The impact of tillage in sugar beet fields on the seasonal abundance of carabids (Coleoptera: Carabidae) in Western Nebraska

Several arthropod taxa play an important role in agroecosystems because of their ability to regulate insect pest numbers and weed population densities. In order to benefit from the ecological services provided by these arthropods, it is important to determine their response to different farming practices (e.g. cultivation practices). The objective of this study is to quantify the seasonal activity of beneficial soil-dwelling arthropods in differing tillage systems in sugar beets in western Nebraska. The taxa monitored include centipedes (class Chilopoda), spiders (order Araneae), harvestmen (order Opiliones), ground beetles (Coleoptera: Carabidae), ladybird beetles (Coleoptera: Coccinellidae), and rove beetles (Coleoptera: Staphylinidae). Activity of these taxa was monitored through pitfall trapping. Pitfall traps were activated for a total of six, one-week intervals during the season, allowing two week intervals between activations. Results from the 2012 field season indicated that ground beetles were the most abundant beneficials in sugar beet fields sampled. Centipede, harvestmen, and coccinellid beetle numbers remained low throughout the season in both tillage types. For both rove beetles and spiders, the mean number of individuals caught per pitfall trap was significantly higher in the zone-tilled plots. The activity of ground beetles was similar in both tillage types throughout the season. The ground beetle species, Harpalus eraticus Say, Elaphropus anceps LeConte, H. pensylvanicus (DeGeer), and Amara carinata LeConte accounted for nearly 80% of the collected individuals. This study indicates differing responses of predatory taxa to annual cultivation practices; therefore the ecosystem services rendered by these organisms may be impacted.