A big part of Jeff Whitworth's job is talking about bugs – how to identify them, whether they're helpful or harmful, and if there's anything to be done about them.

The Kansas State University entomologist has fielded several calls recently about worms feeding in wheat and new alfalfa, particularly in south central and southeast Kansas.

"Those that have been identified so far have been fall armyworms," said Whitworth, who works with K-State Research and Extension. "These larvae will feed on wheat or alfalfa until a killing frost occurs. Until then, however, they can damage some wheat fields enough to require replanting, or alfalfa fields enough to warrant spraying."

Most larvae are relatively small and usually their feeding goes unnoticed as it consists of "window pane"- type damage on leaves. In some cases, there has been enough larval feeding, coupled with dry weather, to cause stand reductions, he said.

"Hopefully, the advent of more seasonably cool temperatures will eliminate the worms before they reduce the vigor of the plants going into the winter. If colder weather doesn't arrive soon, however, and you detect 25 to 30 percent of your wheat with this "window pane"- type feeding, you need to continue to closely monitor these fields."

As the larvae get larger, explained Whitworth, the damage will increase to the point of losing whole plants. The same is true for seedling alfalfa where it only takes one or two larvae per square foot to destroy the entire stand. The small, early instar larvae are difficult to find as they hide in the soil around the base of the plants. If found, they are even difficult to identify as they are very tiny for about the first two to three weeks of feeding.

Another wheat/alfalfa insect pest to be concerned about is the army cutworm, he said. They are usually of more concern in late winter and early spring, but Whitworth said his department had received reports of feeding damage in wheat this fall.

"Adult army cutworms lay eggs in the fall that  hatch and these new, very small larvae feed until a hard frost. They over-winter in the soil at the base of wheat or alfalfa plants and usually are the first to start feeding in the late winter or early spring when the weather starts to warm," the entomologist said.

"Early damage is usually not noticed, but as the larvae mature they consume more and more of the stand. Treatment decisions need to be made before significant losses occur. That's usually when one to two worms are found per square foot in new alfalfa or less vigorous stands of wheat, or four to five  worms are found per square foot of healthy wheat stands or established alfalfa."

Alfalfa weevils also have been active throughout the relatively warm fall, he said.

"They have been actively feeding and laying eggs, setting up the possibility of healthy populations of larvae in early spring," Whitworth said. "Research has indicated that destroying over- wintering eggs by grazing, burning, or crushing of stems reduces larval populations for the following spring. But these results have not consistently reduced early-season damage enough to eliminate insecticide treatments. If any of these strategies fit into your alfalfa management practices, however, they may help suppress early spring emergence on a field-by-field basis."

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans.  Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus in Manhattan.