Citrus Seminars Provide Research Updates

Researchers from the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) and U.S. Department of Agriculture (USDA) delivered several presentations to a standing-room-only audience during the citrus seminars at the Florida Citrus Show in March.

VARIETIES AND ROOTSTOCKS

The citrus session began with a breeder panel discussing research on varieties and rootstocks. Participants were Manjul Dutt and Jude Grosser from UF/IFAS and Matt Mattia and Kim Bowman from USDA.

Grosser noted that a variety referred to as Last Man Standing is a new Valencia about to be released. He said 3-year-old resets of this new variety are already bigger than other 7-year-old Valencias.

Grosser reported that Orange 14 rootstock has been released, which scores high against sting nematodes. In addition, four nearly seedless lemon clones are now available, and a hybrid lime has been released, which is similar to Key lime and makes a good dooryard tree.

According to Grosser, Gator Bites mandarins are performing phenomenally in citrus under protective screen (CUPS). He is hearing consistent feedback that Gator Bites are better tasting than Cuties and Halos.

Mattia noted that some less HLB-tolerant varieties may not be ideal for field production but are performing well in CUPS.

Dutt said that trees need to be evaluated in the field for five years to determine HLB tolerance. Growers need both a tolerant rootstock and a tolerant scion for long-term success, he said.

Mattia reported that 50 top candidates are being evaluated in the Coca-Cola trials. He is also involved in trialing what he refers to as long-shot grapefruit varieties, which include Henderson and Red Blush.

Bowman said up to 450 rootstocks are under trial at USDA, with 30 currently looking outstanding. The goal is for two rootstock releases in 2026, which would likely be called SuperSour 6 and SuperSour 7.

IPC IMPACTS

Sandra Guzmán, UF/IFAS assistant professor, discussed the use of individual protective covers (IPCs) as a potential best management practice. Her research trial showed that when microsprinklers were placed inside IPCs, water was maintained in the upper soil layer longer. She noted that by slowing down the water flow in the upper soil layer right after irrigation, IPCs have beneficial impacts on water conservation and can potentially reduce leaching. Further research is needed to confirm the initial findings. 

Fernando Alferez, UF/IFAS associate professor, also presented research on IPCs. He made the following summary points:

• IPCs are the best management practice for keeping trees free from HLB in Florida’s endemic areas.
• IPCs improve tree growth. This seems to be a direct effect of better environmental conditions inside the bag.
• Vapor pressure deficit is significantly decreased in tied IPCs versus untied IPCs. This likely affects tree growth and water usage.
• Brassinosteroids may recover trees already affected by HLB if no reinfection occurs and if IPCs are used.

OTC TIPS, TOURS AND MORE

Ute Albrecht, UF/IFAS associate professor, discussed optimizing oxytetracycline (OTC) injections. More injection sites were found to be more important to tree health than higher doses of OTC. New research is underway to test an adjuvant to keep OTC stable longer. She said the path forward for citrus will include the combined use of OTC with IPCs.

Michelle Heck, molecular biologist at USDA, gave an update on the Grove-First project, which focuses on solutions to HLB that are safe, affordable and available. After the seminars, Florida Citrus Show attendees had the opportunity to tour the USDA’s Grove-First research plot as well as the UF/IFAS Millennium Block.

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