Biological control represents one alternative to the use of insecticides. Biological control is the conscious use of living beneficial organisms, called natural enemies, for the control of pests. Virtually all pests have natural enemies and appropriate management of natural enemies can effectively control many pests. The natural enemies of insects are a diverse group of organisms that includes predators, parasitic insects, nematodes, and various mircoorganisms. Although biological control will not control all pests all of the time, it is a key component of integrated pest management. The intent of biological control is not to eradicate pests, but to keep them at tolerable levels at which they cause no appreciable harm.
In the upper Midwest, literally hundreds of types of natural enemies occur naturally in the environments of agricultural crops, managed forests, and managed urban and suburban landscapes. These have a major impact on pest populations, and often result in pests being kept below damaging levels. When there is no human activity involved in managing these natural enemies, we refer to the results as “natural control” of the pests. Natural control is of major importance in pest management, but the benefits frequently go unrecognized because the natural enemies are often very small and their activity is easily overlooked.
To get the greatest benefit from both natural control and biological control, it is necessary to recognize natural enemies, understand their biological characteristics (such as life cycle, preferred host insects, and efficiency at controlling pests). Some natural enemies, such as lady beetles, are readily recognized in the adult stage by most people but may not be recognized in the egg, larval, or pupal stages. Other natural enemies, including most parasites, are much more difficult to recognize.
Although birds, mammals, frogs, and other higher animals can be important as natural enemies, they can rarely be effectively managed for biological control. These animals lie outside the scope of this discussion, which deals primarily with the predatory or parasitic insects of pest insects and mites.