Lemons in Florida

Lemons in Florida: Something New Under the Sun?

lemons

By Fred Gmitter, Bill Castle and Jude Grosser

King Solomon once pointed out that “there is nothing new under the sun,” meaning that what has happened before will happen again. Although the idea of growing lemons in Florida is viewed by some these days as a new thing, Florida actually has a fairly long history of lemon production.

FLORIDA LEMON HISTORY
Lemons were a part of the Florida landscape in the late 1800s and were seen as a potentially competitive fresh fruit commodity against the newly developing California lemon business, because of proximity to the eastern U.S. marketplace. There were some production problems in the Florida environment, but there still was optimism that growers could make a go of it. It was a viable plan until Dec. 29, 1894, when the first of two “Great Freezes” struck the state. If there was any hope for lemons after the first freeze, a second even colder wave of Artic air came through Florida on Feb. 9, 1895. In less than five weeks, Florida’s dream of growing lemons was put to rest for the next several decades, as the state’s citrus industry learned that cold is a serious limiting factor for lemon production.

Lemons mostly languished as a fresh fruit option for Florida growers until the late 1950s and 1960s. In 1958, a series of articles was published, led by former Citrus Research and Education Center (CREC) Director Herman Reitz. He described the beginning of the latest craze in Florida citrus: planting lemons for processing into lemonade! L.C. Knorr of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Experiment Station (as CREC was called then) in Lake Alfred reported 3,000 acres of lemons in Florida. By 1972, Robert C.J. Koo, also from CREC, reported that there were some 8,760 acres of lemons in the state.

There was some effort to produce fresh lemons near West Palm Beach, on macrophylla rootstock, but costly tree maintenance requirements and a small and elusive window in the marketplace dominated by California meant profitability also was elusive. But major companies such as Minute Maid and Libby, McNeil and Libby were players in the processed lemon game.

Variety trials were planted that included up to 40 different selections in Avon Park and Indiantown. These trials served as sources of fruit for experiments and budwood for nursery propagations. Minute Maid planted substantial acreage of Bearss lemon on rough lemon rootstock in Indiantown, and Libby had lemons at several locations. But, once again, Artic air put a quick end to the lemon business in Florida with the multiple freezes of the 1980s. Aside from a few modest plantings targeting niche markets, lemons in Florida languished again.

Fast forward to 2014 and 2015, when the Florida citrus business was experiencing its greatest existential threat, huanglongbing (HLB). Production was declining precipitously everywhere in the state. Growers, many of them of multigenerational lineages, were dropping out of the business, like the Hamlin oranges were dropping off of the trees because of HLB. Grapefruit production from the Indian River area declined at an even faster rate than did orange and other specialty fresh fruit types.

Juice processing plants that formerly would run almost non-stop from late November through early June, now were closing for weeks at a time. Truck yards that once were full of dozens and dozens of trailers waiting to dump their fruit loads, then go out and load up again, were now more empty than full of cargo. Simultaneously, contemporary consumers were turning away from orange juice as the signature breakfast drink of generations. Supply was down, demand was down, but the ever-resilient Florida citrus industry began to look for another way to survive and be profitable. And once again, lemons came back into the sun.

TODAY’S DIVERSE LEMON USES
Why lemons now? What hope do they provide? Haven’t we learned from the perspective of historical cold events? Is there something new under the sun?

The lemon is a fruit with diverse uses. It can be grown for the fresh market, as it is in most places worldwide, or for processing into juice and various other products. Economists who monitor the marketplace tell us that one of the few types of citrus beverages for which consumer demand is increasing significantly is lemonade and similar drinks. The idle Florida juice processing facilities potentially could be more active, and therefore more profitable, if they had lemons as raw product for processing, especially given the lack of oranges for juicing.

In addition to juice, lemon peel oil is a very valuable byproduct commodity. Many of the world’s soft drink products are flavor-enhanced with a drop of some part of the essence of the lemon oil. Lemon oil is commonly used in many personal care and cleaning products, and lemon fragrances are also important to the food industry for flavoring a wide range of products. The white portion of the lemon peel, the albedo, is a rich and highly desired source of pectin that has many uses in the dairy, confectionary and healthcare industries. Thus, growing lemons is appealing because of its multiple uses and its noted greater tolerance of HLB.

