Impacts of Management System on Carabid Beetle Community in Northern Great Plain Dry Land Agroecosystems.

As generalist predators of insect pests and weed seeds, carabid beetles are beneficial insects of agroecosystems that can help regulate pest populations.  Previous studies have shown that farming systems can have both positive and negative effects on carabid beetle community structure as cover crops, weeds, pesticides, and tillage can affect their abundance and species composition.  This study was conducted in 2013 at three different sites across Montana (Fort Ellis: FE, Big Sandy A: BS-A and Big Sandy B: BS-B) to assess the extent to which management systems impact carabid beetle communities in dryland agroecosystems.  Management system included chemical based no-till conventional, grazed organic, and tilled organic and crops included wheat and pea.  Pitfall traps were established at all three sites to characterize carabid beetle community characteristics.  Species richness, activity density, and Bray-Curtis similarity index were calculated and compared across systems using a two-way nested ANOVA model.  Forty one carabid beetle species and 1671 specimens were identified from all three sites.  At FE, grazed organic system had higher activity density of beetles compared to chemical based no-till conventional system. However, activity density was not different from tilled organic system. Also, species richness was not different among three systems. Although there was no overall differences in activity density and species richness of carabid between organic and conventional systems at BS-A, organic system had higher activity density during their peak activity time in June. At BS-B, no differences were detected between grazed organic and tilled organic systems in carabid beetles’ species richness and activity density. However, we may need to compare multiyear data from all sites before making any valid conclusion.