Some grasses that have been introduced into native pastures in
northern Australia, such as mission grass and gamba grass have the
potential to cause problems as weeds in the tropical savannas. They
increase the risk of intense late-season fires because they dry out
later in the year than native grasses and are more productive, thus
increasing the fire fuel loads.
Lack of regular burning on cattle properties in the tropical
savannas has also probably been a key factor in the establishment
of introduced shrubs—notably rubbervine, prickly acacia,
mesquite and chinee apple—over wide areas. It has also
allowed the widespread development of thickets of some native
shrubs. These exotic and native woody weeds displace pasture and
make mustering increasingly difficult and expensive, presenting a
major challenge to the pastoral industry in some regions.
Fire to manage weeds
For these weeds, fire offers the best hope for management. Research
in the Victoria River District of the Northern Territory shows that
burning, with a frequency determined by seasonal and local factors,
can be effective in managing the native woody weeds there. While
fires seldom kill the plants, they can burn away most of the wood
and suppress sucker development. In Queensland, research has shown
that one or two fires in a 10-year period may be sufficient to
reduce rubbervine populations, keep the plant at tolerable
densities, and reduce the probability of it spreading further.