North West Weeds 
Your local guide to local noxious weed control (NSW, Australia)
   

North West Weeds
ABN 16 052 158 879
Postal address:
20 Dinoga Street
BINGARA
NSW 2404

PRINT VERSION1  PRINT VERSION2 (mailout flyer)  Identification │ Effect on animals │ More info? │ Control methods │Using pesticides │Disclaimer   

Mimosa bush* (Vachellia - previously Acacia - farnesiana) is an invasive and thorny plant spreading over grazing properties in north-western New South Wales and beyond.  It has taken over large areas around Moree, Pallamallawa, Boggabilla and Yetman.  It continues to spread into new areas.  Mimosa bush is very difficult, and costly, to control (see details of herbicide trials, below).

[*Mimosa bush - not to be confused with northern Australia's Mimosa pigra.  Also incorrectly referred to sometimes as "prickly acacia" - Acacia nilotica.]

Mimosa bush is NOT a declared noxious weed in New South Wales.  It is, in fact, classed as a native plant (despite its origin). Flora of New South Wales states that mimosa bush is:

"Native of trop. Amer., probably introduced into Aust. prior to European settlement. Widely cultivated overseas for its decorative qualities and the essential oil obtained from its flowers for use in the perfume industries. It is grown for hedges and windbreaks, however, it may form dense thickets and become weedy."

Mimosa bush has had some uses: it is regarded by some as a valuable source of food for sheep. Sheep (and goats, camels) tend to keep the plant under control, but over the past 20 years or more changes in land management, reduced sheep numbers and the move into cattle has seen the plant really "take off".  Cattle also find food value in the plant (especially the seed pods), but the viable seeds pass unscathed through the stomach and are a major contributor to the ever-increasing number of new plants every year. This is exactly what has happened to the Yetman Common over the past 10 or so years...as shown in this photo (left).

                        [Click on photos to download a larger picture]

Photo (left) close-up of mimosa bush.  Note the thorns, and the bean-like seed pods.  Each seed pod contains about 10 seeds.  The pods are a good food source, rich in protein.  Cattle feed on the mimosa bush pods.  The seeds pass through the animals and are subsequently dropped at random anywhere in the paddock. Photo (right) close-up of seed pods.

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EFFECT ON ANIMALS
Mimosa bush has useful qualities as a food source at different times of the year.  However, it is a very invasive and drought-resistant plant and if left unchecked severely reduces a property’s stock-carrying capacity. As time progresses, the plants can effectively take over the whole paddock!  The photo, left, shows how Mimosa bush has taken over a travelling stock route in the Pallamallawa NSW area...

IDENTIFICATION
Mimosa bush usually grows to a height of around 1 to 1.5 metres.  Almost every part of the plant contains sharp thorns.  Flowers are fluffy and yellow (see photo).  The seed pods are a prominent feature of the plant.  Stock seek out and eat the pods, spreading the seeds as they move on around the paddock. 

Photo, above left - close-up of mimosa bush leaves and flower - new spring growth - October 2002

HERBICIDE TRIALS
North West Weeds (at that time representing Inverell and Gwydir Shire Councils), in conjunction with NSW DPI, Dow Agrosciences, Dupont, Macspred and the Yetman Common Trust, conducted Mimosa Bush Herbicide Trials on Yetman Common Nov 2006, applying the same mixtures again Mar 2007 to compare timing of applications (see next paragraph for link to trials evaluation.)  This trial plot is still clearly signposted, Bruxner Highway 200m south of Yetman.  [Photo taken during trials evaluation - L to R Clem McLeod, Les Tanner, Stephen Kneller, Tony Cook, Doug Stieger]

