The use of chemical pesticides frequently causes minor pests to become serious problems by disturbing the natural controls that keep them in check. As a result, it is possible to suffer heavier crop losses after pesticides are introduced than before their introduction. Efficient use of pesticides requires complete biological modeling that takes the appropriate predator-prey relationships into account. A bioeconomic model is introduced involving three key species: a primary target pest, a secondary pest, and a natural enemy of the secondary pest. Optimal decision rules are derived and contrasted with myopic decision making, which treats the predator-prey system as an externality. The issue of resistance in the secondary pest is examined briefly.