ABUNDANCE OF CARABID BEETLES AND OTHER GROUND-DWELLING ARTHROPODS IN CONVENTIONAL VERSUS LOW-INPUT BEAN CROPPING SYSTEMS

The abundance and seasonal dynamics of carabid beetles and other ground-dwelling arthropods in conventional and low-input dry bean (Phaseolus vulgaris L.) cropping systems were investigated over two field seasons in Maine, USA. In 1988, carabids and staphylinids were significantly greater in number in the low-input plots. Staphylinids and arachnids were significantly more abundant in the low-input plots in 1989. Elaterid adults were abundant in 1988, and the number in the conventional plots was 23 times higher than in the low-input plots. Multivariate analysis showed that compositions of major ground-dwelling arthropods differed significantly between the two cropping systems from the early to middle season of plant growth. Individual carabid species differed between the two cropping systems. Harpalus rufipes, Pterostichus melanarius, Agonum muelleri, Clivina fossor, Carabus nemoralis, Carabus auratus, and Loricera pilicornis were dominant carabid species in this study. In 1988, Pterostichus melanarius, Carabus auratus, and L. pilicornis were significantly more abundant in the low-input plots, while A. muelleri and Clivina fossor were significantly more abundant in the conventional plots. In 1989, however, only A. muelleri was significantly different between cropping systems and a significantly higher number was trapped in the low-input plots.