Mission Statement of the Nebraska Crop Surveillance Network:
Mitigate the impact of crop diseases and insect pests and safeguard Nebraska's agriculture against threats of bioterrorism.

Insects: Soybean Stem Borer

Taxonomy:

Common Name: Soybean Stem Borer
Scientific Name: Dectes texana

Distribution:

  • A native species that is widely distributed across North America east of the Rocky Mountains

Importance:

  • Is an occasional pest of soybean.

  • May be a concern for counties bordering Kansas.

Identification:

  • Adults are elongate, gray beetles, about 0.25-0.40 inches long.

  • Antennae are longer than the body.

  • Larvae are legless, creamy white with small, brown heads.

  • Bodies are strongly segmented and enlarged near the head and gradually tapering toward the rear.

  • Mature larvae are 1/2 to 5/8 inches long.

Life Cycle:

  • Females lay eggs in the upper leaf petioles of soybean during July and August.

  • Newly hatched larvae initially feed in the petiole pith but soon tunnel to the main stem.

  • Larvae tunnel in the stalk until they complete their development.

  • Larvae over winter in the stalk pupate in early summer, and adults emerge from June to September.

Host Range:

  • Soybeans, cocklebur, sunflowers, and common and giant ragweed.

Injury & Damage:

  • Damage is due to larval, not adult feeding.

  • Trifoliate leaves where eggs hatch and larva began feeding will wilt and die.

  • Mature larvae move down to the bottom of the stem, and internally girdle it 2-4.5 inches above the soil level.

  • Girdling often causes the entire plant to fall over (lodge).

  • 10% yield reduction has been reported from larval tunneling but the greatest yield losses occur due to lodging.

Monitoring:

  • Visual scouting. Look for wilted trifoliate leaves.

Management:

  • Insecticides are not recommended for control of larvae.

  • Adults can be controlled with foliar sprays, but because of their extended period of emergence treatment is not feasible.

  • Cultural practices suggested to reduce losses include harvest of infested fields as soon as maturity is reached, crop rotation, and control of weed hosts.

Notes: