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Poster: Biology & Disease Mgmt: Chemical Control


Evaluation of the Spatiotemporal Dynamics of Oxytetracycline and Its Control Effect against Citrus Huanglongbing via Trunk Injection
J. HU (1), J. Hu (2) (1) University of Florida/IFAS-CREC, U.S.A.; (2) University of Florida, U.S.A.

Citrus Huanglongbing (HLB) or greening is a devastating bacterial disease that has destroyed millions of trees and is associated with phloem-residing ‘Candidatus Liberibacter asiaticus’ (Las) in Florida. In this study, we evaluated the spatiotemporal dynamics of oxytetracycline in planta and its control effect against HLB via trunk injection. Las-infected ‘Hamlin’ sweet orange trees on ‘Swingle’ citrumelo rootstock at the early stage of decline were treated with oxytetracycline hydrochloride (OTC) using trunk injection with varying number of injection ports. Spatiotemporal distribution of OTC and dynamics of Las populations were monitored by HPLC method and qPCR assay, respectively. Uniform distribution of OTC throughout tree canopies and root systems was achieved 2 days post injection. High levels of OTC (>850 µg/kg) were maintained in leaf and root for at least 1 month and moderate OTC (>500 µg/kg) persisted for more than 9 months. Reduction of Las populations in root systems and leaves of OTC-treated trees were over 95% and 99% (i.e. 1.76 and 2.19 log reduction) between 2 and 28 DPI. Conditions of trees receiving OTC treatment were improved, fruit yield was increased, and juice acidity was lowered than water-injected control even though their differences were not statistically significant during the test period. Our study demonstrated that trunk injection of OTC could be used as an effective measure for integrated management of citrus HLB.