Economic injury level concepts and their use in sustaining environmental quality

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The economic injury level (EIL) concept is the basis for decisions in most integrated pest management (IPM) programs. These IPM programs are fundamentally different from control approaches to handling pest problems by focusing on tolerating pest effects. The EIL is essential for IPM programs because it indicates which levels of pests can be tolerated and which cannot. By increasing our ability to tolerate pests, it is possible to eliminate or reduce the need for management tactics. Moreover, we can improve and maintain environmental quality through better decisions on the use of those tactics. EILs help maintain environmental quality by reducing unnecessary use of management tactics, especially of pesticides. However, including environmental considerations explicitly in the decision-making process could greatly improve the ability of IPM to sustain environmental quality. To understand the current and potential roles of EILs in maintaining environmental quality, it is first necessary to examine the components of the EIL. These include economic damage, economic thresholds, and the EIL itself. Of these elements, the economic threshold has been the most problematic because it depends on predictions of pest population growth rates. Most approaches to economic threshold development can be grouped into subjective and objective categories, with the objective category being based on calculated EILs. Increased availability of calculated EILs and their related economic thresholds would reduce unnecessary use of management tactics. Additional attention to the EIL itself could further improve the responsiveness of IPM programs to environmental concerns. In particular, by including direct considerations of environmental factors, as well as economic and biological information, into EILs, it would be possible to develop environmental EILs. An environmental EIL evaluates a management tactic based not only on its direct costs and benefits to the user but also on its effects on the environment. Activities to support greater environmental responsiveness in the EIL include accounting for environmental costs in the C variable, reducing damage per injury by increasing plant tolerance in the D variable, and developing an effective, yet environmentally responsible, K variable by reducing pesticide application rates. Focusing research efforts on these aspects of the EIL concept offers the prospect of improved responsiveness to environmental concerns in IPM, without a reliance on new tactics.