Impact of the Red Imported Fire Ant, Solenopsis invicta (Hymenoptera: Formicidae), on the Growth and Yield of Soybeans

The yield of soybeans, Glycine max (L.) Merr., from experimental plots infested with the red imported fire ant, Solenopsis invicta Buren, was 400 to 575 kg less per ha than that from comparable noninfested plots. The loss was attributable primarily to destruction of germinating seeds and seedlings, as evidenced by significant reductions in plants per meter of row in the infested plots. Evidence obtained from 32p radioisotope studies showed that the ants also fed on growing plants, probably on their roots. Growth, as measured by plant height, was reduced in the ant-infested plots, a factor that could be associated with root-feeding activity. It is suggested that the impact of red imported fire ants on germinating soybean seeds is associated with planting dates (May and June) which coincide with a period of food stress associated with intense brood-rearing activity by the ants.