Sowing the Seeds of Hope for Florida Citrus

Sowing the Seeds of Hope for Florida Citrus


In other words, the Bureau serves to encourage and enable nurseries to establish and maintain private budwood sources (scion and increase blocks), and can supply budwood to nurseries when private sources are insufficient.

However, any trees that wish to be used in this process will have composite testing done at the 36-month period to allow their eligibility for the additional 24 months. This will enable the nurseries to keep these trees in budwood production longer, without having to cycle in new trees. This seems like a simple step, but it is yet another incremental improvement in the process and a means of addressing the pressing needs of industry.

A Numbers Game
There were 21.6% fewer total citrus tree propagations in the 2016-2017 season than the prior year. DPI’s budwood cutting decreased 22%. Sixty-four percent of the budwood used for propagations is now coming from private sources. Essentially, the system is performing as designed. Once better HLB solutions are available, there may still be some lag time in ramping up budwood quantities, but steps are being taken to improve preparedness. Strategically, DPI has been comprehensively studying the entire process of citrus tree production and how they might proactively tackle the next impediment to rapid industry expansion. It would be tragic to have access to better tools to combat HLB, experience a sharp increase in the demand for trees, and not have the ability to produce and supply. These discussions rapidly focused the conversation on rootstock seed availability.

The number of new rootstocks available to nurseries and growers has be rapidly escalating. Many growers are experimenting with a range of scion/rootstock combinations, while larger trial plantings are hoped to produce data that will further inform future planting decisions. Growers are sometimes forced to alter their planting plans as seed for the most popular (and hopefully tolerant) rootstocks (US 942, UFR-5, etc.) is in short supply. Seed availability from UF/IFAS Southwest Florida Research and Education Center (SWFREC), A.H. Whitmore Foundation Farm, and private sources is not meeting demand.

What about rootstock liners from tissue culture (TC)? Doesn’t that solve the problem? Relative to overall demand for citrus trees, TC liners are certainly coming online at just the right time, but more seed is needed. Liners from seed are less expensive for nurseries to produce, and locally produced seed has a higher germination rate than imported seed. Any project to increase rootstock seed availability would be complementary to escalating TC liner production. Seed will continue to be in short supply. TC production will help fill the gap until seed production catches up. There will always be nurseries and growers who prefer one over the other.

Prime Property to Grow On
The Bureau’s Chiefland budwood facility is located on Florida Forest Service property. This location has been ideal for its current purpose, as it is far enough from the coast to provide limited protection from coastal storms and is outside of the main citrus production areas. It just so happens that a 10-acre block of Florida Forest Service land is available (and has been donated) just south/southwest of the existing Budwood facility.

This property has been deemed suitable for a new seed block planting. Since the trees will be outdoors and exposed, it would not be ideal to have the seed block adjacent to the budwood screenhouses. This new seed block site is approximately 1 mile away from the current structures (as the crow flies). The new block will accommodate 40 to 50 rootstock varieties, with greater volumes of those currently in high demand.

The trees for the project will start their life at the FDACS LaCrosse Phase II Budwood Facility. Here, seed has been planted (enough to produce 2,000 trees) to serve as a root system for the seed source trees. Once the base rootstock trees are of sufficient size (it is anticipated that this will be February 2018), they will be grafted with budwood of the target commercial rootstock varieties. All of this will be done inside a clean, protected facility. The plants will then be transferred to the Chiefland block in August 2018. It should take approximately three to four years before fruit is available for seed harvest from these trees. Larger volumes of seed will be available in 2020-2021.

Most of the trees in the new seed block will be planted on X-639, but DPI is considering planting some seed trees from rooted cuttings so that production could be restored more quickly after an extreme cold weather event.

Stocking Up
The Florida Nursery, Growers and Landscape Association administered a grower survey in December to help determine the rootstock varieties that should be included in the new block. As more promising rootstocks are identified, they will be added to the DPI block, and eventually less successful selections will be replaced. All equipment to be used in the management of the new seed block will be dedicated to the farm to further minimize exposure to outside infection. Equipment is being sourced to enable DPI to perform the seed extraction on premises.

