The newly named director of the Citrus Research and Education Center Michael Rogers was in Washington, DC, recently to testify before the House of Representatives’ agriculture subcommittee. Rogers had served as interim director of the Lake Alfred-based facility since November 2014.
Rogers testimony focused on the current challenges brought on by HLB and the need for continued financial support of research.
Rogers told members of the committee, that while HLB was first documented in Asian countries in the late 1800s, there was very little known about the disease when it was first confirmed in Florida in 2005. He said, in those Asian countries, the lack of knowledge about the disease made commercial-scale citrus production not economically feasible. But when the disease hit both Brazil and the U.S. — the leading citrus producers — the quest for knowledge was set into high gear.
In addition to research by the scientific community, growers have adopted more aggressive fertilizer programs and psyllid control regimes. However, these practices come with a cost, pushing up production expenses from $800 to $2,000 per acre. He went on to testify that since HLB has spread endemically, that it was not economically viable to remove infected trees in many cases.
“Instead, growers are attempting to maintain the health of these infected trees using improved fertilization programs,” Rogers told the committee. “These improved fertilization programs appear at best to only slow the rate of tree death, but do little to prevent fruit drop prior to harvest.”
Why So Long?
Rogers told the committee that he is asked all the time why it is taking so long to find a cure to HLB.
“The reason is this is a very tough disease to work with,” he said. “Our research began with minimal accurate information on this disease. This is complicated by the fact the bacterium that causes the disease had not and has still not been grown in culture in the laboratory to date. The inability to grow the bacteria in the lab greatly limits the research that can be done to find a cure.
“Furthermore, a thorough understanding of how the disease develops, from start to finish, is required to develop ‘the cure.’ In the case of citrus greening, this is a disease of a perennial crop that takes years to progress through the disease cycle. Compared to an annual crop such as wheat or corn where you can study a complete disease cycle in a matter of months, studying the disease cycle in a citrus tree takes years. This increases the time to get results and requires lots of funding.”
Despite all that, Rogers said scientists have made tremendous advances in understanding the disease and have learned more about HLB in the last 10 years than was known about the disease the previous 100+ years.
Rogers noted that long-term breakthroughs in HLB most likely will come on the molecular front.
“The genomes of the psyllid, the greening bacterium, and citrus itself have all been sequenced,” said Rogers. “With this information in hand, researchers are now able to target specific genes required for survival of both the insect and the disease-causing bacterium. For example, researchers have used such approaches to successfully control psyllids by interfering with their ability to fly and feed on plants, thus preventing the insect’s ability to spread the disease. Genes also have been identified that could potentially provide resistance to the disease-causing bacteria. Citrus trees with these genes for resistance are being tested in field trials and, the results to date look promising.”
He also noted promising results being seen by UF/IFAS and USDA plant breeders seeking new HLB-tolerant rootstocks and varieties.
“These plants are described as tolerant because while they may become infected with the greening bacterium, field studies have shown they will survive and produce fruit for a longer period of time in the presence of greening compared to varieties previously grown in Florida,” he said “To date, 18 of these potentially tolerant varieties have been made commercially available for growers to use in replanting their groves.
“Progress has been made developing other tools that could soon be used in the near-term for managing greening disease. Examples include the development of compounds that can be applied to the trees to kill the bacteria in the plant. Numerous bactericidal compounds have been screened in laboratory and greenhouse trials. The most promising candidate compounds are now being tested in field trials as possible tools that can be used by growers to reduce or eliminate the effects of the disease.”
Time And Money
While progress is being made on the scientific front, Rogers did caution solutions were still “years out” before becoming a reality in groves.
“While there are many potential research solutions being developed that hold promise, putting that ultimate answer in the hand of growers is still years away,” he said. “If we had a citrus tree today that we knew for certain was resistant to this disease, it would take two to three years to scale-up commercial nursery production of that resistant tree for purchase by growers. If the resistant plant happens to be a GMO, the regulatory red tape adds even more time to make that a reality. Once a grower is able to plant trees resistant to the disease, it will take at least four years for those trees to begin producing a harvestable crop, and additional years beyond that time to recover the costs 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 thanked Congress for the federal research funds already dedicated to finding solutions to HLB and urged them not to give up on Florida’s signature crop.
“Your financial support for further research is crucial for the future of citrus growers not only in Florida, but throughout the entire country,” he said.