Also in this week’s Field Report, a deeper look at the global fertilizer cartel, and the political battle over SNAP continues.
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September 18, 2014
Ben McLean is oddly optimistic for someone fighting, daily, to save his company. The Florida farmer and vice president of Uncle Matt’s Organic says he has seen the fruit on around a third of his citrus trees turn green, hard, and inedible.
McLean’s losses mirror the rest of the state’s citrus industry, which has lost an estimated $4.5 billion to “huanglongbing” (HLB) or Citrus Greening Disease. But as an organic farmer, he can’t spray synthetic pesticides to kill the tiny, scaly insects called the Asian citrus psyllids, known for transmitting Candidatus Liberibacter, the pathogen that causes the disease. In the last year, he has had to approach the problem with a lot of creativity and perseverance. But McLean doesn’t think he’s any worse off than his conventional counterparts.
Much of the coverage of Citrus Greening Disease–including this widely discussed New York Times article from July 2013–has pointed to early trials of a genetically engineered (GE) orange tree bred to be resistant to HLB as the only real solution. But McLean isn’t so sure.
“I don’t know that we’ll ever have a genetically engineered solution approved for the citrus industry, and from what I can tell it’ll probably be 10-12 years before those trees could even be in significant commercial production,” he says.
And, since organic food doesn’t allow for the use of GE varieties, he wouldn’t be able to plant them anyway. But the bind he and other organic citrus producers face might also lead to solutions that can benefit the whole industry.
McLean is using a combination of sprays–including some made with neem oil–as well as Tamarixia radiata, a tiny beneficial wasp that prey on the psyllids alone, and a naturally occurring bacteria that feeds on the psyllids.
“As of today, we can’t get the high levels of psyllid control that conventional folks can. But even then the disease is still spreading rapidly,” he says. “I think we have to manage psyllid populations rather than try to get them to zero, because that hasn’t been achieved by anyone.”
McLean is also working with the Organic Center, and researchers from the University of Florida on an array of other ecologically friendly options.
Looking to the Roots for Answers
Perhaps as important as the presence of the psyllids is the health of the trees’ roots. Earlier this year, researchers at the University of Florida discovered that Citrus Greening Disease attacks roots long before the leaves show signs of damage–a fact that explains why trees may have the disease for as long as two years before it makes itself visible to farmers.
With this in mind, McLean says he has found that regular applications of high-quality compost has made a big difference in terms of how the root systems of the trees he manages are performing. “We’ve found some success in revitalizing root systems using filtered molasses and seaweed mixtures,” he says. “There are also some probiotics out there that have beneficial microbes in them and they have been showing some promise.” The hope, he adds, is that when applied to the soil, those beneficial microbes get into the tree and clean out the pathogenic bacteria causing greening.
“I’m encouraged by what I see,” says McLean of the preliminary results.
Jessica Shade, director of science programs at The Organic Center, shares this sentiment. She is working to raise $300,000–including a $15,000 crowdfunding effort and a possible grant from U.S. Department of Agriculture (USDA)–to continue the collaboration.
Now that The Organic Center is part of the member-based Organic Trade Association (OTA), Shade has a particular interest in saving the organic orange juice industry, which produces around 60 million gallons of juice a year, or around 10 percent of the industry as a whole. But she says she’s also interested in a solution that takes biodiversity into account.
When conventional citrus farmers spray pesticides–many of them systemic pesticides like neonicitinoids–all the Asian citrus psyllids die, but so do the good insect populations that keep those numbers in check. “Over time,” says Shade, “the Asian citrus psyllid numbers will rebound because all of their enemies are dead. We want to make sure that the methods we work with maintain health populations of those native predators.”
University of Florida scientists are also looking at trees that are naturally resistant to the disease. “There are two groves that appear to be resistant,” says Shade. “We don’t know if the tree is resistant to the bacteria, or if it’s not attractive to the Asian Citrus psyllids, but for a long-term solution we’re looking at naturally-occurring resistant genes that can be bred using traditional breeding techniques (no GMOs).”
Will California Oranges Be Spared?
Meanwhile, in southern California, where citrus greening has only been found in one tree but psyllids have spread wide and far, scientists are doing what they can to minimize the damage that is very likely ahead.
The USDA has pledged $1.5 million to help the state–which grows 80 percent of the nation’s citrus sold as whole fruit–to produce and unleash around a million of the psyllid-killing wasps a year.
According to David Morgan, who heads the effort for the California Department of Food and Agriculture (CDFA), about 80 percent of the wasps the state has released have been in a 7, 000 square mile urban area spanning from Ventura County down to Imperial County. “We release them about every three miles,” he says.
The idea is to pre-empt the disease in backyard citrus trees, which could easily become a vector spreading Citrus Greening to farm orchards. They’re also breeding and releasing the wasps on farms, with an increased concentration on abandoned orchards and organic orchards.
“That’s a way of assisting them with their protection of their crop against this pest,” says Morgan. “[The psyllid] is very small and it reproduces very quickly. It has now covered such a huge area that we don’t have enough man power or money to be able to carry out an eradication program, but we’re trying to find a way to reduce the population.”
It’s an ominous wait. “It’s kind of like Ebola,” says Morgan. “Only Ebola takes 21 days. Citrus Greening takes two years.”
When it comes to longer-term solutions, Morgan says that while genetically engineered orange trees might in fact be part of the equation, he sees a great deal of possibility for organic growers as well.
“Somewhere along the lines there’s a possibility that these plants lost their ability to be resistant against this disease. People are actually going back and they’re looking at wild types of citrus and seeing whether any of these are resistant to the disease. They could use classical breeding to do that, but it will also take time,” Morgan says.
Because commercial citrus trees are essentially two trees—the rootstock and a second tree that has been grafted onto it to bear fruit—Morgan believes there are more opportunities to find and breed resistant varieties in the long run. “A lot of what we’re doing is to try to keep the citrus industry alive until then,” he says.
For organic farmers, the cost associated with keeping some or most of their orchards is are not small. Ben McLean says all the solutions he’s tried cost at least several hundred dollars per acre. “But they’re all worth doing and exploring because the only alternative is complete destruction of our crop,” he says.
A few Florida citrus farmers he knows are making the switch to conventional methods, with the hope they will have more tools to fight Citrus Greening. But considering the growing demand for organic juice, Uncle Matt’s Organic is committed to organic farming. Plus, says McLean, “from what I’ve seen, there’s nothing to switch back to. The conventional side is suffering too.”
The Organic Center’s Jessica Shade hopes that the research happening now will ultimately be a boost to the entire industry at a time when every effort matters. “It would be great to see these results incorporated into all citrus greening control strategies, regardless of whether people choose to grow using organic or conventional methods,” she says.
Photo credits, from top: Photo of orange grove courtesy of Uncle Matt’s Organic, photo of oranges affected by Citrus Greening Disease by T.R. Gottwald and S.M. Garnsey / USDA APHIS, and photo of Asian citrus psyllid by Florida Department of Agriculture / Jeffrey Weston Lotz.
June 7, 2023
Also in this week’s Field Report, a deeper look at the global fertilizer cartel, and the political battle over SNAP continues.
http://www.fruitmentor.com/how-you-can-stop-citrus-greening
The transgenic citrus from university of Texas would be on the market now if it really worked.
In Florida there are breeding the flying dragon rootstock into varties for HLB resistance.
https://www.youtube.com/watch?v=Kmu9FdsH3ug
We have found out this technology works on other tree diseases and other trees like apple, peach, pomagrante, and avacoda to produce organic fruit.