The use of oxytetracycline antibiotic trunk injections in a huanglongbing environment and the effect on canopy, root systems, and rhizosphere microbiome

Abstract The global citrus industry has been severely affected by huanglongbing (HLB), a citrus disease associated with the bacterium Candidatus Liberibacter asiaticus ( C Las), vectored by the Asian citrus psyllid. HLB symptoms are seen in the tree's canopy, fruit, and root systems, which include canopy dieback, increased fruit drop, lower fruit Brix, and reduced fine root growth. Eliminating HLB from trees is challenging, as no single method can completely control C Las. There has been an increase in research focused on finding ways to mitigate the effects of HLB. Oxytetracycline hydrochloride (OTC), an antibiotic used in citrus trunk injections, has been gaining attention in citrus growing regions like North America, South America, and South East Asia and Brazil. Research on OTC trunk injections has shown a reduction in HLB symptoms and bacterial titer; however, little is known about the interaction between OTC trunk injections, genotype, environmental stresses, and other biotic stress. Although there is a wealth of information on the HLB pathogen and its effects on trees, a succinct analysis has yet to be done to draw conclusions about whole tree effects across a range of geographies and demonstrate the broad effects of the use of OTC in an HLB environment.