ECOLOGY AND EPIDEMIOLOGY OF FIRE BLIGHT IN NEW ZEALAND

Fire blight symptoms were only seen in apple and cotoneaster flowers and in developing fruitlets when stigmas of individual blossoms were inoculated with concentrations of Erwinia amylovora providing >10⁴ colony forming units.
Using a sensitive DNA hybridisation method (³²P-labelled probe) E. amylovora was detected in the flower parts of those blossoms showing fire blight symptoms. E. amylovora was not detected in symptomless blossoms and developing fruitlets.

The DNA probe was used to determine the spread of E. amylovora from inoculated blight sources (apple blossoms) showing fire blight symptoms. E. amylovora was not detected in calyxes of immature and mature fruit or on the surfaces of mature fruit even from within 5 cm of these blight sources.
The weather was conducive to the spread of the disease over flowering but all inoculated blossoms and those showing symptoms in adjacent blossom clusters either aborted as flowers or as developing fruitlets.

VII International Workshop on Fire Blight

C.N. Hale, R.K. Taylor, R.G. Clark

https://doi.org/10.17660/ActaHortic.1996.411.19