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Physical control methods
Manual control is the use of the hands or handheld tools to deal with weeds (called invasive plants in the Biosecurity Act 2014). An advantage of manual control is that it minimises soil disturbance, and decreases the likelihood of erosion and seed germination.
Hand pulling aims to remove the entire plant, including its roots, from the soil. This method is useful for small-scale infestations. It is best to hand-pull weeds after rain, when soil is moist. Sturdy gloves should be worn to avoid prickles, blisters or sap burns to the skin. It is not appropriate for all weed species, such as those with underground bulbs.
Hand tools such as broad knives and trowels can be used to remove underground parts of weeds (such as bulbs) that may reshoot. In some cases it is necessary to dig out the crown of the plant. This requires the growing part of the plant to be cut beneath the ground using a knife.
Grubbing or chipping
This method requires weeds to be dug out using a mattock or chip hoe. Depending on the plant, it may be important to expose the root system, and remove the crown.
In some cases, the mattock or chip hoe is used to cut the stem of the plant below the ground. This method is useful when the ground is hard. Gloves should be worn to avoid blisters.
Mechanical control is the use of powered tools and machinery to manage weeds and is best suited to larger infestations. Care should be taken to minimise soil disturbance.
Slashing, mowing, dozing, pushing and felling
At times, controlling weeds using mechanical methods is preferred. However, care should be taken when machinery is used in the process.
Disturbing the soil with mechanical control can:
- increase the likelihood of seed germination
- damage native vegetation.
In some cases it's possible to slash weeds using a tractor slasher or ride-on mower. Often this method is used where other favourable species will outgrow the slashed weeds. Some control contractors apply steam after the weeds have been slashed.
Bulldozers and chainsaws can be used on woody and tree weeds where they are pushed or felled and finally snigged (dragged away). These methods are only suitable in certain situations, as they create high levels of soil and vegetation disturbance. Also, shoots and seedlings require follow-up attention.
Grading or scalping the top layer of soil is an effective method of removing a seedbank. As this method greatly disturbs the soil, it is best suited for areas that are to undergo complete rehabilitation.