A new University of Florida Institute of Food and Agricultural Sciences Extension document, Antibiotics in Crop Production, was published in May by Leigh Archer, Ute Albrecht and Pamela Roberts. The authors found that the use of antibiotics has resulted in the successful control of bacterial diseases in some crops but not in others. The publication includes research information on antibiotics used for citrus canker and huanglongbing (HLB).
According to the document, spray applications of streptomycin (an antibiotic) in combination with copper sulfate were shown to provide partial control on citrus canker. “In 2014, an emergency exemption (section 18) was approved by EPA, allowing the use of a hydrochloride formulation of streptomycin on Florida grapefruit,” states the publication. “The combination of streptomycin and copper can increase efficacy and may reduce some of the risk in selecting for antibiotic resistant bacteria.”
In 2015, a section 18 exemption was approved by the EPA to allow the foliar use of streptomycin sulfate, oxytetracycline hydrochloride and oxytetracycline calcium in Florida to suppress Candidatus Liberibacter asiaticus (the causal agent of HLB) and improve tree health.
According to the Extension document: “Use of antibiotics for HLB control was investigated in other countries during the 1970s and 1980s and showed some efficacy, particularly when the materials were injected into the tree (Da Graça 1991). Widespread foliar sprays of antibiotics in commercial citrus orchards in Florida have not yielded the desired results. Recent research showed reduction of pathogen levels and suppression of disease symptoms when oxytetracycline was applied by trunk injection (Hu and Wang 2016). However, this method is currently not labelled for commercial use. Until resistant cultivars are available, growers will have to continue to use an integrated management program including vector control, nutrition and irrigation management, and other strategies to control the disease and manage tree health.”