Nitrogen Fertilizer Management Effects on Soybean Nitrogen Components and Bean Leaf Beetle Populations

Abstract

Bean leaf beetle [Cerotoma trifurcata (Förster)] (BLB) larvae consume soybean [Glycine max (L.) Merr.] root nodules. This study was conducted to determine if different rates of N contained in starter fertilizer affect soybean shoot N components and 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) percent 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 (fine‐loamy, mixed, superactive, frigid Calcic Hapludolls) 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‐N (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.