Variegated cutworms continue to cause problems in Iowa. As noted in previous ICM newsletters, the variegated cutworm has greatly delayed the regrowth of many alfalfa fields across Iowa. Now the variegated cutworm is being found in young soybean fields and the cutworms are eating all the leaves, reducing the plants to stubs. Serious defoliation has been reported from several areas. Doug Johansen, Monsanto Concept Farm, Atlantic, reports stand loss in Monona and Pottawattamie counties. Mark Kouba, New Century FS, Gladbrook, has reported stand loss in Marshall and Tama counties. The photograph shows a soybean field in the Ute area defoliated by this insect.
|Soybean field defoliated by variegated cutworm.|
The variegated cutworm is a very rare pest of soybean and no economic thresholds have been established. However, fields should be scouted for defoliated plants and the presence of cutworms. If the plant population is reduced to a density that is near the minimum plant population then an insecticide should be used. Different areas within a field will have higher or lower cutworm populations so scout across the field to reduce the possibility of missing hotspots.
This article originally appeared on page 125 of the IC-486(15) -- June 25, 2001 issue.