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Citrus Growers Join Researchers for Field Day of Emerging Answers

University of Florida Institute of Food & Agricultural Sciences — More than 50 citrus growers and researchers attended a field day to view 154 new citrus scion-rootstock combinations—some of which will result in the production of market-ready fruit from trees that tolerate the most serious citrus disease worldwide.

The disease is called citrus greening. It has reduced Florida citrus production to about half of what it was when 950,000 acres were under citrus production. Most researchers and growers agree that new scion and rootstock combinations hold a lot of possibility to preserve Florida’s signature crop.

The Millennium Block Drive-Thru Field Day 2021 took place on the morning of Thursday, Oct. 14, at the University of Florida Institute of Food and Agricultural Science’s Indian River Research and Education Center (UF/IFAS-IRREC) in Fort Pierce, Florida.

IRREC researchers guided attendees from information tents positioned at strategic points among 20 acres of carefully managed rows of grapefruit, orange, pummelo, and mandarin trees. Each plot of a scion-rootstock combination was labeled and corresponded to a 12-page packet Ronald Cave and researchers presented to visitors upon arrival. Cave is professor and director of IRREC, and he leads the citrus research project, along with manager Tom James, graduate student Martin Zapien, and agricultural assistant Mac Hossain.

“Our mission for the Millennium Block’s rootstock and scion trials is primarily to provide guidance to growers on the UFR rootstocks. There is also a secondary purpose to evaluate grapefruit and grapefruit-like hybrids,” said Cave. “No other trial like this is happening anywhere, but we need additional funding to continue with the trial until the trees are seven years of age.”

University officials and staff guided visitors to specific trees where growers left their vehicles to observe trees up close.

“The Millennium Block research project is taking the industry’s best scions and rootstocks and mixing and matching them to provide the industry with a brighter future, and some of the matches look promising,” said Doug Bournique, executive vice president of the Indian River Citrus League.

Jeanna Mastrodicasa, UF/IFAS Associate Vice President for Operations, led the event at booth #2. She fanned through the pages of the packet Cave gave her and noted the colored rows and legends. “Here is a great map and a great key that explains how the coding works and which rootstock appears where in the grove,” said Mastrodicasa.

In a row of grapefruit trees across from Mastrodicasa, IRREC Advisory Committee member Pete Spyke pointed to six trees of the same rootstocks. Spyke is a heritage Florida citrus grower who owns Arapaho Citrus Management in Fort Pierce, Florida. He lifted bunches of yellow grapefruit with pink blush from the 2-year-old trees. “Ray ruby grapefruit on UFR-15 rootstock shows the kind of thing we are after in the Millennium Block trials. It’s a very nice fruit—very high quality—excellent performance for a young tree,” said Spyke.  “The tree has two blooms, a regular bloom and a late bloom. We will capture data from both blooms.”

At a second location, where white grapefruit trees grow, Chris Hernandez showed an attendee a tree that produces sweet grapefruit. Hernandez is a UF horticulture undergraduate student and an agricultural assistant at IRREC.

“My favorite grapefruit is Seedless Surprise. The variety is super sweet, the best flavor in a grapefruit I have experienced. And the trees tolerate citrus greening well,”Hernandez said.

At another grove position, viewers gathered around Ken Gioeli, UF/IFAS Extension St. Lucie County Natural Resources Agent, to learn about invasive, venomous, and harmless snakes that may be found in the grove. Gioeli recommends growers to be aware of four venomous snakes found in the Indian River District and how they can increase safety. He urged visitors to report Burmese pythons with a mobile application, I’veGot1.

Several longtime citrus growers were surprised to find some varieties in a condition they did not expect.

“There are some variations in the rootstocks,” said Matt Hamilton. He, along with his family, own Hamilton Grove Services, Inc., in St. Lucie County. “I am surprised that some of the rootstocks I expected would do well are not looking too good, but a few of the UF rootstocks look good.”

“Our family has been in the business since the 1960s,” said Mark Hamilton. “We are grapefruit growers, and we want to stay in business.”

Growers recall many of the Indian River District’s citrus production challenges. Freezes, insects, and diseases have caused setbacks and the scion rootstock combinations may bring a comeback.

“We need to make sure the trends we see today are consistent as time goes on. Next year’s data should be much more enlightening,” said Spyke.

“The approach we are taking to breeding is to find tolerant scions and rootstocks that impart tolerance to the scion. Those combinations will be less expensive to grow and will produce larger crops of good wholesome fruit and those two factors will allow growers to make a good profit in the future. The data will be applicable to any variety growing anywhere in the state, including processed fruit.”

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