Selective vs. Broad-Spectrum Pesticides: When Do Private Decisions Differ from Socially Optimal Decisions?

This paper examines the spatial externalities of conventional and organic pest control methods to determine if, and how, the two types affect each other. These interactions make the problem more complicated than the usual analysis of a single externality. The numerical simulation model includes one organically managed and one conventionally managed field. One pest and one predator of the pest move between the two fields over five seasons. In each season, the conventional grower has the option of applying a broad-spectrum pesticide that kills the predator a selective pesticide that has no adverse effects on the predator but is either more expensive or less effective than the broad-spectrum pesticide. The organic grower can apply an organic pesticide, augment the predator population, or both. The simulation model identifies the socially optimal pest control decisions and the Nash equilibrium decisions of both growers over the five growing seasons. The relative price and efficacy of the selective pesticide, the type of predator, and the type of pest introduction all influence whether or not either or both growers make inefficient decisions. Under certain conditions, regional pest management, equivalent to coordination of pest control across growers, could increase total regional profits.