Growing Finger Limes in Florida: Lessons Learned So Far

Growing Finger Limes in Florida: Lessons Learned So Far

Limes

finger lime
Photo credit: ©Nut/Adobe Stock 

By Manjul Dutt and Jude Grosser

Finger lime, a distant relative of sweet orange and grapefruit, is a relatively new crop species for Florida. It is an Australian native species that has been gaining in popularity and importance in the last few years because of its unique fruit characteristics and disease tolerance, which sets it apart from conventional sweet orange and mandarin cultivars.

The primary characteristic of this species is the round to teardrop-shaped juice vesicles that burst into individual juice sacs when the fruit is cut. The juice vesicles are known as “citrus caviar.” They are consumed either fresh or processed and packaged.

Locally grown finger lime can be a useful addition to the “Fresh from Florida” portfolio and could bolster local food production systems, leading to increased sales to restaurants, bars (think margarita and mojito cocktails!) and grocery stores.

One of the pressing issues limiting large-scale production of finger limes in Florida is the lack of knowledge about the cultural conditions to successfully cultivate it in a huanglongbing (HLB) endemic environment. Recently, with funding from the Florida Department of Agriculture and Consumer Service’s Specialty Crop Block Grant Program, a rootstock and fertilizer evaluation trial was established at the University of Florida Institute of Food and Agriculural Sciences (UF/IFAS) Citrus Research and Education Center (CREC) in Lake Alfred.

The objective of this study is to understand how the different commercially available rootstocks and fertilizer regimes (slow release vs. conventional) impact finger lime growth and production. This article presents observations on the initial three years following planting.

GREENHOUSE GROWTH
The Division of Plant Industry’s finger lime accession, DPI-50-36, was the scion cultivar evaluated in this study. It was budded onto 14 different rootstocks approximtely 6 months old.

Figure 1. A) In the greenhouse, finger lime DPI-50-36 scions show different growth rates based on rootstock. B) A 6-month-old finger lime scion is budded onto Kuharske rootsock.

Table 1 and Figure 1 show the nursery growth rate of the budded plants. Nursery plant growth was considered rapid if the scion shoots grew 6 inches or more after bud break at the end of three months. A poor plant growth rate ranged from 1 to 3 inches at the end of three months.

The most vigorous scion growth in the nursery was on the Volkamer lemon, US-802 and UFR-4 rootstocks. Scions on the popular Swingle and Kuharske rootstocks had acceptable growth rates and would be viable rootstocks for finger limes. Scions on C-22, Cleopatra mandarin and UFR-16 performed relatively poorly.

FIELD PERFORMANCE
A field trial was set up at the CREC with three fertilizer treatments replicated in a split-plot design. The three fertilizer treatments were:

  1. 11-6-20 granular controlled-release fertilizer (CRF) with 3.15 percent calcium, 1.5 percent magnesium, 0.05 percent manganese (Mn), 0.02 percent boron, 0.10 percent zinc (Zn), 0.05 percent copper and 0.15 percent iron (Fe)
  2. 11-6-20 CRF supplemented with Tiger Sul Micronutrients® Greening Guard Citrus Mix (65 percent sulfur, 3 percent Fe, 7 percent Mn and 6 percent Zn)
  3. Conventional 8:8:8 fertilizer treatment

The fertilizer application rate was based on UF/IFAS guidelines for citrus trees and applied at the higher recommended rate (year 1: 0.30 pound nitrogen (N)/tree/year, year 2: 0.60 pound N/tree/year and year 3: 0.90 pound N/tree/year). The Tiger Sul Micronutrient Mix was applied at the rate of 0.5 pound/tree.

The trees were planted in the spring of 2017. Observations reported here are for the first three years following planting. Results will be updated in subsequent years.

Initial soil pH at the finger lime grove at the time of planting ranged from 6.4 to 6.6. Phosphorus levels were adequate, but N and potassium levels were low. Trees were planted with a 10-foot spacing within the row and 20 feet between rows. Fertilizers were applied twice a year, in early March and September.

In 2017, the finger lime grove was battered by Hurricane Irma six months after planting. Several trees were uprooted and subsequently replanted. Interestingly, this did not have a detrimental effect on most of the trees, which resumed normal growth the following spring. Soil was sampled on a yearly basis, just before the fall fertilizer application.

Year 1
There were no differences in tree height after one year of planting. In fact, trees were observed to have very little growth in the first eight months after planting. An appreciable decrease in the soil pH was not observed in treatments containing the Tiger Sul Micronutrient Mix in year one. There were no differences in tree growth among all the treatments, and all trees were HLB negative.

Figure 2. A two-year-old DPI-50-36 finger lime scion on Cleopatra mandarin rootstock (A) shows less growth than a two-year-old DPI-50-36 finger lime scion on Volkamer lemon rootstock (B). The plants are part of the Citrus Research and Education Center finger lime field trial (C).

