Red imported fire ant, Solenopsis invicta (Burden) (Hymenoptera: Formicidae), abundance and arthropod community diversity affected by pasture management

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 3.4x more S. invicta mounds and 4.6x 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.