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Ray Ruby grapefruit grown in the UF/IFAS Citrus Under Protective Screen system. Credit: Arnold Schumann/UF/IFAS.

NIFA-Funded Research Results in Technological Innovation That Saves Florida Citrus Industry

Nifa Authors
Lori Tyler Gula, Senior Public Affairs Specialist

The citrus industry in the United States is valued at more than $3.3 billion with major production concentrated in Florida, California and Texas. However, citrus production in the United States is threatened by an invasive bacterial pathogen transmitted by a tiny insect, the Asian citrus psyllid (ACP), that transmits the Huanglongbing (HLB) disease.  

CUPS system at the Dundee Citrus Growers Association. Credit: Steven Callaham/Dundee Citrus Growers Association
CUPS system at the Dundee Citrus Growers Association. Credit: Steven Callaham/Dundee Citrus Growers Association 

Also called citrus greening, HLB is the most devastating citrus disease in the United States. Since HLB was detected in Florida in 2005, Florida's citrus production has fallen by 75%, including 90% of grapefruit production. Growers in the United States have been seeking a solution to HLB for nearly 20 years.  

As a result, USDA’s National Institute of Food and Agriculture (NIFA) has invested more than $250 million to date to find a solution for U.S. citrus growers dealing with HLB. 

"Given the complexity of the HLB-ACP pathosystem, solving the citrus greening problem is akin to curing cancer,” said Dr. Erica Kistner-Thomas, NIFA national program leader who manages the Emergency Citrus Disease Research and Extension Program (ECDRE). “There is no silver bullet here. NIFA funds teams of interdisciplinary scientists and citrus industry representatives to find scientifically sound solutions to combat and prevent HLB at the farm level. NIFA-funded research projects are combating citrus greening from a variety of angles including conventional breeding, gene editing, novel biotechnology, anti-microbial therapeutics and protective screens.”  

One example is the Citrus Under Protective Screen (CUPS).  

In 2014, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) scientist Dr. Arnold Schumann and his colleagues began testing a proof of concept for the Citrus Under Protective Screen (CUPS) in their effort to give the Florida citrus industry a technology to thwart HLB. Researchers built a 55,000-square-foot CUPS system at the UF/IFAS Citrus Research and Education Center. The CUPS system was adapted from a shade-house protected agriculture idea developed by a California farmer.   

Inside the CUPS system at the Dundee Citrus Growers Association. Credit: Arnold Schumann/UF/IFAS.
Inside the CUPS system at the Dundee Citrus Growers Association. Credit: Arnold Schumann/UF/IFAS. 

UF/IFAS scientists re-purposed that system so that it excluded psyllids and protected from HLB, making them the first to use psyllid-excluding screen houses to produce HLB-free fruit in endemic areas. Two subsequent USDA Specialty Crop Block Grants allowed scientists to share the early proof of concept and demonstrate how the system worked to the first interested Florida growers.  

“The Citrus Under Protective Screen research project focuses on growing citrus like grapefruit, oranges and mandarins for the fresh market in special protective screen houses,” Schumann said. “These screen houses shield the trees from harmful pests like the Asian citrus psyllid and the devastating citrus greening disease that they spread. CUPS also protects citrus trees from stormy weather, creating a healthier environment for the trees to thrive. This results in higher growth rates, better fruit quality and higher yields while reducing the need for chemical pesticides, fertilizers and irrigation water.” 

In 2018, USDA NIFA awarded UF/IFAS a $3.5 million grant from the ECDRE program that allowed researchers to advance the scope of their research and Extension. The result? CUPS is currently the only successful technology that allows growers to profitably produce HLB-free citrus. 

Florida CUPS grapefruit in a grocery store showing the Eco-Grown and Florida Rubies label. Credit: Arnold Schumann/UF/IFAS
Florida CUPS grapefruit in a grocery store showing the Eco-Grown and Florida Rubies label. Credit: Arnold Schumann/UF/IFAS 

“The return on investment of this research project is high,” said Schumann. “Based on results from a research grant investment of $3.5 million over six years, we estimate that the Florida citrus growers have invested about $75 million in CUPS screen houses, allowing more than 1,200 acres of HLB-free citrus production by more than 200 growers, with an estimated annual yield of 1 million boxes of red grapefruit producing a net fruit revenue return of about $20 million per year.”  

Steven B. Callaham, CEO of the Dundee Citrus Growers Association, was an early adopter of the technology. The Dundee Citrus Growers Association is one of the largest fresh fruit cooperatives in the Florida citrus industry, harvesting multiple citrus varieties from more than 10,000 acres throughout the state of Florida. 

