Herbivory by Insects on Oak Trees in Pure Stands Compared with Paired Mixtures

Abstract

(1) The communities of herbivorous insects and their feeding on oak (Quercus petraea) trees in pure stands or in mixtures with alder (Alnus glutinosa), pine (Pinus sylvestris) or spruce (Picea abies) were investigated. (2) The species of insect found on a particular tree species were the same whether the tree was growing in a pure or in a mixed stand. (3) The densities of insects were different in pure and mixed stands. The numbers of all herbivore groups were highest on oak in the oak/alder mixture and lowest on oak in the oak/spruce mixture. (4) Feeding damage was significantly different on trees in pure and mixed stands. The major contributors to this damage were also different. For example, leafhoppers caused little damage in the pure oak and oak/spruce but caused almost as much damage as caterpillars on oak planted with alder. (5) It is concluded that patterns of planting significantly affect both the densities and damage caused by insects.