Funding for this project is being provided through the Citrus Health Response Program. This is a one-time funding source intended to address Florida’s declining rootstock seed production over the past seven years. HLB has reduced the volume of fruit on rootstock source trees and in some cases, the volume of seed per fruit. The seed block will be maintained using other funding sources moving forward. One additional staff position will be required for the project, but the seed block will be managed through the FDACS Chiefland office.

Though there are no guarantees, the industry continues to demonstrate its belief that better days are ahead and solutions will be found. Any actions that will enhance Florida’s capacity to recover are welcomed and appreciated; as is the forward thinking responsible for their implementation.


Engineering HLB Tolerant/Resistant Tress

Progress on Engineering HLB-Tolerant/Resistant Citrus

By Manjul Dutt and Jude W. Grosser

Huanglongbing (HLB) threatens the survival of the Florida citrus industry. Both conventional cultivars and genetically engineered cultivars that can grow in the presence of HLB have been developed at the University of Florida’s Citrus Research and Education Center (CREC) in Lake Alfred. Among the two citrus improvement techniques, engineering citrus remains the fastest method for the improvement of an existing commercial cultivar and has been a key component in CREC’s overall citrus improvement strategy.

In nature, plants are constantly attacked by pathogens; however, most attacks do not lead to infection. Plants resist getting infected with several invading pathogens by turning on their internal defense system, which is similar to the human immune system. This internal defense system is activated by a localized resistance reaction, which subsequently spreads throughout the plant. As a result, several protein molecules are produced inside the plant. These proteins, called the pathogenesis-related (PR) proteins, are ultimately responsible for preventing the invading pathogens from causing disease. The overall process of this immunization technique is called systemic acquired resistance (SAR).

Engineered citrus, which can manipulate the way in which these PR proteins are activated, can potentially keep the plant primed against infection and effectively combat diseases. This mechanism of induced defense can confer long-lasting protection against HLB.

Currently, a population of engineered sweet orange trees expressing the Arabidopsis NPR1 gene is being monitored for resistance to HLB. Several transgenic lines have been observed to provide durable resistance against HLB. Several lines have remained HLB-negative for over five years, although they have been planted at a site with >95 percent HLB infection (see Figure 1).The Arabidopsis (a mustard plant relative)-derived NPR1 gene plays an important role in priming the production and expression of PR proteins. This gene acts as a switch and aids in the activation of the PR proteins. CREC study has shown that citrus trees that are engineered with this gene have many activated disease-fighting PR genes.

Unfortunately, these transgenic Hamlin plants also contain the green fluorescent protein (GFP). GFP-expressing plants cannot be commercialized currently, as the GFP gene has not yet been approved for human consumption (although it comes from jellyfish that are consumed by humans). Selected sweet orange cultivars such as EV1, OLL-8, Valencia, Vernia and others are being retooled to express the Arabidopsis NPR1 and protect trees against HLB. These new trees are being produced without GFP.

Additional genes, such as the tobacco-derived SA-binding protein 2 (SABP2) or the citrus-derived β-1,3glucanase (BG)gene, have also been inserted into citrus with promising results. The SABP2 gene is critical for the plant immune response; although BG is a PR gene, it may also reduce phloem plugging. Several transgenic rootstock lines expressing NPR1 have also been produced. These are now being grafted with commercial, non-GMO sweet orange scions for field-testing to determine if the improved tolerance can be transmitted to the scion.

Gene stacking involves the expression of multiple genes in plants. Citrus is a long-lived perennial tree, and it is indeed possible that Candidatus Liberibacter asiaticus (CLas), the bacterium that causes the HLB disease, could mutate over time and become tolerant to the effects of a specific gene. This could result in the breakdown of disease resistance. Thus, the CREC team is engineering trees (scions and rootstocks) that contain two or more transgenes stacked in the plant that can back each other up. These plants are in the primary stages of evaluation, and their long-term ability to resist CLas is presently unknown.

