Comparison of arthropod communities among different forage types on the Texas high plains using pitfall traps

The decline in water supply for irrigation in the Texas High Plains is encouraging some growers to produce dryland forages. 'WW-B.Dahl' Old World bluestem [OWB, Bothriochloa bladhii (Retz) S.T. Blake] is a drought-tolerant grass in dryland and limited-irrigation conditions. This grass reportedly repels red imported fire ants (RIFA, Solenopsis invicta Buren); however, broader insect communities associated with OWB have not been investigated. We characterized the ground-active arthropod community occurring in OWB, OWB-alfalfa (Medicago sativa L.), alfalfa, and native mixed grass pastures by using pitfall traps over 3 years. Forty-seven families among 10 insect orders and five families of five non-insect arthropod orders were collected. Beside ants (Hymenoptera: Formicidae), the most abundant taxa collected were ground beetles (Coleoptera: Carabidae) and click beetles (Coleoptera: Elateridae), house flies (Diptera: Muscidae), butterflies (Lepidoptera: Pieridae), and field crickets (Orthoptera: Gryllidae), with jumping spiders (Araneae: Salticidae) and sow bugs (Isopoda: Oniscidae) representing the non-insect taxa. Pastures containing OWB had nearly zero (P < 0.001) RIFA and harvester ants (Pogonomyrmex spp.), but no other arthropod family responded to forage treatments. Ant abundances were greatest in the native mix and intermediate in the alfalfa and teff [Eragrostis tef (Zucc.) Trotter] pastures. The relatively low abundances of RIFA and harvester ants in the OWB and OWB-alfalfa mixture compared to the other forage treatments suggest that WW-B.Dahl OWB might act to deter activity of ants, yet further studies are needed to determine the specific mechanisms and insect-deterring traits of these forage systems to support strategies for pasture management.