PRODUCTION PROS AND CONS
However, growing lemons is a bit more challenging than growing other citrus varieties mostly because of the growth and fruiting habits. Lemon trees are vigorous and thorny. The latter is no small consideration because of harvesting and extra costs generated by special approaches associated with wiry, thorny trees.

Despite Florida’s repeated experience with growing lemons, it has been hard to avoid the need to relearn the knowledge and tricks needed to produce this fruit. Nevertheless, there is excitement in the air about lemons because they are HLB-tolerant, fast-growing and precocious. Thus, commercial production begins early. If grown for the processing market, there are several options for use of the fruit, all with good income potential. Also, management of a juice-fruit grove is likely more forgiving when it comes to cultural and harvesting costs and practices.

But what of the cold sensitivity of the lemon trees that has spelled disaster many times before? Lemons can be quite cold tolerant, but only if they have the opportunity for good cold acclimation. Such conditions in the widely fluctuating Florida winter climate do not really exist. We cannot say that the threat is not real, despite the increasing average annual temperatures. There still can and will be those few very cold nights. But there are some things to keep in mind about this threat as well.

The serious freeze events that killed lemon groves in the past generally took place before the widespread use of microirrigation systems to weather through the freezes. So, when there are severe cold events in the future, it may be possible for growers to keep at least the trunk and main scaffold limbs alive. If microirrigation succeeds, then the inherent vigor of the lemon tree can regrow new productive canopy faster than probably any other type of citrus tree. For example, the Argentine lemon industry in Tucuman suffered great losses just a few years ago to uncommonly severe freezing, only to see production quickly rebound a mere two seasons later. The lemon crop in Florida would be harvested generally before the coldest times of the year.

ADVANCES IN LEMON BREEDING
One of the lesser known aspects of the UF/IFAS CREC citrus breeding program has been a project to develop new true lemon cultivars that will produce greater quantities of the “liquid gold” that is lemon peel oil. Researchers planted more than 4,000 new lemon clones developed using the same approaches that were successfully used for sweet orange improvement. They measured peel oil production in the Florida environment annually. The goal was to find lemon varieties that had consistently high oil yields, exceeding 8 kilograms per metric ton.

lemons

They succeeded in finding more than a dozen that averaged well over this threshold across at least five seasons of data collection (see graph). These new varieties have been approved for release, and the top three soon will be made available to Florida citrus growers. In addition, a nearly seedless clone will also be released for Florida growers who have interest in the fresh option.

Lemons can be grown more cheaply in other parts of the world, and their concentrated juice can be shipped globally. But when the economic benefits and value of the peel oil are factored in, it begins to seem more plausible for this old crop to be grown profitably once again under the Florida sun. The UF/IFAS broadly targeted citrus breeding program may once again contribute to the suite of options available to the Florida citrus industry to continue to thrive.

Fred Gmitter and Jude Grosser are professors, and Bill Castle is an emeritus professor, all at the UF/IFAS CREC in Lake Alfred.

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Fungus to Target Asian Citrus Psyllid

Scientists Set to See if Fungus Can Stop Asian Citrus Psyllid

Fighting plant disease with jet blast sprays is standard practice for Florida citrus growers fighting Asian citrus psyllid — the vaunted vector of  citrus greening. But, to spray a fungus to control a single insect that carries a disease-causing pathogen is uncommon. With that, scientists from UF/IFAS and the Florida Research Center for Agricultural Sustainability are collaborating to test an insect-killing fungus applied with horticultural oil sprays in a Vero Beach, FL, citrus grove.

Pasco Avery, a Biological Scientist based at IRREC, tested the fungus against the psyllid under laboratory conditions. His findings, which are published in Insects, Biocontrol Science and Technology as well as Florida Entomologist, document the fungus’ promise as an effective biological control agent against the Asian citrus psyllid.

