Stem Borer - Scouting

The first sign of damage from the soybean stem borer are wilted leaves that have been tunneled as the larvae move from the leaf petiole into the main stem. Photo by Phil Sloderbeck, © Kansas State University

Larvae of the soybean stem borer. Photo by Phil Sloderbeck, © Kansas State University

A good way to recognize stem borer infestations is to look for individual wilted or dying leaves in the middle of the canopy during mid summer.  Infestations can be confirmed by splitting the stems and looking for tunneling and larvae.

Later in the season, look for lodged plants. The plants will be broken off smoothly near the soil line. The surface of the break on the stubble (the upper face of the roots) will be smooth and often show no sign of tunneling . This is because the larvae tend to plug the tunnel above them after they girdle a plant. Therefore, if you see lodged plants with no obvious cause, split stem bases and see if signs of tunneling and a stem borer larva can be found.

Stem bases can also be split after harvest to get an idea of the infestation that had been present in the field during the growing season.

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