1. The risk of pest damage in forest monocultures is a growing concern as the area ofplantation forest expands world-wide and sustainable management is becoming ageneral goal. Numerous studies have demonstrated that pest insects are less abundantin more diverse agroecosystems, but limited experimental evidence exists for a similarrelationship in forestry. Because plantation forests are usually mosaics of single-speciesstands, the aim of this study was to test the effect of forest diversity at a landscape levelon pest insect infestations