Interaction between the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), and carabid beetles: Field and molecular approaches

Since the invasion of the soybean aphid, Aphis glycines, in North America in 2000, several investigations have been conducted to determine the potential of predators as biological control agents. Carabid beetles are generalist predators that can feed on various crop pests but, even if they had been previously sampled in soybean fields, a direct trophic link between carabid beetles and A. glycines, as well as their contribution to reduce A. glycines populations remain to be established. The first objective of this study was to characterize the species composition and abundance of carabid beetles in commercial soybean fields in Québec. The second objective was to determine the extent to which the three most dominant carabid species feed upon A. glycines in 2006. Carabid diversity and abundance were monitored from 2004 to 2006 by pitfall traps. Until 13 species of carabid were collected from 2004 to 2006. Pterostichus melanarius (Illiger) was the dominant species as it represented until 86% of the carabid fauna abundance. A molecular gut-content analysis was developed to identify A. glycines-carabid interactions. On the three dominant species caught in 2006, A. glycines DNA was observed in gut of 21% of P. melanarius, 58% of Harpalus rufipes (DeGeer) and 14% of Harpalus pensylvanicus (DeGeer) analyzed. The implications of this study for A. glycines biological control will be discussed.