EPA approves two technologies to fight citrus greening

Florida workforce halved, processors drop from 54 to 4

For 20 years, an incurable bacterial disease has ravaged Florida’s orange groves, causing fruit to drop before it is ripe and leaving it tasting bitter. Florida’s orange production—more than 90 percent of which is used for juice—is down 95 percent since the arrival of the disease, called citrus greening, with about half a million acres now sitting dormant. Last year alone, 60,000 acres — roughly 26 percent of the state’s remaining total — went out of production, with other abandoned groves absorbed for cattle grazing or Florida’s lucrative development sprawl.

The disease clogs trees’ vascular systems, choking off water and nutrients. It is carried by the Asian citrus psyllid, a non-native insect so tiny it can be mistaken for pollen, and spreads Candidatus Liberibacter asiaticus as it sucks sap from the plants, traveling from grove to grove with little more than a light breeze. Pesticides have proven difficult to control the pathogen.

The two technologies approved by the EPA this year take different routes against the disease. Soilcea submitted data showing its CRISPR-edited rootstocks are thousands of times more resistant to the greening bacterium than existing trees — high enough to be considered uninfected by scientific standards. The EPA approved commercial use in April, making it the first commercially released CRISPR-edited crop specifically edited to fend off disease, according to Nian Wang, the University of Florida microbiologist who identified the genes that enabled the technology.

“This is the future of our industry,” said Fran Becker of Peace River Citrus Products.

An orange tree is really two plants grafted into one. The rootstock forms the roots and lower trunk and helps determine how well the tree withstands disease and its environment. The scion above it determines the type of fruit. Soilcea sells only the rootstocks. It uses a harmless bacterium to insert DNA into the rootstock exactly where it is needed to give the tree resistance. Agromillora Nurseries is growing more than a million of the modified trees, and citrus growers have already signed up to buy them. Gary Farmer, the nursery’s head grafter, says it is the first real hope he has had in 20 years.

“I’ve seen millions of trees come through here, and every one has more or less perished,” Farmer said.

The second technology comes from Silvec, which recently received EPA approval to help trees already standing in Florida’s groves.

In earlier efforts to signal immune responses in plants, scientists had encountered a big problem. Peptides—essentially biology’s fast signaling agents—break down quickly. In a plant, that means any antibacterial effect they have fades quickly.

“It was like taking only one pill of your antibiotic regime,” says Rafael Simon. The former venture capitalist formed Silvec with his sister Anne Simon, a virologist and professor of cell biology and molecular genetics at the University of Maryland in College Park. Anne Simon aimed to make the peptides bigger so they don’t break down as quickly, and use a harmless virus to produce those peptides continuously.

Silvec licensed the technology from U.S. Sugar and has developed it further, increasing levels of the antibacterial peptide in treated trees by at least 100 times, with bacterial counts in treated trees dropping by at least 90 percent, according to the company. The company is seeking fast-tracked authorization for thousands of acres of experimental plots of a stronger, commercial version. Growers are gathering on Sept. 30 to preorder the trees, with inoculated scions being propagated at Philip Rucks’s nursery.

The company is also testing a small patch containing the virus that can be tapped onto the trunk of trees that are already infected, allowing it to enter the tree and begin producing resistance.

Florida is providing subsidies to growers for the resistant trees through a $330 million package over two years. But rebuilding will require more than new plantings. University of Florida studies show the industry lost more than half its workforce between 2003-04 and 2020-21. Only four companies remain in the state that process Florida oranges for juice — down from a peak of 54 in the 1980s.

“What we really need is people to come back into the business. If we don’t, I’m scared of where we might end up,” said Fran Becker, senior vice president at Peace River Citrus Products, one of the four remaining processors.

Philip Rucks, a longtime citrus and nursery owner in Frostproof, has turned his own nursery into a real-world laboratory for the new technologies. About a decade ago, with greening pushing him toward bankruptcy, Rucks diversified into blueberries, bamboo, and ornamental plants.

“We’re just desperate trying to find alternatives,” Rucks said. Driving through Frostproof, where he grew up, Rucks pointed to railroad tracks once lined with citrus packing houses. Today, a giant junkyard sells equipment from dismantled juicing plants.

“This used to be a vibrant town,” he said.

Florida’s growers have weathered previous catastrophes — freezes in the 1980s that ruptured fruit cell membranes and turned new growth black, citrus-canker lesions in the early 2000s that prompted state contractors to fan out with woodchippers to destroy trees, and three successive hurricanes that tore through the spine of Florida’s citrus belt and uprooted entire groves — but none proved as ruinous as citrus greening.

Even if growers can rebuild supply, demand is uncertain. Orange juice consumption has fallen by more than half since the onset of the greening crisis, driven by soaring prices for not-from-concentrate juice and competition from other beverages at breakfast.

The new technologies may be able to help the wider agriculture industry, as well as citrus growers. Both of the new solutions can be adapted to provide a defense against a variety of diseases that plants can’t fight on their own. Anna Whitfield, who works with emerging plant disease and global food security at North Carolina State University’s Department of Entomology and Plant Pathology, says scientists hope to use the technologies to fight things like Pierce’s disease, a fatal bacterial infection in grapevines, and maize lethal necrosis, which stunts and destroys corn.

“The sky is the limit with using these Crispr technologies and with using viruses,” Whitfield said.