For this reporting period, rainfastness experiment was conducted on heirloom tomato plants (heat tolerant variety Florida 91) in triplicates. Plants were sprayed with agri-grade TSOL-UP (field trial samples) at foliar spray rate of 800 ppm of metallic zinc. Plants were then washed following an industry recommended protocol with simulated rainfall for 3 consecutive days. Whole plants were then harvested, dried, digested with aqua regia solution (a mixture of nitric acid and hydrochloric acid in a molar ratio of 1:3) and analyzed for zinc content by atomic absorption spectroscopy (AAS) technique. Our results suggested that maximum zinc content was observed after 1st wash (2.4 mg/gram dry wt. of plant sample) while the zinc content was stabilized for 2nd and 3rd wash (1.2 and 1.3 mg/gram dry wt. of treated plant sample respectively over the water-sprayed control). Colony forming unit (CFU) or viability assay was performed with both TSOL-U and TSOL-UP (field trial agri-grade samples). For both the versions of TSOL, the MIC appeared to be at 80 ppm (metallic zinc) for Escherichia coli bacteria. In case of Xanthomonas alfalfae, the MIC of TSOL-U was found to be 80 ppm and for TSOL-UP the MIC was 40 ppm. The concentration of samples picked for CFU study was one concentration above and one below MIC values. For example, in case of E. coli, the three concentrations chosen for both TSOL-US and TSOL-UP are 40, 80 and 160 ppm of metallic zinc (because the MIC was 80 ppm of metallic zinc). Based on the CFU studies, it appears that at MIC concentration (80 ppm in E. coli), the bacterial load was reduced by 4 logs (>2 log reduction is considered significant) compared to the untreated control. At 160 ppm, there was complete killing of bacteria whereas at 20 ppm (below MIC), there was no significant killing observed as expected. For the upcoming reporting period we plan on extracting plant sap and analyzing it further to detect the presence of zinc content along with other components.