Integrated control of fire blight in a pear orchard in Turkey using prohexadione-CA and bacterial antagonists

• Published in: Acta horticulturae no. 896; pp. 441 - 446
• Main Authors: Ozaktan, H, Akkopru, A, Aslan, E, Ilhan, K, Koltuksuz, T
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01-01-2011
• Subjects: antagonists; bacteria; biological control; blight; Erwinia amylovora; freeze drying; fruit trees; Pantoea agglomerans; pears; Pseudomonas fluorescens; shoots
• ISSN: 0567-7572; 2406-6168
• DOI: 10.17660/ActaHortic.2011.896.64

Fire blight, caused by Erwinia amylovora, has threatened pear cultivation in Turkey since 1985. Biological control with epiphytic bacteria against E. Amylovora has been considered as a potential method for controlling the disease on pear blossoms. Pantoea vagans strain C9-1 (formerly Pantoea agglomerans C9-1), and Pantoea agglomerans strain Eh24, and Pseudomonas fluorescens strain A506 were produced as freeze dried bioformulations. The efficacy of these bioformulations against blossom infections from natural populations of E. Amylovora in a commercial pear orchard was evaluated. The freeze-dried formulations of antagonistic bacteria were applied as single strains and in combination at 30 and 100% bloom in a pear orchard. In the pear orchard trial conducted in 2010, freeze-dried formulations of antagonistic bacteria, applied as single strains, reduced the percentage of blighted blossoms in the pear orchard by 27 to 54%, and strain C9-1 was more efficacious than PfA506 and Eh24, as significant reductions in blossom blight were observed in the orchard experiment. Two different combinations of bioformulations such as C9-1+PfA506, Eh24+PfA506 and C9-1+Eh24 which were applied on pear blossoms were found as effective as the treatment of C9-1 alone on a pear orchard to protect the blossom infections. Antagonistic bacteria successfully colonized on pear blossoms and resulted in a 10- to 100-fold increase in surviving bacteria within 14 days after the last application. Prohexadione-Ca (ProCa, Regalis, BASF), which was a new plant bioregulator for application in pome fruit trees was also applied to the same pear orchard at the beginning of petal fall and 14 days after the first application to test the control of shoot blight by E. amylovora. Application of P. Vagans strain C9-1 and then ProCa treatment on pear trees gave the best reduction in the incidence of shoot blight on trees under conditions of natural infection.