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Florida citrus growers and stakeholders invited to experimental citrus varieties exhibition drive-through event

FORT PIERCE, Fla.— Florida citrus growers are invited to view which of the new 154 citrus scion and rootstock combinations of grapefruit, pummelo, mandarin, and navel oranges, some of which show early tolerance for the most serious citrus disease worldwide, at a drive-through field day Oct. 14 at the Indian River Research and Education Center.

Citrus industry veteran Thomas “Tom” James, and graduate student Martin Zapien will host the Millennium Block Varieties Trials Drive-Through Field Day 2021, a motor vehicle grove tour — and view of a large-scale research trial — for growers and other citrus industry stakeholders.

The event will be held on Thursday, Oct. 14, from 9:30 a.m. until noon, at the University of Florida’s Institute of Food and Agricultural Science’s Indian River Research and Education Center (UF/IFAS-IRREC). The street address for the Millennium Block is 7850 Pruitt Research Road, Fort Pierce, Florida, located within a couple of miles from both Interstate 95 and Florida Turnpike exits. Those interested may register at the following link: https://www.eventbrite.com/e/ufifas-irrec-millennium-block-drive-through-field-day-2021-tickets-170290362057

“We recommend visitors drive their personal or company-owned pick-up trucks or other off-road vehicles and remain on designated areas within the grove,” said James. “Swales are present next to canals and the grove is an active research site.”

Zapien said university-wide COVID-19 protection guidelines will be in practice at the event and participants are encouraged to wear face masks. Field day attendees will stop at tented information booths positioned at the trial entrance and at other points throughout the grove. Researchers, graduate students, and Extension professionals will respond to questions and provide printed maps and key tree growth data for each citrus rootstock and scion under study.

“The evaluation of multiple rootstocks by using scions of grapefruit, mandarins, and navel oranges in IRREC’s Millennium Block is a very visual display of some of the great citrus research happening at IRREC,” said Ronald D. Cave, professor and director for IRREC and principal investigator for the citrus research. “The project is giving and will continue to give Indian River growers a clear look at what rootstock and scion combinations are the best in our region.”

Cave said the Millennium Block is a novel research effort to help citrus producers continue to grow Florida’s signature fresh fruit crop and all its varieties. The grove is a 20-acre field in which more than 5,000 2-and-1-year-old citrus trees grow.

Each experimental unit is comprised of five trees identified by a code tag and replicated six times across the trial. Participants who wish to take an electronic survey will have an opportunity to demonstrate their previous knowledge of the Millennium Block varieties and report their learning experience during their field day tour.

“Attendees will have the opportunity to see grapefruit, mandarin and navel orange selections during their juvenile stage,” said Zapien. “Participants may identify the cultivar and rootstock combinations that show superior horticultural attributes as the trees cope with citrus greening.”

Zapien said fruit is present on many of the red grapefruit trees. However, oranges and mandarins are fruiting more slowly.

In the Indian River District, citrus greening disease has reduced citrus grapefruit production by 90%. The bacterial pathogen that causes the disease is vectored by an invasive insect, the Asian citrus psyllid, from infected trees to healthy trees. The disease presents itself in citrus trees as leaves change from deep to lighter shades of green.

Infected trees drastically reduced yield in previous years, but best practices developed by UF/IFAS scientists help growers sustain trees for many more years with good fruit yield.

“Some studies report higher density plantings may bring early profits to growers, and we are seeing some compact cultivars that can fit for such purpose,” said Zapien. “Of course, this is just one piece of the puzzle. We look forward to seeing other important components of the equation such as yield and fruit quality.”

The Citrus Research and Development Foundation gave UF/IFAS a grant, and UF/IFAS also funded the research. Early funding was provided by the UF/IFAS Office Research under Jackie Burns.

Plant breeders Jude Grosser and Fred Gmitter at the UF/IFAS Citrus Research and Education Center in Lake Alfred, Florida, developed citrus varieties they expect will tolerate citrus greening. Geneticists Ed Stover and Kim Bowman with the U.S. Department of Agriculture Horticultural Research Laboratory in Fort Pierce also contributed citrus varieties for the study.

Cave, James and Zapien emphasize the need to continue the Millennium Block varieties research program. “There are a couple of rootstocks in the grove that show desired results, but we need at least six years and additional funding to continue the work to capture science-based results and the best recommendations for the industry we serve,” James said.

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