Farmers aren’t the only ones waiting to see how wheat comes out of dormancy this year. Army cutworms may also be lurking just beneath the surface, ready to eat newly green winter wheat.
Oklahoma State University entomologist Tom Royer said he has early reports of cutworms attacking wheat and canola in the state. “I just want growers to be alert to watch for them because this is the time of year when they can become a problem, and farmers aren’t often looking for them,” Royer told DTN.
South Dakota wheat growers also saw early activity from army cutworms last year, South Dakota State Extension entomologist Adam Varenhorst noted in a university newsletter. “Due to the higher-than-average temperatures, it is possible that the army cutworm populations may be observed earlier than normal in 2017,” he wrote. “Once fields begin to break dormancy, they should be scouted for army cutworm populations.”
Cutworms are hard to spot because they burrow just below the soil surface during the daytime hours. However, their feeding — which happens at night — is quite distinctive. Small wheat and canola plants can literally disappear overnight, as the caterpillars cut their stems and pull the plant underground to feast on it in private.
“I’ve heard farmers say that it looked like the plants just turned around and went back into ground,” Royer said.
Army cutworm infestations are hard to predict. The moths migrate down from the Rocky Mountains each fall and tend to lay their eggs in bare fields, which makes newly planted or prepared winter wheat fields a good target. However, no field is ever safe from them, Royer warned; one of the infestation reports he received recently came from a no-till field in Oklahoma.
Scouting involves stirring up soil 2 inches deep around each wheat plant at five or more locations in the field — a pocketknife works well here. The grayish-green worms will be curled up into tight balls.
If you graze cattle on wheat, flip any cowpies over, too, Royer added. The army cutworms like to bed down under them.
In dry conditions — which cutworms thrive in — two to three worms per foot of a row is likely enough to justify an insecticide treatment, Royer said. If the field has good moisture, you can hold off until four to five cutworm caterpillars are spotted per row foot, he added in an Oklahoma State Extension pest alert.
Insecticide treatments this early in the season may be a tough pill to swallow for growers facing low wheat prices, but fortunately the cutworm is extremely sensitive to the lowest labeled rate of pyrethroids, Royer said.
Winter grain mites have also caused some visible injury to winter wheat in the Southern Plains this spring, so growers should keep an eye out for this pest, Royer said.
“In a typical year, we don’t see much injury from winter grain mites,” he said. “But when we have drier conditions and the wheat is not growing vigorously, the feeding shows up as plant injury and can set [wheat] back.”
Bird cherry-oat aphid populations are also starting to build up in southwestern parts of Oklahoma where moisture has been more plentiful, so growers should add that pest to their scouting list in the coming weeks, Royer added.
For more information on scouting for and managing army cutworms, see this North Dakota State guide: http://bit.ly/….
See Royer’s Extension pest alert here: http://bit.ly/….
Emily Unglesbee can be reached at Emily.firstname.lastname@example.org
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