Reliance is placed on naturally occurring parasites and predators and diseases to control insect and mite pests. Natural control works much of the time. Sometimes, long-term weather conditions or some other factors that are not obvious allow pests to escape from the natural controls so that they are able to cause widespread, spectacular damage. The elm spanworm, for example, defoliated hundreds of thousands of acres of woodlands in the late 1950's in western North Carolina. Most urban landscapes are not amenable to the basic concept of natural control.
Natural control is best suited to wilderness areas or large tracts of mixed woodlands or forests.
These areas sometimes attract pine voles and meadow mice which attack the bark of ornamental shrubs and consume flower bulbs. Voles are of little importance in large tracts of forest where owls, foxes and other predators limit their populations. However, voles can be a torment in the home yard where owls and foxes are rare. Sometimes natural controls may be objectionable. For example, when woodpeckers attack the natural wood siding of a structure to eat the carpenter bee larvae inside, when skunks and moles dig up the fine turf of golf courses to eat grubs and earthworms, and when scoliid wasps swarm over turf infested with green June beetle grubs in order to parasitize the grubs.