These are stem borer adults. It is also commonly referred to as Dectes stem borer. Stem borer is usually a small long horned beetle whose larvae attacks soybeans. Adult beetles are gray to bluish gray. They have long antennae and alternating light and dark gray bands. Newly hatched larvae are creamy white but darken as they mature.
Female lays eggs into the stems at the petioles. When the eggs hatch the larvae bore into the stem and begin to feed on the outer stem then later bore into the main stem. Larvae feeding weakens the stem causing the plant to lodge. This damage reduces the plant's ability to translocate water and soil nutrients to developing pods and seeds, leading to significant yield losses in heavily infested fields. Lodging can cause difficulties in harvesting and significant yield loses.
Cultural control options are reccomeded including: control of weeds that may act as alternative host plants. Harvest the crop as soon as it matures to help reduce losses associated with lodged plants. Crop rotation and use of resistant cultivars.