According to Avery, the fungus kills the psyllid but is compatible with beneficial insects like lady beetles, lacewings and parasitic wasps. “The fungus is not a panacea, but it is expected to greatly reduce the problem we have in managing the psyllid populations.”

Bob Adair, Executive Director at the Florida Research Center for Agricultural Sustainability, heard about Avery’s work with the fungus and approached him about using commercial sprayers to distribute the fungus in his groves. Adair has partnered with UF/IFAS on multiple occasions over the years to conduct agricultural research.

Avery carried out experiments in his lab to determine if the oils were compatible with the fungus. He found the oils sustained the fungus and helped it to grow and thrive, he said.

Adair said the next step was to determine its efficacy in field trials in citrus groves. The fungus needs to be tested in outdoor groves to determine whether it can suppress the Asian citrus psyllid population to the point where trees will be protected and that the psyllid will not become resistant to the sprays.

Avery and Adair conducted a first field spray trial in mid-June. About 1 acre of trees was sprayed on one side of the row. The scientists mixed 1% of a commercial product containing I. fumosorosea with stylet oil for 65 pounds of spray. The spray was applied to the trees at dusk with a pull air blast sprayer hitched to a tractor.

Avery said the fungus was effective in suppressing the psyllid population and that it lasted for up to 14 days after application. “What we found with this first experiment was that the fungus was as effective as the active ingredient of the insecticide spinosad,” Adair exclaimed.

A second field trial is scheduled for September. For that trial, both sides of the trees in the same grove will be sprayed with fungus added to the horticultural oil.

These CRISPR-modified crops don’t count as GMOs

These CRISPR-modified crops don’t count as GMOsAuthor

Increasing crop yields through conventional plant breeding is inefficient – the outcomes are unpredictable and it can take years to decades to create a new strain. On the other hand, powerful genetically modified plant technologies can quickly yield new plant varieties, but their adoption has been controversial. Many consumers and countries have rejected GMO foods even though extensive studies have proved they are safe to consume.

But now a new genome editing technology known as CRISPR may offer a good alternative.

I’m a plant geneticist and one of my top priorities is developing tools to engineer woody plants such as citrus trees that can resist the greening disease, Huanglongbing (HLB), which has devastated these trees around the world. First detected in Florida in 2005, the disease has decimated the state’s US$9 billion citrus crop, leading to a 75 percent decline in its orange production in 2017. Because citrus trees take five to 10 years before they produce fruits, our new technique – which has been nominated by many editors-in-chief as one of the groundbreaking approaches of 2017 that has the potential to change the world – may accelerate the development of non-GMO citrus trees that are HLB-resistant.

You may wonder why the plants we create with our new DNA editing technique are not considered GMO? It’s a good question.

Genetically modified vs. gene edited

Genetically modified refers to plants and animals that have been altered in a way that wouldn’t have arisen naturally through evolution. A very obvious example of this involves transferring a gene from one species to another to endow the organism with a new trait – like pest resistance or drought tolerance.

But in our work, we are not cutting and pasting genes from animals or bacteria into plants. We are using genome editing technologies to introduce new plant traits by directly rewriting the plants’ genetic code.

This is faster and more precise than conventional breeding, is less controversial than GMO techniques, and can shave years or even decades off the time it takes to develop new crop varieties for farmers.

There is also another incentive to opt for using gene editing to create designer crops. On March 28, 2018, U.S. Secretary of Agriculture Sonny Perdue announced that the USDA wouldn’t regulate new plant varieties developed with new technologies like genome editing that would yield plants indistinguishable from those developed through traditional breeding methods. By contrast, a plant that includes a gene or genes from another organism, such as bacteria, is considered a GMO. This is another reason why many researchers and companies prefer using CRISPR in agriculture whenever it is possible.

