| Abstract: | The methods used to evaluate and categorise the effects of pesticides on beneficial arthropods are reviewed, including the potential significance of indirect, ‘sub-lethal’ activity and the importance of bioavailability of pesticides under semi-field or field conditions. Interspecific and intraspecific differences in the susceptibility of natural enemies (parasitoids and predators) to pesticides are considered, including the use of resistant strains in Integrated Pest Management (IPM) systems. The potential impact of pesticide resistance in the target pest on its natural enemies is also discussed. The need to assess the influence of the host plant/cultivar on the efficacy of pesticides for use in integrated control programmes (ditrophic effects) and of the possible effects of such chemicals on host plant/cultivar-pest-parasitoid systems (tritrophic effects) are then described with specific reference to the diamondback moth and key endolarval parasitoids. Finally, the potential for manipulation of tritrophic interactions to enhance parasitism by application of low doses of toxicants is demonstrated. |
