Journal of Animal & Plant Sciences, 2010. Vol. 8, Issue 3: 1006- 1015. Publication date: 28/10/2010,The study was conducted to assess the presence of seedborne bacteria in four tomato seedlots, the efficacy of seed treatments in reducing bacterial contamination and to determine influence of seed treatment or mulch on crop development and yield. Tomato seedlots were treated using hot water, chlorine, and Ridomil® followed by seedborne bacteria pathogen detection. Seedlings from treated and non-treated seedlots were grown in the field in mulched and non-mulched plots. Results showed that all seedlots assessed were contaminated with Clavibacter michiganensis subsp. michiganensis (CMM), Xanthomonas campestris pv. vesicatoria (XCV) and Pseudomonas syringae pv. tomato (PST). ‘Tanya G1’, ‘Tanya G2’ (first and second generation farmer-saved seeds respectively) and commercial ‘Cal J’ seedlots were more highly contaminated with XCV than commercial ‘Tanya’ seedlot. ‘Tanya G2’ had the highest PST contamination but did not differ from other seedlots for CMM. Chlorine and hot water significantly reduced bacterial populations on seeds. Ridomil seed treatment did not affect bacterial contamination compared to the untreated control. Marketable fruit yield differed statistically (P = 0.01) for commercial ‘Tanya’ and ‘Cal J’ seedlots. Commercial ‘Tanya’ and ‘Tanya G1’ had higher yields compared to ‘Cal J’ and ‘Tanya G2’. There was no statistical difference (P = 0.05) among seed sources with respect to incidence of blossom end rot (BER) and sunscald disorders. Chlorine and hot water treatments led to higher number of fruits per plant and increased yield compared to Ridomil treatment and the control. Seed treatment had no significant influence on BER. Plants from hot water treatment produced statistically fewer sunscald fruits compared to control, because of more vigorous growth that provided protective shade. The effect of mulch on the yield components and in reduction of sun-scalded fruits was highly significant (P = 0.0001). Seed treatment and mulch therefore can reduce disease infestation and improve tomato yield.