Biological control in agroecosystems: the case of Coccidophagy by Coccinellids

Coccinellids are important natural enemies that provide ecosystem services, such as the biological control of pests, in multiple cropping systems. Scales are essential prey items for a large proportion of coccidophagous coccinellid species. A well-known example where classical biological control was successfuly attained was the control of the cottony cushion scale Icerya purchasi Maskell on citrus in California using the coccinellid Rodolia cardinalis (Mulsant). In this chapter, results regarding the importance of coccidophagous coccinellids as natural control agents of scale insects (Coccoidea) are discussed. This work is the outcome of the last ten years of research related to the study of the natural enemies of the black scale Saissetia oleae (Olivier), a pest of the olive tree (Olea europaea L.), in the northeast of Portugal. The biology, ecology and feeding behavior of coccidophagous coccinellids have been presented and used to develop conservative strategies that can promote the action of these natural enemies. Special attention is given to the importance of coccinellids as biocontrol agents and to trophic relationships established between coccinellid species and the different developmental stages of coccids, by integrating both field and laboratory research.