Conservation biological control using selective insecticides – A valuable tool for IPM

Abstract

Conservation biological control (CBC) has widely benefited from ecological practices that enhance both the crop and its surrounding environment. However, use of insecticides, whether biological or synthetic compounds, is often detrimental to natural enemies. By definition toxic to insects, insecticides may cause direct mortality of natural enemies, reduce food resources (prey/host), or disrupt behavioral and biological processes. Therefore, choosing a selective insecticide or selectively applying are important decisions for conserving natural enemies if insecticide is required. In situations where both insecticide and natural enemy do not share the same target pest, an additive outcome is expected and CBC can minimize pest outbreaks and resurgence. Given that new, selective insecticides are usually more expensive than older ones, using the former typically adds cost per treated area. Therefore, choosing a selective insecticide becomes a matter of benefits and costs, considering the cost compared to other available treatments and potential pest problems. Beyond the differential toxicity of selective insecticides to natural enemy and target pest species, some human decisions may produce insecticide selectivity, including application of minimal effective rates, and spatiotemporal separation of nonselective insecticides and natural enemies. These concepts are discussed here using two major crop commodities in Brazil: soybean and cotton. We show that natural enemies and selective insecticides can be effectively combined to manage arthropod pest populations even in agroecosystems highly dependent on chemical control.