How long will Florida growers be able to fight citrus greening?

By Sarah Gonzalez

© Copyright Agri-Pulse Communications, Inc.



WASHINGTON, July 1, 2015 - As researchers continue testing potential solutions for citrus greening disease that is plaguing Florida's $10 billion fruit industry, more groves and packing houses are shutting down or consolidating.

Florida growers first detected citrus greening disease, technically known as Huanglongbing (HLB), in 2005. The bacterial disease then proceeded to spread to most of the state's citrus counties by 2008 and now affects most of the fruit-bearing trees in Florida. HLB is transferred by the Asian citrus psyllid, and is so devastating that 30 percent of the root mass of the tree is lost before above-ground symptoms are observed.

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Florida had 845,000 acres in citrus in 1998, a figure that fell to 515,000 acres by 2013.  Recognizing the urgency of the problem, Congress authorized $125 million in research related to HLB over five years in the 2014 farm bill.

Michael Rogers, of the Citrus Research and Education Center at the University of Florida, testified during a House Small Business subcommittee hearing last month that the disease is reducing Florida's orange crop to the smallest since 1966. The 2015 harvest is predicted at 96.4 million 90-pound boxes, down from 240 million in 2003.

Peter Chaires, executive director of the New Varieties Development and Management Corp., told Agri-Pulse that the Florida citrus industry has essentially been cut in half since it first discovered the disease.

“Florida citrus faces another round of brutal consolidation this next year, as companies try to survive until a tool is available to combat HLB,” Chaires said.

Michael Sparks, CEO of Florida Citrus Mutual, in a briefing to the Florida congressional delegation, explained that the state lost 24 fresh fruit packinghouses in the past decade as well as 20 small juice-processing plants.

Meanwhile, the genomes of the psyllid, the greening bacterium, and citrus itself have all been sequenced, helping to accelerate genetic research into the disease.

One of the potential solutions to citrus greening is a genetically engineered orange tree variety being tested in field trials right now. However, Rogers noted that it could take three years to scale up commercial nursery production of a resistant tree for purchase by growers.

An additional obstacle to a biotech variety is the regulatory process that genetically engineered plants must go through at USDA and FDA, which will add to the timeline before they can be commercialized.

“The approval process is a serious obstacle, as many Florida citrus companies can't survive long enough for products to be cleared through traditional procedures,” Chaires said.

For now, some growers are relying on new conventional varieties that hold up to the disease for a longer period of time than previous plants.

“We don't know how long this tolerance will last but anything that growers can use as bridge to the future...they're taking advantage of it,” Chaires said.

These varieties consist of newly developed rootstocks with heightened levels of tolerance, as well as scions that are stronger in the field. A rootstock is the root system of the plant, which greening depletes first. The plant part grafted onto the rootstock is the scion.

According to Rogers, 18 of these potentially tolerant varieties have been made commercially available for growers to use in replanting their groves-a process that can be especially costly.

Even when a new variety is planted, the tree doesn't bear a harvestable crop for four years, and it takes even more years to recover the cost required to grow the trees to that point."

“This is a discouraging prospect, especially for the small citrus grower who is currently struggling to stay in business,” Rogers noted.

Chaires noted that other growers are “waiting on a bactericide” before risking replanting. A bactericide, or any form of antibiotic that kills the bacteria that lives within the tree, is needed to sustain current trees while the industry waits for a truly resistant plant, he explained. 

The HLB bacteria lives in the phloem, a layer of tissue in vascular plants, making delivery of a bactericide very difficult as most substances contain molecules that are too large to get to the disease. The challenge is being addressed in research labs around the globe, but once a viable solution is discovered the substance will have to go through EPA and FDA approvals.

As growers experiment with new rootstock varieties and thermal heating applications that may prolong an infected tree's productivity, they are doing everything they can to monitor and nurse the health of their groves. Florida citrus growers provided more than $90 million in research funds over the past 10 years through self-imposed taxes on their production, Rogers noted.

He said temporary improvements in citrus health include better psyllid management programs, as well as improvements in tree care through nutrition and root health programs.

“However, simply put, these improvement are just a bandage on a gaping wound,” he told the House Small Business Subcommittee on Agriculture, Energy and Trade. “They won't solve the problem, but instead serve to slow the bleeding.”

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