Year 2
Rootstock differences in tree growth were recorded in the second year. The vigorous rootstocks like Volkamer lemon, sour orange and US-802 generally had taller tree heights than the other rootstocks. Cleopatra mandarin and C-22 produced the shortest trees. Soil pH was reduced by an average of 0.2 in the Tiger Sul Micronutrient Mix supplemented treatment. All trees remained HLB negative.

Year 3
Growth trends were similar to year 2 among all the fertilizer treatments. Finger lime on Volkamer lemon, sour orange and US-802 continued to produce the tallest trees, whereas finger lime on Cleopatra mandarin and C-22 were the shortest. Kuharske and Swingle rootstocks produced comparably sized trees. A few trees suspected of being infected with HLB were tested. All had qPCR Ctvalues over 34 and considered negative to Candidatus Liberibacter asiaticus infection and HLB disease. Sporadic flowering and fruit set occurred in some trees.

General Observations

  • The DPI-50-36 finger lime is compatible with most commonly available rootstocks. However, there is a definite rootstock-tree growth interaction.
  • C-22 had low bud take in the greenhouse and poor growth in the field.
  • Trees are slow to establish in the initial year after planting with very little vegetative growth. This has also been observed in other plantings not connected to this study.
  • Thus far, no major differences have been observed in tree performance among the three nutrition treatments.
  • Trees flowered from year three onward.
  • Trees have remained HLB free.

Acknowledgments: The authors thank Jack Zorn (Tiger Sul) for donating the Greening Guard Citrus Mix and Ward Gunter (ICL Specialty Fertilizers) for assistance in developing the dry granular CRF treatments.

Manjul Dutt (manjul@ufl.edu) is a research assistant scientist and Jude Grosser is a professor, both at the UF/IFAS CREC in Lake Alfred.

Juice Imports, Fruit Prices and Production Costs

Juice Imports, Fruit Prices and Production Costs

prices
Ariel Singerman

In a recent presentation titled “Juice Imports, Fruit Prices and Cost of Production,” Ariel Singerman provided the price and yield required to break even growing oranges in Southwest Florida.

“Average cultural cost of $1,847 requires prices for E&M (early and mid) and Valencias to be $2.31 and $2.01 per pound solids, respectively, just to break even,” the University of Florida Institute of Food and Agricultural Sciences economist said. A table in the presentation indicates the break-even yields at those prices are 203 boxes per acre for early/mids and 202 boxes per acre for Valencias.

The components of the $1,847 production cost are $584 for sprays, $528 for fertilizer, $281 for tree replacement, $220 for weed management, $201 for irrigation and $33 for pruning.

Trying to cut costs to achieve profitability has its pitfalls. According to Singerman, “Significantly reducing cost of production to adjust to lower prices will have long-run consequences on grove productivity.”

Singerman indicated the number of pound solids per box in Florida decreased significantly from the 2008-09 season to the 2018-19 season. In that period, the Valencia yield dropped from 6.54 to 6.11 pound solids per box; the early/mid yield plummeted from 6.24 to 5.27.

The economist detailed the drastic reduction in orange juice consumption in recent years, noting that per-capita consumption tumbled from between 4.5 to 5 gallons in 2004-05 to less than 2.5 in 2018-19.

“A high percentage of fruit will be out of contract in 2020-21,” stated Singerman. He added that “processors that were not in the market (for fruit) this season (are) likely to come back (due to their contracts with suppliers abroad expiring).” Some growers say they received no offers or very low price offers for their fruit in recent seasons because processors committed to buy large amounts of foreign juice after Hurricane Irma damaged Florida groves in 2017.

Singerman’s presentation is one of the first from the cancelled 2020 Florida Citrus Growers’ Institute to become available online. The annual event was cancelled in April because of COVID-19. UF/IFAS is working to make additional presentations available to growers.

See Singerman’s full presentation here. A PDF version is also available online.

Top Picks From Citrus Variety Display Days

Top Picks From Citrus Variety Display Days

Variety Display
Industry members give their feedback on new varieties of fruit during Citrus Variety Display Days at the Citrus Research and Education Center.

By Yu Wang, Fred Gmitter, Jude Grosser, Joon Hyuk Suh and Peter Chaires

The Citrus Variety Display Days at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center (CREC) have been a unique platform to fulfill one of the core missions of the Florida citrus industry. These events help identify new selections with superior traits to improve Florida citrus growers’ competitive position in the marketplace.

New Varieties Development & Management Corporation (NVDMC) and the UF/IFAS plant improvement team have been collaborating to move the most promising material forward for both the processed and fresh fruit markets, as well as to gain feedback for future variety improvement.

In the HLB era, production in Florida of large quantities of high-quality citrus is needed to keep pace with projected market growth and for the citrus industry to remain viable. Successful development and marketing of new varieties for both fresh market and processing should be driven by industry and consumer interests. Therefore, in addition to developing disease resistance and high yield for growers, Citrus Variety Display Days develop sensory quality and consumer preference information to guide which selections move forward toward commercialization.

