June 2011 Mesquite Prosopis spp.
WHAT IS IT? There are four naturalised species of mesquite (genus Prosopis) and a range of hybrids in Australia - collectively, they are suited to the climate of much of inland Australia Mesquites are mostly thorny and can be either a multi-stemmed shrub or a single- stemmed tree The mesquite species that are weeds in Australia are natives of Central America, northern South America and southern North America, and plantings have subsequently escaped in every mainland Australian state Prosopis pallida is also known as algaroba Mesquite outside of its natural habitat – Image by Forest & Kim Starr. www.hear.org Synonyms of Prosopis are: Neturna, Mimosa, and Acacia
WHY IS IT A PROBLEM? Damages environmentally sensitive areas such as watercourses and native grasslands; forms impenetrable barriers, particularly around water sources Competes with and excludes native vegetation by shading and by depleting soil moisture Reduces pasture causing loss of production, and increases the difficulty and expense of mustering stock Thorns can cause serious injury to people; and damage vehicles Provides refuges for feral animals Feral animals (e.g. wild pigs) gather and
feed on seed pods Landscape invaded by Mesquite – Image by Forest & Kim Starr. www.hear.org
What are State Alert Weeds? These are invasive weeds that are not known to be in South Australia, or if present, occur in low numbers in a restricted area, and are still capable of being eradicated. An Alert Weed would pose a serious threat to the State’s primary industries, natural environments or human health if it became established here. All Alert Weeds are declared under the Natural Resources Management Act 2004: their transport and sale are prohibited (Sect. 175 and 177), plants must be destroyed (Sect. 182), and if found on your land their presence must be notified to NRM authorities (Sect. 180) – refer overleaf. DESCRIPTION Multi-stemmed perennial shrubs or single stemmed trees with a spreading canopy growing 3-15 m tall. Mesquite branches have a distinctive zig-zag structure and fern-like leaves at each point where the branch changes direction, often with a pair of spines at the base. Creamy-yellow cylindrical shaped flower spikes are 50-80 mm in length. Bark is smooth and red-green in young stems, and rough grey in older stems. It has a large branched tap root reaching a depth of 20 m, and roots can also grow upwards to capitalise on soil surface moisture.
HOW IT SPREADS Plants re-establish by seed and vegetatively. Animals eat the highly sought after seed pods, which can take up to 8 days to pass through the gut. Seed can be distributed long distances if eaten by livestock that are transported. P. juliflora flower. Image by “Forest & Kim Starr” www.hear.org. Floodwaters, run-off, machinery and vehicles can also spread plants.
HABITAT Found in semi-arid and arid regions, infestations commonly begin along watercourses (natural and constructed), but can rapidly invade upland country.
ORIGIN Native to northern South America, Central America and southern United States of America.
DISTRIBUTION IN AUSTRALIA Current: Prosopis species are naturalised in every Australian state and territory with the exception of Tasmania and the ACT. Prosopis juliflora and perhaps P. velutina have been naturalised in SA as small populations in the rangelands, but
P. juliflora – Leaves, thorns & seedpods. are mostly now removed. Images by Forest & Kim Starr Potential: All Australian states and territories have suitable climatic conditions for mesquite, considering its ability to survive droughts, and a diverse range of soil types. It is well adapted to the monsoonal woodland of northern Australia. In South Australia it is a weed threat in the semi-arid rangelands.
HOW IT GOT HERE Mesquite was introduced to Australia for fodder, livestock shade and shelter, erosion control and shade around stations in the early 1900s.
WHAT CAN YOU DO? Be on the alert for this plant using this Fact Sheet as a guide. If you see a DISTRIBUTION suspicious plant that may be this State Alert Weed, please report it to your local Current distribution based on Natural Resources Management (NRM) Board (contact details at herbarium records www.nrm.sa.gov.au). For more information on weeds, including Alerts, contact your local NRM Board or visit either www.pir.sa.gov.au/biosecurity Potential distribution based on climate modelling (phone 08 83039620) or www.weeds.org.au.
Disclaimer: This publication is provided for the purpose of disseminating information relating to scientific and technical matters. The Government of South Australia does not accept liability for any loss and/or damage, including financial loss, resulting from the reliance upon any information, advice or recommendations contained in this publication. The contents of this publication should not necessarily be taken to represent the views of the participating organisations.