Talking Trunk Injection at Citrus & Specialty Crop Expo

The educational program on the first day of the Citrus & Specialty Crop Expo focused on trunk injection of oxytetracycline (OTC) being applied to citrus to treat HLB. Trees have received their second OTC treatment, and growers are hopeful trees will respond with better fruit retention and improved quality.

Ute Albrecht, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) associate professor, spoke about her research on trunk-injection therapy, which now has spanned several years. She says her research shows promise.

“The good news is after several years across all of our field trials, we are finding OTC injections are effective,” Albrecht said. “You may not get with one injection a pre-HLB tree, but we usually get a healthier, denser canopy. We have more fruit and better quality fruit in terms of size and peel color, and much improved juice quality.” 

In her trials, some of the yield and juice quality improvements were significant. However, results were variable based on the state of the trees. She noted that some results were not as positive as hoped for after initial treatments in growers’ groves. 

Albrecht said she has seen in her trials and heard grower reports of phytotoxicity after trees are treated. The symptoms usually include yellowing, bronzing or narrowing of leaves. Generally, the trees recover and grow out of the phytotoxicity.

There have been differences among rootstocks in how trees react to the OTC treatments. Albrecht advised growers to consider that when planting new trees. 

She said after two seasons growers are learning best practices for trunk injection. One of those is that multiple injection sites on both sides of the trunk improve OTC treatments throughout the tree. This helps reduce the “sectoring” of response to the treatments where improvements in canopy show up on the side of the tree where the injection occurred.

During a Q&A session, a few growers expressed optimism that trunk injection could be a path to help rehabilitate trees. Jim Graham, UF/IFAS professor emeritus, said during a panel discussion that OTC is the first product to actually work in reducing the HLB bacteria in infected trees in the nearly two decades that the disease has plagued Florida.

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