In recognition of the consumers’ role as a key driver for product success, sensory attribute analysis and consumer preference studies have been conducted. Ideally, multiple groups, including segments of the citrus industry, consumers and marketers/buyers, would be surveyed. However, because many potential new varieties have been developed and market/consumer studies are complex, information from the citrus industry is being gathered first to help direct future studies.

At the Citrus Variety Display Days, participants are invited to complete a survey on their perceived impression of fruit sweetness, sourness, bitterness and overall flavor based on an 11-point scale (0 = none, 10 = strong). The final question asks if each selection should be moved for rapid release/commercialization, revisited next year or destroyed.

During the 2019–20 season, five display days were conducted. This article lists the top varieties from the current season’s display days by category, along with their sensory attributes and consumer preferences. According to the Food & Health Survey conducted by the International Food Information Council Foundation, flavor has been the top-ranking driver of food/beverage purchasing decisions, followed by price, which indicates consumers are willing to pay more for better tasting products. Therefore, the top selections are highlighted based on their overall flavor rating, while recognizing that other attributes such as seedlessness, ease of peeling, color, postharvest behavior and other factors are also critical characteristics for success.

Variety Display

HIGHEST RATED JUICES
Figure 1 shows the sensory attributes (e.g., sourness, sweetness and overall flavor) of the top five juice samples. There was no significant difference among these samples, but compared with other juice samples, these were the highest ranked for overall flavor (~8 on a 11-point scale). The intensity of sweetness and sourness were around 7 to 8 and 4 to 5, respectively. Selections 18A-4-35 and 18A-6-14 are orange-like mandarin hybrids. Fifty percent of the responders recommended to release these two immediately, while the other half preferred revisiting them next year.

True sweet orange OLL-20 (Orie Lee Late #20), which was approved for release last year, was recommended for immediate commercialization by approximately 70 percent of responders. When comparing OLL-20 with Valencia, 57 percent of people reported the flavor balance of OLL-20 was just right, but only 22 percent thought the same of Valencia. In the comparison of juice color, 78 percent and 50 percent of responders believed OLL-20 and Valencia were just right, respectively. This limited data set shows the potential for both new sweet oranges and new orange-like hybrids to improve not-from-concentrate products.

Variety Display

GRAPEFRUIT AND PUMMELO PICKS
The sensory attributes of the top five grapefruit and pummelos are shown in Figure 2. Bitterness, a key attribute, could overwhelm other attributes of grapefruit flavor. Therefore, participants were asked to focus more on the bitterness and overall flavor rating. Like the results of orange juice, the overall flavor ratings of these top five varieties were around 8. Except for cybrid Flame, the bitterness ratings were around 4, which was quite low.

A large majority of responders (90 percent) concluded that 914 should be commercialized immediately due to its exceptional flavor, flavor balance and flesh color, while 50 percent of responders indicated rapid release for the remaining varieties. Triploid hybrid selections C2-5-3 and C2-5-17 showed similar traits such as seedlessness, large size and pinkish internal flesh color. N40W-6-14 (a cybrid grapefruit) was seedless as well, but with a dark red flesh color. C2-5-3 showed exceptional quality in October, very early in the season for a grapefruit-like hybrid.

Variety Display

TOP 10 MANDARINS
The top 10 mandarin varieties have been selected based on their overall flavor rating (Figure 3).  Bitterness was not a detectable attribute in all the top orange and mandarin varieties, so only sweetness, sourness and overall flavor were rated. The overall flavor rating of most varieties was in the 7 to 8 range, but selection 1801 showed an exceptional rating of over 9. 1801 is a seedless mandarin variety with a good flavor balance.

For the next step, there were different opinions due to the slightly small size of the fruit. Among these 10 varieties, Sugar Belle showed the highest rating (83 percent) for rapid commercialization, followed by 1424 at 70 percent. BB4 8-20 was the only variety with no support for rapid release.

MOVING FORWARD
Overall, the UF/IFAS CREC plant improvement team has benefited from information collected during the Citrus Variety Display Days. With some improvements, these events can become even more informative and valuable to the team regarding decisions on rapid commercialization of the most promising selections.

As mentioned above, in addition to flavor as a major fresh market attribute, seedlessness, ease of peeling with minimal peel oil, etc. are also critical for consumer preference. For example, an extremely delicious fruit that has seeds and cannot be easily peeled will be very unlikely to succeed, despite having the highest flavor rankings.

There is a need to refine the process to improve the response rate and to develop a selection index that will most accurately predict success. Studying all attributes together is a great challenge, so researchers are developing approaches and studies to address the challenge. Greater levels of industry involvement will help to ensure the best information for business decisions in generated. Look for an improved format in the 2020–21 season!

Yu Wang is an assistant professor, Fred Gmitter and Jude Grosser are professors and Joon Hyuk Suh is a postdoctoral associate — all at the UF/IFAS CREC. Peter Chaires is executive director of NVDMC.

