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The plant must be eradicated from the land and the land must be kept free of the plant. Landholders are legally required to control or treat mesquite across all mainland states and the Northern Territory.
Why Is It Bad?:
Is regarded as one of the worst weeds in Australia because of it's invasiveness, potential for spread and economic and environmental impacts. It forms such dense thickets and large thorns that it prevents stock accessing watering holes and makes musteirng difficult. It reduces pastoral country by taking over grasslands and using valuable water resources. Mesquite also causes damage to animal hooves and vehicle tyres from thorns, and the poisoning of livestock which consume excessive amounts of seed pods.
To view a Youtube video about Mesquite, copy and paste this link into the address bar: http://www.youtube.com/watch?v=3KVbGglSx94
Mesquite species come in a range of shapes and sizes, they can be multi-stemmed shrubby bushes or single stemmed trees with a spreading canopy, growing from 3 to 15m tall. Branches have a characteristic zig zag structure. Leaves are fern like. They occur at each point where the branch changes direction (the zig-zag) in groups of one to three pairs, often with one or two thorns.
Greenish cream-yellow flowers are arranged on a cylindrcal-shaped spike which resembles a 'lambs tail', 50 - 80 mm in length.
The seed pod (up to 200mm long) is straight or slightly curved with only very slight constrictions between the seeds.
The tap root is large and much branched and generally grows to a depth of 20m.
The new approach to controlling mesquite involves integrating all control methods together with grazing management systems to minimise impacts over the long term. Integration involves chemical control, mechanical control, fire, grazing control and biological control.
The basal bark and cut stump techniques used with an appropriate registered herbicide are effective on mature trees. Basal bark treatment (spraying around the entire stem up to 750mm from the ground) should be used during the growing season (approximately October to April, depending on species and location.) The cut stump method of applying a herbicide directly onto a horizontally cut stump is effective year round. Seedlings can be controlled by spraying foliar herbicide over the entire plant. This is effective for dealing with actively growing, dense stands of mesquite up to 1.5m tall.
Fire can give good control particularly after mechanical control such as chaining, which can provide enough fuel for it to burn. Fire can reduce seed production by removing vegetation and killing seed lying on the ground surface
Slashing & Cutting:
Two insect species from Argentina have been released since a biological control program was iniated by CSIRO Entomology in 1994. A leaf tying moth (Evippe sp.#1) that causes defoliation and a leaf sucking bug (Prosopidopsylla flava) that causes dieback were released in 1998. The first species has established itself and is having an impact on mesquite, particularly in the Pilbara region. The second species is doubtful that it will establish itself.
Grazing management is an important part of the integrated approach to mesquite control for three reasons:
* Cattle are mainly responsible for the spread of seeds and therefore infestations.
* Grazing may need to be reduced before burning in order to allow the build-up of sufficient fuel.
*Grazing should be discouraged after any control efforts, to encourage growth in perennial grasses and help reduce mesquite seedling germination and establishment. Preventing stock during seed drop will reduce the spread and density of mesquite. Stock should be quarantined before being transported to unaffected areas.
Cultivation & Scalping:
Mechanical control techniques, such as blade ploughing, grubbing and chaining are aimed at removing as much of the root system as possible to prevent the tree reshooting. Mechanical control has varying levels of success depending on size and species of plant, but the plant will die if the roots can be removed to a depth of 300mm. Blade ploughing is considered to be the most cost effective form of mechanical control. Mechanical control can assist in the germination and growth of pasture grasses, especially if the area is reseeded following blade ploughing. But mesquite seedling germination will also occur, requiring follow up control. Grubber attachments on bulldozers gained best results in late autumn and winter in a normal wet season year. Chain pulling is the cheapest method buth the least effective.
Preventing the spread of mesqite is the most cost effective management strategy. Quarantining stock before movement into unifested areas is an important way of preventing further spread. Ongoing follow up control is required because there will be large numbers of mesquite seeds remaining in the soil that can survive for many years. In the past, when mesquite control has not been followed up, it has rapidly returned.