This was done by enhancing the expression of the citrus flowering locus T (FT) gene. FT has been implicated in the induction of flowering in many plants. Like the NPR1 described before, FT can also travel through the plant’s vascular tissues. The hope is that an engineered precocious rootstock can stimulate the above-ground scion to flower in a much shorter time than naturally possible.

Depending on the cultivar, citrus can remain juvenile for three to 10 years. This long juvenile phase hinders the evaluation of hybrids in the conventional breeding program as well as the engineered citrus developed from juvenile tissues. A reduction in juvenility can significantly reduce the assessment time for both, thus accelerating commercialization. Engineered Carrizo citrange rootstocks that flower within the first two years (Figure 2) have been developed.

This would enable rapid cycling through the breeding population to identify select lines that can be subsequently evaluated on a larger scale. Moreover, it would aid in the rapid evaluation of the CREC-engineered lines. In a preliminary test, a juvenile grapefruit clone grafted to one of the CREC-engineered Carrizo rootstock lines flowered only in its second flush, which was an exciting development.

All crop plants have evolved through the induction of mutations. Many navel orange and grapefruit cultivars are products of natural mutations. CRISPR/Cas9 is a tool that creates mutations in a plant’s DNA, but this process can be manipulated to occur much faster than that obtained through natural methods. CRISPR/Cas9 can target specific parts of a plant’s DNA and make necessary changes without affecting the rest of the plant.

In citrus, there is a potential to create an HLB-tolerant plant using this technology. Citrus contains a native NPR1 gene that is not very effective in protecting against HLB. A primary issue preventing its expression is the presence of other genes that suppress the function of this endogenous NPR1 gene.

The CREC research group has pioneered the cell culture and protoplast technologies that assist the endeavor to create targeted mutations in the citrus DNA. CRISPR/Cas9 technology is being utilized to target several negative regulators (proteins that suppress other useful proteins) of the SAR process and citrus NPR1 activity. It is expected that citrus plants would effectively combat HLB infection without the presence of these negative regulators. An added advantage is that these plants would be considered non-GMO (genetically modified organism), allowing for an easier commercialization process.

To address public perception issues that arise from the utilization of bacterial or viral components in the engineered plants and to have a more consumer-friendly appeal, a system has been developed that utilizes all plant-derived genetic elements coupled with a visual selection system using a citrus-derived anthocyanin gene (replacing the GFP above). The process involving the development of engineered plants is highly dependent on the ability of the researcher to select the genetically engineered cells from the background non-engineered cells.

Genetic markers such as the GFP are short pieces of DNA that visually indicate the presence of certain genes in an engineered plant. In contrast to the existing systems, a system has been developed that relies on the ability of cells to express anthocyanins in the initial stages of selection. This newly developed system also prevents the genetic marker gene from being expressed in the resulting engineered plants, but at the same time allows the expression of the beneficial gene(s) that allows the engineered plants to be protected from CLas.

The CREC team has developed anthocyanin, overexpressing, purple Mexican limes as a proof of concept during the evaluation of the anthocyanin system as a genetic marker. (Purple margaritas are just a side benefit!) The tropical and subtropical citrus plants do not produce anthocyanins, with the blood oranges producing anthocyanins only after a prolonged cold chill. While blood oranges can be grown in Florida, they lack the intense coloration.

IS GENETICALLY ENGINEERED CITRUS REALLY NEEDED?Anthocyanins are health-promoting compounds found in commonly consumed fruits such as blueberries, grapes and strawberries. CREC-developed plants offer proof that engineered citrus can result in the incorporation of an additional health-promoting component to the existing citrus portfolio (see Figure 3).

As with conventional breeding techniques, there are pros and cons to developing engineered citrus. Many believe that engineered citrus provides the best hope for a permanent solution to HLB.