Summer Tree Care Practices to Improve Fruit Quality and Yield

Citrus Industry Magazine 

yield
Image credit: © Tierney / Adobe Stock

By Fernando Alferez and Tripti Vashisth

As summer approaches and citrus trees bear developing fruit, growers can engage in several practices to improve fruit quality and yield.

As temperatures rise and daylength increases, conditions are conducive for enhanced photosynthesis and accumulation of soluble sugars in the fruit. It is important to note that, in general, the temperature is negatively correlated with the amount of free acids in the juice. This means that the acid content decreases and sugars increase as temperatures increase. However, extremely high temperatures have the opposite effect, and acid content decreases less, especially if relative humidity is low. This causes high evapotranspiration, stomata closure and less photosynthesis, which reduces sugar supply to the growing fruit.

In subtropical areas such as Florida, internal maturation is faster than in temperate citrus-growing regions. This article reviews some of the current knowledge associated with summer tree care as well as nutrient and fruit load management practices for better fruit quality, retention and yield. Data is also presented from ongoing experiments that study factors to improve fruit retention.

THE ROLE OF NUTRITION
The highest demand for nutrients in the tree begins at the end of the winter and extends to the first part of summer, as fruit set and early fruit development occur. This means that spring vegetative flush competes for resources with the growing fruit, which in turn is a high-demanding nutrient sink. Then, after the fruitlets drop (June drop), the tree retains only the fruit that it can support during development and maturation. Hence, after May-June drop, nutritional requirements for fruit development decrease compared with spring. As a rule of thumb, any time there is growth in the tree, nutrient supply should be higher so there are enough nutrients available.

It is well known that potassium (K) increases fruit size, especially if applied in summer. This nutrient accounts for more than 40 percent of the total fruit mineral content and is a major component of cell walls. The beneficial effect of K is visible immediately after bloom, i.e. during the fruit cell division phase. Deficit in K during this phase and during the fruit cell enlargement phase, which occurs in summer, has been linked to albedo weakness leading to peel creasing. This is a deleterious peel disorder, especially in mandarins and early Navels.

In grapefruit, late summer foliar applications of K may increase fruit size, although this effect seems to vary depending on each growing season. However, regarding internal fruit quality, foliar K applications seem to have no effect on juice volume, acid, Brix or Brix/acid ratio. In Valencia, summer K sprays combined with previous pre- and post-bloom applications may increase average fruit diameter.

In general, later summer applications can be performed in a wetter-than-normal summer. An additional consideration is that since summer is the rainy season, leaching may occur, especially with nitrogen (N) fertilization. N uptake and assimilation is greater in summer, as water availability and temperature foster plant growth.

STRATEGIES TO REDUCE DROP
Trees displaying fewer HLB symptoms or less HLB-induced decline and better canopy density tend to have less preharvest fruit drop and can hold on to fruit for a longer time. Studies are currently being conducted to determine the effects of off-bloom on fruit retention in HLB-compromised trees.

Hamlin and Valencia orange trees present several off-blooms, resulting in new fruit set as the current crop is already developing. This is common in healthy trees growing in subtropical and tropical regions. In HLB-affected trees, off-blooms can compromise fruit retention and ultimately yield, due to competition for carbohydrates and early fruit drop. A decrease in the fruit detachment force (FDF) of the developing fruit has been measured when new bloom and fruitlets are present at the same time. This is especially true for Hamlin oranges during late summer, and it may increase the incidence of preharvest fruit drop of more mature fruit.

Preliminary experiments indicate that removal of fruitlets increases FDF in maturing or nearly mature Hamlin fruit, maintaining above 6 kilograms, which is the consensus threshold for fruit retention in mature fruit (Figure 1). Hence, removing the off-bloom fruitlets could be a strategy to maintain mature fruit on the tree and increase yield.

yield
Figure 1. Effect of fruitlet removal after fruit set on retention of maturing Valencia fruit. Fruit detachment force (FDF) in maturing fruit was measured 15 days after fruitlet removal. Data are means ± standard error of 30 fruit in five trees per treatment.

SUMMER CANOPY MANAGEMENT
Traditionally, for juice-producing varieties such as Hamlin oranges, light maintenance pruning through hedging can be conducted throughout the summer with no effects on fruit yield. Severe pruning should be avoided as loss of canopy can result in significant fruit drop.

In Valencia oranges or late-harvested grapefruit, hedging may be problematic due to overlapping canopies. In this case, hedging should be performed in late spring, after the old crop has been harvested and the new crop is already set. A light maintenance topping may be performed in late summer because regrowth will not be as vigorous as in spring.

Light maintenance topping should not affect fertilizer requirements or application. Always remember that after severe hedging or topping, nitrogen application may need to be increased because a vigorous vegetative regrowth could negatively affect fruit yield. Therefore, N applications should be adjusted according to the severity of hedging and/or topping. Reducing or omitting an N application before or after heavy hedging will reduce both cost and excessive vegetative regrowth.

