ABSTRACT Huanglongbing (HLB) is the most destructive citrus disease worldwide, and it has been disseminated by the Asian citrus psyllid Diaphorina citri , the vector of the causing agent Candidatus Liberibacter asiaticus. Although processed kaolin reduces psyllid infestation, long‐term field data from commercial orchards are limited. In this study, we evaluated the effects of low kaolin rates (≤ 2% w/v) and different spray regimes on D. citri populations and HLB incidence in large‐scale citrus orchards. Experiments were conducted at the edges of three commercial orchards using a randomised complete block design. In these experiments, D. citri populations were assessed fortnightly using yellow sticky cards (YSC), and HLB incidence was assessed quarterly through visual inspections. In experiment 1 (young orchard), fortnightly kaolin (2%) sprays combined with insecticides every 10 or 20 days reduced D. citri captures by 63% and 51%, and HLB incidence by 52% and 38%, respectively, compared with insecticides alone. In Experiment 2 (adult orchard), kaolin applied monthly (January–June) and fortnightly (July–December) reduced psyllid captures by 25% and disease incidence by 40%. Meanwhile, spraying kaolin only during the psyllid peak (July–December) achieved a 20% reduction in HLB incidence compared to insecticides alone. In Experiment 3 (young orchard), kaolin spraying at 2% only from July to December was ineffective. However, after the spray regime was changed to year‐round applications at 1% (January–June) and 1.5% (July–December), psyllid captures decreased by 48% and HLB incidence by 46%. Frequent applications of processed kaolin at low concentrations (1%–2%) substantially reduced D. citri populations and HLB incidence under commercial citrus conditions. Continuous application throughout the year was essential in young orchards, where shoot flushing and psyllid activity are constant. These findings support kaolin as an environmentally safe and effective, complementary tactic for integration into HLB management programmes.
Miranda et al. (Fri,) studied this question.