Several questions remain unanswered. Will these CRISPR/Cas9 induced mutations have the desired effect? Will the engineered plants hold up against HLB over time? Will the stacked gene-containing plants have a better effect than plants containing a single gene in the long term, such as after 10 years in the field? Currently, the answers to all these questions are unknown. However, the possibility of viable options can be predicted for future citrus plantings — including conventionally bred, engineered trees or a combination of both — in Florida. Current results give hope that research is well on its way to winning the fight against HLB.

Manjul Dutt ( is a research assistant scientist and Jude Grosser ( is a research professor, both at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.

Citrus Patterns Tolerant to Greening

The US already has some 20 citrus patterns tolerant to greening

Mª Angeles Forner, the person responsible for citrus patterns at the Valencian Institute of Agricultural Research (IVIA), stated at the Picassent’s XXXI Citrus Congress that the United States already had nearly twenty citrus patterns that were potentially tolerant or resistant to the greening or HLB disease that is sweeping the plantations of Florida and other North American states, as well as those in Brazil and several countries of that have a relevant orange production.
Four of the twenty North American patterns of interest are in California and the remaining 16 in Florida. Mª Angeles Forner said that, even though researchers from both states were working with them, they were still in the first stages of this research, so it was still too early to know the scope and virtues of each pattern.
Given the obvious interest of these findings, a farmer attending the congress asked Forner if they had brought any samples of these patterns to the IVIA so they could study their characteristics there and where they could get the appropriate plant material in case the greening affected the plantations in Valencia and in the rest of Spain. The researcher acknowledged that the IVIA still had not taken any decision in this regard, and that they hadn’t imported any of the referred patterns so far, which surprised the audience who believes they should have already undertaken some initiative of this type.
No alternatives
At the moment, the bacteria causing the greening disease hasn’t been detected in Spain, but it has been a long time since insects vectors that can propagate it, whose populations are spreading throughout the territory, were detected in Portugal, the Canary Islands, and Galicia. This means that if the pathogen arrives, in any clandestine import of infected plant material (which don’t have many controls), the propagation could be easier, as the vectors are already close to the country, which could lead to a truly disastrous situation.
Faced with this negative possibility, the technical services of the agrarian administrations have been carrying out controls to determine the hypothetical presence of vectors (which fortunately have not been found in the Valencian Community) and of the disease itself, of which there is no presence in Spain or Portugal. However, the disease could arrive to the country, something that is dreaded by technicians and politicians, who constantly recommend the care that must be taken to prevent a catastrophe like the one suffered in Florida or Sao Paulo, which lost hundreds of thousands of hectares to this pest.
The country’s prevention work is suitable, but it is clear that Spain must also try to quickly dispose of plant material that, if the disease spreads, could be a viable alternative for it; something that is being done in the United States, but not here. Perhaps Spain hasn’t taken this measures because the disease hasn’t been detected in the country yet, so they haven’t experienced its disastrous effects.
However, it would not hurt to start acting in this direction just in case. Spain should intensify its research to try to find resistant or tolerant hybrid patterns, get samples of all the work obtained in this direction from around the world and, at the same time, work to develop biotechnological applications that can contribute in this direction. There are more and more specialized opinions that point to the convenience of deepening the applications of the CRISPR biotechnology tool, which was created by Valencian researcher Francisco Mojica, from the University of Alicante.
It worth noting that when Spain was affected by the expansion of the tristeza virus, which killed more than a hundred million orange trees and mandarins, the country at least had the effective alternative of patterns that were tolerant to that disease, on which its current citriculture is based. If these patterns had not existed, there would hardly be any orange production left in the Valencian Community. The new potential threats, the greening and Xylella (which can also affect citrus), could have a similar negative effect on the crops, with the aggravating circumstance that the country still doesn’t have any alternatives to face it. The country has to look for them.


