Trunk injection of oxytetracycline (OTC) has been proposed as a means to manage HLB in citrus. University of Florida research shows OTC injections increase yield and fruit quality but cause tree injury. TJ BioTech expects to receive EPA registration in late fall of this year for an OTC product that could be injected into trees.
Florida citrus industry growers and representatives share their thoughts on OTC injection:
“The experimental field trials are in their infancy,” notes citrus grower Chip Henry, owner of McGuire Groves. “Results are certainly promising; however, it’s also possible that there are some conceivable long-term risks that could sooner or later outweigh the perceivable short-term benefits.”
Rick Dantzler, chief operating officer of the Citrus Research and Development Foundation, shares a similar sentiment: “Long-term negative effect is a concern because we don’t have research that spans many years,” he says. “We have research underway to answer these questions, but that will take time, and time is something we don’t have much of right now.”
“One potential outcome is the permanent weakening of the main columnar support of the tree,” notes Henry. “Citrus trees bear hundreds of pounds of fruit each crop season. One or more dead wood pockets imbedded deep in the sapwood will be the fracture point in the event the tree is subjected to high-velocity winds.”
Henry also is concerned the HLB pathogen has the capability to become resistant or immune to OTC over time. He points to the use of OTC in peaches as an example: “Southern state peach growers, including some in Florida, have recently been dealt a serious setback by unwittingly creating an OTC-immune pathogen commonly known as bacterial leaf spot. They applied foliar OTC sprays for decades to control the disease, and when the bacterium became extremely difficult to manage, they resorted to trunk-injection treatments. In just a few years, that method has also failed to quell the pathogen and now there is nothing else available to deploy in its place.”
“The companies developing these (OTC) products have said it is possible to apply too much product, resulting in phytotoxicity or even death to the tree, which is why it will be critical for growers choosing to use them to follow the directions on the label,” says Dantzler.
Matt Joyner, executive vice president/chief executive officer of Florida Citrus Mutual, is optimistic about current OTC research results. “Research presented by both the University of Florida and private organizations shows that the use of OTC through trunk injection is safe, very effective and critical to the fight against citrus greening,” says Joyner. “Data has shown that following the withdrawal period, there was no detectable trace of OTC in orange juice derived from trees receiving injection applications. Additionally, research has shown that the use of OTC through injections has no identifiable, adverse effects on either humans or the environment.”
Paul Meador, citrus grower and president of Everglades Harvesting & Hauling Inc., says he is hopeful the industry will have OTC trunk injections available this fall. “Though I do not like the idea of killing wood within the tree, there are no other options from my perspective,” Meador says. “I’m hopeful it will be a bridge to get us to a better tree in the near future.”
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