16. A Comparison of the Ecology and Conservation Management
333
situations favour the development of pathogenic activity by a leaf spot
fungus Aulographina eucalypti and can lead to epidemic levels of premature defoliation and shoot death (Palzer , 1978). Eucalypts killed by the
disease cannot regenerate without disturbance to the understory, and so
the disease may contribute to an accelerated succession to rainforest
(Wardlaw, 1990).
Phytophthora cinnamomi is an introduced root-rotting fungus capable
of killing a wide range of host plant species in Tasmanian rainforests
(Podger & Brown, 1989). The fungus has been isolated from 39 species of
host plants, particularly in the Epacridaceae, Eucryphiaceae, and Proteaceae. The fungus is active in rainfore st only in disturbed areas such as
roadsides and recently burned areas where soil temperatures are elevated
above 15°C. It has not been found in undisturbed forest , and Podger and
Brown (1989) consider that while no single rainforest species is under
threat of extinction, susceptible species which are either shade intolerant
or which lack efficient dispersal mechanisms may be at risk of local
elimination from fire-disturbed sites or regeneration.
Myrtle wilt (Elliott , Kile, Candy, & Ratkowsky, 1987) is a disease of
the rainforest dominant Nothofagus cunninghamii, caused by a native
fungal pathogen Chalara australis (Kile & Walker , 1987). The fungus is
found throughout rainforest areas and appears to be air and/or water
borne . It infects tree wounds although there is some evidence of underground spread of infection by root graft (Kile, Packham, & Elliott, 1989).
The disease is associated with a pinhole borer Platypus subgranosus
(Howard , 1973), which apparently is attracted to infected trees, and the
frass left by the insect provides an early indication of disease. In undisturbed rainforest, Nothofagus cunninghamii death and gap formation
caused by wilt appear to be in equilibrium with regeneration processes
(Packham, 1990; Packham et aI., 1990), but disease expression is typically
exacerbated by disturbances such as roads or logging (Elliott et aI., 1987).
Chalara species are known also from the Nothofagus forests of New
Zealand, but do not appear to be a conservation problem there or in
South America . However, it may become relevant for forest conservation
there given the increasing levels of disturbance which are occurring.
Weedy plant species are not a serious problem in undisturbed rainforests , but they may invade into disturbed vegetation , especially near
urban areas along roadsides, in cut-over areas and after fires. Some of
these species have the capacity to alter the structure, composition and
ecology of the native forest (Duckett, 1990). Potential problem species in
this regard include species of Fuchsia, Rubus, Digitalis, Clematis,
Leycesteria, Genista, Sarothamnus, and Cortaderia spp. There have been
no concerted approaches to these problem species, except for Cortaderia.
Following the recent importation of a new species and an effective pollen
source, for the existing vegetatively propagated females the species has
become a potentially invasive threat. A high profile publicity campaign
and active work by land managers have controlled the spread to date
(Duckett, 1990).
333
situations favour the development of pathogenic activity by a leaf spot
fungus Aulographina eucalypti and can lead to epidemic levels of premature defoliation and shoot death (Palzer , 1978). Eucalypts killed by the
disease cannot regenerate without disturbance to the understory, and so
the disease may contribute to an accelerated succession to rainforest
(Wardlaw, 1990).
Phytophthora cinnamomi is an introduced root-rotting fungus capable
of killing a wide range of host plant species in Tasmanian rainforests
(Podger & Brown, 1989). The fungus has been isolated from 39 species of
host plants, particularly in the Epacridaceae, Eucryphiaceae, and Proteaceae. The fungus is active in rainfore st only in disturbed areas such as
roadsides and recently burned areas where soil temperatures are elevated
above 15°C. It has not been found in undisturbed forest , and Podger and
Brown (1989) consider that while no single rainforest species is under
threat of extinction, susceptible species which are either shade intolerant
or which lack efficient dispersal mechanisms may be at risk of local
elimination from fire-disturbed sites or regeneration.
Myrtle wilt (Elliott , Kile, Candy, & Ratkowsky, 1987) is a disease of
the rainforest dominant Nothofagus cunninghamii, caused by a native
fungal pathogen Chalara australis (Kile & Walker , 1987). The fungus is
found throughout rainforest areas and appears to be air and/or water
borne . It infects tree wounds although there is some evidence of underground spread of infection by root graft (Kile, Packham, & Elliott, 1989).
The disease is associated with a pinhole borer Platypus subgranosus
(Howard , 1973), which apparently is attracted to infected trees, and the
frass left by the insect provides an early indication of disease. In undisturbed rainforest, Nothofagus cunninghamii death and gap formation
caused by wilt appear to be in equilibrium with regeneration processes
(Packham, 1990; Packham et aI., 1990), but disease expression is typically
exacerbated by disturbances such as roads or logging (Elliott et aI., 1987).
Chalara species are known also from the Nothofagus forests of New
Zealand, but do not appear to be a conservation problem there or in
South America . However, it may become relevant for forest conservation
there given the increasing levels of disturbance which are occurring.
Weedy plant species are not a serious problem in undisturbed rainforests , but they may invade into disturbed vegetation , especially near
urban areas along roadsides, in cut-over areas and after fires. Some of
these species have the capacity to alter the structure, composition and
ecology of the native forest (Duckett, 1990). Potential problem species in
this regard include species of Fuchsia, Rubus, Digitalis, Clematis,
Leycesteria, Genista, Sarothamnus, and Cortaderia spp. There have been
no concerted approaches to these problem species, except for Cortaderia.
Following the recent importation of a new species and an effective pollen
source, for the existing vegetatively propagated females the species has
become a potentially invasive threat. A high profile publicity campaign
and active work by land managers have controlled the spread to date
(Duckett, 1990).