91 N.J. Bostanian et al. (eds.), Arthropod Management in Vineyards: Pests, Approaches, and Future Directions, DOI 10.1007/978-94-007-4032-7_5, © Springer Science+Business Media B.V. 2012 5.1 Introduction Biological control has been defined as: ‘ The action of parasites, predators or pathogens in maintaining another organism’s population density at a lower average than would occur in their absence’ (De Bach 1964). Therefore, successful biological control of arthropod pests relies on the presence and viability of effective predators, parasitoids and/or entomopathogens in sufficient numbers and at critical seasonal periods to provide population regulation. Predators, such as entomophagous mites, lady beetles and lacewings are free- living organisms and consume a large number of prey (Huffaker et al. 1976), while parasitoids have immature developmental stages that are found on or within a single host and their feeding results in host death (Reuter 1913). Pathogens are disease-causing organisms that can kill or debilitate the host and include nematodes, protozoa, bacteria, fungi, and viruses (Federici 1999). In this chapter, biological con- trol agents are grouped into three key categories: predaceous arthropods, parasitic arthropods and pathogens. The brief review of the predaceous vineyard arthropods discussed herein will include predatory spiders and mites (Arachnidae, Phytoseiidae, V.M. Walton (*) Department of Horticulture, Oregon State University, Corvallis, OR 97331-7304, USA e-mail: waltonv@hort.oregonstate.edu K.M. Daane Department of Environmental Science, Policy and Management, University of California, 130 Mulford Hall, Berkeley, CA 94720-3114, USA e-mail: daane@uckac.edu P. Addison Department of Conservation Ecology and Entomology, Faculty of AgriSciences, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa e-mail: pia@sun.ac.za Chapter 5 Biological Control of Arthropods and Its Application in Vineyards Vaughn M. Walton, Kent M. Daane, and Pia Addison