OTC Trunk Injection

Injection timing

• Injections are best performed during spring and early summer.
• Inject at least 180 days before harvest.
• Injections performed in August and September can cause higher fruit residues.
• Trees should be well-hydrated at the time of injection.
• Inject during mid to late morning when transpiration rates are high.
• Do not inject during the main bloom.
• Injecting during a major leaf flush may result in leaf deformations.

Performing the injections

• Follow label instructions to determine the correct oxytetracycline (OTC) dose.
• Ensure the water used to dissolve the OTC is acidified correctly.
• Use only freshly prepared OTC solution. The solution should be yellow and clear.
• Do not inject any OTC solution that is brown and cloudy.
• Use a sharp brad-point drill bit and do not drill deeper than necessary.
• Use a smaller drill bit and applicator tip for smaller trees.
• Try not to inject directly in line with a main branch. Instead, inject in line with the crotch of the scaffold branches.
• Both rootstock and scion injections are effective, but young trees and trees with a short trunk are better injected into the rootstock.
• Subsequent injections should be performed opposite to the previous injection or spaced apart by several inches. Do not inject right next to, or into a previous injection site.

Phytotoxicity and sectoring 

• Moderate (leaf yellowing, bronzing) to severe (leaf drop, twig die-back, fruit drop) phytotoxicity may occur after injection.
• Stressed trees may be at a higher risk for phytotoxicity.
• To reduce phytotoxicity try splitting the desired OTC dose into two (or more) lower doses injected into opposite (different)
  sides of the trunk. This will also reduce sectoring.
• Consider using smaller applicator tips or injectors when splitting the injections.

Aftercare

• So far, there is no evidence that wound sealants promote healing and reduce trunk damage.
• Good tree care, including proper irrigation and nutrient management, are important for tree recovery.
• Continue to manage psyllid populations with insecticides. Oxytetracycline injections are no replacement for
  psyllid control!

Resources

Trunk Injection to Deliver Crop Protection Materials: An Overview of Basic Principles and Practical Considerations

Antibiotics in Crop Production

Wound reaction to trunk injection of oxytetracycline or water in huanglongbing-affected sweet orange (Citrus sinensis) trees

Evaluation of Trunk Injection Techniques for Systemic Delivery of Huanglongbing Therapies in Citrus

Trunk Injection as a Tool to Deliver Plant Protection Materials—An Overview of Basic Principles and Practical Considerations

Trunk Injection of Oxytetracycline for Huanglongbing Management in Mature Grapefruit and Sweet Orange Trees

Trunk injection of oxytetracycline improves plant performance and alters the active bark and rhizosphere microbiomes in huanglongbing affected citrus trees