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Mesquite infestation at Mardie
Station
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The largest mesquite infestation in Australia is located
in the Pilbara region of Western Australia. Most of it is
contained within a ca 150000 ha area, of which approximately
30,000 ha is dense. The core infestation is located entirely
on a single property, Mardie Station, although it is also
spreading onto stations to the south and isolated mesquite
has also been recorded from many other properties in the region.
The climate on Mardie station is hot all year round, with
summer temperatures frequently well into the 40's and, on
one occasion, reaching 50.5C (19 February 1998). Annual rainfall
is low, with most falling between January and June. It is
also highly variable and unpredictable. Most summer rain is
the result of cyclonic activity, while winter rain is from
[northern limits of south-western winter-rainfall regions].
Over 300 mm of rain has been recorded within a 24 hour period,
while in some years no rain has fallen at all (in 1924 no
rain fell for 15 months).
The current infestation was the result of active planting
of a "thornless variety" by pastoralists on Mardie
Station in the 1930's. Mesquite quickly naturalised, spread
and thickened. Since 1952 the huge scale of the problem has
led to concerted efforts to manage the infestation by costly
mechanical and chemical means. Although these may have had
some effect in slowing spread, the infestation continued to
spread and thicken at an alarming rate. The switch in 1998
from sheep to cattle, which are a far more efficient disperser
of seed, had the potential to further increase rates of spread.
The release of the leaf-tying moth, Evippe, in 1998 has almost
certainly had a dramatic impact in reducing invasiveness but
will not, on its' own, be sufficient in managing this infestation.
The PMMC is currently developing
and implementing a strategy for the longterm containment and
management of mesquite in the Pilbara.
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