The Citrus Research and Development Foundation (CRDF) governing board on Jan. 25 approved a project aimed at reducing fruit drop by using potassium, zinc, gibberellic acid and the herbicide 2,4-D in different timing scenarios. The funding will allow University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researcher Fernando Alferez to finish two years of work that CRDF Chief Operating Officer Rick Dantzler termed “quite promising.” Alferez works at the UF/IFAS Southwest Florida Research and Education Center (SWFREC) in Immokalee.
Fruit drop has been a major problem for Florida citrus growers since HLB was discovered in the state in 2005. A 2021 Citrus Industry article summarized current knowledge about HLB-associated preharvest fruit drop.
The CRDF board also heard presentations about injections of the antibiotic oxytetracycline in an effort to curtail the impact of HLB disease on citrus trees.
The first presentation was by Tom Johnson of TJ Biotech, who is injecting oxytetracycline at a pH of 2 into trees. At that pH level, the antibiotic, when mixed with muriatic acid, stays in a liquid form and is readily taken up by the transpiration of the tree, Dantzler said. No sediment forms, but sediment does form when the pH is closer to the natural pH of a tree’s phloem, which is 6.8.
UF/IFAS researcher Ute Albrecht made the second oxytetracycline presentation. She shared her findings about injecting the antibiotic into trees. The SWFREC scientist has done much work on phytotoxicity, residuals and trunk damage from conventional injection devices.
Neither Johnson’s nor Albrecht’s work on oxytetracycline is funded by CRDF.
Since 2016, federal authorities have allowed Florida citrus growers to spray oxytetracycline solutions on their trees to combat HLB. A UF/IFAS study published in 2019 suggested that the bactericide would be more effective if it were injected into citrus tree trunks.
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