D3439: Effect of processed kaolin sprays on Diaphorina citri population and Huanglongbing incidence in large citrus areas

Processed kaolin is a promising tactic for managing Diaphorina citri (Hemiptera: Psyllidae) and Huanglongbing (HLB) in citrus orchards. The effect of processed kaolin (2%) on D. citri population and HLB incidence in commercial citrus orchards was assessed throughout 3-4 years. The experiments were performed in two sweet orange orchards (6 months old and 4 years old) in a randomized block design with four blocks (3 hectares/block). In the young orchard, the treatments were: 1) fortnightly kaolin (Surround WG) sprays and 10-day interval insecticide sprays; 2) fortnightly kaolin sprays and 20-day interval insecticide sprays; and 3) 10-day interval insecticide sprays (no kaolin sprays). In the adult orchard, the treatments were: 1) fortnightly kaolin sprays during psyllid population peak (PPP) and monthly kaolin sprays for the remaining period of the year; 2) fortnightly kaolin sprays only in PPP, and 3) no kaolin sprays. In this experiment, all treatments were insecticide sprayed every 10 days. Overall, at the young orchard, in the kaolin-sprayed plots, the number of psyllids/yellow stick card (mean of 0.32 psyllid) and HLB incidence (mean of 7.7%) were, respectively, 52% and 45% lower than in plots without kaolin sprays. At the adult orchard, in the kaolin-sprayed plots, the number of psyllids/yellow stick card (mean of 0.07 psyllid) and HLB incidence (mean of 19.3%) were, respectively, 25% and 30% lower than in plots without kaolin sprays. This study shows for the first time that kaolin sprays reduce the psyllid population and HLB incidence in commercial citrus orchards.