Integrated management of Asian citrus psyllid, Diaphorina citri Kuwayama, for protecting young citrus trees from Huanglongbing

The Asian citrus psyllid, Diaphorina citri Kuwayama, is a serious pest of citrus because it transmits a phloem limited bacterium, Candidatus Liberibacter asiaticus (C. Las), that putatively causes Huanglongbing (HLB). Also known as citrus greening disease, HLB is considered the most destructive disease of citrus worldwide causing yield loss and decline of the infected trees. There is no cure for the disease, thus current management practices focus on controlling vector populations through frequent use of insecticides. However, the threshold level for vector management is near zero, given the fact that even a single D. citri can transmit C. Las. Protecting young citrus trees is particularly difficult because D. citri reproduce exclusively on soft leaf tissues of newly developing shoots (flushes) and young citrus trees frequently produce flushes throughout the year and thus are attractive to D. citri. Furthermore, many of the effective insecticides are of conventional broad spectrum chemistries that entail negative impacts, heavy use of which cannot be sustained. Therefore in this dissertation, the first set of studies investigated kaolin particle film as a potential alternative to broad spectrum insecticides for control of D. citri. Second, the efficacy of intensive insecticide application regimes utilizing currently available insecticides and kaolin particle film were evaluated for mitigating transmission of C. Las under commercial citrus growing conditions. Lastly, the impact of recurring infestation and inoculation of C. Las by D. citri on tree vigor was assessed to determine whether insecticide use for D. citri control will be value in maintaining fruit production for already HLB-diseased trees. The results showed that kaolin particle film application deterred psyllid feeding thereby reduce HLB infection in young citrus trees, and that intensive D. citri control programs utilizing combination of foliar and soil applied insecticides significantly reduced the D. citri infestation and overall infection level in the field compared to the untreated.