Impact of Nitrogen and Rhizobial Seed Inoculants on Soybean Aphid (Aphis Glycines Matsumura) Densities

Soybeans are able to obtain nitrogen from two different sources, nitrogen found in the soil (e.g. from fertilizers) and biologically fixed nitrogen (from symbiotic bacteria called rhizobia). Nitrogen source and degree of reliance on N-fixation can impact plant nitrogen dynamics, which has the potential to impact above-ground herbivore performance. We examined the impact of nitrogen availability and rhizobial association on soybean aphid biology and reproduction in a series of greenhouse and field experiments. Aphid establishment on plants was not significantly affected in any experiment. However, aphid reproduction was significantly affected by rate of nitrogen fertilization, rhizobial inoculation, and type of rhizobial seed inoculant. In general, aphid densities were not correlated with plant parameters associated with plant nitrogen or N-fixation. Producers commonly use fertilizers and rhizobial seed inoculants, thus it is important to continue exploring the mechanisms underlying how plant nitrogen dynamics impact soybean insect pests