September 19, 2008

Pockets of Thayer, Fillmore and Clay counties in south cerntral Nebraska are reporting stem borers in soybean. This beetle (Dectes texanus texanus) has been moving into Nebraska from north central Kansas over the last several years.

A UNL Extension group is trying to determine how widespread the soybean stem borer is in Nebraska. If you suspect this pest or have identified it in your fields, please contact Jenny Rees, UNL Extension Educator, at (402) 762-3644. Extension also is looking for producers who would like to collaborate next year on research on controlling this pest. Contact Rees if you're interested.

For information on identifying the soybean stem borer and its damage, see the August 15 CropWatch article, Soybean Stem Borer Active in Nebraska.

Control

Entomologists at Kansas State University have been studying this insect as a pest on soybeans for several years. They have not identified resistance in any commercially available soybean cultivars, and labeled planting time and foliar insecticide applications were not effective in managing this insect. KSU has conducted a great deal of research on this insect. Their reports and extension publications can be found online at Soybean Stem Borer.

Fields with a history of injury or with symptoms this year should be carefully watched. Fields with extensive stalk tunneling by Dectes stem borer are at risk for lodging and harvest losses, depending on weather conditions. Those fields should be targeted for harvest first to minimize harvest losses due to stem borer injury.

In the future:

• Avoid planting continuous soybeans in affected fields and where possible, avoid planting soybeans in fields adjacent to these infested fields.  Research from Kansas State University indicates that the soybean stem borer beetle is unable to fly great distances.   
• Control annual sunflowers, cocklebur, and ragweed, both in fields and ditches as this pest survives in these weeds.
• Plant longer season varieties as they do not seem to mature and lodge as quickly as shorter season varieties.
• North Carolina research has shown that breaking and burying soybean residue 2-3 inches deep can reduce damage from this pest by 60% to 70%.
• If you’re no-tilling, manage this pest with a longer crop rotation, good weed control, and a longer season variety.

Jenny Rees
Extension Educator, Clay County
Bob Wright
Extension Entomologist, Lincoln