Carabid Assemblages (Coleoptera: Carabidae) in a Rotation of Three Different Crops in Southern Alberta, Canada: A Comparison of Sustainable and Conventional Farming

Abstract

Carabids were sampled in 2000 (pretreatment year) and 2003-2005 in experimental plots in southern Alberta, Canada, after a rotation of beans, wheat, and potato under sustainable and conventional farming practices. Each phase of the rotation was present in every year. Crop type had a stronger effect than sustainable treatment on carabid-expected species richness, diversity, and species composition. However, carabid activity density was consistently higher in plots under sustainable treatments than those maintained conventionally. Potato plots, which were sprayed with insecticide for pest control, showed a significantly lower carabid activity density than the other crops. These results support other studies showing the beneficial effect of sustainable farming on activity density of carabid beetles.

Impacts of the agricultural transformation of the Canadian Prairies on grassland arthropods

“…Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al 2008). However, other agricultural practices and inputs varied between the crops in the rotation, confounding the results (Bourassa et al 2008).…”

“…Insecticide use generally decreases the activity and density of carabids (Floate et al 1989;Bourassa et al 2008). In a crop rotation study, Bourassa et al (2008) observed that the activity density of carabid species, based on pitfall trap data, was significantly less in the insecticide treated potato crop relative to other crops in the rotation that received no insecticides.…”

“…Insecticide use generally decreases the activity and density of carabids (Floate et al 1989;Bourassa et al 2008). In a crop rotation study, Bourassa et al (2008) observed that the activity density of carabid species, based on pitfall trap data, was significantly less in the insecticide treated potato crop relative to other crops in the rotation that received no insecticides. In a study of alfalfa fields managed for hay production (no insecticide application) and for seed production (with insecticide application), Uddin (2005) noted that the overall carabid assemblage did not differ between the two management systems; however, some species were negatively affected by the spring insecticide application, including Poecilus corvus and Agonum cupreum Dejean (Coleoptera: Carabidae).…”

“…However, in a related mark-releaserecapture experiment, individuals of the adventive, dominant, and mobile carabid Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) entered the intercrop more often than the monocultures, suggesting an effect of vegetation structure on habitat choice for this species (Cárcamo and Spence 1994). At Vauxhall, Alberta, Bourassa et al (2008) found that carabid species composition differed among small plots of wheat, bean (Phaseolus vulgaris Linnaeus; Fabaceae), and potato. Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al 2008).…”

“…At Vauxhall, Alberta, Bourassa et al (2008) found that carabid species composition differed among small plots of wheat, bean (Phaseolus vulgaris Linnaeus; Fabaceae), and potato. Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al 2008). However, other agricultural practices and inputs varied between the crops in the rotation, confounding the results (Bourassa et al 2008).…”