Florida’s Citrus Trees Face Extinction. Are Antibiotics the Only Answer?

Florida citrus growers say antibiotics are necessary to save their industry from the devastating effects of citrus greening. Consumer advocates say their use on crops is irresponsible.



In 1998, a tiny interloper was detected in the vast commercial orange groves that stretch for the endless flat, green miles of lower Florida. Called the Asian citrus psyllid (Diaphorina citri), the nailhead-sized pest delivers a double disservice as it munches a tree’s tender new shoots and leaves: It deforms foliage while also infecting its host with a fatal vascular bacterial disease called huanglongbing (HLB), also known as citrus greening. The disease’s presence was confirmed in Florida in 2005.

Known and battled for more than a century in its native China—its vector is thought to have arrived in this country on imported plants—HLB can take up to five years to incubate in citrus trees whose leaves have been nibbled by those psyllids. It stunts the tree and then kills it outright, causing salty, bitter fruit to drop long before ripening. HLB has turned up elsewhere—Brazil, Reunion Island in the Indian Ocean, and California (the psyllid has also been found in Hawaii but the disease has not yet been found there). But in Florida, where the orange juice industry is a dominant agricultural force, an estimated 100 percent of all mature commercial trees are presumed to be infected with the disease.

The state has tried and failed to eradicate HLB in the past, including by spraying the antibiotic oxytetracycline in 2016, ’17, and ’18. Nevertheless, in December, the U.S. Environmental Protection Agency (EPA) approved non-emergency spraying of oxytetracycline, a decision that could bring as much as 388,000 pounds of the antibiotic to Florida’s 480,000 citrus acres—and more, potentially, to citrus farms in states such as California, where the disease has so far been confined to backyard trees.

A citrus psyllid adult. (Photo by the USGS Bee Inventory and Monitoring Lab)

A citrus psyllid adult. (Photo by the USGS Bee Inventory and Monitoring Lab)

The EPA’s approval raises the question of whether staving off the collapse of a multi-billion-dollar industry is worth risking possible bacterial resistance to a medically important antibiotic for human use. (The EPA was not available for comment for this article due to the ongoing government shutdown.)

“This kind of spraying wildly is nutty,” says Consumer Reports’ senior scientist Michael Hansen. It’s “an irresponsible, dramatic expansion” of the drug’s use in plant agriculture. Oxytetracycline is also used, much less extensively, to treat fire blight on apple and pear trees, and bacterial spot on peaches and nectarines. “We already know that [overuse of] antibiotics are a huge risk in human health and [we’re] trying to reduce their use in animals,” says Hansen, where, despite the fact that they’re usually added to feed and water, the risk of environmental contamination is less extreme.

Some Florida citrus growers argue that treating trees with oxytetracycline, the active ingredient in FireLine—manufactured by a company called AgroSource, one of the companies behind the petition to the EPA—is a stopgap measure vital to saving their devastated industry. Florida citrus growers lost $1.7 billion in direct revenue between the years 2006 and 2011 (the industry has a total economic impact of $7.2 billion per year). The struggle to provide any relief from HLB is ongoing.

“Greening leads to biological death for the plant at some point, but it becomes commercially dead long before that,” explains Rick Dantzler, COO of the Citrus Research and Development Foundation in Lake Alfred, Florida, which is pumping money into HLB research—some of it attempting to eliminate or alter an increasingly pesticide-resistant psyllid, some of it earmarked for trying to produce a genetically modified cultivar. “Growers are just trying to hang on till a greening-resistant or -tolerant tree can be created.”

Ned Hancock, a farmer on whose Florida plantations suspected HLB-infected trees were found early on, says using antibiotics has lessened the fruit drop from some of his trees and improved their overall health. He knows the use of oxytetracycline is not a cure for HLB, but rather, “a short-term measure that gets us to the next step—and I have no idea what the next step is,” he says. “But we’re in a fight for our actual lives here.”

Weighing the Risks

Hancock believes damage from Hurricane Irma in 2017 halted the rebound he’d begun seeing in his orchards after emergency antibiotic spraying in previous years, and also may have given HLB renewed vigor. Asked if he’s afraid of consumer backlash to the use of antibiotics in his industry, Hancock admits it’s a concern, but says that AgroSource has assured citrus growers that they’ve so far found no impact of antibiotic usage on wildlife or soil.

