Increased concern for the environmental effects of pesticides has led to considerable interest in optimal management strategies for controlling pest populations affecting agricultural production. This issue has been considered by a number of researchers (Feder and Regev; Hall and Norgaard; Hueth and Regev; Lazarus and Swanson; Marsolan and Rudd; and Talpaz and Frisbie). With the exception of Feder and Regev, these studies considered only one species. This approach involves serious limitations since a grower is generally confronted with multiple species during the production period For example, insect prey-predator relationships may exist in the field (Feder and Regev). Alternatively, as an insect pest develops through a number of growth stages, multiple pests in effect exist (Reichelderfer and Bender).