By Robin Koestoyo

FORT PIERCE, Fla. — Florida’s grapefruit industry, devastated by citrus greening, may find hope in four ½-acre white-mesh screenhouses in a research field in Fort Pierce thanks to a $3.5 million grant from the U.S. Department of Agriculture awarded to the University of Florida.

Studies for the grant will take place inside and outside these structures, where 512 young “Ray Ruby” grapefruit trees are already in production since September 2013.

The project focuses on growing and protecting high-quality fresh grapefruit inside 14-feet-high screenhouses, or “Citrus Under Protective Screen,” also known as CUPS.

Trees have recently been grown in screenhouses to shield the crop from the Asian citrus psyllid, an invasive insect that carries the pathogen that causes huanglongbing, or HLB, commonly known as citrus greening. The pathogen has reduced Florida’s citrus production, including grapefruit and oranges, from 292 million boxes during the 2003 through 2004 production season to fewer than 78 million boxes at the end of the 2016 through 2017 growing season, according to U.S. Department of Agriculture’s Florida citrus statistics.

“The primary purpose of growing citrus under screen is to exclude psyllids and therefore block transmission of CLas, the bacterial agent of HLB disease,” said Arnold Schumann, who is leading the CUPS research as project director. Schumann is a professor of soil and water sciences at the University of Florida Institute of Food and Agricultural Science’s (UF/IFAS) Citrus Research and Education Center (CREC) in Lake Alfred, Florida. The research station is the world’s largest facility dedicated to the study of a single crop — citrus.

Schumann said the protective screen house drastically alters the citrus growing environment, including the microclimate, tree growth rates, and small pests and pathogens not excluded by the screen.

“A major goal of the grant is to develop a sustainable integrated growing system for fresh market citrus, customized for the modified environment in CUPS,” said Schumann. “Research topics include integrated pest and disease management, automated robotic pest scouting, canopy management adapted for CUPS, advanced fertigation, selective light spectrum enhancement, rootstock and scion evaluation, and comprehensive economic analysis.”

The funded project will also support new CUPS research in California, to be located at the Lindcove Research and Education Center of the University of California.

“Growers and buyers share a mutual desire to restore the grapefruit industry that was once a highly profitable export business,” said Rhuanito “Johnny” Soranz Ferrarezi, a citrus horticulture scientist at the UF/IFAS Indian River Research and Education Center (IRREC) in Ft. Pierce. Grapefruit produced in the Indian River District, situated from Micco — just south of Melbourne, Florida — and as far south as Stuart, Florida, is ranked as the world’s highest quality fresh grapefruit product, said Ferrarezi.

Nine scientists and Extension agents will work together to complete the grant objectives. Six collaborators represent Florida; there are two in California and one in Australia.

Philippe Rolshausen, an Extension specialist with the University of California, Riverside, will serve as a project co-director. Rolshausen strives to identify biotic and abiotic factors that limit the productivity of fruit crops. His work is to develop and implement sustainable strategies to improve grapefruit production.

At this time, California exports the highest amount of grapefruit, but citrus greening is now present in that region as well and is increasing rapidly. The California citrus industry is now planning to look at CUPS for HLB management, said Rolshausen.

Another collaborating scientist and extension professional is co-principal investigator Jawwad Qureshi, an entomologist working on pest management at IRREC. Qureshi said CUPS provides a different environment for pests and diseases and the use of biological and chemical methods for their management.

The economics of CUPS is an equally important research topic.

Ariel Singerman, a CREC assistant professor of food and resource economics, will contribute with a cost-benefit analysis for the grant. Singerman’s work will engage UF/IFAS Extension agents Chris Oswalt, a multi-county citrus agent working from Polk and Hillsborough counties, and Stephen Futch, representing CREC, which is situated in the state’s legendary “Florida Ridge” production region.

“Proof of concept studies showed that high yielding trees could be grown under protective screen structures for fresh fruit production by completely excluding the Asian citrus psyllid and therefore the HLB disease,” said Singerman.

Other horticultural methods the scientists will employ with their research include selective canopy management, sensor-based irrigation, suitable varieties, rootstocks to boost yields, and comprehensive economic analysis, the grant documents show. The scientists plan to incorporate each step of the research in screenhouses at the UF facilities and on privately owned citrus production lands, Ferrarezi said.

“The CUPS technology and infrastructure is readily available to growers,” said Ferrarezi. “It can be adopted by specialty growers to revitalize the Florida fresh citrus industry and to prevent the California citrus industry from reaching a similar stage of decline.”

To learn more about the grant award, please contact Robin Koestoyo at 772-577-7366 or koestoyo@ufl.edu.

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By: Robin Koestoyo, 772-577-7366, koestoyo@ufl.edu

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

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