By Lauren Fessler Mathews, Ana Redondo and Ozgur Batuman
The positive impact of oxytetracycline (OTC) trunk injections for citrus production in HLB-infected trees has been well established. Additionally, there has been extensive work showing that plant defense inducers (PDIs) can help boost tree health and reduce symptom development from a variety of pathogens. Based on this, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers wanted to discover the effect that combining these two techniques would have on overall citrus health and performance in HLB-endemic conditions.
A UF/IFAS study looked at injecting OTC and spraying a proprietary PDI (PDI7). For this study, 100 milliliters of 11,000 parts per million OTC were injected once in the spring, and PDI sprays were applied approximately once monthly. This study was conducted in two mature Hamlin groves, one in Collier County and one in Charlottle County.
As shown in Figure 1, the combination of OTC injections plus PDI7 sprays helped to increase the performance of trees at both plots, even exceeding OTC injections alone. These encouraging results show the potential of using these techniques in combination to boost tree performance.
In addition to aiding tree performance in HLB-endemic conditions, PDIs are also known to reduce the severity of citrus canker infections. This benefit further incentivizes the use of combining these techniques for both processed and fresh fruit operations. Future studies are planned to test OTC injections used in combination with foliar or drench applications of commercially available PDIs.
Acknowledgment: The authors thank the grower collaborators for use of their grove sites, the Citrus Research and Development Foundation for funding (Project nos. 23-014, 24-003 and 24-004) and all citrus pathology members for their assistance in the trials.
Lauren Fessler Mathews is a graduate research assistant, Ana Redondo is a research coordinator, and Ozgur Batuman is an associate professor — all at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.
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