Some Florida citrus growers have recently started oxytetracycline hydrochloride (OTC-HCl) injection into tree trunks to help manage HLB. Other growers are considering it. Researcher Ute Albrecht offered a list of best practices for the product’s use during a Jan. 31 presentation in Immokalee.
The presentation was made at the University of Florida Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center, where Albrecht is an associate professor of plant physiology. Multi-county citrus Extension agent Mongi Zekri hosted the event, which was also presented virtually via Zoom.
Albrecht shared the following recommendations:
- Inject after harvest and after the main flowering period to prevent exposure to pollinators.
- Uptake and distribution of injected materials are driven by transpiration. Therefore, inject when leaves are fully expanded (not during leaf flush) to ensure efficient uptake and distribution of injected materials, and inject during mid- to late morning when trees are actively transpiring. Injections in the afternoon are likely less effective and may also increase the risk of phytotoxicity.
- Avoid injecting during the hottest time of the season (and day). There have been reports of phytotoxicity (manifested as leaf bronzing) when injections were conducted in August.
- Use a sharp brad-point drill bit for drilling the hole to minimize injury.
- Drill the hole no deeper than necessary. The deeper the drill bit, the more damage occurs in the trunk.
- Do not use any wound sealants or plugs to seal the wounds; these inhibit the trees’ ability to heal.
- Remember that trees will become reinfected. OTC-HCl injections are not replacements for psyllid control.
- Although the label allows it, it is not recommended to inject trees with a trunk diameter of less than 2.5 inches.
- Inject trees only once annually and leave a pre-harvest interval of at least 180 days.
- Follow label directions. The label is the law.
RESULTS AND COSTS
Albrecht said research has indicated that trunk injection of OTC-HCl in HLB-infected trees is likely to result in significantly reduced fruit drop, increased yield, improved fruit color, increased Brix, increased fruit size and increased tree growth.
The major concern with the injections is the possibility of tree injury. Albrecht said OTC-HCl delays wound closure and increases the wound size.
The researcher cited a maximum cost for OTC-HCl injection of $202 to $406 per acre, not including labor and injection devices. That’s assuming a planting density of 150 trees per acre, with a maximum cost of $1.34 to $2.70 per tree.
Learn more about Albrecht’s research on trunk injection of OTC-HCl.
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