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BNI December 1996 Vol 17. No.6 : Review


Vanneste, J. L. (1996) Honeybees and epiphytic bacteria to control fire blight, a bacterial disease of apple and pear, BNI 17(6) Back to BNI Reviews
 
Abstract: Incidence of fire blight (Erwinia amylovora) can be reduced by spraying apple and pear flowers with some strains of E. herbicola or Pseudomonas fluorescens. Most of these beneficial bacteria were selected in the laboratory using an assay on immature pear fruit, which has also proved useful to study their mode of action. Recently, an assay on crab apple flowers has also been developed. Pre-emptive colonisation by beneficial bacteria of the stigmas, where E. amylovora usually multiplies, can be enough to prevent the pathogen from multiplying and infecting the plant. In addition, most strains of E. herbicola produce compounds inhibitory to E. amylovora, some of which have been shown to play a role in reducing incidence of fire blight. To prevent selection of strains of E. amylovora resistant to these inhibitory compounds and to ensure control over a wide range of climatic conditions, the possibility of using mixtures of beneficial bacteria has been investigated. Taking advantage of the fact that the interaction between the pathogen and biological control agents has to occur on the stigmas and that beehives are already present in orchards for pollination, honey bees have been used to bring the biological control agents to the flowers. Biological control agents can be integrated with antibiotics currently used to control fire blight and some of these agents might also reduce frost injury and russeting. Future strategies for control of fire blight will take advantage of our increased understanding of the mechanisms involved in biological control and of the technological advances in fields such as plant biotechnology.