Antibiotic trunk injections save citrus trees but quietly harm soil nutrient microbes
Castellano-Hinojosa A, de Freitas J, de Carvalho DU, Monus BD, González-López J
Soil Health
Citrus groves across Florida and California are being treated with antibiotic trunk injections to fight an incurable disease, and this study shows the soil microbes that ferry nitrogen and phosphorus to those roots are quietly declining - a shift invisible in diversity data but potentially consequential for long-term orchard health.
Citrus greening is a deadly disease killing orange trees worldwide, and there's no cure for it. Scientists injected an antibiotic directly into infected tree trunks and it worked: trees produced more fruit and the disease bacteria dropped. But underground, the microbes that help roots absorb nutrients took a quiet hit - not in how many types were present, but in what those types were actually doing, with nutrient-cycling activity declining in the soil closest to the roots.
Key Findings
OTC trunk injection reduced citrus greening pathogen abundance in leaves and improved fruit yield and juice quality in infected sweet orange trees without altering overall microbial alpha diversity.
Belowground compartments (fibrous roots and rhizosphere) showed consistent functional reductions in carbon-, nitrogen-, and phosphorus-cycling microbial pathways, driven by rare low-abundance taxa rather than dominant community shifts.
Resistome profiles showed no detectable increase in antibiotic resistance genes in response to OTC treatment; resistance patterns were strongly compartment-dependent rather than treatment-driven.
chevron_right Technical Summary
Trunk-injected oxytetracycline suppresses the bacteria driving citrus greening disease and improves fruit yield in infected trees, but causes hidden functional disruption in the root-zone microbiome concentrated in rare organisms responsible for nutrient cycling - without changing overall microbial diversity or generating detectable antibiotic resistance shifts.
Abstract Preview
Original paper
Compartmental and functional responses of the citrus microbiome and resistome to the systemic delivery of oxytetracycline by trunk injection.
Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), severely limits citrus production worldwide. We investigated how oxytetracycline (OTC) trunk injection affects the citrus ho...
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