Red and White Kaolin Particle Films Enhance Growth and Yield of HLB-infected Sweet Orange Trees

The Florida citrus industry is severely impacted by huanglongbing (HLB), a bacterial disease spread by the Asian citrus psyllid ( Diaphorina citri ), leading to reduced production and extensive management challenges. Additional stresses, such as excessive sunlight, heat, and water deficits, further weaken the affected trees. Kaolin particle films (PFs), including white and recently developed red-dyed types, alleviate the effects of water and heat stress on citrus physiology, help suppress psyllid populations, and delay HLB infection. However, there is limited knowledge about the long-term effects of these PFs, especially red-dyed PF, on production capacity of citrus trees affected by HLB. This study aimed to evaluate the impact of these PFs on both growth and yield of HLB-infected trees. We conducted a field experiment on young ‘Hamlin’ sweet orange ( Citrus ×sinensis ) trees grafted onto ‘Kuharske’ citrange ( C. sinensis × Poncirus trifoliata ) rootstock, treated with foliar applications of white and red-dyed PFs, insecticides, or left untreated. Treatments began before infection and continued after infection with Candidatus Liberibacter asiaticus ( C las), the causal agent of HLB. We assessed tree growth and yield over two years following C las infection. Trees treated with either PF had greater yield and growth, including canopy area, volume, density, and height than insecticide-treated and untreated controls. The red-dyed PF increased some growth variables to a greater degree than the white PF. The results suggest that kaolin PFs offer substantial horticultural benefits, including enhanced growth and yield, and may serve as an effective strategy for mitigating the impact of HLB in citrus orchards, even after infection.