When ignorance is not bliss: Pest control decisions involving beneficial insects

Recent survey data revealed that many California citrus growers did not know whether or not important beneficial insects were found on their fields while other growers were relying heavily or even entirely on these insects for pest control. Some pesticides are toxic both to the targeted pest and the predaceous or parasitic insect that could provide pest control. Alternative pesticides with fewer or no negative effects on the beneficial insect often exist but can be more expensive. Additionally, some beneficial insects are commercially available and can be purchased and released in the field. This paper models the pest control decisions of a grower who utilizes a pesticide and a predaceous insect to control the crop pest and compares these decisions to that of a grower who does not know that the predaceous insect exists. The results show that the latter grower will drive the predator population to zero and will overutilize chemical control. When the predator is known and utilized, the optimal decisions involve entirely mitigating the negative effects of the pesticide as well as releasing additional predators.