A citrus leaf infected with citrus greening or huanglongbing.

A citrus leaf infected with citrus greening or huanglongbing.

Consumer Reports’ Hansen disagrees with this assertion: “We already know what spraying will do to bees, since there’s good work showing antibiotics disrupt their gut microbes, making them more susceptible to [fatal] disease.” Furthermore, he says the EPA did not conduct adequate studies on the effects of oxytetracycline on soil microbes, field workers, or drinking water.

According to the EPA’s own Risk Assessment of the use of oxytetracycline, there’s a high probability that it could lead to antibiotic-resistant bacteria, and a medium concern that human health could be impacted. The U.S. Food and Drug Administration (FDA) requires monitoring for resistance when these drugs are used in livestock, but Steve Roach, food safety program director for Keep Antibiotics Working, says no such monitoring is being undertaken by the EPA: “There’s no requirement for fruit.”

Nathan Donley, senior scientist at the Center for Biological Diversity, calls the allowance “a lousy solution to a complex problem … that could end up causing more harm than good.” He points out that Brazil and the European Union have also battled HLB, and banned the use of antibiotics to treat it. The worst-case scenario, at least when it comes to human health, could be antibiotic resistance.

“The more you use antibiotics, the more likely it is that bacteria that are not affected will survive and multiply,” Donley explains. “The DNA that makes bacteria resistant can also move between species of bacteria. So, the worry is that bacteria that can cause human disease will develop resistance to these drugs and then they won’t work when we really need them to.”

Donley also says that studies show that when plants are treated with oxytetracycline, the drug can have an effect on levels of certain microbes in soil. “The potential for soil health degrading is there,” he says.

Still, he’s sympathetic to citrus growers and says that if the antibiotics actually saved the trees, “we’d be having a very different conversation right now.” The most oxytetracycline spraying can do is extend the life of the trees—but eventually, growers will be forced to destroy them, then replant. This may sound like a reasonable solution, but the average commercial orange tree takes five years before it starts “producing enough fruit to pay the rent,” says Dantzler.

Planning an Alternative Citrus Future

Still, Consumer Reports’ Hansen says replanting is probably the best method for controlling the spread of the disease. In countries with antibiotic bans for citrus, he points out that the disease has been successfully controlled in this way, and also by using integrated pest management, in which parasitic insects such as wasps are introduced to eat the psyllids; these methods have all but eradicated the disease on Reunion Island. Dantzler points out that the USDA’s Farm Service Agency does offer monetary help to replant via its Tree Assistance Program but “it doesn’t come close to covering all the costs.”

Trapping and tenting new young trees with plastic covers have also been shown to be effective. The latter technique can effectively block the psyllid and raises the temperature under the tent to 120° Fahrenheit, which Hansen says kills the HLB bacterium. In fact, such control measures are what are available to the organic citrus industry in its own battle against HLB, as current standards disallow the use of antibiotics.

Thermotherapy trucks cover infected citrus trees with a canopy to heat treat them significantly reducing the amount of disease in the trees and increasing their productivity. (Photo CC-licensed by the USDA)

Thermotherapy trucks cover infected citrus trees with a canopy to heat treat them, significantly reducing the amount of disease in the trees and increasing their productivity. (Photo CC-licensed by the USDA)

Hansen believes that the U.S. citrus industry’s partial focus on genetic engineering is misguided. “Even if they find [a disease-resistant tree], how long before the bacteria evolves past the resistance?” he says.

Donley agrees, and points to larger, structural issues at play. “This greening outbreak is more of a symptom of the problem with growing crops in vast monocultures; we’re creating perfect conditions for outbreaks to occur,” he says. “With climate change, these things are going to get worse and if we keep growing crops this way, we’re inviting further disease and reliance on pesticides.”

Although the EPA has approved it, the Florida Department of Agriculture has yet to sign off on oxytetracyline’s approval; industry experts expect that to happen in February.

Top photo: USDA Agriculture Research Service entomologists inspect Florida orange trees for Asian citrus psyllids. (USDA photo by Stephen Ausmus.)

