Oak Leaf Extract Tested as HLB Tool

Ernie Neff HLB Management


In the search for solutions to HLB, a formulation based on oak leaf extract has been developed by citrus growers Travis Murphy and Tom Thayer, the Indian River Citrus League’s October River Ramblings newsletter reported. The formulation was developed following the growers’ observations that citrus trees under oak trees were free of HLB compared to nearby field trees that had HLB.

The formulation is being field tested by growers and the U.S. Department of Agriculture (USDA) to determine its effects on citrus trees with HLB.  

Large-scale grower trials were initiated in spring and summer of 2021 by Murphy and include more than 20 growers and thousands of trees. A USDA field trial started in June 2021 at the Picos Road farm site in Fort Pierce is treating 122 fruit-bearing trees. The study includes Minneolas, Hamlins, Ruby Red grapefruit and Valencias.

Randy Niedz, USDA research geneticist, set up a data collection system, based on gestalt theory, to rapidly screen for effects observed in the grower and USDA field trials. Observations are summarized and distributed as biweekly updates to the participating growers.

The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) has also been conducting research to learn more about oak leaves as a possible tool in the fight against HLB. A September 2020 Citrus Industry article quoted UF/IFAS researcher Lorenzo Rossi as saying, “there is something in the oak leaf that can work.”

Rossi and other researchers soaked oak leaves in water overnight to obtain oak leaf extract. They applied the extract to HLB-affected citrus trees via soil drench. Rossi said the plants treated with the extract “were looking really, really nice” and had bigger roots and greener leaves than control trees.

The UF/IFAS researchers are also investigating the use of oak mulch in groves.  

Source: Indian River Citrus League

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