
Fire ants’ northern migration seems to be limited by where the soil freezes deep enough to reach the overwintering ants. Mississippi fire ants have survived this type of winter before, and Layton said any reduction in fire ant numbers in early spring will surely be overcome by fall. Entomologists will be watching Argentine ants to see if this winter had any effect on their northern march.
Household pests are not affected by winter temperatures because they live in protected environments.