Watch for stem borers in soybeans, cutworms in corn

The soybean stem borer, a longhorn beetle which deposits eggs into the stems of soybean plants, has become more prevalent in west Tennessee in the last few years, possibly due to more no-till farming, which prevents destruction of its overwintering sites, says Charles R. Patrick, Tennessee Extension entomologist.

“In some locations in west Tennessee (last year), there were reports of some fields with over 30 percent lodging due to the insect,” he said. “Presently there are no pesticides specifically labeled to control stem borers.”

There is only one generation per year in Tennessee and the immature larva overwinters in the bases of soybean stems. Fields which have significant past history of damage should be tilled to destroy overwintering larvae, Patrick says.

Alternate hosts of the insect are giant ragweed and cockleburs. Stem borers will readily use these host plants.

Patrick asks that any west Tennessee farmers seeing this pest notify him 731-425-4718 or [email protected]) so that the problem can be better understood.

“Some studies have shown certain varieties may be more resistant than others, but the mechanism is unknown,” he said.

West Tennessee corn producers who are planting fairly early should remember the potential dangers caused by cutworms, said Patrick. These insects can cause serious damage to stands if unchecked and uncontrolled in many fields.

Fields which are planted into a no-till situation are more likely to have cutworms, especially fields which have had winter weeds.

“In Tennessee, cutworms have been know to damage stands to the point of forcing replanting the corn,” Patrick said.

“Simple precautions can be made to eliminate or reduce this damage. Many synthetic pyrethroid compounds are labeled to control cutworms in corn. Some producers are putting in one of them when they apply herbicides at planting. The only concern is that if no cutworms are present, the material does not have much effect. These materials do not provide season-long control when applied at planting. They are at best good for a couple of weeks at control levels.”

Farmers will need to scout those fields which are most susceptible to damage from the pest. It is recommended that inspections be made twice weekly when the plants first emerge — the growth stage most vulnerable to the insects.

Among the list of insecticides, Patrick said, are: Mustang Max, Capture 2, Pounce, Ambush, Asana and Baythroid — all pyrethroid compounds.

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