Publication date: 10/31/2017

Mandarin Popularity

Mandarins new driver of citrus category

As with other citrus production this year, mandarin volume out of California is expected to be down, growers say.

But the category continues to explode in sales, often at the expense of navel oranges.


This year’s mandarin deal should get underway with satsumas in October, with clementines and murcotts beginning after the first of the year and going into April and May, said Bob Blakely, vice president of the Exeter-based California Citrus Mutual.

The category had a pretty good year in 2016-17 and the industry anticipates more success, if a bit lower volume, in the upcoming season, Blakely said.

Jacobsen said last year was a success.

“We had bigger sales than ever before,” he said.

Orange Cove-based Mulholland Citrus, which offered the Delite as the first California mandarin in the marketplace 20 years ago, has taken the product to a new level by offering Delites through Valencia, Calif.-based Sunkist Growers Inc., said Heather Mulholland, chief operating officer.

“We’re looking at 8 million 5-pound equivalents,” she said.

Hot weather in the late spring and early summer months will tamp down mandarin volume this year, but there will be plenty of product available, said Joan Wickham, Sunkist spokeswoman.

The addition of Mulholland’s fruit will help, she said.

“We are taking the opportunity to refresh our mandarin program, and are introducing retailers this season to Sunkist Delite mandarins,” she said. “Delite is the original California mandarin brand, created by the first family to grow and market murcott mandarins in California. Sunkist is bringing the name back into the marketplace with this program, leveraging the heritage of quality that it represents.”

Delano, Calif.-based Wonderful Citrus anticipates continued growth of its Halos mandarins, said Adam Cooper, vice president of marketing.

Wonderful and Paramount Citrus also held the Cuties brand before Pasadena, Calif.-based Sun Pacific Shippers acquired the trademark in 2013. That year, Wonderful Citrus launched the Halos line.

“Overall, across the citrus category, mandarins have been driving growth,” he said. “We’ve seen it’s now well over a $1 billion category.”

Cooper said Halos now own a 53% market share of mandarin sales.

“In four years since Halos launched, we’ve represented 73% of that category growth,” he said.

Halos have influenced citrus sales, and more, Cooper said.

“Last year, Halos alone accounted for 12% of total produce department dollar growth, so they’re driving sales in the whole produce department,” he said.

Ground Cover For New Citrus Plantings

New citrus planting method stops bugs, yields additional benefits

September 26, 2017 by Kathleen Phillips

New citrus planting method stops bugs, yields additional benefits
Raised beds covered with plastic mesh have proven to stop the life cycle of the Diaprepes root weevil on citrus trees in Texas. Scientists are now documenting other positive effects of the novel planting technique. Credit: Texas A&M AgriLife Research

A planting design that outwitted a weevil in Texas citrus groves has yielded numerous other benefits for growers and brought better quality oranges and grapefruits to consumers, experts say.

Enter the Diaprepes root weevil in 2000. The insect was found to be chewing up Texas citrus tree roots underground, then busting through the soil and up the tree to feast on leaves. Researchers began looking for a way to disrupt the weevil’s path.

By 2009, studies found all it took to stop the pest was a layer of mesh over the soil beneath the tree, according to lead scientist Dr. Mamoudou Sétamou, professor of entomology at Texas A&M University-Kingsville Citrus Center in Weslaco.

The plastic forms a barrier that the weevil cannot penetrate either from the ground up or from the tree to the soil, the researchers on the project explained, and thus the pest’s life cycle was interrupted, and it could not live there.

But after several years, Sétamou and others on the project realized that with field work, irrigation of the and washing rains, soil would become deposited on top of the plastic mesh layers. That led the team to try planting citrus trees on raised beds of soil and then covering the beds with plastic mesh. This design has proven effective in stopping Diaprepes root weevils and preventing soil accumulation to build.

And that might have been the end of the story, but the research team began to notice other benefits after years of watching for the weevils.

Dr. Olufemi Alabi, Texas A&M AgriLife Extension Service plant pathologist, Weslaco, said the planting method also has proven to save the growers money on inputs while yielding more fruit per acre.