Changing the plant blueprint

The gene editing tool we use is called CRISPR – which stands for “Clustered Regularly Interspaced Short Palindromic Repeats” – and was adapted from the defense systems of bacteria. These bacterial CRISPR systems have been modified so that scientists like myself can edit the DNA of plants, animals, human cells and microorganisms. This technology can be used in many ways, including to correct genetic errors in humans that cause diseases, to engineer animals bred for disease research, and to create novel genetic variations that can accelerate crop improvement.

To use CRISPR to introduce a useful trait into a crop plant, we need to know the genes that control a particular trait. For instance, previous studies have revealed that a natural plant hormone called gibberellin is essential for plant height. The GA20-ox gene controls the quantity of gibberellin produced in plants. To create a breed of “low mowing frequency” lawn grass, for example, we are editing the DNA – changing the sequence of the DNA that makes up gene – of this plant to reduce the output of the GA20-ox gene in the selected turf grass. With lower gibberellin, the grass won’t grow as high and won’t need to be mowed as often.

The CRISPR system was derived from bacteria. It is made up of two parts: Cas9, a little protein that snips DNA, and an RNA molecule that serves as the template for encoding the new trait in the plant’s DNA.

To use CRISPR in plants, the standard approach is to insert the CRISPR genes that encode the CRISPR-Cas9 “editing machines” into the plant cell’s DNA. When the CRISPR-Cas9 gene is active, it will locate and rewrite the relevant section of the plant genome, creating the new trait.

But this is a catch-22. Because to perform DNA editing with CRISPR/Cas9 you first have to genetically alter the plant with foreign CRISPR genes – this would make it a GMO.

A new strategy for non-GMO crops

For annual crop plants like corn, rice and tomato that complete their life cycles from germination to the production of seeds within one year, the CRISPR genes can be easily eliminated from the edited plants. That’s because some seeds these plants produce do not carry CRISPR genes, just the new traits.

But this problem is much trickier for perennial crop plants that require up to 10 years to reach the stage of flower and seed production. It would take too long to wait for seeds that were free of CRISPR genes.

My team at the University of Connecticut and my collaborators at Nanjing Agricultural UniversityJiangsu Academy of Agricultural SciencesUniversity of FloridaHunan Agricultural University and University of California-San Diego have recently developed a convenient, new technique to use CRISPR to reliably create desirable traits in crop plants without introducing any foreign bacterial genes.

We first engineered a naturally occurring soil microbe, Agrobacterium, with the CRIPSR genes. Then we take young leaf or shoot material from plants and mix them in petri dishes with the bacteria and allow them to incubate together for a couple of days. This gives the bacteria time to infect the cells and deliver the gene editing machinery, which then alters the plant’s genetic code.

In some Agrobacterium infected cells, the Agrobacterium basically serves as a Trojan horse, bringing all the editing tools into the cell, rather than engineering plants to have their own editing machinery. Because the bacterial genes or CRISPR genes do not become part of the plant’s genome in these cells – and just do the work of gene editing – any plants derived from these cells are not considered a GMO.

After a couple of days, we can cultivate plants from the edited plant cells. Then it take several weeks or months to grow an edited plant that could be planted on a farm. The hard part is figuring out which plants are successfully modified. But we have a solution to this problem too and have developed a method that takes only two weeks to identify the edited plants.

One significant difference between editing plants versus human cells is that we are not as concerned about editing typos. In humans, such errors could cause disease, but off-target mutations in plants are not a serious concern. A number of published studies reported low to negligible off-target activity observed in plants when compared to animal systems.

Also, before distributing any plants to farmers for planting in their field, the edited plants will be carefully evaluated for obvious defects in growth and development or their responses to drought, extreme temperatures, disease and insect attacks. Further, DNA sequencing of edited plants once they have been developed can easily identify any significant undesirable off-target mutations.

In addition to citrus, our technology should be applicable in most perennial crop plants such as apple, sugarcane, grape, pear, banana, poplar, pine, eucalyptus and some annual crop plants such as strawberry, potato and sweet potato that are propagated without using seeds.

We also see a role for genome editing technologies in many other plants used in the agricultural, horticultural and forestry industries. For example, we are creating lawn grass varieties that require less fertilizer and water. I bet you would like that too.

