Strategies for Improving the Efficacy of Bacteriophages for Controlling Bacterial Spot of Tomato

ABSTRACT (cont.): The use of these formulations resulted in 4,700, 38,500 and 100,000-fold increase in phage populations two days after application compared to the non-formulated phage populations. The PCF, Casecrete and skim milk formulations and the non-formulated phages all significantly reduced disease severity in field trials on tomato compared to the standard copper-mancozeb treatment by 22, 33, 27 and 19%, respectively. The PCF and the Casecrete formulations reduced the disease severity compared to the non-formulated phage by 11 and 21% in average in three field experiments, respectively. The skim milk formulation reduced the disease severity by 10% compared to the non-formulated phage application in one field experiment. The co-application of skim milk-formulated phages and copper-mancozeb treatment resulted in a superior disease control efficacy, which was significantly better than the control achieved by any of the treatments. The integration of phage application with Actigard treatment resulted in a significant increase in efficacy only with the PCF formulation but not with Casecrete formulation. The lowest phage titer that significantly reduced disease development in greenhouse experiment was 1,000,000 PFU/ml.