Conservation biological control of insect pests

Conservation biological control increases the control effect of locally occurring natural enemies and has two approaches. Ecological engineering of the agroecosystem involves improving the environment in favour of natural enemies. The second approach is to devise ways of improving the ratio of natural enemies to pests by applying an insecticide in a partially selective manner. The tools of ecological engineering are to provide pollen and nectar sources as an adult food for beneficial insects, to increase floral diversity to increase the numbers of other insects that provide alternative food for beneficials, perhaps to add a single plant species to support an essential alternate host for a predator or parasitoid, or to use plant diversity to raise humidity in the crop. These tools have long been available, but have only been exploited more recently as the public and governments have required greater environmental sustainability and pests have increasingly become tolerant to the available insecticides. Few insecticides offer intrinsic selectivity in favour of natural enemies, but selectivity of broad-spectrum compounds can be obtained by reducing the dose of the insecticide or by restricting its application in time or space. Whatever approach is considered, its practical application is usually quite simple.