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Rainforest
Masks a Deadly Disease Phytophthora cinnamomi is a fungal organism
which has a destructive reputation of global proportions. It is blamed for
"forest dieback" in native forests of Victoria and Western Australia
and is responsible for millions of dollars of damage annually to the
horticultural and forestry industries. In fact, the potential damage is so severe that
the Australian Government lists the disease as a key threatening process under
the Endangered Species Protection Act. One scientist likened the advance of the disease
through the heathland as a 'front of death'. From the air, the scourge of
Phytophthora is evident by the conspicuous patches of dead trees it leaves in
its wake. Research conducted in the 1970s and early 1980s
by Dr Bruce Brown, a scientist with the Queensland Forestry Service, uncovered
Phytophthora cinnamomi throughout the Wet Tropics rainforests. This threat to
Australian rainforests, in its own soils, may have a more devastating effect
than the latest bout of coral bleaching which is impacting the Great Barrier
Reef. However, scientists have remained baffled for more than a decade by the fact the
disease does not appear to be as rampant in the rainforests as elsewhere. Its
impact seems to be limited to isolated patches
of rainforest dieback.
One
of the patches of tree dieback at Mt Lewis caused by Phytophthora cinnamomi The organism is very hardy and its infective
agent can be carried on motor vehicle tyres and footwear. It can also be spread
through ground water or by animals, including feral pigs. Once it finds a foot
hold, it is nearly impossible to eliminate. However, with increased demands for sustainable
utilisation of Australia's rainforest resources, forest managers are worried
that Phytophthora could hitch a ride elsewhere on the shoes or The Workshop Against such a background, it is clear that
there is an urgent need to update scientific knowledge of the biology and
ecology of Phytophthora as it relates to wet tropical rainforests. In late April, Rainforest CRC scientists joined university colleagues from
around the country, landmanagers and representatives of the tourism industry to
review the 'state of play' on Phytophthora. It was the first time a group of
plant pathogen pundits and other interested parties had come together through a
shared concern over this potent and potentially devastating disease. Research projects identified Workshop convenor and James Cook University scientist,
Dr Paul Gadek said funding would be sought for a series of research projects to
increase understanding of the disease and contribute to future management plans. "The
workshop was very timely, coming after a 16
year hiatus
in the research effort into Phytophthora cinamomi in the tropics," said Dr
Gadek. “We have identified some priority research
projects for which we are seeking funding to answer specific questions, such as,
'where are the areas of the Wet Tropics that are most likely to have a problem
with Phytophthora cinnamomi?', 'what
plant communities are in danger?', and 'how do we monitor and isolate pathogens
from the rainforest environment?'" Dr Gadek said. The rainforest may hold the secret to controlling the devastation in other areas
of Australia and even around the world. "We know that Phytophthora exists in the rainforest but we don't know why it does
not appear to be adversely affecting the trees and plants. It may be that native
rainforest vegetation is immune to infestation," he added, "but that
is difficult to say because Phytophthora in
the rainforest has been so understudied." Specific conditions including human disturbance
might trigger the
organism to produce its infective agent and kill trees. The workshop
participants agreed that more needed to be known about the factors that trigger
that reaction. "If it is in the rainforest, we don't want
to carry it out into areas of high risk such as fragile heathlands. On the other
hand, if it is not native to the rainforests, we don't want to track it in from
areas where it might be prevalent," said Dr Cadek. Nurseries and agricultural industries have applied practices of containment and
mitigation like injecting root systems with a retardant but
these would be impractical for native rainforests. "We are told that once a tree is infected, you can't get rid of it. So the
idea is to stop the infection happening in the first place," Dr Gadek said. Tour operators supportive Dr Gadek applauded the role being played by the
tourism sector which has backed the concern over potential forest dieback with
support for the Phytophthora cinnamomi workshop
and the proposed research program. "The tourism operators don't want to kill
the goose that lays the golden egg. They use the Wet Tropics as part of their
business. They, quite rightly, want to know as much about the disease as we
do," Dr Gadek said. The workshop produced a volume of papers which will generate a technical report
to support funding applications for Phytophthora
cinnamomi research projects. The Rainforest CRC will seek funding to allow
such projects to get underway later this year. The research program will increase scientific
knowledge, he 'front lines' to make sure the Phytophthora blight doesn't rear it ugly head in the Wet Tropics.
For
more information
The CRC for Tropical Rainforest Ecology and Management is a formal partnership between the
CSIRO,
James Cook University of North Queensland, The University of Queensland, Griffith University and the Wet Tropics Management Authority.
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