In HLB or canker-affected trees, hedging and topping in early summer may induce heavy flushing in late summer and contribute to increased populations of leafminers and psyllids, which spread canker and HLB, respectively. For fresh fruit production, pruning in summer is not recommended as it may stimulate vigorous vegetative (flush) growth that would compete with the developing fruit for resources.

In summary, considerations to follow during summer months to improve fruit yield and quality include specific nutrition practices with a special focus on K and N, and canopy management through light pruning.

Fernando Alferez and Tripti Vashisth are University of Florida Institute of Food and Agricultural Sciences assistant professors.

Retail orange juice sales rise during pandemic to highest levels in 5 years

Retail orange juice sales rise during pandemic to highest levels in 5 years

Retail orange juice sales rise during pandemic to highest levels in 5 yearsRetail orange juice sales have been falling in the United States each year since 2010, but during the U.S. onset of the current COVID-19 pandemic, sales for orange juice rose. One reason for the increase is that U.S. consumers may have sought methods to increase their intake of vitamin C, a nutrient commonly believed to build up a healthy immune system, and orange juice sales during the four weeks leading up to April 11, 2020 subsequently reached the highest level in five years at 44.5 million gallons. The average price of frozen concentrate orange juice in April rose 5 percent from the previous month to $2.40 per 12 oz. can, the first March-to-April increase in sales price observed since 2012. In 2019, orange juice consumption in the United States had fallen to 2.25 gallons per capita, a 40 percent decline from 2010. The decrease in orange juice purchases is attributable to both demand and supply-side factors. Research has indicated that declining consumer interest in sugary beverages may be contributing to reduced purchases. On the supply side, citrus greening disease, an insect-borne illness, has decimated the Florida orange juice industry, decreasing bearing acreage of juice oranges by 30 percent since 2005. After their surge in April, sales of orange juice already are showing signs of retreating but are still well above average sales for this time of year. This chart is based on the March 2020 Fruit and Tree Nuts Outlook and updated with Florida Department of Citrus A.C. Nielsen Sales data.

Fresh Citrus Opportunities Florida Growers Should Not Miss

The prevailing conversation with Florida’s citrus industry this past spring seemed to center around field trials. Clearly, the breeding programs have successfully filled the pipeline with selections with potential utility for fresh, processed, and dual-purpose applications. Some folks are questioning whether sufficient trials exist to collect, compile, and disseminate data to support planting decisions for processed growers.

On the fresh side of the equation, there is some agreement that the UF/IFAS FAST TRACK, and similar programs designed to move promising material to interested growers and nurseries early in the process, have value and should continue. However, FAST TRACK has not yielded the level and quality of data that was originally hoped. Perhaps the model needs tweaking, and an additional trial component would fulfill this need. However, while the industry hammers out these issues, growers can still gain experience with new selections through trial opportunities at whatever scale matches their risk tolerance.

This month, we will explore a couple fresh opportunities that have been largely missed by the industry.

The ‘Marathon’ mandarin was the latest release into the improved FAST TRACK model. This variety is a cross between ‘Daisy’ mandarin and ‘Makaku Kishu’. It’s an easy peel selection that is seedless in all circumstances. The fruit shape is much like a Honey tangerine, but it generally colors more uniformly.

Perhaps the ‘Marathon’ mandarin’s most attractive feature is that it matures very early (August in some years; September might be a more realistic expectation) but holds well on the tree. Brix start at about 12.5 and go up into the 17 range at the end of the harvest window. Indications are the fruit remains marketable through December and into January.

Marathon mandarin sliced feature

‘Marathon’ can be degreened if necessary and can usually be picked without clipping. Early postharvest work indicates good shelf life. It is HLB susceptible but does not appear to be overly sensitive. UF/IFAS is working on methods to optimize flowering and fruit set on young trees, and grower trials may contribute to this process.

The fact that the new FAST TRACK has no registration deadline seems to have resulted in an “I’ll get to it sometime” approach to registrations. Only about a dozen growers registered since the press release and grower meetings announcing its availability. This is certainly a variety worthy of more widespread trial. The new model permits growers to perform trials of whatever scale they choose, with the option to venture into commercial applications if they like the results.

Interested growers can contact the New Varieties Development and Management Corp. (NVDMC) office at 321-214-5214 or Lucy.Torres@ffva.com for registration information and grower agreements. Roughly 10 nurseries have budwood, and new nurseries can be added at any time.

USDA Mid-Season Low-Seeded Tangerine

Those who attended the past few USDA-ARS December Field Days at the Whitmore Foundation Farm near Leesburg have had the pleasure to follow the 1-42-65. This ‘Fortune’ x ‘Encore’ cross has a harvest window of December to January. It peels easy, doesn’t plug much, and has great internal and external color as well as exceptional flavor. So far, HLB susceptibility appears to be middle of the road. It’s not highly susceptible, but not on the high-tolerance range either. This may be a good candidate for advanced nutrition programs.

