Functional Response and Predation Potential of Carabus elysii Adults against the Terrestrial Slug Agriolimax agrestis

SIMPLE SUMMARY: Agriolimax agrestis is one of the most important cash crop pests in China, widely affecting tobacco, vegetables, edible mushrooms, and other crops. Not only does it cause direct damage to plants but it also spreads bacteria that are harmful to plants and humans. Currently, the control of A. agrestis relies mainly on chemical agents; however, the heavy application of chemicals often leads to ecological damage. In this study, using Carabus elysii as a natural enemy, the predatory ability of adult C. elysii on A. agrestis was assessed under indoor conditions for the first time. The results show that C. elysii adults have a strong predatory ability on different sizes of slugs, especially juvenile slugs, and the female adults have a better predatory ability than the male adults. In general, C. elysii has strong potential to control A. agrestis and can be used as an effective control measure. ABSTRACT: Terrestrial slugs are a prominent agricultural pest worldwide. To mitigate the negative effects of chemical pest control, biological control involves the use of natural enemies to reduce the impact of target pests. Numerous insects are natural predators of slugs. This study evaluated potential of the predatory species, Carabus elysii Thomson (Coleoptera: Carabidae) to biologically control the terrestrial slug, Agriolimax agrestis. Laboratory experiments were conducted to investigate the functional response, searching efficiency, and interference effect of female and male C. elysii adults regarding adult, immature, and juvenile A. agrestis individuals. The results show that both female and male ground beetle adults are functionally capable of preying on different sizes of terrestrial slugs. C. elysii exhibited Holling type II functional responses when preying on A. agrestis. The maximum daily prey consumption was 35.5 juveniles, 25.1 immatures, and 17.1 adults for adult females and 26.9 juveniles, 20.3 immatures, and 11.6 adults for adult males. The searching efficiency of female C. elysii adults regarding A. agrestis was always higher than that of male adults for identical ages and densities of A. agrestis. Moreover, the predation of C. elysii on slugs was affected by predator density. The disturbance coefficient of male C. elysii were the highest on adult A. agrestis. The results of this study suggest that female C. elysii exhibit a high potential for the biological control of A. agrestis.