Knowledge Box

Effects of Fertilizer and Bradyrhizobium japonicum on growth of Spodoptera exigua

HSB 3rd Floor Student Commons

Host plant chemistry is thought to be a key feature in determining the performance of herbivorous insects. Typically higher nitrogen content in plants results in faster insect developmental rates and mass. With a positive correlation between both nitrogen and plant growth and nitrogen and insect growth, it is important to address whether agricultural utilization of fertilizers or inoculation of seeds with nitrogen-fixing bacteria could potentially affect insect performance. This study examined the relationship between nitrogen-enhancement of soybeans (Glycine max) and the resulting development of a common insect pest, beet armyworms (Spodoptera exigua). Four treatment groups were utilized: control (no fertilizer or inoculation), inoculation with N-fixing bacteria (Bradyrhizobium japonicum), nitrogen-fertilized (Osmocote), and both inoculated and fertilized. 100 larval beet armyworms were randomly assigned groups and reared on the appropriate foliage (n=25 per treatment group). Larval mass was measured and development time noted. Preliminary results show that both fertilization and inoculation of host plants can affect insect herbivores.