LANDHOLDER CONCERN
Approximately 150 people attended a MIMOSA BUSH FIELD DAY at YETMAN NSW 10th December 2007, all looking for answers to effectively manage this pest plant.  Photo, right, shows some of the attendees during the speaker presentation in Yetman Hall. The day also included an on-site demonstration of a mulching machine by Asplundh Tree Expert Co and an inspection of the Yetman Common herbicide trials referred to above.  Tony Cook (NSW DPI) presented a Yetman Common Mimosa Bush herbicide trial evaluation sheet rating effectiveness of the various herbicide formulations after the first 12 months period.  An update on these original 06/07 trials is now attached - May 2010 - LRT

Much information was exchanged at the Mimosa Bush Field Day but, sadly, there were no magic solutions to the problem. The one clear message from the herbicide trials was that early detection and treatment of new plants is the only way to stop mimosa bush from spreading.

Looking ahead: Gwydir Shire (with assistance from Tony Cook, DPI Tamworth) applied for two (2) APVMA general permits: one to use a mix of Grazon® and Uptake Oil® (or equivalents in other brands) and the other to use Graslan® pellets (or equivalent).  The permit for the pellets has been approved (see table below). 

Again, like other herbicides already registered, there is no guarantee these two new mixtures will do the complete job. It seems we have to accept the fact that most mature plants will require a second treatment, whatever we use.  That is why it is so important for landholders to get in early and stop this plant before it becomes established. Small plants are not hard to kill.

Further trials are in progress  Inverell Shire Council is trialling various times and rates of Lontrel®, Grazon Extra®, pellets etc at other sites in the Yetman Common, immediately adjacent to the Bruxner Highway on the southern exit from Yetman.  Results to date confirm Lontrel® and tebuthiuron pellets as the two most cost-effective herbicide options.  The latest (11 May 2010) method to be trialled was the Wetblade® system comprising simultaneous slashing and herbicide application (see photo, right). Data from this work will be published on this website in due course.

Latest results - April 2011    2-page assessment summary Yetman mimosa bush herbicide trials

MORE INFORMATION:
Plants of Western New South Wales, by Cunningham, Mulham, Milthorpe & Leigh (published by Inkata Press).

CONTROL METHODS - SUBJECT TO COMPLIANCE WITH NATIVE VEGETATION ACT

Mimosa bush is a native plant, and subject to Native Vegetation Act restrictions.  Without Catchment Management Authority approval, control can only apply to new/regrowth plants that have appeared since 1 Jan 1990.  For more information on your legal requirements in this regard check out the CMA website, in particular www.nativevegetation.nsw.gov.au,   Or, talk to your local CMA representative! - in your area this plant may be classed as an Invasive Native Species, meaning less restriction on clearing.

Non-Chemical Options:  Manual control, in the form of pushing plants out of the ground with a tractor blade or the like, is NOT RECOMMENDED unless whole area followed up with careful herbicide treatment or ploughing, cropping etc.   While clearing gives an immediate impression that the problem has been solved, the same area will soon be infested with regrowth from broken root parts.  And, dozens of small seedlings will also emerge because the parent plants have been taken out.   Again, these control options are subject to the requirements of the Native Vegetation Act. 

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Chemical Options: At this time, there are four (4) herbicides registered for use in New South Wales for treatment of Mimosa bush (see table, below). None of them will do a 100% job every time, because mimosa bush is just so hard to kill - especially when the plants get a bit of size on them!  Timing is another factor - like all plants, they need to be healthy and with plenty of leaf to absorb the herbicide.

IMPORTANT:  USE OF PESTICIDES – ALWAYS READ THE LABEL
Pesticides must only be used for the purpose for which they are registered and must not be used in any other situation or in any manner contrary to the directions on the label.  Never use a herbicide in any way contrary to the label recommendations.

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DISCLAIMER:   The information contained in this web site is based on knowledge and understanding at the time of writing. However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of North West Weeds or the user’s independent adviser.
LRT - 31/08/2009

Send mail to northwestweeds@aapt.net.au with questions or comments about this web site.
Copyright © 2007-2013 Last modified: 23-Feb-2012 - North West Weeds