Articles
DETECTION OF ERWINIA AMYLOVORA, THE CAUSAL AGENT OF FIRE BLIGHT, IN THE ROYAL BOTANIC GARDENS, MELBOURNE, AUSTRALIA
This report triggered one of the most intense survey and diagnostic programs in the history of plant industries in Australia.
Detailed surveys of the parks and urban areas surrounding the RBG were commissioned to look for host plants and characteristic symptoms of fire blight.
State and National surveys did not detect classic symptoms of fire blight outside the RBG, Melbourne and E. amylovora was not identified in any commercial or urban environment.
A dedicated diagnostic laboratory was established at the Institute for Horticultural Development, Melbourne, which processed all samples from the field surveys.
Bacterial isolations from symptomatic wood samples and molecular characterisation of Erwinia amylovora-like bacteria were also conducted at Macquarie University, Sydney, Australia (Dr.
M. Gillings) and at the Max Planck Institute, Heidelberg, Germany (Prof.
K. Geider). The findings of the New Zealand laboratory were confirmed when E. amylovora was isolated from one Cotoneaster plant and one Sorbus plant in the RBG, Melbourne by Prof.
Geider.
Despite comprehensive tests, neither of the Australian laboratories were able to confirm the presence of E. amylovora in plant samples from the RBG, Melbourne.
The plants from which E. amylovora was isolated showed dieback of leaves and shoots.
These symptoms could have been caused by E. amylovora but are also similar to diseases caused by wood invading fungi such as Botryosphaeria and Phompsis, both of which were frequently present on the wood samples.
The Cotoneaster plant in the Melbourne RBG which E. amylovora was isolated from were transported to a high security facility and maintained at 23°C, 16 hr day length, for 6 months.
Several attempts at reisolating E. amylovora from symptomatic material on these trees were unsuccessful.
Prof.
Geider was flown in to Melbourne in June, 1997, to assist with the complex process of interpreting the results from diagnostic tests.
His conclusions were that the low levels of E. amylovora in the plant samples in the Melbourne RBG and the lack of obvious symptoms indicate that fire blight was at the lowest levels of detection.
A comprehensive paper on the diagnostic protocols used and the results obtained from the 1997 Autumn survey in the RBG, Melbourne is in preparation (Jock et al., 1998, in prep.). Preliminary data about detection, isolation and characterisation of E. amylovora from the RBG, Melbourne will be presented in another contribution of this issue (Jock et al.)
In Spring 1997, an intense host eradication program was implemented in the Melbourne RBG and surrounding areas.
Over 900 trees were removed from the Melbourne RBG and surrounding gardens.
Feral bee hives were also removed from the gardens and surrounding areas.
Pollen samples were collected fortnightly from strategic