Prickly acacia, originally from the Middle East, was introduced
early in the 20th century for shade and fodder. During the early
part of the 1900s, seeds were carried in saddlebags and distributed
from horseback by graziers. The distribution of prickly acacia
however did not become problematic until production in the area
shifted from sheep to cattle. While sheep can digest the majority
of the prickly acacia seeds they consume, cattle cannot and so act
as major vectors.
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Prickly
acacia converts grasslands to shrublands
Photo: Joel Brown |
This small tree/shrub competes with native grasses, gradually
converting productive grassland to unproductive shrubland. This is
particularly important in the productive Mitchell Grasslands where
the heaviest infestations of prickly acacia are estimated to cover
more than 500,000 hectares.
Prickly acacia can produce more than 175,000 seeds per plant per
year, and can rapidly displace native vegetation to form dense
thickets. Wet years can generate a thousand-fold increase in plant
numbers in some areas.
Weed control programs so far have failed to contain the spread
of this pest. In July 1999, a Prickly Acacia Containment Line was
developed in central west Queensland an effort to help stop the
spread of the weed. Inside the line are five 'islands' of core
prickly acacia areas. These stretch from Barcaldine north to
Hughenden and west to Winton and Julia Creek. Eradicating prickly
acacia inside these areas is currently impractical or not
economically feasible and efforts concentrate on researching
biological control agents. Outside this line, the weed is
eradicated with the support of Queensland Department of Natural
Resources SWEEP program.
To see a recent list of research findings on prickly acacia
click here.
Click here to read more about weeds in the
Mitchell Grasslands.
