Plant-based essential oils and kaolin to control Asian citrus psyllid

Despite intensive control efforts, the Asian citrus psyllid, Diaphorina citri Kuwayama, the vector of Candidatus Liberibacter asiaticus the bacteria causing citrus greening, remains the most devastating pest of citrus. Diaphorina citri typically relies on tactile, visual, and odor cues to detect host. By combining an irritant, a visual masking, and a true repellent we aim to repel significantly ACP from citrus trees. We tested the use of kaolin with food colorant as irritant and visual masking, respectively; and the combination of true repellents with kaolin. Closed-cage bioassays were conducted to compare D. citri behavior between 1) kaolin-coated citrus and citrus; kaolin and red kaolin; and kaolin and blue kaolin, and 2) lavender + kaolin and kaolin; fir + kaolin and kaolin; thyme+ kaolin and kaolin; and coriander + kaolin and kaolin. When individuals were given a choice between uncoated and kaolin-coated plants, a significant number of D. citri chose the uncoated plants over those coated with kaolin. We found fewer D. citri settled on red kaolin-coated plants than on kaolin-coated plants. In contrast, the number of D. citri settled on blue and white kaolin-coated plants was not different. Similarly, we observed an additive effect of the combination of thyme and kaolin compared to the others as there were fewer individuals of D. citri on thyme and kaolin-coated plants than on kaolin-coated plants. Our findings suggested the possible use of red kaolin or the combination of thyme and kaolin as a means of reducing D. citri infestation in citrus.