Two Zinkicide formulations (film forming plate structure or nanoparticle structure) provided better citrus canker control in a grapefruit field trial compared to industry standard copper-based products when applied at the same pounds metallic rate. The project was extended to cover a second year of field trials because the timing of funding did not align with the canker management season. The Zinkicide formulations remained effective against Xanthomonas at much lower rates than copper in culture media, so half and quarter rates were tested in the second year of the field trial. All rates of the plate forming Zinkicide and the half rate of the nanoparticle Zinkicide continued to be more effective than copper. However, the quarter rate nanoparticle Zinkicide formulation lost some efficacy and was equally effective as copper. This was surprising since the nanoparticle Zinkicide formulation was about 4 times more effective than the plate structure Zinkicide. It is hypothesized that this results form systemic movement. The entire applied rate of the plate structure Zinkicide would remain on or in the leaf keeping an effective concentration. If the nanoparticle Zinkicide moves systemically as supported by preliminary greenhouse soil drench experiments, the concentration of Zinkicide would be diluted by systemic movement. The loss of effective dose at the leaf surface suggests that the dose used in HLB trials was underestimated. In continuing projects funded by the USDA, we have adjusted our Zinkicide application rates to adjust for dilution from systemic movement in an attempt to get effective concentrations distributed throughout the plant vascular system. HLB field trials were applied at the half rate described above, which likely suffered from the same dilution problems. No significant changes in bacterial titer was observed with this low rate of Zinkicide. However, significant increases in fruit size were observed in Zinkicide treated trees, suggesting that some beneficial effects of Zinkicide on HLB were observed at these low rates. Ongoing trials funded by the USDA are using increased rates to attempt to match greenhouse efficacy observed with soil drenches on citrus canker and HLB. Without the relatively rapid canker field data, the application rate problem that limited control, but is suggestive of systemic movement, would have been overlooked. Commercialization and registration of Zinkicide is actively being pursued by Dr. Santra’s lab and an industry licensee.