Predatory response of Xylocoris flavipes to bruchid pests of stored food legumes

摘要

Biological control may provide an affordable and sustainable option for reducing losses to pest Bruchidae in stored food legumes, a crucial source of human dietary protein. Previous investigations have focused primarily on the role of parasitism in bruchid biological control, while the potential of generalist predators has been comparatively unexplored. The true bug Xylocoris flavipes (Reuter) (Heteroptera: Anthocoridae) exhibited a Type II functional response to the majority of cosmopolitan bruchid species evaluated when data were fit to Holling's disc equation. A negative correlation was detected between mean pest species body weight and rate of predation. The rate of attack on adult prey was quite low but fairly consistent, with the larger-sized female predators generally more effective. The eggs and neonate larvae of Acanthoscelides obtectus Say (Coleoptera: Bruchidae) were the only accessible immature stages among all prey species examined; predation on A. obtectus eggs and larvae was higher than on any adult bruchids. Mean predator kill of A. obtectus immature stages was 40 first instars or 10-20 eggs per 24-h interval. Further investigation of the biological control potential of X. flavipes against pest Bruchidae is merited due to the predator's ability to kill adult stages of all prey species evaluated.