Trap–treat–release: horizontal transfer of fipronil in field colonies of black carpenter ants, Camponotus pennsylvanicus

AbstractBACKGROUNDHorizontal insecticide transfer is thought to play an important role in controlling a wide range of urban pests including ants, bed bugs, cockroaches, and termites. Despite decades of research and numerous laboratory studies, horizontal transfer has never been demonstrated in the field. As a result, the importance of horizontal transfer (and the resulting secondary kill) for practical pest management remains unknown. The goal of this study was to provide the first experimental examination of horizontal transfer under field conditions. The specific objective was to investigate horizontal transfer of fipronil in field colonies of black carpenter ants, Camponotus pennsylvanicus.RESULTSLaboratory experiments demonstrated that fipronil is effectively transferred from treated donors to untreated recipients and causes significant secondary mortality. Fipronil was effectively vectored to untreated ants from donors exposed via residual and direct spray applications, and 100% mortality was achieved with both exposure routes. Furthermore, horizontal transfer continued beyond secondary mortality and resulted in significant tertiary mortality, which has not been previously demonstrated in ants. Field experiments utilized a novel, three‐step control method consisting of trap–treat–release and demonstrated that fipronil is effectively transferred when foraging workers are trapped, treated, and subsequently released back into their colonies.CONCLUSIONThe current study is the first field demonstration of the importance of horizontal transfer for the control of pest ants. The trap–treat–release method may be an effective alternative to broadcast spray applications and could help alleviate problems such as insecticide run‐off, environmental contamination, and non‐target effects. This method has the potential to provide effective management of invasive and pest ants and should be further tested across a wider range of ant species, habitats, and active ingredients. © 2019 Society of Chemical Industry