“Traditionally, the planting density in the Rio Grande Valley is 121 trees per acre,” said Alabi, who joined the project in 2013. “With the new planting design, growers can easily increase this to 165-218 trees.”

The raised beds are 10-feet wide at the base, slope to 8 feet at the top and are about 18 inches tall, Alabi said. The plastic mesh is applied across the beds in a continuous length from one end of the row to the other.

The configuration has saved irrigation water, Alabi said, because the plastic mesh reduces evaporation from the root zone meaning less water is needed. The method also reduces the need for chemical sprays against the weevils and weeds, which can’t grow through the plastic mesh.

Alabi said now that citrus greening has also emerged as a threat against citrus production, the novel planting method is being examined as a potential aid against that disease as well.

“Our hypothesis is that the new planting design will bring young citrus trees to earlier production compared to the traditional method, so the productive capacity of the grove can be realized prior to and even in the presence of ,” said Alabi, who is collaborating on the study with Setamou, growers and the Texas Citrus Pest and Disease Management Corp. The project was funded by the U.S. Department of Agriculture-Huanglongbing Multi-Agency Coordination Group.

That study is also recording additional benefits of the planting design in 30 acres planted in the study at the Citrus Center in Weslaco and another 100 acres planted by cooperating growers, Alabi said. Another 145 acres are likely to be planted in the new style by the end of the year.

“Ironically, despite the disease and pest issues, citrus acreage in Texas has been steadily increasing the last three to four years,” Alabi said. “And more interesting is an increase in gross returns per acre due to a combination of factors, including the outputs of these research efforts.”

Almost 27,000 acres of citrus in a three-county area of the Lower Rio Grande Valley annually yield more than 9 million cartons of fresh grapefruit and oranges plus 5 million cartons of juice fruit valued at more $100 million dollars, according to Texas Citrus Mutual.

Lemon Production in Floirda on the Rise

More Florida Citrus Producers Pondering the Lemon Pledge

Florida lemon grove
Lemons are in high demand not only for juice, but also oil.
Photo by Peter Chaires

The lemon craze certainly appears to be in full swing in Florida. Growers are gravitating to the prospect of a citrus crop that continues to produce in an HLB environment, even when surrounded by infected trees. Growers need a citrus variety that will hold on the trees and that is in relatively high demand. Though nurseries remain the primary source of information and guidance relative to planting decisions, some nurseries are reticent to engage on the issue; because like the rest of the industry, they have very little experience with lemons.

Other than some specialized lemon plantings for the fresh market and small volumes for processing, Florida has been a minor player in the lemon market since the 1962 freeze. Coke (Minute Maid) did plant some acreage in the 1960s and the Seminole Tribe of Florida followed suit in the 1970s, collectively producing an estimated 550,000 boxes of lemons. It has been reported Minute Maid abandoned its acreage in 1980s after freezes and eventually for economic reasons. However, necessity remains the mother of invention and growers now appear willing to put their frost-protection skills to the test in order to supply market demand.

Demand for the Product

Lemon demand flows from two markets: juice and oil. Lemonade and variants thereof are among the fastest growing products in the beverage category. Florida’s climate is ideal for juice production. When you add robust tree performance into the discussion, it should come as no surprise that Florida citrus growers are gravitating to lemons. What adds another dimension to the lemon conversation is the second and perhaps more important market: lemon oil. Global demand for lemon oil remains strong. This summer, the price was hovering around $24 per pound. Oil recovery and oil quality will be key factors for processing plants entering this market. Both factor into grower returns and decisions related to varieties.

Lemon tree in Florida full of fruit
Photo by Peter Chaires

Fresh vs. Processed

Undoubtedly, most of the new lemon plantings will go into the processed channel. Florida has only one fresh packinghouse running lemons. Indian River Exchange Packers (IREP) starts its season with lemons, and has a level of expertise with harvesting, packing, and marketing. Lemons require a different de-greening temperature range than other citrus, and IREP has made this investment and is well positioned to benefit from recent plantings. That being said, production of Florida lemons for the fresh market presents a load of challenges.

