Title: Nitrogen fertilizer management effects on soybean N components and bean leaf beetle populations Authors
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 7, 2011
Publication Date: August 8, 2011
Citation: Riedell, W.E., Osborne, S.L., Lundgren, J.G., Pikul, J.L. 2011. Nitrogen fertilizer management effects on soybean N components and bean leaf beetle populations. Agronomy Journal. 103:1432-1440. DOI: 10.2134/agronj2011.0113. Interpretive Summary: With widespread cultivation of soybeans, coupled with milder winters, the bean leaf beetle has increased in abundance across the Upper Midwest. The larval stage of this emerging insect pest feeds on below-ground portions of the plant. Because larvae consume soybean nodules, cultural practices that affect soybean nodule growth and function may also affect bean leaf beetle populations in soybeans. Our objective was to investigate the effects starter fertilizer treatments containing different levels of nitrogen on soybean shoot nitrogen components, bean leaf beetle larval and adult population abundance, and on larval and adult body size. Our research demonstrated that the high nitrogen fertilizer treatment increased shoot nitrate nitrogen during beginning bloom and reduced the accumulation of fixed nitrogen in shoots during the pod through beginning maturity stages compared to the no nitrogen fertilizer treatment. High nitrogen fertilizer treatment also increased adult emergence from the soil during the hot and very dry 2007 growing season as well as increased a measure of adult body size (hind tibia length). Thus, increasing N levels in starter fertilizer treatments may interact with growing season environments to increase bean leaf beetle populations and their body size which in turn may increase populations and intensify the damage caused by this emerging insect pest in soybeans.
Technical Abstract: Bean leaf beetle [Cerotoma trifurcata (Förster)] larvae consume soybean [Glycine max (L.)] root nodules. This study was conducted to determine if different rates of N contained in starter fertilizer impact soybean shoot N components and bean leaf beetle (BLB) populations. The effects of starter N fertilizer treatments, consisting of 112 kg ha-1 of 24-16-11 (high N treatment), 7-16-11 (intermediate N), or 0-16-11 (no N) elemental N-P-K, on soybean shoot NO3-N and ureide-N and on BLB larval and adult abundance and body size were investigated on a Barnes clay loam near Brookings SD. High N fertilizer increased shoot NO3-N from the beginning bloom to beginning pod stage and reduced ureide-N at the full bloom, beginning pod, and beginning seed stages when compared to the intermediate and no N treatments. Fertilizer N treatments had no effects on larval numbers or body size. High N fertilizer resulted in greater adult emergence (1.73 insects m-1) than no N (0.42 insects m-1) in the hot and dry 2007 growing season, but not in the cooler and less-dry 2006 growing season. Across both years, adult hind tibia lengths, but not head capsule widths, were greater in insects that emerged from high (1.86 mm) and intermediate N (1.85 mm) compared to no N (1.79 mm) treatments. High N starter fertilizer, which altered shoot N components and increased BLB adult numbers and size under hot and dry conditions, may increase BLB populations and intensify the damage caused by this insect pest.