Update: This article has been updated to reflect the fact that the Asian citrus psyllid has been found in Hawaii, but the disease huanglongbing has not yet been discovered there.

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  1. Tim Eyrich
    Wednesday, January 23rd, 2019
    Curious how would one go about producing citrus in a non-monoculture system? Takes 5 to 7 years to get to profitable production, it is a tree! When someone makes such comments it shows they have little understanding of agriculture. Also the steam tents have shown to be very ineffective against HLB, both in the US and Brazil.
  2. Wednesday, January 23rd, 2019
    Excellent article, highlighting the madness of vast monoculture plantations that are inevitable targets of pests. Warfare against those pests, and the diseases they vector, is one approach, but the article wisely hints at the true solution: regenerative agriculture. Replacing monoculture with polyculture, enhancing rather than degrading the soil, optimizing soil microbiology, using integrated pest management - let's go that route rather than daring evolution to wipe out all orange trees and, just maybe, humans.
  3. Wednesday, January 23rd, 2019
    I agree with Tom - the only true solution will be more multifaceted and take the ecology of the environment into account. The Organic Center just published a peer-reviewed article and an accompanying grower guide that looks at holistic, organic tools that farmers can use now to slow the spread and impact of citrus greening disease (https://www.organic-center.org/combatting-citrus-greening/ ). The paper is really comprehensive and will provide a lot of relief for farmers, but what we really need is more research on a systems-approach for controlling this disease. Organic solutions aren't just for organic farmers - they can be adopted by everyone and may be more effective on the long-term than these short-lived "quick fixes".
    • Thursday, January 24th, 2019
      jessica,

      We have some of the best organic citrus growers in the world in this state and they are not having success against the disease. The rest of the industry is getting pummeled. If there were solutions that actually worked, why would they not use them? I went through the paper briefly and I didn't see any large-scale evidence of efficacy of any treatments, simply a list of hypotheses to test. I'm not sure these are "solutions". Glad that you thought about this, as we share a concern for the industry. I'm just sad to see more non-solutions touted, especially when your organization stands against the genetic solutions that hold the most promise in the shortest time to implementation.
  4. Eric Bjerregaard
    Thursday, January 24th, 2019
    You can't find a worse source than Hansen. That guy ignores that fact that decades might pass of successful control before any resistance to the GE trait develops. It also ignores the fact that by then. a better way may have been found, Hansen is short sighted in his bigoted opposition to GE.
  5. Thursday, January 24th, 2019
    Wow, where to start. This is such a destructive kind of article because it is just filled with misinformation. Right now this industry needs science and answers, not uninformed opinion.

    1. Oxtetracycline is not used in human therapies (at least for the most part) so even if resistance occurs it does not affect humans.

    2. Hansen is clueless and has been shown to be wrong constantly. He represents interests that hate technology of any kind on the farm. here's where he's wrong in this article: A. the "tenting" experiments have not been very successful. B. Hansen cites the bee gut microbiome paper where researcher fed antibiotics to bees in sugar water at 2x the level used to kill bacteria in cultures. The antibiotics used target gram neg and gram pos bacteria. OF COURSE the microbiome will be affected! The bees will be sick and more susceptible to other infections, etc. Spraying trees in a grove that is not flowering is not the same as poisoning bees in the lab. He also (as predicted) bashes genetic engineering, which has showed some promise.

    3. Just plant young trees? The industry tries this and it is expensive and not as productive.

    Overall, this article should be ignored. It is a non-issue anyway as I am unaware of the oxytetracycline or streptomycin treatments having any real effect on trees. Some anecodtal data suggests it works to a minor degree, but the disease is in the phloem and antibiotics are difficult to get into this tissue.

    The part that bothers me is that this is an industry suffering and may limit the production of fruits that can be of benefit to the diet. The wealthy will always be able to afford them coming in from Brazil or China. I'd like to see American farmers and consumers have continued access to safe and affordable fruit.
  6. skip clements
    Thursday, January 24th, 2019
    Would like to talk to someone about a safe anti biotic that was recommended to the USDA as well as the Florida Department of Citrus years ago. I often wonder if the University of Florida really doesn't care about finding a cure for Greening and Citrus Canker. They have a severe case of the not invented here syndrome. But at the same time I guess that if they did discover a cure for both diseases, the University of Florida wouldn't continue receiving the millions of research dollars each year from the USDA.