Growers in the Northern production areas have inquired about cold susceptibility, and this is really not known. Fruit size typically ranges from 150 to 210. Size is typical of many of the easy peelers in the market today. The 1-42-65 has a lot going for it, but it is seedy. Due to its popularity, USDA irradiated budwood and, with industry input, moved one of the resulting low-seeded selections forward. To avoid compromising the patentability of the low-seeded selection, photos have not been included.

Two nurseries have been increasing budwood for grower trials. Growers interested in the fresh market would be well served to give this one a try. Agreements are available through NVDMC and trees will be propagated to order (contact the NVDMC office). At this time, only a handful of growers have registered. As with ‘Marathon’, this variety merits attention.

Don’t Let FAST TRACK Pass You By

Please remember, any of the FAST TRACK selections from previously released suites that have moved to commercial production are available to any interested nursery and grower. Those who are not in the Tier II Commercial program can register as a Tier III grower and plant trials or commercial acreage. As with all new selections, there is a learning curve. It is hoped your plantings will help identify best practices when it comes to nutrition, canopy management, cropping, and harvesting. Varieties from earlier collections that are available include: RBB 7-34 (Navel-like hybrid), 914 (sweet, low-acid, seedless red grapefruit-like fruit), 950 (December easy peel, seedless mandarin), ‘UF Glow’ (October to November easy peel seedless mandarin), and ‘Bingo’ (October to November easy peel seedless mandarin). Contact the NVDMC office for more information.

Orange Appeal

If you are interested in UF/IFAS sweet orange releases, visit the Florida Foundation Seed Producers website. This site identifies released UF/IFAS orange cultivars made available for trial and scalable commercial plantings. The site also lists the nurseries that carry each cultivar. Growers waiting on large-scale field trial data can still benefit from first-hand experience growing these varieties.

Oranges are available with maturities ranging from December to June. Though targeted at processing, packers and fresh-market growers are encouraged to plant these in their trial blocks. Fresh market growers can learn a great deal from 20 or 30 trees. Consult with your nursery and get some trees in the ground.

Florida’s finger lime potential

BY CARL COLLEN

Florida’s finger lime potential

Researchers believe the fruit could be a popular new addition to supermarket shelves

Florida's finger lime potential

Image: UF/IFAS

 

A University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researcher believes that finger limes may be the next food trend, that could continue to fortify Florida’s role as a citrus producer for the world.

Manjul Dutt, a research scientist with the UF/IFAS Citrus Research and Education Center, has received funding to explore how finger limes could be grown and marketed by Florida citrus growers.

Finger limes are an oblong, finger-shaped fruit about 4 inches long with red, pink or green-yellow pulp filled with tangy juice.

They are a culinary delicacy used as garnishes for sushi, vegetables, salads and pasta, currently grown mostly in Australia, California and Hawaii, and Dutt believes Florida’s climate, agricultural expertise and soils are perfect to develop an emerging agricultural enterprise.

“An added benefit is that finger limes have the potential to tolerate Huanglongbing (HLB or citrus greening disease), use less fertiliser and require less pesticide than other forms of citrus,” said Dutt.

In the project, scientists will plant several finger lime plots across the state at UF/IFAS and stakeholder facilities to measure how successful the plants are in different conditions, while researchers will also assess the best production methods to grow finger lime under Florida conditions.

UF/IFAS citrus breeders will help with the research, evaluating the fruit’s tolerance to HLB, which will include sequencing the finger lime’s DNA to identify disease-resistance genes.

This in turn may provide insights to enhance existing research underway to breed a citrus greening-resistant tree.

Researchers will also look at market opportunities for finger limes in Florida and potential for distribution both in institutional and consumer markets.

Tasting sessions will evaluate if consumers find the finger limes flavourful, appealing to taste and smell, and whether it looks good on a grocery shelf.

Dutt has been studying finger limes since 2012 and established a finger lime trial in 2017 with funding support from the Florida Department of Agriculture and Consumer Services’ Specialty Crop Block Grant Program – a pilot study that attracted the interests of several citrus and specialty crop growers who are enthusiastic about the project.

“We are excited about the possibility that a new citrus variety might be available to Florida growers,” said Anna Jameson of Brite Leaf Citrus Nursery.

“We envision a steady growth of the market and there has been increased demand for this crop in the last few years,” Dutt continued. “The UF/IFAS citrus breeding programme has some improved cultivars that are potentially superior to currently available varieties.”

The current 18-month project is funded by the UF/IFAS Support for Emerging Enterprise Development Integration Teams (SEEDIT) program, designed to fund integrated research, extension and economics faculty team science to alleviate barriers in developing emerging enterprises for the state of Florida.

Dutt has also received financial support from the UF/IFAS Plant Breeding Graduate Initiative to fully support a doctoral student who will be researching the HLB tolerance characteristics of the finger limes.

