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Bacterial leaf streak (<i>Xanthomonas campestris</i> pv. <i>translucens</i>) has recently emerged as a serious disease of wheat in the mid-western U.S. Information is scarce regarding factors that influence disease development. This study was conducted under controlled environmental conditions to determine the effect of inoculation method, bacterial concentration, and plant age on disease development in moderately resistant and susceptible genotypes. Five inoculation methods were examined. Six inoculum concentrations were tested on plants from 12 to 49-days old. After inoculation, plants were immediately placed beneath a misting system to facilitate infection. Disease severity was assessed as percentage leaf area diseased at 14 days after inoculation. Results showed that inoculation method, inoculum concentration, and plant age had significant effects on disease development on both resistant and susceptible genotypes. All plants inoculated via leaf-infiltration and spray-inoculation methods showed distinct symptoms. Plants showed susceptibility to the pathogen at all growth stages; however, symptoms on 12-day old seedlings were most severe. No symptoms were observed with the lowest inoculum concentration (3 x 10⁴ cfu/ml). Disease severity increased significantly with an increase in inoculum concentration from 3 x 10⁵ to 3 x 10⁹ cfu/ml. Findings of the study can be applied to further research leading to the development of routine germplasm screening techniques. <p><p>Keywords: Bacteria-Phytoplasma-Spiroplasma-Fastidious Prokaryote, Cereals-Grains, Wheat