Reports Of Severe Insect Injury To Sorghum

By Adam J. Varenhorst

Incidences of severe insect injury to sorghum, specifically grain sorghum, have been reported in South Dakota. Sorghum plants are being cut at the base, which is indicative of several species of cutworms. However, due the difficulty of observing cutworms during the day and the timing of these reports we were unable to visit the injured fields. Therefore, an exact identification of the cutworm species responsible for damaging these sorghum fields is not possible. For future issues with these pests, please contact us for identification of the culprit.

Cutworm injury to sorghum

Cutworm species vary in how they feed and injure sorghum plants, and the best management practice for these pests will depend on which species of cutworm is present in the field (Figure 1). Some species of cutworm cut plants near the base, either at or just below the soil surface (black cutworm, pale western cutworm). Other species may feed on above ground foliage, causing leaves to look ragged in appearance (dingy cutworm, army cutworm). There are yet more species of cutworm that feed on the roots under the soil surface, killing younger sorghum and stunting the growth of larger plants.

Figure 1. Some examples of cutworm caterpillars that feed on sorghum; (A) pale western cutworm, (B) army cutworm, (C) black cutworm, and (D) dingy cutworm. Photos courtesy of John Capinera, Joseph Berger, Adam Varenhorst, and B. Christine, respectively.