Get an Inside Look at the Latest Citrus Scion Trials

Bingo citrus planting in Central Florida

Recent industry discussions related to plant improvement and evaluation of new citrus material have highlighted the need for a process with more scientific design than FAST TRACK (an expedited process developed for UF/IFAS fresh selections) and faster than traditional replicated field trials. While there is value in maintaining a process to flow new selections to nurseries and growers very early in the process for observation and experiential learning, the high variability of conditions, production practices, and rootstock/scion combinations makes it difficult to glean and compile valuable information for the next generation of growers.

Most FAST TRACK growers will share their observations, but few possess the willingness and/or skill set to collect and submit uniform data from a designed trial. Long-term trials produce the rich data the industry craves, but Florida growers need answers sooner than later.

Some global production areas share Florida’s struggle with HLB, and others continue to operate in a pre-HLB environment knowing that its arrival looms on the horizon. I contacted entities in other citrus production areas engaged in trial and evaluation to specify what information they collect and document. This exercise didn’t illuminate a magic path forward, but perhaps it will further inform our dialogue.

Fresh Fruit Scion Varieties

  • Below is a compilation of factors that comprise the focus of private and public evaluations:
  • Trueness to type
  • Harvesting time and holding time on tree
  • Some, but not all, include trunk diameter and tree size — to guide density decisions.
  • Fruit size and range, including the percent in each marketable size range. Shape: height, diameter
  • Fruit weight
  • Tree vigor: low, intermediate; growth habit
  • When relevant, climate suitability
  • Performance on a range of rootstocks
  • Determine whether special cropping measures are necessary
  • Disease susceptibility
  • Flavor (subjective appeal, plus brix/acid and ratio)
  • Including after storage. This flushes out off-flavors that may develop
  • Pulp texture and color
  • Juice content
  • Peel color. Does it naturally develop? If not, does it degreen or will it color after harvest with additional cooling?
  • Aroma when peeling or cutting. Focus on oils. Pleasant, indifferent, unpleasant
  • Peel disorders and texture, including those that will cause spoilage and those that would diminish packout or, worse yet, be a market access issue.
  • Fruit firmness. Easy peelers tend to be called “soft citrus” for a reason, but they can’t be so soft they don’t make it to market or require additional, expensive packaging. This applies to both export and domestic shipments.
  • Included in firmness is whether the fruit must be clipped.
  • For fruit that would most likely be peeled — how easy is it to start and complete the peeling process?
  • Seeds. There are still markets in the world that will accept a fruit with superior flavor — with seeds — but these markets are limited. This measure typically includes percent with 0 seeds and percent with 1-2, 3-5, 5-10, >10.
  • Fruit sample size ranged from 10 to 50 per tree. Most measurements start in year three. When volume permits, this is done in the beginning, middle, and end of the maturity range.
  • For fresh fruit, the respondents also were asked how large trial plantings need to be in order to yield beneficial results. The answers ranged from 50 trees to 12.4 acres — not large plantings.
  • Respondents were asked if they produce a manual of sorts for growers, that provide helpful production information. Most do. This ranges from fact sheets with information about variety characteristics, rootstock options, production, and suitability for various conditions, to fully customized production manuals for each variety that include specific practices to optimize fruit set, fruit size, and quality for maximum market value.

Processing Scion Varieties

Below is a compilation of more clear-cut factors, which are the focus of fruit evaluations for processing scion varieties. No surprises here:

  • Trueness to type
  • Harvesting time and holding time on tree
  • Some measure and publish information on tree size — including trunk and canopy
  • Tree vigor: low, intermediate; growth habit
  • Performance on a few different rootstocks
  • Pest and disease susceptibility
  • Fruit firmness. Transport of fruit for processing is harder on fruit than transport for fresh market, and fruit often sits at the plant longer before being processed. It is important to know whether the fruit can make the trip as a full load. Softer fruit may require partially filled trailers to reduce damage, resulting in additional transportation costs.
  • Juice quality: brix/acid/ratio, color, presence of compounds known to cause off-flavor
  • Typical samples are 50 pieces per tree – beginning, middle, and end of maturity range.
  • Ability to be pasteurized or otherwise processed. Not all varieties that pass the standard juice quality assessments can be adequately processed without off-flavors and/or colors.
  • Production: yield per tree, acre, or hectare.
  • For processed fruit, the respondents also were asked how large trial plantings need to be in order to have confidence in the results. The answers ranged from 25 to 99 acres.

Fresh Selections Observations

Considering Florida’s unique circumstance, it is clear all of the aforementioned data is not required for a simple pre-screen. What is most important on the front end is tree health, vigor, fruit set/hold, performance on several rootstocks, and fruit marketability. Early adopters who implement small, private trials can generally glean enough information from their experience to support or decline commercial interest. However, growers who come later will need additional information to substantiate their investment and to maximize the success of the variety.

The industry will gather this information through well-designed trials established for data collection. That said, the early small-scale, private trials may assist in identifying clear losers, negating the need for larger-scale trials, preserving valuable resources. The small-scale informal trials should continue, but selections targeted at the fresh market also will require concurrent larger-scale, formal trials.

