Integrating conservation biological control into IPM systems

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Most agricultural production systems harbor many species of herbivorous arthropods capable of damaging crops. However, the vast majority of these species do not reach damaging levels. In this chapter we explore the role of predators and parasitoids in suppressing pest abundance and damage. In particular, we focus on factors that influence the abundance of beneficial arthropods in agricultural landscapes. Finally, we address ways to manage these systems to increase the effectiveness of beneficial arthropods. There are three primary means by which managers influence biological control of insects. Importation of natural enemies against pests of exotic origin is sometimes referred to as classical biological control, while augmentation is the rearing and release of natural enemies already present to increase their effectiveness. Conservation of natural enemies involves improving conditions for existing natural enemies by reducing factors which interfere with natural enemies or increasing access to resources that they require to be successful (Ehler, 1998). Habitatmanagement is considered a subset of conservation practices that focus on manipulating habitats within agricultural landscapes to provide resources to enhance natural enemies (Landis et al., 2000). Managing agricultural landscapes to improve biological control relies on a detailed understanding of factors that influence both pest and natural enemy abundance (Fig. 12.1). We begin by examining landscape processes that influence pests and beneficial insects at larger spatial scales. Next we focus on processes that influence these organisms and their interactions at local scales. Finally, we detail steps that pest managers may take to alter agricultural habitats and landscapes to favor natural enemies in IPM systems. Throughout, we attempt to show how both temporal and spatial factors influence the outcome of pest–enemy interactions.