Red Imported Fire Ant, Solenopsis invicta (Burden) (Hymenoptera: Formicidae), Abundance and Arthropod Community Diversity Affected by Pasture Management

Abstract The red imported fire ant, Solenopsis invicta (Buren) (Hymenoptera: Formicidae), is one of the most prolific invasive species in the southeastern US. These invaders preferentially colonize highly disturbed land and grassland habitat. Management of livestock in pasture systems can have a profound impact on the level of disturbance in grassland habitats, and we hypothesized that adaptive multi-paddock pasture management would significantly increase S. invicta abundance in southeastern US pastures where arthropod diversity would decrease as S. invicta abundance increases. We studied the effects that adaptive multi-paddock pasture management systems (based on stocking density, rotation frequency, and insecticide/anthelmintic [wormer] application rates) have on fire ant mound abundance and arthropod diversity for the soil, foliar, and dung communities. Solenopsis invicta mounds and mound areas were documented along transect lines in 6 pastures. Soil and foliar arthropod communities were collected along the same transect lines, and dung communities were sampled from pats within the pasture system. Pastures managed under adaptive multi-paddock practices had 3.4× more S. invicta mounds and 4.6× more mound area than their conventionally managed counterparts. However, arthropod diversity did not correlate with S. invicta abundance in any of the 3 arthropod communities sampled. This study shows adaptive multi-paddock pasture management can increase S. invicta mound abundance, but arthropod communities in adaptive multi-paddock pastures do not suffer decreased diversity from increased abundance of S. invicta.