First, harvesting begins (depending on available volume) somewhere between mid-July and mid-August. It requires some careful planning and management to move from lemons to the next earliest varieties without a time gap. Second, like other citrus, lemons for the fresh market must be harvested when they are dry. Since lemons mature during the rainy season and cannot be harvested until early afternoon, and inevitably, the rains come in mid- to late afternoon, the balancing act can be frustrating and expensive.

Adding to the dilemma of handling in the field is the fact lemons have a high degree of susceptibility to skin breakdown. Blue and green molds and sour rot are challenges to the packinghouse.

Finally, Florida is and will likely remain a very small player in the American fresh lemon market, which means we will be a price follower rather than price leader. California and Arizona offer a longer season and retailers will not compromise those relationships. However, for those who can manage the process and the market, there may be opportunity. Bottom line: Unless the grower has a juice contract, the market will be quite limited.

Crop Insurance

RMA is in the process of considering the Florida counties that will be included in the lemon production area where risk of loss to cold weather is manageable. This currently appears to include: St. Lucie, Indian River, Polk, Hendry, Collier, Highlands, and Lee. However, specific situations can be addressed through the crop insurance program.

Current Volume and Projections

Estimations show approximately 200 to 250 acres of lemons currently in production in Florida. Over the past three years, roughly 400,000 trees have been propagated; but nearly 124,000 of those were registered for use as budwood increase. This would leave about 276,000 trees going into commercial production over the past three years. At a 140 trees per acre average – this would be another 1,970 acres of commercial lemons on the way.

This raises the question why so many increase trees are needed. It is likely that this number is too high, the likely result of nursery reporting errors. Nonetheless, even if this number is reduced significantly, it shows nurseries are ramping up for some serious lemon propagations.


One processor offered an incentive plan for growers to plant lemons and fully subscribed its program for 50,000 trees (resulting in average 137 trees per acre, or 365 acres). Other processors have similar incentive programs, but specifics are hard to come by. Estimates are as high as another 5,000 acres, but an additional 1,500 to 2,500 acres is more realistic. To put this in scale, USDA-National Agricultural Statistics Service shows California having approximately 41,500 acres of lemons in production and Arizona about 8,250 acres. Growers interested in planting lemons should contact their processing plant and inquire whether greater allotments of trees will be added to their tree incentive programs and how the pricing will be structured

Vetting Varieties

It is important growers verify with their processor whether there are specific lemon varieties that are preferred for their oil profile. The three main commercial lemon variety types are: ‘Bearss’ (which reportedly has fewer thorns), ‘Eureka,’ and ‘Lisbon.’ Presently, ‘Bearss’ and ‘Eureka’ appear to be the leading varieties for Florida growers. Most processing plants seem to value the oil and juice from both of these varieties. Very few ‘Lisbon’ lemons are being planted (probably due to lack of experience with the variety).

The ‘Harvey’ lemon, another Florida variety, is thought to be good for fresh packing, but its value for processing is still under evaluation.

New Twist to Freeze Protection

Lemon trees are susceptible to damage and loss of bloom due to freeze. Proper use of microjet irrigation will certainly improve one’s odds, but one grower is taking a different twist. He has been growing lemons successfully in Lake County for almost 20 years. His lemons are utilized in processing. He plants all of his trees as rooted cuttings, so that if the trees freeze to the ground, they come back as lemons and he is able to recover more quickly.

Fine Tuning Citrus Nutrition

How Florida Growers are Fine-Tuning Citrus Fertility


Citrus growers have always scrutinized their plant nutrition programs, but with HLB now in the mix, that scrutiny is on hyperdrive. And the programs are sort of like fingerprints — each different based on individual circumstances. Over the years, growers have honed in approaches that appear to be helping infected trees stay as productive as possible.

