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The use of biological control for the management of pest insects pre-dates the modern pesticide era. The first major successes in biological control occurred with exotic pests controlled by natural enemy species collected from the country or area of origin of the pest (classical control). Augmentative control has been successfully applied against a range of open-field and greenhouse pests, and conservation biological control schemes have been developed with indigenous predators and parasitoids. The cost–benefit ratio for classical biological control is highly favourable (1:250) and for augmentative control is similar to that of insecticides (1:2–1:5), with much lower development costs. Over the past 120 years, more than 5000 introductions of approximately 2000 non-native control agents have been made against arthropod pests in 196 countries or islands with remarkably few environmental problems. Biological control is a key component of a ‘systems approach’ to integrated pest management, to counteract insecticide-resistant pests, withdrawal of chemicals and minimize the usage of pesticides. Current studies indicate that genetically modified insect-resistant Bt crops may have no adverse effects on the activity or function of predators or parasitoids used in biological control. The introduction of rational approaches for the environmental risk assessment of non-native control agents is an essential step in the wider application of biological control, but future success is strongly dependent on a greater level of investment in research and development by governments and related organizations that are committed to a reduced reliance on chemical control. [ABSTRACT FROM AUTHOR]

To determine the influence of pesticide treatments on the population dynamics of the whiteflies Trialeurodes vaporariorum (Westwood) and Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and their naturally occurring parasitoids, we performed field experiments on insecticide sprayed and unsprayed fields during a cropping season of snap bean in Pradera, Valle del Cauca, Colombia. Substantially larger populations of whitefly nymphs occurred in the unsprayed field than in the sprayed field. Parasitoids were more frequent in unsprayed than in sprayed fields with Encarsia nigricephala Dozier being more prevalent than Amitus fuscipennis MacGown & Nebeker. In sprayed fields the nymphs parasitized by E. nigricephala exceeded the unparasitized whitefly nymphs at the end of the cropping season. Our results suggest that while under current agricultural practices whiteflies on snap beans cannot be exclusively controlled by naturally occurring parasitoids, parasitoids may be integrated with chemical control in order to reduce crop damage. [ABSTRACT FROM AUTHOR]