Response of Soybean Insect Communities to Row Width Under Crop-Residue Management Systems

The impact of narrow-spacing and crop-residue management systems on soybean insect communities was investigated from 1993 to 1995. Field studies were conducted to determine the effect that row width has on the population dynamics of phytophagous insects and their natural enemies in soybeans [ Glycine max (L.) Merrill] grown under 2 crop-residue management systems. Soybeans were planted in a split-plot design with no-till and reduced-till residue management, and with narrow and wide row spacings. The above-ground insect populations were estimated by sampling at 2-wk intervals. In addition, several environmental factors, including air and soil temperatures, relative humidity, leaf area index, and estimated weed escapes percentage were recorded and used to explain the insect population dynamics. The predominant insect pests found were potato leafhoppers [ Empoasca fabae (Harris)], green cloverworms [ Hypena scabra (F.)], bean leaf beetles [ Cerotoma trifurcata (Förster)], brown stink bugs ( Euschistus spp.), differential and red-legged grasshoppers [ Melanoplus differentialis (Thomas) and Melanoplus femurrubrum (De Geer), respectively], and tarnished plant bugs [ Lygus lineolaris (Palisot de Beauvois)]. Common natural enemies found were damsel bugs ( Nabis spp.) and insidious flower bugs [ Orius insidiosus (Say)]. No significant differences were detected between populations of insect pests from narrow versus wide row-spacing treatments; however, population densities of potato leafhoppers and bean leaf beetles were significantly greater in the reduced-till plots compared with the no-till plots. Likewise, no significant differences were observed among natural enemies for the tested combinations of row spacing and tillage practice. The results of this study support the hypothesis that different row widths do not dramatically affect insect communities in soybean grown under no-till and reduced-till crop-residue management systems.