LEAF SURFACE BACTERIAL POPULATION OF FIVE DIFFERENT FIRE BLIGHT HOSTS

Fire blight was observed for the first time in a single orchard in southern Sweden in 1986. During 1989 until 1991 the pathogen spread rapidly in the southern and south-western parts of the country.
The spread has since then been limited with no severe outbreaks (Gråberg 1993, Persson 1995). When the disease reached and rapidly spread along the south-western cost of Sweden it was speculated that the causing pathogen Erwinia amylovora could have been present without symptom expression years before the visible outbreaks.
This cost area is very close to Denmark where the disease had been present since 1968. The ecology of the E. amylovora has been internationally studied over many years mainly in regions with a milder climate than the Swedish.
The question arose if the pathogen can be present on leaves of symptomless host plants.
Could this be possible in a cool and humid Swedish climate although results had shown the opposite e.g. for a warm and dry inland climate in France (Manceau et al., 1990).

The aim of the present study was to investigate if E. amylovora could be detected from leaves of fire blight hosts grown in an area where fire blight had been present some years earlier.
The aim was also to see if the surface bacterial flora differed between hosts and if this bacterial flora changed in time.

VIII International Workshop on Fire Blight

P. Persson

https://doi.org/10.17660/ActaHortic.1999.489.85