Burning rubbervine at Wrotham Park in November
produced a 100 per cent kill rate. Photo: Faiz Bebawi
A blazing, white-hot fire that turns
rubbervine to ashen "snow" is beating infestations of the
destructive pest plant in the far north of Queensland.
Researchers at the Queensland Department of Natural Resources
recently trialled large-scale burns as a means of managing the
invasive weed on the cattle station Wrotham Park, 70 kilometres
west of Chillagoe. The trials have been some of the most successful
undertaken for controlling rubbervine. Although prescribed burns
took place at Wrotham Park two years before the trials were started
(in 1997), researchers believe the trials have proved burning is a
viable option for large areas.
Within the experimental plots, the first burn produced a
rubbervine kill of 80 per cent. However, if that first burn was
followed up with a second burn 12 months later, 99 per cent of the
weed was killed.
"The trials have shown the follow-up burn is essential. If a
follow-up isn't done, the 20 per cent of the weed that is not
killed will regenerate from the base," project leader Dr Faiz
Bebawi said. Wrotham Park manager Henry Burke agreed the results of
the trials were outstanding. "Fire is proving to be the most
successful and econo-mical way of controlling rubbervine," he said.
"From this experience we'll continue to use this strategy to
control the rubbervine."
It is believed rubbervine was introduced into Australia as an
ornamental shrub in the late 1800s. The weed, which is declared in
Queensland, first invades waterways where seeds germinate in moist
silt layers after rain. The plant smothers riparian vegetation and
forms a dense thicket. This degrades the native vegetation and
prevents access to both stock and native animals.
Infestations expand outward from waterways, colonising hillsides
and pastures, which results in loss of land for grazing and
difficulty in mustering stock. Dr Shane Campbell, who also worked
on the trials, explained fire trials were carried out on rubbervine
that had previously been infected with rubbervine rust disease.
This disease was first released in Queensland in 1995. It causes
heavy infection in the weed resulting in defoliation and reducing
seed production. However, it does not kill established plants.
"The presence of the rust disease appears to have contributed to
the success of the fire, and the amount of rubbervine killed," said
Dr Campbell. "Rust reduces the vigour of the plants, making the
plants more susceptible to fire as well as enabling more pasture
growth and therefore an increased fuel load."
The prescribed burns took place over two years—the first
in October 1997 over an area of 16 square kilometres. Some areas
were left unburnt to allow for comparisons. "The purpose of the
trials is to gauge the success of fire as a weed management
strategy to control rubbervine infestations that spread over a
large area," Dr Bebawi said.
He added that fire was the most economic means of control for
land-holders with large tracts of rubbervine infestations, a point
supported by Mr Burke. He said Wrotham Park would continue to do
follow-up burns on the larger infestations. The trials also had the
added benefit of flushing out 500 head of cattle hiding in the
thick rubbervine near streams!