Controlling mesquite in northern Australia

Pilbara mesquite

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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 150 000 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 40s and, on one occasion, reaching 50.5 °C (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 millimetres 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).

Aerial view of the Mesquite infestation at Mardie Station, Pilbara region.

Mesquite infestation at Mardie Station, Pilbara region.

The current infestation was the result of active planting of a 'thornless variety' by pastoralists on Mardie Station in the 1930s. 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 long-term containment and management of mesquite in the Pilbara.

References

  • Cordo HA, DeLoach CJ. 1987. Insects that attack mesquite (Prosopis spp.) in Argentina and Paraguay: their possible use for biological control in the United States. United State Department of Agriculture, ARS-62. South American Biological Control Laboratory, Hurlingham, Buenos Aires. Argentina.
  • De Loach CJ. 1985. Conflicts of interest over beneficial and undesirable aspects of mesquite (Prosopis spp.) in the United States as related to biological control. In: Delfosse ES. (Ed.). Proceedings of VI International Symposium on the Biological Control of Weeds 1984. Minister of Supply and Services. Vancouver, Canada. Pp. 301-40.
  • Impson FAC, Moran VC, Hoffmann JH. 1999. A review of the effectiveness of seed-feeding bruchid beetles in the biological control of mesquite, Prosopis species (Fabaceae), in South Africa. African Entomology Memoir. 1:81-88.
  • Paulsen HA, Ares FN. 1961. Trends and carrying capacity and vegetation on an arid southwestern range. Journal of Range Management. 14: 78-83.
  • Ward CR, O'Brien CW, O'Brien LB, Foster DE, Huddlestone EW. 1977. Annotated checklist of New World insects associated with Prosopis (mesquite). United States Department of Agriculture, Research Services Bulletin. 1557.