Quantifying Economic and Environmental Tradeoffs of Walnut Arthropod Pest Management.

Many arthropod pesticides used by California walnut growers in the United States have been linked to water quality impairment, however lower risk alternatives are often associated with higher costs. The purpose of this paper was therefore to (1) identify currently practiced pest management strategies with probable high water quality impact, (2) quantify the importance of different factors affecting any economic tradeoffs associated with lowering water quality impact, and (3) identify the types of pest management strategies that could potentially lower water quality impact with less economic consequence. Through an integrated analysis using environmental, economic and pesticide-use data, we concluded that 96% of the pest management strategies analyzed were candidates for lowering impact to water quality, with the following six characteristics listed in order of importance regarding their influence on economic tradeoffs: (1) biological control efficacy (2) the number of pests targeted by a pest management strategy without potential to be controlled by natural enemies, (3) the cost/acre of organophosphates, (4) the cost/acre of miticides, (5) the cost/acre of alternative products, and (6) the cost/acre of pyrethroids. In addition, we found that 43% of the pest management strategies analyzed could be replaced by a low water quality impact strategy with little economic consequence, if biological control was effective. These pest management strategies were generally characterized by high miticide and organophosphate costs, treating solely codling moth, aphid, and/or mite.  The results indicated that if these pest management strategies had been replaced by alternative strategies, total organophosphate, pyrethroid, and miticide active ingredient use would have been reduced by an average of 4.5 lbs/acre per year while simultaneously lowering the grower’s pest management costs by an average of $52/acre, thus contributing to both economic and environmental long run sustainability.