The influence of tillage on beneficial, edaphic insect communities in sugar beets in western Nebraska

The beneficial, edaphic arthropod assemblage and abundance encountered in conventional-tilled and zone-tiled sugar beets was monitored over the growing season in western Nebraska from 2011-2012. Concomitant to this, the degree of prey and weed seed removal rendered by these arthropods were also determined. The activity density and identity of soil-dwelling beneficial arthropods in the two tillage systems was monitored by means of pitfall trapping. The rate of weed seed removal was determined for four, regionally-common weed species (yellow foxtail, barnyardgrass, common lambsquarters, and kochia) through the use of vertebrate exclosure cages. Additionally, we also measured prey-removal rates, using waxworms (Galleria mellonella) as surrogate prey, to measure both diurnal and noctural predation. Ground beetles (Coleoptera: Carabidae) were the most abundant beneficial taxa collected in both tillage types (n = 2,050 in conventional-tilled and n = 1,682 in zone-tilled sugar beets). Few (n=7) ground beetle species dominated the total number of individuals; most individuals were Harpalus eraticus or Elaphropus anceps. Both tillage (F=12.59, P=0.0015) and weed species (F=8.62, P<.0001) impacted weed seed removal. Weed seed removal was highest in treatments with reduced tillage for all weed species. In contrast, tillage (F=0.01, P=0.92) did not impact predation as measured in this study; however, nocturnal predation predominated (F=47.74, P<0.0001) under both tillage conditions.