P-643 - Prevalence and genetic diversity of Candidatus Liberibacter asiaticus and Asian Citrus Psyllid monitoring in seven commercial citrus groves in Georgia

A major concern for the growth and sustainability of Georgia’s citrus industry is the spread of Candidatus Liberibacter asiaticus, the cause of huanglongbing (HLB), and its insect vector, the Asian Citrus Psyllid (ACP). To assess the potential threat of HLB to citrus in Georgia, seven commercial groves in Pierce, Wayne, Ware, Coffee and Bacon counties were selected based on previous CLas detections in nearby areas. Tree surveys and insect monitoring were carried out during 2023 and 2024 to determine the in-grove distribution of CLas and document the prevalence of ACP. DNA was extracted from the collected leaf samples (n=799) and tested for CLas via qPCR. Groves were scouted and monitored for ACP for 14 months using yellow sticky traps, and each ACP collected was confirmed morphologically and tested for CLas. To genetically characterize CLas strains from positive samples, sequences of the 16S rDNA and prophage regions were analyzed. Among the 799 tested trees, 15 (1.9%) present in clusters on the edges of four groves in Wayne, Ware and Pierce counties were determined to be CLas positive. ACP were recovered from the monitored groves in Pierce County only, and 14 of 123 (11.4%) tested positive for CLas via qPCR. Based on analysis of the CLas 16S rDNA region, no major genetic variations were observed; however, prophage typing revealed that at least 4 CLas strains had prophage type 1-2, while 9 strains had type 1 only. These findings provide valuable information on the prevalence of CLas and ACP and the diversity of CLas strains in affected commercial groves in Georgia.