16. Pest management

Insects become pests when they conflict with our welfare, aesthetics, or profits. For example, otherwise innocuous insects can provoke severe allergic reactions in sensitized people, and reduction or loss of food-plant yield is a universal result of insect-feeding activities and pathogen transmission. Pests thus have no particular ecological significance but are defined from a purely anthropocentric point of view. Insects may be pests of people either directly through disease transmission (Chapter 15), or indirectly by affecting our domestic animals, cultivated plants, or timber reserves. From a conservation perspective, introduced insects become pests when they displace native species, often with ensuing effects on other non-insect species in the community. Some introduced and behaviorally dominant ants, such as the big-headed ant, Pheidole megacephala, and the Argentine ant, Linepithema humile, impact negatively on native biodiversity in many islands including those of the tropical Pacific (Box 1.2). Honey bees (Apis mellifera) outside their native range form feral nests and, although they are generalists, may out-compete local insects. Native insects usually are efficient pollinators of a smaller range of native plants than are honey bees, and their loss may lead to reduced seed set. Research on insect pests relevant to conservation biology is increasing, but remains modest compared to a vast literature on pests of our crops, garden plants, and forest trees.

In this chapter we deal predominantly with the occurrence and control of insect pests of agriculture, including horticulture or silviculture, and with the management of insects of medical and veterinary importance. We commence with a discussion of what constitutes a pest, how damage levels are assessed, and why insects become pests. Next, the effects of insecticides and problems of insecticide resistance are considered prior to an overview of integrated pest management (IPM). The remainder of the chapter discusses the principles and methods of management applied in IPM, namely: chemical control, including insect growth regulators and neuropeptides; biological control using natural enemies (such as the coccinellid beetles shown eating aphids in the vignette of this chapter) and microorganisms; host-plant resistance; mechanical, physical, and cultural control; the use of attractants such as pheromones; and finally genetic control of insect pests. A more comprehensive list than for other chapters is provided as further reading because of the importance and breadth of topics covered in this chapter.

Chapter 16