EFFICACY OF BACTERICIDES AND BIOLOGICAL ANTAGONISTS FOR THE CONTROL OF FIRE BLIGHT OF APPLE IN THE SAN JOAQUIN VALLEY OF CALIFORNIA

During 'Granny Smith' and 'Fuji' apple blooms in 2005 and 2006 the following materials were evaluated for the control of fire blight: the commercial rate of Pseudomonas fluorescens strain A506 (BlightBan A506), with and without the organo-silicon surfactant Breakthru (Polyether-Polymethylsiloxane-Copolymer) at 0.5%; a higher than commercial rate of P. fluorescens A506; a combination treatment of P. fluorescens A506 and Pantoea agglomerans C9-1, P. agglomerans C9-1 by itself and followed by Kasumin (kasugamycin); the systemic acquired resistance material Physpé 4 (also known as Vacciplant, a plant defense elicitor extracted from brown algae), Serenade (dried fermentation culture of Bacillius subtilis QST713), and Cuprofix A MZ (copper sulfate); famoxate (experimental bactericide) against a combination treatment of Agri-mycin 17 or Firewall (streptomycin sulfate) and Mycoshield or FlameOut (oxytetracycline calcium complex); and an untreated control. In 2005 Cuprofix A MZ, A506 + Breakthru 0.5%, streptomycin + oxytetracycline, Serenade, P. agglomerans C9-1, P. fluorescens A506 + P. agglomerans C9-1 and Physpe 4 significantly reduced disease incidence on Granny Smith when compared to the untreated control. There was less disease in both the high rate of P. fluorescens A506 and the commercial rate of P. fluorescens A506 when compared to the control but differences were not significant. In 2006, P. agglomerans C9-1 followed by Kasumin showed the least disease followed by, Firewall (streptomycin) + FlameOut (oxytetracycline), Serenade, Cuprofix A MZ, FlameOut, Firewall, P. fluorescens A506 + Breakthru 0.5% and Physpe that significantly reduced disease when compared to the untreated control. High rates of Breakthru at early bloom appear to enhance the efficacy of the biological antagonist P. fluorescens A506.