Water barrel graphic depicting Liebig's law of the minimum
The barrel depicting Liebig’s law of the minimum has become a common sight in citrus fertilizer presentations.
Graphic courtesy of UF/IFAS

Sharing Insights

In the spirit of open dialogue to help the industry fight the scourge of HLB, many growers are sharing what is working or not in their fertility programs. Once such grower is Marty McKenna who farms with his brother, Pat. He recently spoke at Florida Citrus Mutual’s Citrus Industry Annual Conference on McKenna Bros.’ fertilizer program and its successes.

He began by crediting Maury Boyd for bringing attention to Liebig’s law of the minimum, which states: the rate of growth of a plant, the size to which it grows, and its overall health depend on the amount of the scarcest of its essential nutrients that is available to it.

Both McKenna and Boyd are past winners of Florida GrowerSM magazine’s Citrus Achievement Award.

“Our situation is we are 100% infected with HLB,” McKenna told conference attendees. “We quickly realized we are not going to stay in business if we spent more than we were taking in. So, we had these two issues as we tried to get in the right direction to stay in business.”

McKenna said his brother Pat drove down to visit Ed English’s grove to observe his program of applying micronutrients to the root system, which was appearing to have success.

2016 Florida Grower Citrus Achievement Award winner Marty McKenna
Marty McKenna
Photo by Frank Giles

“As he was driving back, Pat called me and said, ‘Marty, I just saw the prettiest Valencia orange grove I have seen in 10 years,’” he said.
After the visit, the brothers began trying figure out a way to duplicate the program on their groves.

“It is not a one size fits all, but the beauty of minor elements applied on the ground in the presence of greening is anybody can try it,” McKenna says. “I think it is important that you can utilize the equipment you already have in groves with this approach.”

The McKennas have been using fertigation for more than 30 years. This guided their program to deliver minor elements to the roots via fertigation. After a lot of trial and error and tracking, they developed a 5-0-7 mix.

“It is basically an all nitrate fertilizer program,” McKenna said. “We alternate this due to the [Liebig’s law of the minimum] with a 5-4-7 mix, which has the boron, molybdenum, and phosphate. So, we are alternating these applications weekly [weather permitting].”

The program is more expensive than more conventional approaches. McKenna said they were backing off a little on nitrogen and would likely be below 200 pounds per acre, or perhaps even less than 150 pounds per acre given the right conditions. The brothers also are dialing back the intensity of their psyllid control applications to free up dollars for the fertilizer program.
McKenna continues to further supplement trees with a foliar nutrition program.

Hybrid Approach

Understanding the importance of root health and providing a steady source of nutrition, Rob Atchley, General Manager of Groves for Duda Citrus Division, and his team have developed a hybrid fertilizer program that focuses on the benefits of controlled-release fertilizers.

Rob Atchley
Rob Atchley

From 2013 to 2015, Duda put in a number of large plantings. The homogenous prill slow release materials they used were safe enough to put in tree holes at planting and provided a steady source of early nutrition and cut down on leeching.

“By putting it down in the hole, the fertilizer stays right there with the tree, and we’ve had very good luck with,” Atchley says. “Beyond that on the young trees, we use a lot of foliar nutrition, which goes out about every three to four weeks.”

The controlled-release fertilizer and foliar program carried the young trees to about year two. Atchley then moved on to what he calls a hybrid fertilizer approach, which combines conventional fertilizers with controlled-release fertilizers, along with foliar applications. “We apply dry fertilizer at the normal times most growers do (January, April, and October),” he says. “We vary my percentage of controlled-release fertilizer to match the weather patterns for certain times of the year. We also rely heavily on soil and leaf sampling to direct our applications. When you are spending that much on sampling, you don’t really want to use a cookie-cutter approach to fertilization.”

Atchley says the combination of their hybrid fertilizer program and continued strong commitment to psyllid control is paying off in Duda’s groves.