    Skip
    772-341-8033
    • Friday, January 25th, 2019
      Hi Skip, Keep in mind that I'm just one voice at UF and my thoughts may not represent those of others or the institution. That said, I can tell you that researchers here would love to never get another dollar to study citrus greening because the disease was eradicated and we can move on to other exciting research in sustainable citrus production.

      We have faculty deeply connected to the citrus industry, and it is a critical part of our state economy, our growers' livelihoods, and employment for thousands of people. There are new potential solutions tested daily from genetics, to nutrition, to physical barriers, to insect control-- and everything in between. We want to solve this problem.

      Furthermore, the university is just a source of innovation, research and technology-- we don't control what the farmer adopts. That is their decision. Sure, we influence it with a great pipeline of products and information, but at the end, they decide what to use. If there is an approved antibiotic, and it worked, they'd be using it!

      If you want to share some specifics about what this antibiotic is, send it by email and I'll follow up with you. kfolta at ufl. edu

      One thought about your note is that citrus canker has been de-prioritized since citrus greening disease (HLB) started in 2005. That might also be a reason for fewer therapies for canker. That disease is less of an issue than a dying grove from HLB.

      If disease problems were solved we would celebrate. There are many things that we'd rather work on, such as improvement of trees to require less management and labor. Mechanisms of robotic harvesting. Trees requiring less water and nutrition. Trees that produce better fruit that the customer loves. There will always be more research to do.

      If we don't solve the disease problem then there is no need to do that other exciting research. While I understand your concern and the apparent optics, I completely disagree. You have people here spending careers dedicated to solving this issue.
    • Saturday, January 26th, 2019
      Kev...Could the problem originate with an antibiotic like Roundup? Along w weeds soil bacteria are decimated and minerals are tied up leading to nutritional deficiencies and immune failure. Applications of minerals and biologicals were found to reverse greening....Glyphosate and other toxins like arsenic in the Roundup formulation do cause human disease, just as nutritional deficiencies, toxins and pharmaceutical side effects do. Beekeepers are avoiding chemical citrus groves due to horrible losses..So I tend to side w Skip...follow the money...Modern IFAS style agriculture is poisoning the planet and destroying the oceans, so why double down on official stupidity??? Legit research would consider the downside of profitable technologies over industry grants.
  7. Jim Nelson
    Sunday, January 27th, 2019
    " it munches a tree’s tender new shoots and leaves... in citrus trees whose leaves have been nibbled by those psyllids"


    Both of these phrases are wrong. The insect can neither "munch" nor "nibble". Its mouthparts allow it only to pierce and suck, not to chew.
  8. Greg Koshak
    Sunday, January 27th, 2019
    What about bacterial phage treatment?

    Bacteria have viral enemies or they would colonize the entire planet. The beauty of using phage treatment is that the viruses also adapt to bacterial defenses.

    There should be a chance of control if the correct species can be found. Certain Eastern European countries denied antibiotics during the cold war kept this knowledge alive for human treatment and recently have provided help for specific cases of antibiotic resistant infection.

    Because the virus targets a specific species of bacteria there is very little chance the cure will run amok in the environment.
  9. Rhodomel
    Wednesday, January 30th, 2019
    The use of the word Extinction is way overblown! It just so happen that most oranges and grapefruits are affected by greening diseases it doesn't mean the extinction of citruses!

    Calamondins, Fortunelas, and some Papedas are highly resistant to greening disease, in fact some cultivars thrive in the middle of greening disease haven.

    Some mandarins and pomelos are also very resistant or tolerant of greening disease.

    When guavas are interplanted, citrus orchards lasts very long and the infection rate significantly lowered that it is just a matter of replacing a few trees affected each year.
  10. Saturday, February 9th, 2019
    i am curious how the disease and pest is being dealt with in china? also, how would replanting trees work if the conditions for this pest is still there? the organic method of raising the temperature within a canopy over the tree seems reasonable and logical and would avoid the issue of using anti-biotics. thank you for the article and bringing this critical agricultural issue into focus.