Minimising insect pests in eucalypt plantations: A review in the context of the concepts of optimal area, polycultures and patchiness

Summary Because nothing appears to have been published on the entomological benefits of increasing patchiness by intercropping eucalypts in plantations or of choosing a particular unit area for plantations, I have reviewed the ecological and biogeographic literature relevant to these concepts. The main findings are that: there should be an optimal range of unit areas for plantations in which the number of insect herbivore species is minimized and the number of species of parasitoids and invertebrate predators is maximized; intercropping with other tree species should increase the abundance of species of natural enemies and decrease the abundance of insect herbivore species; neither of the above two points is sufficient to guarantee that one or more of the insect herbivore species present will not become a pest; within a plantation patchiness may or may not reduce the likelihood of insect outbreaks. These four concepts are worth testing with eucalypt plantations and may complement traditional management techniques of preventing or containing insect outbreaks.