With little snow and relatively mild winter temperatures, some insects may be problematic this spring. However, complex life cycles and spring weather make predicting insect problems difficult. Watch out for alfalfa weevil.

During January this year, on particularly sunny days, you could see honey bees flying and big black flies buzzing groggily around sun-warmed southern exposures.

In the Midwest, it's hard to complain about such nice weather in January, but among circles of crop growers you could hear the complaint: "I wish it would get cold enough to kill the bugs."

Cold weather doesn't affect all overwintering insects. If you visit with entomologists and agronomists, however, you will find that one pest in particular takes advantage of mild winters--alfalfa weevil.

While some insects go through a period called obligatory diapause, which is essentially a sustained hibernation, pests like the alfalfa weevil actually weave in and out of winter's rest and become active on unusually warm days.

Kevin Steffey, a University of Illinois extension entomologist, said that 2002 looks to be a banner year for alfalfa weevil. He said that as early as February, he got reports from colleagues in Oklahoma that the number of overwintering alfalfa weevil eggs was unprecedented.

In regions like southern Missouri and Oklahoma, alfalfa weevils hit growers with a double punch in the spring.

"They overwinter as both eggs and adults," Said Steffey. "So in the spring, as soon as the temperature gets warm enough, the fall-laid eggs begin hatching. At the same time, the overwintering adults are mating and laying more eggs. So there are two main peaks of activity. One from fall-laid eggs and one from spring activity."

MFA staff agronomist Lyndon Brush said that some growers in south Missouri may have to treat alfalfa stands as early as mid-March, but controlling early hatches of the pest doesn't mean the secondary peak of feeding won't cause more damage.

For alfalfa weevil control, the important thing is to pay attention.

"It takes very aggressive early scouting. As soon as temperatures warm up and any alfalfa growth activity begins to occur, it is time to start scouting," said Steffey.

Growers in cotton country will find that warm winters are a sign that boll weevil populations will survive in higher numbers.

"They overwinter successfully in the leaf litter that is well drained," said Phil Tugwell, entomologist at the University of Arkansas. "They're able to endure subfreezing temperatures in those types of environments. But they don't survive as well in ditches and other poorly drained habitat or areas with bad cover."

Tugwell said it is difficult to predict how insect populations will react to a warm winter because so many variables are involved.

"Generally, things go well for the insect if they don't have to endure cold, but that doesn't mean they'll be a problem. It might be that their natural enemies, whether it is a fungal disease or another insect, may survive better, too. The consequences may be serious for the pest. I can't predict those. But the boll weevil is sensitive enough to the cold, it is easier to make generalizations. It's such a pest in the cotton area that we're attuned to watching for cold weather."

Tugwell said that the well-drained fields along Crowley's Ridge in southeast Missouri make an excellent overwintering site for boll weevil.

"Of course, Missouri and much of northern Arkansas are in the boll weevil eradication program. A mild winter may make that more difficult. But it isn't impossible. Compared to places farther south, which have had successful eradication programs, there are fewer weevils [in Missouri] to begin with."

For all the bugs that like a balmy winter, some couldn't care less. For insects that go through obligatory diapause (that physiological slow down that allows them to survive extremely cold temperatures) cold weather isn't typically a threat to survival.

The European corn borer, for example, overwinters as a larva and goes into diapause.

"They have something similar to antifreeze in their blood," said Steffey. "It prevents their cells from freezing. It's very strong. It keeps them from freezing unless it is extremely, extremely cold."

Another insect that fits that category is corn rootworm. They overwinter as eggs in the soil. Temperatures must get extremely cold and stay that way for a period of time to cause mortality on the insect. And even then, mortality rates are affected by how deep the eggs are in the soil profile.

Steffey said that corn flea beetle can be considered a pest that benefits from mild winters, but for commercial corn growers flea beetles are only a threat if they reach overwhelming numbers on young corn.

"If the average temperature of December, January and February hits a certain level, we anticipate problems with flea beetles," said Steffey.

At press time, he said the average temperatures looked like they would measure high enough for growers to pay attention.

A couple of years ago, flea beetle was economically damaging to parts of Missouri's corn crop. Much of that can be attributed to cold and wet conditions that kept corn stunted. Brush said that under good growing conditions, corn plants typically outgrow flea beetle damage.

"Really, most flea beetle concern is for growers of inbred corn. The flea beetle is a vector for Stewarts wilt. So seedcorn growers will look into applying Gaucho or Prescribe," said Steffey.

Insects like black cutworm aren't affected by mild winters here; they migrate north from warmer southern overwintering grounds. But Steffey points out that sometimes the weather that produces mild temperatures in the Midwest can affect insect populations in southern locations.

"There was a year several years ago when we had a mild winter, but they had a rough winter weather down south. We just didn't get many black cutworms that year. We've watched some strange weather down south this year. That might affect their populations."