Fine-Tuning Trunk Injection

Josh McGill HLB Management

Growers have concluded their first round of injecting their citrus trees with oxytetracycline (OTC) and now are anxiously awaiting the results. So far, trees seem to be responding with larger leaves and fruit, but fruit retention will tell the story if the treatment is moving the needle against HLB.

trunk injection
Under ideal conditions, oxytetracycline uptake will take only 10 to 30 minutes per tree.
(Photo by Ute Albrecht, UF/IFAS)

For many years, there was a perception among growers that if you had to touch the tree (e.g., trunk injection), the treatment was not viable. But that perception is changing according to Rick Dantzler, chief operating officer of the Citrus Research and Development Foundation.

“Two things have driven the change in heart — desperation to find something to fight HLB and the ability of labor crews to inject at faster rates than anyone thought possible,” Dantzler says.

As is often the case with any new practice, growers find ways to tweak the process to make it more efficient. Glenn Beck, co-owner of Beck Bros. Citrus, treated all of his citrus with OTC this past season.

trunk injection
Last season, Glenn Beck treated all of his acreage with oxytetracycline. This season, he plans to inject trees while the harvest crews move through groves.

“We’ll be changing our approach a little when we make our second round of injections,” Beck says. “We will have our labor crews making the trunk injections as they finish harvesting a tree. We were not able to do this on the first injection because of when we received the clearance to use this treatment. This should improve efficiency because we’ll have the labor already there for harvest.”

Beck adds early indications are that OTC is benefiting HLB-infected trees. “Our groves are continuing to improve. This probably is not going to be reflected in this upcoming crop, because we didn’t get the clearance to make trunk injections in time to affect the fruit set,” he says. “But hopefully, it will help us hold what we have on the tree and improve quality.”

Ute Albrecht, associate professor of plant physiology with the University of Florida Institute of Food and Agricultural Sciences, has been the lead researcher studying the use of OTC to treat HLB. She, too, has heard that some growers are tweaking the trunk-injection process.

“Some growers have developed a conveyor-belt-like system/structure to fill their injectors,” she says. “Some also have made their own tools to make it easier to insert the injectors, to prevent leaking and to repair the injectors, which apparently needs to be done a lot. In general, I think organizing the process efficiently is key.”

So, what does an efficient trunk injection look like? The answer will differ among growers and groves. But Albrecht has some tips on best practices. She says one key is taking time to avoid mistakes.

“It is very important to do the injections properly to prevent any negative side effects like trunk damage or phytotoxicity and to maximize uptake and distribution. I have seen some injection wounds that looked ugly because it was not done correctly,” she says. “Our research has shown that, when done correctly, the wound at the injection site is minimal.”

Under ideal circumstances, the uptake of OTC will only take 10 to 30 minutes, but it can take a couple of hours. It is important that the trees are well watered before injecting to ensure efficient uptake. Injecting during drought conditions is not recommended.

“Weather conditions and time of day can also influence the uptake rate,” Albrecht says. “Injecting under very cloudy and rainy conditions should be avoided, and it is best to inject during mid-to-late morning when the trees are most actively transpiring. Uptake and distribution are driven by transpiration; therefore, any conditions that enhance transpiration are likely to enhance uptake and distribution.”

Because the OTC in solution is very sensitive to heat and light, Albrecht recommends injection as soon as possible (on the same day) after preparing the formulation. This will help ensure best results.

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Frank Giles


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