The routine use of many crop protection chemicals has led to the debilitation, or even the local elimination, of biological control agents. This has made many crop parasites more damaging, and more difficult to control. This biological anarchy has already been discussed (see 7.16.1) and it is difficult to assess its overall importance. The best indication comes from the fact that many successful examples of integrated pest management (IPM) depend very heavily on a restoration of biological controls that were lost because of pesticide use. This damage to biological control may turn out to be a much more important side effect of pesticide use than is currently realised. It is needless to add that the use of horizontal resistance does not damage biological controls. Indeed, it is the best means of restoring them.
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