HLB Resistance Update

Fred Gmitter

Updates on the search for trees that are resistant to HLB drew more than 40 growers and others to an OJ Break in Bartow on Jan. 9.

Leadoff speaker Fred Gmitter, a plant breeder with the University of Florida Institute of Food and Agricultural Sciences, discussed an effort to see if so-called “survivor” trees might offer a solution. Survivors are apparently healthy trees found in heavily HLB-infected groves. Several years ago, Gmitter and others asked growers to tell UF about such trees so that research could be conducted.

“We looked at dozens of (survivor) trees that growers told us about and Extension agents found,” Gmitter says. “We collected samples of budwood, grew off trees, inoculated them (with HLB). They all came down with the disease. We looked at possible rootstock effects.” However they manipulated the trees, all ultimately became infected with HLB. “So I wouldn’t say it’s impossible that we’re going to find something like that (HLB resistance among survivors), but it really is a huge challenge and the likelihood is so small, based on our experience, that we’re going to find a truly resistant, HLB-immune tree by this process.”

Gmitter says it’s likely the survivor trees were just the last in the grove to be infected. “There always had to be the first tree that got infected, and it stands to reason that there eventually would be the last tree to get infected. And in most cases that seems to be what we were finding.”

According to Gmitter, the time frame for getting true resistance or immunity to HLB is probably longer than what the citrus industry has time to wait for. While waiting for resistant trees, he says there are “lots of things that growers can cobble together, and hopefully if done in the right way, can make a profit and stay in business.” Those things include the use of HLB-tolerant rootstocks and scions, new pest management techniques and nutrient management.

The other speaker at the OJ Break was U.S. Department of Agriculture (USDA) researcher Ed Stover, who provided an update on USDA efforts to develop HLB-resistant trees.

The OJ Break was hosted by multi-county citrus Extension agent Chris Oswalt.

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Ernie Neff

Ernie Neff

Senior Correspondent at Large