Dectes stem borers, Dectes texanus texanus LeConte, can cause serious lodging in soybean, but there variation from field to field that can not be explained. We examined the effects of three soybean varieties (three maturity groups) planted on 4 planting dates (April 15 through 1 June) on Dectes infestations and Dectes stem girdling in these plantings. In-season non-destructive counts of infested stem nodes (stem entry holes) in early August indicated a decreasing rate of infestation with later planting. The late August the non-destructive counts indicated the middle plantings were infested more than the early and late planting. The late September dissection of plants indicated that the maturity group 2 soybean had low infestations, but this appeared to be caused by poor plant health, this variety had charcoal rot. The other soybeans were heavily infested with Dectes stem borers with only a slight decrease for the last planting. However, the percent of infested plants that were girdled was higher in the first two plantings (55-59%) than in the last two plantings (12-25%). The percent plants girdled was highest for the maturity group 3 variety, where there were 45%, 45%, 17% and 9% plants girdled in the 4 planting dates, respectively. Since there was only a single variety of each maturity group it was difficult to separate maturity group from variety effects. In 2003 we will include additional varieties of each maturity group.
Species 1: Coleoptera Cerambycidae Dectes texanus texanus (Dectes stem borer, Soybean stem borer)
Keywords: Soybean Pests, Cultural Control
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