New Hope for Citrus

Jun 13, 2023

by PAUL CATALA

Although not yet widely tested, oxytetracycline hydrochloride injections are taking the spotlight as the latest hope to fight citrus greening.

TJ BioTech's oxytetracycline hydrochloride (OTC) ReMedium TI trunk injection most likely won't be available for purchase until mid-December, but it has already created a buzz among growers because of its potential to suppress Candidatus Liberibacter asiaticus (CLas), the bacterium that causes the disease Huanglongbing (HLB) in citrus.

On October 28, the Florida Department of Agriculture and Consumer Services granted ReMedium TI a special local-need registration. Applications for its use can begin post-harvest of the 2022–23 citrus season.

Research by TJ BioTech shows that injecting citrus trees with oxytetracycline hydrochloride has proven to be successful in the greening battle. Basically, using a device called a "FlexInject," the ReMedium TI bactericide is injected into trees.

A single worker can inject about 250 citrus-bearing trees and 350 non-citrus-bearing trees in nine hours.

Rick Dantzler is the chief operating officer of the Citrus Research and Development Foundation. He and his board asked TJ BioTech to make a presentation to the Citrus Research and Development Foundation, while he and Matt Joyner, executive vice president and CEO of Florida Citrus Mutual, met with state regulators in Tallahassee to emphasize the dire state of the citrus industry. Joining them were growers who were able to see one of the ReMedium field trials.

Dantzler says although TJ BioTech is currently the only company manufacturing the trunk injection systems, at least two others are working to get manufacturing approval. He says he supports the decision to approve the tree injection.

"It is the only therapy that we see on a short-term horizon that can provide more than just incremental benefit," he says, adding there are few, if any, side effects if directions for use are followed.

Field trials have shown the citrus tree injections have improved tree health and biomass while reducing fruit drop by as much as 60 percent. Dantzler says there may still be room for improvement, such as whether spraying for Asian citrus psyllids can be reduced by using ReMedium TI. He adds that there are other therapies that can provide incremental benefits, but that wouldn't be enough for many of the growers.

Overall, Dantzler says the injections should help "turn the corner" and get the citrus industry back on the track of sustainability.

"It is legal to spray this bactericide now but spraying requires far more product and hits non-target species, so this is better environmentally," he adds.

To apply the ReMedium TI, a grower or grove worker will use a TJ BioTech FlexInject injection device. That mechanism is used to drill a hole into citrus trees’ trunks above the soil line and inject the product. Growers are cautioned to explicitly follow label instructions to stay within federal guidelines because the product can only be used once a year for trees bearing citrus or twice a year for non-citrus-bearing trees.

Although no one is currently using the trunk injections, Geoff Roe, director at Noble Ag Management in Winter Haven, calls the introduction of trunk injections "earth shattering" compared with other proposed greening solutions. Noble Ag Management, now in its 85th year, manages about 3,000 acres of citrus in Polk, Highlands, Glades, and Manatee counties.

"I think (ReMedium TI) is like the silver-looking bullet," Roe says. "I think through the trials, it looks extremely promising and will help increase pound solids per acre."

As far as the use of OTC and specifically ReMedium TI, Ray Royce, executive director of the Highlands County Citrus Growers Association, Sebring, expects it to be used widely throughout the citrus industry once it's on the market. He says there are growers in Highlands County with application crews already in training and that by citrus harvest season December to May, the use of OTC trunk injections should be widespread.

Highlands County has about 62,000 acres of citrus with about 175 growers contributing 17 to 18 percent of Florida's citrus harvest. Royce adds the success of the injections will also be based on the condition of the trees prior to applications and results six to eight months later.

"I’ve talked to growers that feel like it's maybe an investment they just have to make," he says. "But I don't know if anything's the magic cure. I don't think this raises anything from the dead. I do think that if a tree obviously has been affected and symptomatic but has been receiving generally good care otherwise, this may well be the thing that pushes it back to higher production and much lower fruit-drop rates."

But to get into the hands of grove-tenders and owners, the citrus injection systems need to get to the market and ag-related businesses such as Griffin Fertilizer Co. in Frostproof.

Mike Roberts, Vice President of Griffin Fertilizer, says he's already heard growers expressing "much interest" in ReMedium TI, the only injection product legally labeled on the market.

Roberts says ReMedium TI will be sold in 165-gram packets, which is dissolved into 15 liters of water. He says based on the size and health of a tree, an application can treat 100 to 600 trees while only injecting about 150 milliliters of solution into each healthy tree.

Each packet will retail for $325 and Roberts explains that those in the ornamental tree business have been using trunk injection for "a long time." He says the formula gets injected into a tree's xylem and phloem, where bacteria are located. He explains that the process will most likely require more than one application each year.

"There are a lot of variables on this we’re going to have to figure out," says Roberts. "But based on the research that I’ve seen, it looks like it's going to be very effective. Time will tell."

"I don't think anybody thinks this is the final answer; the UF and plant breeders are still working on trees that will have resistance," says Roberts. "I think we all feel like this is a stop-gap to get us there, and it does look encouraging."