WEED CONTROL METHODS
This website has avoided giving specific recommendations about the type of herbicide to be used for each weed, as new herbicides are constantly being developed. Herbicides are meant to be used only on the plants for which their use is registered. For some environmental weeds, there is as yet no herbicide registered for use. However, there may be an off-label permit which covers these species. The following two publications provide weed by weed details of the appropriate herbicides and application rates, and alternative control methods:

Noxious and Environmental Weed Control Handbook 2001/2002.
Weed Control in Lucerne and Pastures 2001/2002.

Both are produced by NSW Agriculture and can be obtained from that department. Offices are at Bega (phone 6492 1733), Berry (phone 4464 1251) and Orange (6391 3100). The handbooks are not currently available on-line, but may become so in future. If you cannot locate the weed you are concerned with in these publications, check with your local Council noxious weed staff, or contact the National Registration Authority in Canberra (phone 6272 5158).

Weeds thrive on disturbance. As well as taking action to remove weeds, you need to look at what has contributed to the infestation, and treat the causes, as well as the symptom (the weeds). If reliance is placed on simply spraying weeds whenever they appear, you are embarking on an expensive spiral of increasing disturbance and increasing infestation. Healthy, vigorous native vegetation or pasture is relatively weed-resistant.

Timing is crucial in weed control. Remove weeds before they produce seed. If you are too late, collect the seed and burn it, bury it deeply, or place it in plastic bags in the sun to rot. However, the rotting process requires moisture so make sure you include some moist, green material. Plastic bags are easily broken, so DON’T take weeds carrying light wind blown seed to landfill, whether in bags or not.

Removing a weed may simply result in its replacement by another rapidly growing coloniser of empty space, most likely another weed. Look at the whole picture, and decide what you want to achieve before starting a weed control program.

Hand pulling or digging is the cheapest method of weed control for small infestations, but it is time consuming. Young plants are often easy to pull out if soil is moist. If soil is dry or plants are big, you are likely to leave enough material still in the ground for the plant to grow again. Some plants will recover unless every bit of the root system is removed, and these are better sprayed. Digging is better avoided if it will cause a lot of soil disturbance in an otherwise relatively undisturbed site, as this will only encourage the germination of more weed seed in the soil. A sharp knife is a useful tool in hand weeding, as it can be used to cut the roots below the crown on smaller weeds such as grasses and herbaceous plants. Try to minimise the amount of soil disturbance when removing weeds this way.

Slashing or mowing can be used to delay production of seed if more permanent control can’t be undertaken till later. However, it is not a permanent method of control itself, and if plants have already seeded, it can result in spreading that seed even further. If repeated frequently enough, it can exhaust the underground food reserves of some plants, and eventually get rid of them. Bracken is an example.

Goats and other grazers can be used similarly to prevent seeding. Any stock applied at the right time and in adequate numbers can minimise seeding of annual grasses. Goats are particularly useful on some woody weeds, notably blackberry and briar rose. However they need to be stocked in fair numbers to have much effect, they need good fencing, and they can be hard on any bush in the paddock. Sheep may be useful in controlling fireweed, but they need to be present in large numbers at the crucial times of year.

Solarisation involves heating weeds to lethal temperatures under clear (or coloured) plastic. It can be useful for low-growing and semi-aquatic weeds but will work best when they are growing in full sun. It may or may not kill any seed stored in the soil. Best used for small infestations. Plastic may need to be left in place for months, and should be well weighted down.

Fire can play a part in controlling weeds, though it can also pave the way for weed infestation by creating bare ground. Timing is important. Burning in autumn could encourage weeds by leaving the ground bare all winter. Burning in spring is less likely to have this effect. Burning of native grasses which are not being grazed has been shown to be necessary for their health. Without regular burning grasses such as kangaroo grass (which forms much of the native pasture in the region) can lose vigour, and become much more susceptible to weed invasion. Lack of burning in the bush around towns may allow exotic plants which would not survive fire to become dominant. Fire can also be used to stimulate mass germination of hard-seeded species such as broom, which can then be sprayed.

