Ground beetle (Coleoptera: Carabidae) assemblages in mulched and non-mulched garden plots

Ground beetles (Coleoptera: Carabidae) are important generalist predators in a variety of habitats, where they prey on many kinds of pest insects. We used pitfall traps for weekly collections by Master Gardener volunteer researchers for 13 weeks in 1998 and 12 weeks in 1999 to assess species composition and temporal patterns of ground beetles in plots of potatoes in home gardens in Illinois and Indiana. Potato plots were either mulched with straw or were left unmulched, having bare soil between plant rows. A total of 82 individuals of 9 species was found in 1998 in mulched plots, versus 79 individuals of 10 species found in unmulched plots. In 1999, 639 individuals of 23 species were collected in mulched plots, versus 380 individuals of 31 species in unmulched plots. Significantly more Cyclotrachelus sodalis (LeConte) were found in mulched plots than in unmulched plots in 1999, whereas there were no significant differences between mulched and unmulched plots in numbers of Cyclotrachelus convivus (LeConte), Harpalus pensylvanicus DeGeer, Pterostichus permundus (Say) or Scarites subterraneus F. Species diversity, as measured by the Shannon Diversity Index, was significantly greater in unmulched plots than in mulched plots in 1999. Fourteen species collected in unmulched plots in 1999 were not found in mulched plots, whereas 6 species found in mulched plots were not found in unmulched plots. Although ground beetle assemblages differed as a function of habitat manipulation, exact diets of carabids need to be understood to know the potential to impact pest management in hone gardens.