University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers have discovered another possible solution to the plague of citrus greening that is impacting Florida’s citrus groves. This new information adds to the growing portfolio of knowledge that UF/IFAS scientists are amassing to fight the disease.
Led by UF/IFAS microbiology and cell science professor Claudio Gonzalez, a team of plant pathologists, horticulturists and citrus breeders identified new management practices that slowed the spread of the damaging bacterium and supported increased fruit yield.
“Our findings present another solid block of information in the foundation of finding solutions to citrus greening,” said Christopher Gardner, a biological scientist who was a member of the research team.
The three-year project, funded by the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture, included greenhouse and commercial field trials. Researchers injected solutions of benzbromarone (benz), tolfenamic acid (tolf) and a combination of both benz and tolf into trees of varying ages in both environments. Results showed that the treatment decreased infection in the roots of citrus trees compared to the control trees and increased fruit production (15 percent) following 12 months of treatment with benz and tolf.
Two field trials were conducted in Florida, where benz, tolf and the combination of the two were evaluated for effectiveness against the greening bacterium in sweet orange and white grapefruit trees, ranging from 8 to 12 years old. Treatments were delivered by trunk injections.
The amount of Citrus paradisi fruit classified in categories of higher marketable value significantly increased after the treatments; the combined benz and tolf treatment was the most effective. Trees that received injections formulated with the combined treatment were found to produce 15 percent more fruit (by fresh fruit weight) when compared to the control group. C. paradisi trees that received tolf trunk injections had 7 percent more fruit at the time of harvest when compared to controls that received buffer only.
“Considering that treatments were only administered for one season, we found these results to be remarkable, as reduced fruit size is one of the primary adverse effects of citrus greening disease,” said Gardner.
The treatments did not compromise tree viability or the soil surrounding the trees. Nor did the treatment create any negative long-term effects that would inhibit the safety of the fruit. The chemical treatments included in the project have not been assessed or approved by the Food and Drug Administration or USDA for use in agriculture. Researchers will continue testing compounds with similarities to those they have already identified (benz and tolf) to find chemicals with higher efficacy against Liberibacter asiaticus. While more research is needed, the findings contributed to the growing portfolio of knowledge on fighting citrus greening.
The research was recently published in Nature Scientific Reports.
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