Infestations of the soybean stem borer, Dectes texanus, were first reported in Edwards, Barton, Kiowa, Ford and Pawnee counties in 1985. Borer larvae caused severe lodging problems in north-central and southwestern Kansas, where infestations of 50 to 80 % of plants with tunneling are common. In Republic Co., some sites have approached 100% infestation. Damaging populations are expanding westward in soybeans and more recently in sunflowers, with infestations reported in an additional 59 counties. Expansion may be due to reduced availability of alternate host plants such as wild sunflower, increased borer larvae winter survival, increased soybean acreage, or increased adoption of non-tillage practices.
Though interest in management and control of soybean stem borer has increased, strategies remain limited. For example, early harvesting has helped reduce some yield losses if infestations are detected early in the growing season. Commercial insecticides do reduce adult stem borer numbers, but several applications are necessary for better results, making this option cost-prohibitive. Fipronil seed treatments serve to effectively control larvae in the plant stem, but this insecticide remains commercially unregistered for use on soybean stem borer and unavailable.
To date, soybean varieties adapted to the High Plains or Midwestern U.S. contain no genetic traits for resistance to soybean stem borer larval damage. However, our results have provided a source of borer resistance and a reliable method for identifying resistance. Several genes are involved in PI165673 resistance suggesting that breeding for borer resistance will benefit from marker-assisted selection to accurately and efficiently locate the PI165673 resistance genes.