As growers decide how to use U.S. Department of Agriculture (USDA) funding to recover from damages caused by Hurricane Irma — and as they cope with the ongoing impact of citrus greening — University of Florida researchers are suggesting varieties for them to replant.
Producers can grow varieties that show tolerance to greening — also known as huanglongbing, or HLB. Such varieties include Sugar Belle®, but it has a fairly narrow market window, said Fred Gmitter, a horticultural sciences professor with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS).
They could also plant the Orie Lee Late (OLL) sweet orange varieties, though they’re still “young” varieties, meaning they’ve only been available for around four to five years, so there’s limited experience with them, said Gmitter, a faculty member at the UF/IFAS Citrus Research and Education Center (CREC) in Lake Alfred.
Growers also can plant the UF/IFAS-bred UFR rootstocks, which seem to make trees more tolerant to greening, especially when they’re combined with scion varieties like the OLLs and Sugar Belle, he said.
“Industry is catching on,” Gmitter said. “Nearly 1 million OLLs have been propagated by licensed nurseries, and there are also several hundred thousand UF/IFAS rootstocks out there, too.”
“UF/IFAS CREC breeding research is beginning to make a major difference for the future of Florida citrus growers,” he said. “Several hundred thousand LB8-9 Sugar Belle® and Bingo mandarin hybrid trees have been planted because they show a very high degree of greening tolerance and superb fresh-fruit quality, to keep our fresh-fruit industry competitive in the marketplace.”
Gmitter and Jude Grosser — a fellow UF/IFAS horticultural sciences professor at CREC — base their recommendations for the latest citrus varieties to plant on their cumulative knowledge from multiple trials.
Grosser recommends combinations of citrus rootstocks and scions.
“Nearly all trees in Florida groves are grafted combinations,” he said.
In the field, about 6 to 10 inches above ground and down is the rootstock portion of the tree, Grosser said. Anything above this is the scion portion that produces the fruit.
For example, for mid-season oranges, Grosser recommends Valquarius or Vernia scions on UFR-1, UFR-4, UFR-5, UFR-6, UFR-15, UFR-16 or UFR-17 rootstocks.
“Both of these oranges produce Valencia-quality juice, and they can be harvested beginning in mid-January,” Grosser said. “The UF release Valquarius has an advantage over Vernia for fresh market, because it has superior fruit shape and external color.”
For late-season oranges, new UF releases OLL-4, OLL-8 or Valencia B9-65 are good choices, on these same rootstocks, Grosser said.
Primary funding for Gmitter and Grosser’s research has come from the USDA, the Citrus Research and Development Foundation, the Citrus Research and Education Foundation, the Florida Citrus Production Research and Advisory Council, the New Varieties Development & Management Corporation and Orie Lee.
The trials also include support from Orie Lee, Tropicana, Jim Hughes, the English Brothers, Jackson Citrus, Conserve II, USDA Picos Farm and others, Grosser said. Tom Hammond and Greene River Citrus have also supported their efforts.
For more information about the varieties selected from these trials, see:
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