Tips for Trunk Injection of Oxytetracycline

By Ute Albrecht and Ozgur Batuman

Follow these important tips for proper trunk injection of oxytetracycline as a citrus therapeutic.

The tree hydration status is important for uptake and distribution of the injected formulation. Therefore, ensure that trees are well watered before performing injections.
Injections should be performed after the harvest and in compliance with the 180-day preharvest interval. To ensure efficient uptake and distribution, inject when the leaves are fully expanded. Avoid injecting during leaf flush to prevent leaf deformations.
For optimal uptake and distribution, injections are best performed during spring or early summer and during mid- to late morning (9:00 a.m. to 12:00 p.m.), when transpiration rates are highest.
To achieve the best results, inject trees as soon as possible after preparing the formulation. This will minimize degradation from heat and UV and help preserve the product’s efficacy.

Before performing injections, measure the diameter of the tree trunk to determine the appropriate dosage and size of the injector. Choose the smallest drill bit recommended for the trunk diameter.
Find a site on the tree trunk with no existing damage or disease. The label recommends injecting in the rootstock, but this may not always be possible.
Inject in line with the crotch of the scaffold branches, especially if the tree trunk is short. Do not inject right beneath a major scaffold branch as the formulation will then only move into the part of the canopy that is supported by that branch.
Use a sharp brad-point drill bit. Do not drill/inject deeper into the trunk than necessary. For bearing trees, the depth should not exceed 1 inch when using the large FlexInject^TMinjector and a 17/64-inch drill bit. The deeper (older) wood is less metabolically active than the newer wood and therefore less effective in compartmentalizing the wound caused by the injection. Injecting too deep will also hinder effective distribution throughout the tree.

Implement good tree care, including proper irrigation and nutrient management, to support tree recovery after injection.
Continue to manage psyllid populations with insecticides. Trunk injection of oxytetracycline is no replacement for psyllid control!
Maintain detailed records of the trunk-injection process, including date, type of injection material used, dosage and any observations made during and after the treatment.
If possible, mark the trees with failed injections. This may be an indication of citrus blight. If the number of failed injections in the block is high, consider testing the trees for citrus blight by injecting water with a syringe. If blight is confirmed and the trees are not in good health, replace those trees and do not attempt injections again.
Follow the label instructions. The label is the law.

Ute Albrecht (ualbrecht@ufl.edu) and Ozgur Batuman (obatuman@ufl.edu) are associate professors at the University of Florida Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center in Immokalee.