FORUM Integrating Biological and Chemical Controls in Decision Making: European Corn Borer (Lepidoptera: Crambidae) Control in Sweet Corn as an Example FRED R. MUSSER, 1 JAN P. NYROP, 2 AND ANTHONY M. SHELTON 2 J. Econ. Entomol. 99(5): 1538Ð1549 (2006) ABSTRACT As growers switch to transgenic crops and selective insecticides that are less toxic to natural enemies, natural enemies can become more important in agricultural pest management. Current decision-making guides are generally based on pest abundance and do not address pest and natural enemy toxicity differences among insecticides or the impact of natural enemies on pest survival. A reÞned approach to making pest management decisions is to include the impact of natural enemies and insecticides, thereby better integrating biological and chemical control. The result of this integration is a dynamic threshold that varies for each product and the level of biological control expected. To demonstrate the signiÞcance of conserved biological control in commercial production, a decision-making guide was developed that evaluates control options for European corn borer, Ostrinia nubilalis (Hu ¨ bner) (Lepidoptera: Crambidae), in sweet corn, Zea mays L., where the primary natural enemies are generalist predators. Management options are -cyhalothrin (broad-spectrum insecticide), spinosad (selective insecticide), Trichogramma ostriniae (Peng & Chen) (Hymenoptera: Trichogrammatidae) (parasitoid), and Bacillus thuringiensis (Bt) sweet corn (transgenic variety). The key factors inßuencing thresholds for all treatments are the intended market, predator populations, and the presence of alternative foods for the predators. Treatment cost is the primary factor separating the threshold for each treatment within a common scenario, with the lowest cost treatment having the lowest pest threshold. However, when the impact of a treatment on natural enemies is projected over the 3-wk control period, the impact of the treatment on predators becomes the key factor in determining the threshold, so the lowest thresholds are for broad-spectrum treatments, whereas selective products can have thresholds 6 times higher by the third week. This decision guide can serve as a framework to help focus future integrated pest management research and to aid in the selection of pest management tools. KEY WORDS model, insecticides, biological control, IPM, Bacillus thuringiensis Economic injury levels (EIL) and their related eco- nomic thresholds have been developed for pests in many cropping systems. The EIL is deÞned as “the lowest population density that will cause economic damage” (Pedigo et al. 1986). The EIL does not fore- cast pest density, so most ßuctuation in the EIL for a given pestÐ crop combination is due to economic changes (Brown 1997), namely, crop value and con- trol costs. The economic threshold is the predictive form of the EIL, being “the pest density or plant injury level corresponding to the latest possible date for which a control tactic could be implemented to pre- vent economic damage” (Pedigo et al. 1986). Because the economic threshold is determined when controls can be applied, for some pests such as miners, borers, and soil-dwelling insects, the economic threshold needs to be determined weeks before economic injury will occur. In these cases, mortality from biological and weather factors (e.g., natural enemies, rain, and temperature) in the period between determining the economic threshold and realizing economic damage strongly inßuence the true economic threshold. Therefore, the true economic threshold is dynamic, moving up or down with changes in biological and natural mortality in the period between economic threshold determination and economic injury realiza- tion. However, because these values are generally unknown or unpredictable, a common approach to pest management has been to use a relatively constant economic threshold, limiting variation to different pe- riods of crop maturity (and sometimes crop value or control costs), and using Þxed values for other factors (Brown 1997). Although this economic threshold is not perfect, many growers and crop consultants now base their management decisions on these static eco- nomic thresholds. The result is often a reduction in 1 Department of Entomology and Plant Pathology, Mississippi State University, Box 9775 Mississippi State, MS 39762 (e-mail: fm61@ msstate.edu). 2 Department of Entomology, New York State Agricultural Exper- iment Station, Cornell University, 630 W. North St., Geneva, NY 14456. 0022-0493/06/1538Ð1549$04.00/0  2006 Entomological Society of America