Florida Land Values Strong Thanks to Rising Economy

Improving economic conditions are showing up in the results of the seventh edition of the “Lay of the Land Market Report.” The report provides an accounting of verified land sales from 2017. The update was released in April during the annual Lay of the Land Conference held at Champions Gate near Orlando.

Dean Saunders, owner of Lakeland-based Coldwell Banker Commercial Saunders Real Estate, publishes the report and hosts the conference. He said the real estate market is firing on all cylinders with elevated activity in all sectors of the market.

“Overall, the residential land market in Florida is very strong as a result of the improving economy, combined with the continued influx of almost 1,000 people per day to the state,” Saunders said. “As demand for residential development land increases, sales of agriculture land in the paths of progress increase. With the capital earned from selling land for high development prices, sellers are reinvesting in other rural agriculture land.”

The heart of residential growth is occurring along the I-4 corridor from Tampa to Daytona Beach. Jerry Parrish, Chief Economist for the Florida Chamber of Commerce, gave some perspective on the growth during the conference, noting that from Jan. 1 to April 6, 83,524 people had moved into Florida, and the state’s adjusted gross income grew by $2 billion. People from New York, New Jersey, Pennsylvania, Ohio, and Connecticut (in that order) lead the migration into the state.

Treasure Coast
The real estate market in the Treasure Coast (Indian River, St. Lucie, Brevard, Martin, and Okeechobee counties) is hot. In Indian River County, 5-acre ranchette lots sold at the bottom of the market in the $10,000 to $12,000 range. According to the report, prices are strongest in Martin County with a few sales in the $25,000 to $50,000 range for home sites of approximately 5 acres.

The region’s citrus industry continues its tailspin in the face of HLB and the devastation brought on by Hurricane Irma.

Grapefruit production estimates continue to fall with the May USDA forecast at less than four million boxes.

Citrus groves that are no longer productive are selling in the $3,500 to $5,300 per acre range, while better producing groves are fetching $5,000 to $8,000 per acre.

Other Citrus Lands
Prices for citrus land ranged widely in 2017 in other production areas, according to the report (Polk, DeSoto, Hardee, Hillsborough, Manatee, Highlands, Lake, Collier, and Hendry counties).

Typical buyers were skilled and seasoned growers. While the report didn’t account for sales for residential or commercial development, groves in the path of development are highly desirable. There is demand for higher-quality, better-producing citrus groves. Marginal groves are in demand where alternative crops are desirable.

Approximately 10,994 gross acres and 9,252 net-tree acres were included in 90 selected 2017 sales in this area totaling almost $70 million. The sale prices ranged between $2,500 and $15,000 per gross acre. Net-tree citrus-acre sales ranged between $2,500 and $17,067 per acre. The average for the sales was $6,278 per gross acre and $7,461 per net-tree acre. The midpoint was $6,688 per net-tree acre. The 2017 price per net-tree acre and price per gross acre are both approximately 4.5% less than in 2016. The volume of acreage sold is approximately 5.3% less than in 2016.

Strawberry Sales
In Hillsborough County, there was some activity with seven sales that comprised 90 gross acres. The price per gross acre ranged from $10,417 to $33,500 for the seven farms sold.

There were three additional sales of farmland for transitional uses in southeastern Hillsborough. Two of these farms were sold for solar farms: one for $18,278 per gross acre and $22,262 per upland acre and the other for $30,771 per gross acre and $31,518 per upland acre. Another sale for high-density residential went for $77,778 per gross and upland acre.

There were two sales in the Plant City and Dover growing areas. A tract that went from strawberry farmland to a solar farm sold for $23,936 per gross acre and $34,622 per upland acre. Another strawberry farm that went to commercial development sold for $125,000 per gross and upland acre.

Farmland sales in Hillsborough reflect continual market shifts into transitional uses. Pressure from urbanization has continued to creep into farming country.

Central Florida Sales
According to the report, there were five notable sales of vegetable farmland in 2017. Quality irrigation land prices remained stable in the area.

