In September 2012, FireWall (Agrosource, Inc.) was granted an EPA Section 18 registration for control of citrus canker in Florida grapefruit. The FireWall label restricted use to no more than two applications per season. As a condition for FireWall registration, EPA required monitoring of Xanthomonas citri subsp. citri (Xcc) for streptomycin resistance in commercially treated groves. The objective of the survey was to apply our published protocol (Behlau et al., 2012) for sampling canker-infected grapefruit leaves for isolation and detection of streptomycin resistant Xcc. The survey was conducted in 3 or 4 grove locations each season in November-January. A report of the survey results were submitted each January to FDACS to be forwarded to EPA. No Xcc resistant to streptomycin were recovered from commercial groves during the 3 year survey. Greenhouse assays of sweet orange seedlings injection-infiltrated with Xcc consistently demonstrated that streptomycin, the active ingredient in Firewall, moves trans-laminar and controls Xcc infection in expanding leaves. Furthermore, this assay demonstrated that streptomycin moves upward into the next leaf flush where there is detectable activity against Xcc inoculated 10 weeks after spray application to initial flush. These assay results confirm streptomycin moves upward and explain the consistent performance of streptomycin against canker in field trials. Penetration of leaves by streptomycin insures that it is protected from wash-off by rainfall, weathering and degradation by UV light.