Push-pull and kill strategy for Diaphorina citri control in citrus orchards

The development of sustainable methods to control Diaphorina citri Kuwayama (Hemiptera: Liviidae) is crucial to improve management of huanglongbing (HLB), the most important citrus disease worldwide. In a flushing Citrus x sinensis L. Osbeck (Rutaceae) orchard, this study assessed the combined effects of insecticide-treated Bergera koenigii L. (Rutaceae) trees in the orchard border, as a lethal trap crop, and the application of processed kaolin to the citrus crop, as a repellent (push-pull and kill strategy), in reducing D. citri infestation and dispersal. Additionally, the volatile organic compound (VOC) emission profile and attractiveness of B. koenigii shoots were investigated in indoor experiments. The push-pull and kill strategy reduced the number of D. citri adults on citrus trees by 95, 84, and 63% compared to the untreated control, trap crop only, and kaolin only treatments, respectively. These high reductions can be attributed to the combination of attractive stimuli (VOCs) and repellent stimuli by the trap crop and kaolin, respectively. The number of psyllids observed on citrus trees subjected to treatments with trap crop and kaolin separately was 69 and 86% lower than on untreated control trees, respectively. In addition, all treatments reduced and delayed D. citri dispersal inside the orchard, especially the push-pull and kill strategy. In olfactometric assays, D. citri females showed a significant preference for B. koenigii odors over C. x sinensis cv. 'Valencia' flush odors, likely related with the different VOC emission profiles of the two plants. This study shows the effectiveness of push-pull and kill as a new management strategy to control D. citri and consequently HLB.