Okeechobee County farm sales ranged from $4,849 per upland acre, where conversion from citrus was required, to $7,080 per upland acre for a turnkey farming operation.

The largest farming purchase was in western Manatee County for $6,169 per upland acre. In Polk, Highlands, Hardee, and Okeechobee counties, farmland prices ranging between $5,000 and $7,500 per acre were prevalent.

Institutional investors continue to seek out grower owners willing to sell land for lease-back arrangements on the property.

Everglades Ag Area
Sales of property in the Everglades Ag Area (EAA) were down in 2017. While prices have been increasing in the region, there were only two notable sales last year. One sale was within Palm Beach County and the other one was in southern Glades County. Lands in the central region of the EAA, within Palm Beach County, are the most desirable with prices exceeding $11,000 per acre.

Demand for agricultural lands within the EAA has been high the last few years, but the market’s inventory remains tight.

Residential Development
The land values report tracked residential sales in 17 counties in Florida. Development continues to heat up in the state, particularly around major population centers of Central Florida. Fifteen of the 17 counties showed moderate-to-high finished lot sales activity.

The price for useable, residential land was up 19%, averaging $56,672 per acre. Land values ranged from $223,208 per acre in Martin County to $18,831 in St. Lucie County.

CRDF Rootstock Field Day

The CRDF Rootstock Field Day will begin at 9:30 a.m. The field trial at Peace River Packing Company consists of one common Valencia clone on the following rootstocks: US-812, US-897, US-942, UFR-2, UFR-3, UFR-4, UFR-16, and Carrizo. This site is one of the large multi-location, replicated, three year old trials of Valencia on six candidate HLB-tolerant rootstocks compared to standard trees on US-812. Other locations are on the Ridge (Blumberg) and Flatwoods (LaBelle). Horticultural performance will be discussed along with the distribution of summary data and maps. Attendees will be free to explore the location. Drs. Jude Grosser and Kim Bowman will be speaking. There will be one CEU in crop management for CCAs. For more information, please contact Chris Oswalt, 863-519-1052, wcoswalt@ufl.edu

The Status of Orange Juice Supply

The Status of Orange Juice Supply

orange juice

By Marcos Fava Neves

The newest estimate from the U.S. Department of Agriculture for the 2017–18 season shows Florida with only 46 million boxes of oranges coming from 50 million trees, which represents 33 percent lower production than the 2016–17 season. High droppage and small fruits are also expected.

Rabobank estimates Florida’s juice production at 235,000 tons [frozen concentrated orange juice (FCOJ) equivalent] in 2017–18 and 250,000 tons in 2018–19. Total output in 2016–17 was 390,000 tons. The orange juice chain is fortunate that Brazil has 385 million boxes and is able to supply the world markets. However, if a huge price increase occurs, that could further damage juice consumption.

BRAZILIAN EXPORTS UP
Since the beginning of the current season, exports from Brazil are 25 percent higher in volume and 32 percent higher in income. Because of Hurricane Irma’s damage to Florida citrus, approximately 30 million boxes now have to be crushed and diverted to the United States, complicating logistics.

Rain came back in Brazil, but extreme weather created problems for the first bloom. The effects on the 2018–19 crop are unknown at this point, but will be announced on May 10. Rabobank estimates Brazilian 2017–18 production at 1.2 million tons of FCOJ, including approximately 335 million boxes for crushing and 50 million for the internal market. Rabobank’s 2018–19 projection of 950,000 tons is a little bit more conservative. The estimate also shows a demand decline of 4 percent per year in the next two years.

BIG BRAZILIAN CROP
The new Fundecitrus estimate published on Dec. 11 for the current crop in the Brazilian orange belt is 385 million boxes, coming from roughly 175 million trees. It is 57 percent higher than last year, nearly 3 percent larger than the last estimate, and 5.69 percent greater than the initial estimate published in May.

Fruits have bigger weight due to above-average rains at the beginning of the crop and better treatment of the orchards. As of mid-December, early-season oranges are almost all harvested, mid-season oranges are 90 percent picked, and late-season oranges are approximately 60 percent harvested. Factories are working at full capacity to process this large crop.