“This season, our four-year-old CUPS groves produced 800% more fruit per acre than our mature traditional groves,” said Callaham. “We have hired 12 new full-time employees as a direct result of CUPS. CUPS has allowed us to produce more with less. We are using 90% less land, water and fertilizer to produce each piece of fruit as compared to traditional growing methods. We are highly optimistic about our future with CUPS."  

This is consistent with what other growers using CUPS have experienced, according to Schumann. Commercial CUPS growers that adopted the scientists’ recommendations have reported annual grapefruit yields that are four to five times higher than conventional HLB-impacted groves, starting as early as two and a half years after planting. This exceeded the researcher’s expectations. CUPS grapefruit yields also have exceeded those in pre-HLB Florida groves.  

Scientists also discovered that citrus canker was suppressed by CUPS, and the system provided protection from severe storms. Due to the compression of given fruit yields over less time, using less space than conventional systems, there are considerable savings of input costs including fertilizers, pesticides, irrigation water, fuel and labor per unit of fruit production compared to pre- or post-HLB conventionally grown citrus. 

A high-quality seedless tangerine, Early Pride, grown by KLM Farms in a CUPS system. Credit: Jerry Mixon/KLM Farms.
A high-quality seedless tangerine, Early Pride, grown by KLM Farms in a CUPS system. Credit: Jerry Mixon/KLM Farms. 

“The ultimate savior will be disease-resistant plant material,” Callaham said. “However, developing that material takes years and possibly decades to reach commercial significance.  Our industry and our organization couldn’t wait that long. CUPS was a solution for Dundee Citrus Growers Association that could begin immediately. A solution for not only surviving but a solution for thriving. Without NIFA funding, the idea and proof of concept of CUPS may not have been possible, and commercial adoption may have been delayed at best or not happened at all.” 

Scientists and growers in California, Texas and Louisiana also have set up similar research facilities with guidance from the Florida team because their citrus industries are increasingly being threatened by HLB. Additionally, CUPS technology helps control another serious disease called citrus canker by reducing the impact of windblown rain that spreads the bacterial disease, acting like an effective windbreak. 

Jerry Mixon, owner of KLM Farms and 6M Farms in Winter Haven, Fla., said growing fresh citrus in CUPS has sustained the company.  

“Without the successes -- and they have outweighed the challenges -- our decision to stay in citrus would be foolish,” Mixon said. “With CUPS grown citrus, we can work with local nurseries and caretaking companies, packing houses, harvesting companies and ag input companies to keep our acres in citrus.”  

“Importantly, the products we are producing are amazing. As a grower, I want to be proud of the products we produce,” he said. “In CUPS grown citrus, not only is our product great to look at but it is great tasting. The full impact in the marketplace is beginning to be felt and retailers are requesting CUPS grown product.”  

Top CUPS Research Findings  

  • ACP vectors of HLB disease were sufficiently excluded from the research CUPS screen houses to restrict HLB incidence to less than 2% in 10 years. 
     
  • Screen made from high density polyethylene and with 40 to 50 mesh sizes prevents entry of ACP and other similar-sized insects from CUPS, while permitting reasonable airflow, 80% visible light transmission and rainfall penetration. 
     
  • Daytime air temperatures in CUPS screen houses are up to 10 degrees higher than outside. In CUPS, wind speeds are reduced at least 75%, humidity is higher, and light diffusion is better than outside. Diffused light allows very high planting densities without detrimental competition from shading. Researchers successfully grew red grapefruit at 1,361 trees/acre for 10 years in CUPS system, with cumulative yields of 8,313 boxes per acre. 
     
  • Smaller arthropod citrus pests like spider mites, rust mites and thrips penetrate the 40 to 50-mesh screen and must be controlled with conventional pesticides. 
     
  • Many citrus varieties produce seedless fruit due to the absence of pollinators in CUPS, which increases their market value. 
     
  • Grapefruit is the top citrus variety currently grown in CUPS because of consistent high yields and good adaptation to the CUPS microclimate. 
     
  • Citrus tree growth rates in CUPS are about twice the rates in conventional HLB-free groves. This leads to earlier commercial production (e.g. 2.5 years for red grapefruit), and savings on all annual production costs (water, fuel, labor, fertilizer, pesticides, insurance, etc.) 
     
  • Yields in the protected CUPS environment are higher for some varieties like red grapefruit than they would be in conventional groves without HLB. 
     
  • Fruit quality is exceptional with less external scarring from wind, leading to a high pack-out rate (typically 80-90%). 
     
  • Trees and fruit in CUPS are well protected from hurricanes, with negligible damage or fruit losses. 

 

Farm Bill Priority Areas
Plant health, production, and products
U.S. States and Territories
Florida

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