Processed Selections Observations

The scale of the plantings and the complexity of the data collection makes it more difficult for a small, private cooperator to complete the entire process. Larger corporate trials can certainly perform this function, but the sharing and comingling of data may be an issue. Trials for selections predominantly intended for processing likely will continue with private cooperator volunteers, combined with scientific trial design and data collection mechanisms.

Data generated from these trials will be of value to academics, growers, and the nursery segment. As with fresh selections, observations from early adopters will play a key role in determining the appropriate scale of larger trials and the overall suitability of the cultivar.

Fresh Florida-Grown Citrus Sales to Increase

Fresh Florida-Grown Citrus Sales to Increase

fresh

Even with a projected downturn in production, “fresh citrus movement is projected to increase as a result of new plantings and other favorable conditions,” a Florida Department of Citrus (FDOC) official reported recently. Florida Citrus Packers, the trade association for fresh fruit packers and shippers, agreed.

Marisa Zansler, FDOC director of economic and market research, noted that the production forecast for Florida citrus was slightly reduced in April. But, she added, “During the 2019-20 season, Florida’s certified fresh grapefruit utilization … will most likely reach close to 4.4 million cartons, a 22 percent increase over the previous season.” Much of the grapefruit crop is exported to other countries.

“At the same time, certified fresh orange and tangerine shipments are also projected to increase by 13 percent and nearly 10 percent, respectively,” Zansler stated. “Serving primarily the domestic market, Florida will likely supply more than 1 million cartons of specialty and more than 5 million cartons of fresh oranges this season. Total revenue (is) expected to exceed $93 million, a 10 percent increase over last season.”

“Meanwhile, consumer demand for fresh citrus has increased by as much as 60 percent for some varieties during the month of March,” Zansler reported. She stated that “consumers increased trips to traditional grocery stores to stock up on essential items and sought out healthy snacks to support the immune system.”

Florida Citrus Packers Executive Vice President Peter Chaires agreed with and expanded on Zansler’s report. “Excellent Florida grapefruit eating quality surely helped elevate movement this season,” Chaires said. “The fruit has been truly exceptional. Grapefruit movement through April 26 was over the 4 million carton level. We saw a bump in fresh movement early in the COVID-19 crisis, then a lull as consumers had seemingly stockpiled, and now a very healthy and steady movement of fresh oranges. We expect the orange trend to carry through May, easily surpassing 5 million cartons. This was a good season for specialty fruit. Some new specialty plantings are starting to come online, and fruit quality continues to improve as the earlier plantings get a few years on them.”

New Citrus Greening Treatment Shows Promise

New Citrus Greening Treatment Shows Promise

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers have discovered another possible solution to the plague of citrus greening that is impacting Florida’s citrus groves. This new information adds to the growing portfolio of knowledge that UF/IFAS scientists are amassing to fight the disease.

Led by UF/IFAS microbiology and cell science professor Claudio Gonzalez, a team of plant pathologists, horticulturists and citrus breeders identified new management practices that slowed the spread of the damaging bacterium and supported increased fruit yield.

“Our findings present another solid block of information in the foundation of finding solutions to citrus greening,” said Christopher Gardner, a biological scientist who was a member of the research team.

The three-year project, funded by the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture, included greenhouse and commercial field trials. Researchers injected solutions of benzbromarone (benz), tolfenamic acid (tolf) and a combination of both benz and tolf into trees of varying ages in both environments. Results showed that the treatment decreased infection in the roots of citrus trees compared to the control trees and increased fruit production (15 percent) following 12 months of treatment with benz and tolf.

Two field trials were conducted in Florida, where benz, tolf and the combination of the two were evaluated for effectiveness against the greening bacterium in sweet orange and white grapefruit trees, ranging from 8 to 12 years old. Treatments were delivered by trunk injections.

The amount of Citrus paradisi fruit classified in categories of higher marketable value significantly increased after the treatments; the combined benz and tolf treatment was the most effective. Trees that received injections formulated with the combined treatment were found to produce 15 percent more fruit (by fresh fruit weight) when compared to the control group. C. paradisi trees that received tolf trunk injections had 7 percent more fruit at the time of harvest when compared to controls that received buffer only.

“Considering that treatments were only administered for one season, we found these results to be remarkable, as reduced fruit size is one of the primary adverse effects of citrus greening disease,” said Gardner.

The treatments did not compromise tree viability or the soil surrounding the trees. Nor did the treatment create any negative long-term effects that would inhibit the safety of the fruit. The chemical treatments included in the project have not been assessed or approved by the Food and Drug Administration or USDA for use in agriculture. Researchers will continue testing compounds with similarities to those they have already identified (benz and tolf) to find chemicals with higher efficacy against Liberibacter asiaticus. While more research is needed, the findings contributed to the growing portfolio of knowledge on fighting citrus greening.

The research was recently published in Nature Scientific Reports.

Source: UF/IFAS