MARKET OUTLOOK
Some recovery of the very low and dangerous juice stock levels will be seen, but we will still be dependent on a good 2018–19 crop to bring normality back. Current prices are good for farmers.

I expect juice prices in Europe to be near $2,400 to $2,500 (bulk FCOJ price per metric ton) for the coming months. If Brazil’s current crop (July to June) was as small as last year’s crop, combined with the problems of the Florida crop (October to September), there would be a huge shortage, causing terrible problems for the world’s orange juice supply. With Brazil’s large expected production, fortunately this is not the case.

Marcos Fava Neves is a professor at the University of São Paulo (Brazil), international adjunct professor at Purdue University (Indiana) and author of “The Future of Food Business” (World Scientific, 2014).

* Courtesy of SE AgNet Media

Citrus officials cleared to use bactericides another year

“It’s a good thing we got it so we can re-evaluate it,” said John Barben, an Avon Park grower and president of Florida Citrus Mutual in Bartow, the growers’ trade group. “It’s a tool in our toolbox, and we need all the tools we can get.”

The EPA had long approved use of the three bactericides — two brands of oxytetracycline and a streptomycin compound — for stone fruit and other crops but not for citrus. Research sponsored by the Lake Alfred-based Citrus Research and Development Foundation Inc., the chief scientific agency in the fight against greening, showed the bactericides could diminish the effects of greening, including increased levels of pre-harvest fruit drop and smaller fruit.

In March 2016, the agency approved a one-year “Section 18” special-use exemption for citrus. The EPA on Jan. 17 approved a third year of the exemption.

“I applaud the EPA’s decision to once again allow the use of antimicrobials on diseased citrus trees,” said U.S. Sen. Marco Rubio in a press statement following the decision’s announcement. “Our iconic citrus industry has long battled greening, and especially following the devastation of Hurricane Irma, this announcement is greatly appreciated. However, Florida agriculture is still in desperate need of disaster relief to help replace lost trees, rehabilitate flooded groves, and assist beleaguered farmers. I continue to work with my colleagues in Congress to secure this much-needed support for Florida farmers.”

Barben said he and many other citrus growers began using the bactericides right after the 2016 announcement. He said he plans to continue using the bactericides this season but at reduced rates because of the economic impact from the fruit lost to Irma.

“It’s an expensive spray,” he said. “These days you have to be careful what you put out there. You have to consider how much bang for the buck you get.”

Harold Browning, the chief operating officer at the Citrus Research Foundation, welcomed the EPA announcement, but he acknowledged the scientific data on the bactericides’ effectiveness is “noisy,” meaning there’s conflicting data.

Irma has complicated the ongoing effort to assess their effectiveness, he said. That’s because the storm dramatically reduced citrus tree yields, the number of fruit harvested per tree, one of the chief bactericide benefits.

Barben saw a 12 percent decline in the harvest of early and mid-season orange varieties, picked November to March, this season, he said. But he counted about one box of fruit per tree on the ground because of Irma, which would have meant an increased harvest but for the storm.

There was some good news about bactericides from Tom Jerkins, president of Premier Citrus in Vero Beach, one of the state’s largest growers, Browning said.

In a presentation earlier this week at the Florida Citrus Show in Fort Pierce, Jerkins reported a 15 percent yield increase in his 2016-17 crop of Valencia oranges, picked from March to June, he said. He had been using bactericides since 2016.

The increase is similar to results in some other studies, Browning said.

“There seems to be come convergence” on the 15 percent increase, he said.

In an email to The Ledger, Jerkins declined to make the presentation available. He could not be reached on Friday to comment.

EPA officials have indicated they will have a decision on full approval of the bactericides for citrus in the first half of this year, Browning said. However, that date could be extended.

Greening is a bacterial disease that eventually kills a citrus tree. Infected trees produce fewer and smaller fruit, and they tend to drop what fruit they do produce before harvest.

Kevin Bouffard can be reached at kevin.bouffard@theledger.com or at 863-401-6980.