Physical or mechanical methods of weed control may determine includes cultivation,slashing, mowing, mulching, fire, steam, animal intervention, hand pulling and may even include reforestation.

This article details Physical/Mechanical methods of weed control


Cultivation is a proven way of controlling weeds. Implements range from large tractors and ploughs to hand tools such as chipping hoes. This method results in direct control of weeds.

Cultivation is an option that must be used wisely. Smaller weeds can be rapidly, efficiently and cheaply destroyed by cultivation. Shoots can be buried deeply to prevent regrowth, roots can be exposed to dry out, shoots can be separated from the roots, or a combination of all three.

Cultivation aims to to prevent seeding and destroy the existing plants. Cultivation can be used to halt weed problems before they get out of control. However, eradication of perennial weeds by cultivation can be difficult and depends on the root system. Some types of weeds can be controlled by repeated passes, where the roots are dragged to the surface to dry out and die. However this is seldom entirely effective.

Cultivation should be used strategically, choosing the most appropriate equipment for the varying stages of crop and pasture production. For effective control by cultivation, weeds should be attacked before flowering and under reasonably dry conditions.

Manual cultivation using chipping hoes, mattocks and other suitable hand tools is another viable means of weed control in small-scale situations or for follow-up control.


Slashing can be used to prevent tall growing weeds from flowering and setting seed. This method can be undertaken with a tractor and slashing implement or by using a hand-held brush-cutting machine.

Slashing can also be used to remove unpalatable or inedible weeds left after stock have selectively grazed a paddock and to prevent these weeds taking over, however slashing may also encourage the growth of less desirable prostrate species.

Slashing is not effective for eradicating a weed, but is useful for temporarily controlling weeds until they re-shoot. Continual slashing may provide control if a desirable prostrate-growing species is present and is encouraged to replace the weed.

Slashing can be used for the control of vegetation and weeds along roadsides, but is not suitable for the control of weeds in crops.


Mulching involves the use of physical barriers such as black plastic sheeting, woven paper products or woven cloth to exclude sunlight and prevent weed establishment. Mulching has been used in various situations, particularly in row crop production where machinery is available to lay black plastic. Woven black plastic is also useful along roadsides, steep banks and cuttings where areas need to be revegetated. This option is viable for small areas and can assist in weed control, bank stabilisation and erosion.


Fire has been used for many years as a form of vegetation and weed control. Its success depends on the amount of fuel, the speed and intensity of the fire, and the time of year that burning takes place. Fire can play a major role in the management of woody weeds in western regions of NSW and can also be a useful option for the control of lantana and blackberry in certain situations.

The best fire strategy for woody weeds is a controlled managed burn. The aim is to burn only the desired area, using firebreaks and back-burning techniques. Unlike a wildfire, a managed burn is controlled and minimises damage to the environment without damage occurring to property and livestock.

Controlled burning for managing woody weeds can help restore land to an open condition more suitable for pasture growth or providing access for further weed control. The direct costs of managed burning are far lower than those of alternative techniques such as chemical treatment and mechanical clearing.

An integrated management program may be required when using fire for weed control. For example, lantana can be controlled with a combination of fire, improved pastures, and follow-up spot spraying. Large, dense woody weed infestations are most suitable for fire control, as larger areas burn more effectively.


Reforestation is a long-term method of weed control. The aim of reforestation is to form a dense tree canopy that restricts sunlight penetration to weeds on the forest floor. Reafforestation can be in the form of revegetation with mixed native vegetation species or through establishment of a single species in a plantation.

Mature trees compete for moisture, nutrients and sunlight and restrict potential weed establishment and growth. It can take 5 to 10 years before trees form a dense canopy and, during this establishment phase, weed control can be critical to the success of the plantation. It may therefore be necessary to use other forms of weed control, such as herbicides and mechanical means, to assist in this establishment phase. A competitive, desirable, shade-tolerant grass or legume can also assist with forest management and weed control.

Large areas of land are more suitable for reforestation, as other forms of weed control can become uneconomic or impractical.

NSW DPI can help with tree selection, site preparation, planting and general forest management. A weed control program can also involve agro-forestry principles, which include tree growing in conjunction with other agricultural enterprises such as cropping or domestic animals.

The effectiveness of reforestation for weed control depends on the tolerance of various weeds to shading, the added competition, and forest management.

Reforestation to control groundsel bush has been tried in a number of situations but is not satisfactory unless good forest management methods are adopted. Trials are also being carried out to assess the effectiveness of reafforestation to control serrated tussock and giant Parramatta grass.


The ability of goats to control weeds in Australia has been well documented. Goats have been used for sustainable pasture management and weed control in a range of weed situations. They can be integrated with sheep, cattle and cropping enterprises to provide weed control and pasture improvement. In most situations, goats should be seen as only one aspect of an integrated weed control program, which can also include burning, mechanical removal, spraying and pasture improvement.

Goats control weeds by preferentially grazing them, thereby placing the weeds at a disadvantage by preventing them from flowering and by ring-barking and structurally-weakening some shrub species. Goats eat a variety of undesirable plants and shrubs that sheep and cattle avoid, and often the nutritional value of these species is quite high. They are efficient browsers and grazers of weeds in steep, rocky areas, around trees, and in other inaccessible areas where conventional control methods are not applicable.

The use of goats for weed control is a medium-to-long-term proposition and, therefore, expectations should be realistic. In some situations, goats can give effective control of a weed. In other cases, they may only limit the spread or have very little effect on the weed at all.

For goats to be effective, stocking rates, timing, weed palatability and farm management strategies need to be considered. In most cases, it is also important to have a competitive pasture to overcome the weed and colonise bare areas.
There are many weed species that are eaten by goats; the degree of control depends on the palatability of the weed.

Highly palatable weeds include: blackberry, sweet briar and scotch broom.

Palatable weeds include: scotch thistles, variegated and nodding thistles, Paterson’s curse and horehound.

Other species that are moderately palatable and eaten occasionally include fireweed, groundsel bush, St John’s wort, serrated tussock and spear grass.

Hot water application

Hot water application or steaming is a relatively new weed control method. Applying hot water to a weed results in the loss of the plant’s waxy coating, a reduction in moisture, and dehydration.

The system operates by plumbing water under pressure through a heated chamber onto the weeds. The combination of heat and water pressure breaks down the cellular structure, causing discolouration and death within hours or over a few days. One treatment can kill most annuals and some young perennials. The top growth of older perennials is scorched off, but the impact on the roots is minimal unless treatment is repeated frequently.

This form of weed control is still in the developmental stage. A number of large city councils have trialled the equipment, reporting mixed results on its effectiveness. Trial work and assessments in various situations are still being conducted.
Field trials carried out in New Zealand have shown that hot water application has similar results to glyphosate, except in controlling perennial weeds. Preliminary observations indicate that hot water treatment kills annual weeds in 24 hours. The foliage from some perennials also dies within 24 hours, but regrowth recurs from the roots within a week or two.