Herbicides are very useful in the battle against weeds, but need to be used carefully. The use of non-selective herbicides (which kill every plant they contact) creates bare ground, which only encourages further weed invasion. It is always best, if there is the option, to spray with the appropriate selective herbicide to minimise damage to non-target plants.

Remember herbicides are poisons, and take precautions to avoid getting them on your skin or breathing the vapour. Wear overalls, rubber gloves and a face mask when working with them. If spraying, stay upwind of the target plants, and do not spray in windy conditions. Always read the instructions on the label before use. Be aware that there are restrictions on using herbicides near waterways.

Herbicides are meant to be used only on the plants for which their use is registered. Check the label. For many non-agricultural weeds not listed on product labels, there may be an off-label permit which covers them. If in doubt, contact NSW Agriculture , the National Registration Authority, Council weeds officers, or the product manufacturers. Note that under the Pesticides Act 1999 it is an offence to use a herbicide in a manner that could cause injury to a person, damage to another’s property or harm to a non-target plant.

• Only if no other effective and efficient method is available, and only after you have read the label.
• Apply herbicide when the plant is actively growing. This may be in winter for some species (such as bridal creeper).
• Do not use herbicide when the plants are drought stressed, in extremely hot or cold conditions, or when plants are diseased.
• Don’t spray if it looks like rain or is windy.
• For many plants the best time to treat is between flowering and fruit set.
• Spray deciduous plants in late spring through to early autumn, when in full leaf. If leaf colour has begun to turn it is too late.

Methods of herbicide application
Spraying should not be done in windy conditions. If plants are tall, it may be easier and safer to slash them first and spray when there is vigorous regrowth. If old grass tussocks do not contain many actively growing leaves, they may also be better slashed first to promote new growth which will take the chemical up more readily. Avoid spraying non-target plants, especially when spraying vines whose foliage may be entangled with that of the supporting plant. To minimise damage to other plants use a selective herbicide if possible. Mix it to the right concentration for the target species (found on the label) and spray to thoroughly wet foliage, but no more. If the plant you are treating has waxy leaves, you may need to add a penetrant to improve take-up of the herbicide. Adding dye makes it much easier to see where you have sprayed.

Weed wipers can be used to apply herbicides to foliage in a more controlled manner. There are a range of possibilities here, from wiping herbicide onto individual plants with a sponge in a gloved hand (useful for bulb foliage), to hand-held wick wipers, to larger wipers towed behind a tractor or quad bike. This method can be useful for removing taller weeds without affecting the pasture beneath them. Generally wiping with two passes at 90º to each other is needed to ensure sufficient coverage. Check whether the chemical you plan to use is registered for this method of application.

Cut and paint is suitable for woody weeds. The plant is cut off close to ground level with a horizontal cut, and undiluted herbicide (usually glyphosate) applied immediately to the cut surface. If you are too slow air is sucked into the sap vessels, preventing take-up of the herbicide. In some plants, such as willows, it may be necessary to apply herbicide to both the stump and the cut end of the rest of the tree. This ensures that the top part of the plant dies, rather than taking root again if it is left lying on moist soil. For a larger stump, only the outer edge, just inside the bark needs to be treated, not the whole surface. Wear rubber gloves, and avoid moving around carrying an open container of herbicide. This method and the two below are best done as a two person job.

Scrape and paint is used for large vines and scrambling plants with a woody stem. Scrape 20 to 100cm of the stem with a knife, to expose the sapwood just below the bark. Within 20 seconds, apply undiluted herbicide to the scraped section. Don’t scrape right around the stem, do only a third of the diameter. Stems over 1cm in diameter can be scraped on two sides. If killing vines with herbicide, leave them to die in place. Pulling them down can damage the plants they are growing over.

Stem injection is used on woody weeds where you want them to die in place, rather than cutting them down. There are purpose-built stem injection devices, but the job can also be done with a hammer and chisel or a cordless drill. You need to make an angled cut or hole down into the sapwood, just below the bark, and apply undiluted herbicide into the cut immediately. Don’t drill too deeply, or you will get into the heartwood, which does not take up the herbicide.

Basal bark treatment is used on young woody weeds and root suckers. Diluted herbicide (check label for rates) is painted or sprayed onto the bark at the base, from ground level to 30cm high.