A Grove-First Approach

Josh McGillHLB Management, Research

Citrus industry stakeholders were invited to the U.S. Horticultural Laboratory in Fort Pierce to learn more about the grove-screening project.

In the nearly two decades that huanglongbing (HLB) has plagued Florida citrus groves, about $1 billion has been spent in the search for solutions. A lot of great scientists in Florida and around the world have worked on the problem, and a silver bullet, if there is one to be found, has been elusive. Researchers, along with growers, have developed tools and practices to hang on, but the disease has continued to spread throughout the state and take production down to historic lows.

When a disease continues to defy science and all efforts to defeat it, new approaches are needed, such as the trunk injection of oxytetracycline (OTC) many growers are using to treat HLB-infected trees. Growers have learned that labor crews can move through groves more efficiently than previously anticipated to make these injections, so the idea that treating individual trees is not viable is changing.

In the science of HLB, a common practice has been that research must start in the lab. Work then moves to the greenhouse to be confirmed before going into the grove for testing in new plantings or existing trees.

Scientists at U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) are challenging that research orthodoxy by starting evaluations in the grove, because after all, that is where it counts.

Now that growers are adopting trunk injection, the researchers are injecting HLB-infected trees in their grove at the USDA-ARS U.S. Horticultural Laboratory in Fort Pierce, Florida, with a wide range of different molecules in search of those that can horticulturally rejuvenate HLB-infected trees.

The research is being funded by a grant from the USDA’s National Institute of Food and Agriculture. Michelle Heck and Randall Niedz of USDA-ARS lead the research team, including Nick Larson (USDA-ARS) and Guilherme Locatelli and Lorenzo Rossi, cooperators from the University of Florida. A broader team meets weekly and is involved with molecule selection.

I was invited to see the early phases of this work, along with other industry stakeholders, in September. It is safe to say everyone was impressed by this approach and some of the trees we saw in the grove.

The research team is examining 88 different materials that have been injected into the trees. They are looking for “big effects” — something that makes you stop and wonder what’s going on with a tree to look good in a grove infected with HLB. A decent number of these materials have a more “friendly” profile when it comes to future regulatory scrutiny.

These trees were injected after the crop was harvested, much like the OTC timeframe growers are currently following. It is still early days of the research, but 13 of the injected materials have the scientists’ attention. They will be the first to say that they don’t know what’s happening yet, but the trees seem to be responding positively.

There’s still a ways to go. The trees will be critically evaluated during four points in the season. Measurements of canopy, leaf size and other elements will be collected during the summer flush, in the fall when HLB gets active, the fruit drop phase and harvest. How much fruit is harvested and its quality will be the ultimate measures. We’ll know more about that next year.

Those materials that continue to display “big effects” after these evaluations will get more due diligence to better understand what is causing the effects. There are many more details to explain about this process and how it works. We’ll be covering that in the months to come. 

In the meantime, a tip of the hat to the scientists for taking an outside-the-box approach to HLB research. Even if this work turns up only a few materials that can effectively mitigate the disease, it will be a success.

About the Author

Frank Giles


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