Impact of Solenopsis invicta Buren Suppression on Arthropod Ground Predators and Pest Species in Soybean

Abstract

The red imported fire ant, Solenopsis invicta Buren, reportedly contributes to the biological control of key soybean pests. However, S. invicta may negatively affect ground-dwelling natural enemies such as ground beetles and earwigs. Information on the interactions between natural enemies is important for anticipating the success of biological control in agroecosystems with multiple interacting entomophagous species. Ground arthropods were monitored in soybean using pitfall traps in the 2000 and 2001 growing seasons to determine their response to selected fire ant controls. Three treatments were examined: an untreated check, Amdro™ (hydramethylnon) bait (ant-specific), and Lorsban™ (chlorpyriphos) (broad spectrum) plus Amdro. Fire ant captures in pitfall traps were lower in the Amdro and in the Amdro plus Lorsban treatments compared to the untreated control. Reduced fire ant density plus chemical treatment impacted the abundance of certain ground predators. Spiders, primarily Lycosidae, were significantly more abundant in the untreated control plots on some sampling dates; whereas, the earwig Labidura riparia Pallas was more abundant in the Lorsban and Amdro plots, presumably due to the removal of fire ants and other natural enemies. Ground beetles (Carabidae) were not different between treatments on any sampling dates. This study supports the assumption that spiders are compatible with fire ants as natural enemies and that earwigs are not compatible with fire ants. Numbers of lesser cornstalk borer, Elasmopalpus lignosellus Zeller, were not affected by the suppression of fire ant predation or the chemical treatments in 2000, the only year when they were captured. Crickets (Gryllidae), mole crickets (Gryllotalpridae), click beetles (Elateridae), scarab beetles (Scarabaeidae), and false darkling beetles (Melandryidae) also were not different between the fire ant suppression treatments.