White and red-dyed kaolin particle films reduce Asian citrus psyllid populations, delay huanglongbing infection, and increase citrus growth

Florida citrus production has declined severely due to huanglongbing (HLB; "citrus greening disease") caused by Candidatus Liberibacter asiaticus (CLas), a phloem-limited bacterium transmitted by the Asian citrus psyllid (ACP; Diaphorina citri Kuwayama). Kaolin particle films are a tool used to repel insect pests and improve growth. The film covers the natural color of the leaves, which attracts ACP. Kaolin, naturally white in color, has been found to reduce ACP in citrus plantings. Previous research suggests adding a red dye might lead to further ACP reductions by reducing ultraviolet and blue light that attract ACP. We implemented a field experiment to test the effects of white and red-dyed particle films on ACP pressure, CLas infection, and citrus growth over the course of a two-year field study. In this study, white and red-dyed kaolin particle films were applied in young, non-bearing 'Hamlin' sweet orange (Citrus x sinensis) trees. The white and red-dyed kaolin treatments reduced ACP pressure and delayed HLB infection, and the red-dyed kaolin particle film was more effective in reducing ACP and in delaying CLas infection. Trees in both the white and red kaolin treatments had greater relative growth rate of trunk cross-sectional area (TCSA) than controls. This effect was observed regardless of CLas infection. Both particle film treatments resulted in greater final TCSA. Our results suggest particle films are an effective alternative to insecticide-based management of ACP and have the added benefit of increasing citrus tree growth under HLB pressure.