Systemic characterization of three Mg-Zn gel based multi-metal formulations containing Cu A.I. [Cu:Mg:Zn (10%:45%:45%, MM10C45M45Z), Cu:Mg:Zn (15%:42.5%: 42.5%, MM15C42.5M42.5Z) and Cu:Mg:Zn (20%:40%: 40%, MM20C40M40Z)] is in progress. The hydrodynamic size of as-prepared materials was measured through dynamic light scattering (DLS). MM10C45M45Z, MM15C42.5M42.5Z, and MM20C40M40Z showed increased hydrodynamic size with higher Cu content (290.2 nm, 334.7 nm, and 354.2 nm respectively), suggesting Cu could induce the aggregation of primary particles. The primary particle size of multi-metal formulations (MM25C75M, MM25C75Z, MM10C45M45Z, MM15C42.5M42.5Z, and MM20C40M40Z) will be evaluated through electron microscopy. The electron microscopy results for the as-prepared multi-metal formations will be included in the next report.The antimicrobial efficacy of as-prepared materials was tested in vitro against Pseudomonas syringae. To determine the minimum inhibitory concentration (MIC) of the as-prepared materials and selected controls, a macrodilution assay was performed (Nature Protocols, 2008, 3, 163-175). The MIC value was determined by measuring the optical density at 600 nm after 48 h incubation at 27 °C under shaking (150 rpm). The MIC value of MM25C75M, MM15C42.5M42.5Z, and MM20C40M40Z was 80 ppm of metallic Cu, which was similar to copper controls (copper nitrate and Kocide 3000). The MIC value of MM10C45M45Z was 40 ppm of metallic Cu. The enhance antimicrobial efficacy may due to the smaller particle size. The MIC value of MM25C75Z was 5 ppm of metallic Cu. This result suggests that MM25C75Z formulation might contain ultra-small size particles. To determine the minimum bactericidal concentration (MBC) of as-prepared materials and selected controls, a colony-forming unit (CFU) assay was performed (Nature Protocols, 2008, 3, 163-175). The MBC value of MM25C75M, MM25C75Z and MM10C45M45Z was 80, 10 and 40 ppm metallic Cu respectively. All multi-metal formulations showed enhanced bactericidal efficacy when compare with commercial copper bactericide control (Kocide 3000, MBC: 320 ppm metallic Cu).To evaluate the systemic mobility of the Cu A.I., a plant uptake study was performed using Citrus reshni (Cleopatra mandarin) seeding in a growth chamber (Panasonic Environmental Test Chamber, Model MLR-325H, Kadoma, Japan). Temperature and relative humidity were maintained at 35 ºC and 85%. The citrus seeding was foliar-sprayed using a hand-pump sprayer with 300 ml of MM25C75M, MM25C75Z, MM10C45M45Z (500 and 1000 µg/ml metallic Zn concentration) and deionized water as a control. After 48 h incubation in the plant growth chamber, citrus seedlings were removed from the soil and gently washed with 1% cleaning detergent (Alconnox ®, Alconnox Inc.) and 0.1% HCl. Leaves, roots and stem sections were separated after washing and left in an oven for 48 h (45 ºC). Then, the dried leaves, roots, and stems were acid digested (EPA method 3050 B Acid Digestion of sediments, Sludge, and Soil). Cu, Zn and Mg contentions in leaves, stems, and roots will be quantified with Atomic Absorption Spectroscopy (AAS). The AAS results will be included in the next report.