How to control Woody Weeds

Woody weeds are hardy plants of various species that can be incredibly difficult to eradicate. Many species fit under the woody weed banner, including shrubs, vines, and trees, but they all have one thing in common — their ability to spread and harm the environments they infiltrate.

To ensure woody weeds don’t take over your pastures, there are a few key things to know, from how to pick woody weeds out of a line-up to the top tips for keeping them at bay.

What are woody weeds?

A number of plants can be classified as woody weeds, but they often fall under one of a few categories — invasive plants, noxious weeds, weeds of national significance, National Environmental Alert List weeds, and native plants considered to be weeds. Common types of woody weed include blackberry, willow, yellow box, bracken, ragwort, and thistle.

Weeds of national significance are introduced species considered problematic as they are highly invasive. This list of weeds is set and maintained by the Australian Federal Government, and is based on invasive tendencies, the potential for spread, and socioeconomic and environmental impacts. Some weeds of national significance include lantana, prickly acacia, alligator weed, asparagus fern, and bitou bush.

National Environmental Alert List weeds are a set of non-native species in the early stages of establishment in Australia that could become a serious threat to biodiversity if they are left unmanaged. This list was established in 2001, and includes 28 species such as leaf cactus, cyperus, heather, Chinese violet, and rosewood.

How to identify woody weeds

All in all, there are many species of woody weeds — perhaps too many to keep track of, which is why it’s important to quickly identify any weed that you fear may be encroaching on your pasture or property.

One thing most of these weeds have in common is their ‘woodiness’, as the name suggests. Many species of woody weeds have wooden branches and/or thorns, whether they are bushes, shrubs, vines, or trees. Another notable feature of woody weeds is their tenacity — they tend to grow in a wide variety of climates and terrains, and can be difficult to get rid of once they have spread.

Why should you control woody weeds?

It’s beneficial for farmers to control woody and noxious weeds for several reasons. By eradicating woody weeds, farmers can improve their pastures and livestock-carrying capacity, enhancing the value of their property as a result. It also makes mustering livestock easier, as woody weeds can complicate the process of finding and moving stock, and reduces livestock fatalities by eliminating potentially poisonous growth.

From a pasture perspective, the risk of fire is greatly reduced when woody weeds are controlled, particularly during dry and drought periods. Woody weeds also hide pests like wild pigs, rabbits, and other vermin that can inflict harm on farms and community spaces like national parks. Removing woody weeds minimises any potential damage to properties and the natural environment.

Finally, getting woody weeds under control is crucial from a legal perspective. According to Australian government legislation, it is the responsibility of farmers and local councils to control noxious weeds — so, the time to nip these pesky plants in the bud is now!

How to get rid of woody weeds

There are many ways to reduce woody weeds, including cultivation, livestock grazing, slashing and burning, and using herbicides. Some methods are more beneficial than others, so depending on the urgency and spread of woody weeds in your area, it’s important to pick carefully.

Cultivation: This method can be hit and miss, and generally does not provide an effective long-term solution against woody weeds. When paired with other methods, cultivation’s efficacy increases, as it can help to damage the plant’s root system. However, it does not reduce the potential for spreading, which means you run the risk of infecting a greater area and ending up back at square one.

Livestock grazing: Grazing can reduce woody weed seedlings and prevent them from establishing and growing into mature plants. However, this treatment’s efficacy is also sporadic, as seedlings can grow in out-of-reach areas and mature without intervention from stock. Livestock also tends to target preferred pasture species over woody weeds, which can lead to overgrazing without tackling the real issue at hand.

Slashing and burning: This method can work well in the first year of growth to reduce the area of infestation you are dealing with. When used in conjunction with herbicides, slashing and burning can be even more successful. However, be mindful that this technique can also encourage the rejuvenation of many woody weed species.

Herbicides: When applied at the right time and correct rates, herbicides offer the best chance of woody weed eradication. Always treat weeds in their growth phase for optimal results.

Like most things, prevention is better than a cure, so the top thing to keep in mind when faced with woody weeds is implementing a control strategy right away. By putting a weed management strategy into place early, you’ll drastically lower the risk of spreading and have more control while weeds are still small.

The best application techniques to control woody weeds with herbicides

If you’re considering employing herbicides to control woody weeds on your property, there are a number of different application techniques suited to various contexts. Let’s explore each one in detail, including advantages, disadvantages, and corresponding herbicide recommendations.

Foliar spray application for woody weeds

What is foliar spray application?

Foliar spraying is the most widely used herbicide application method in Australian agriculture. It involves diluting herbicides with water at a specific rate and spraying them over foliage until runoff occurs, ensuring every leaf is wet, but not dripping.

This method allows the herbicide to be absorbed through the leaves, where it then travels systemically through the plant and down to the roots, disrupting growth processes and ultimately killing the weed.

Foliar spraying can be carried out using several application techniques, including boom spraying from a vehicle or aircraft for large infestations, hose-and-handgun units for medium-sized patches, knapsack or backpack sprayers for spot-spraying individual plants, and splatter guns, which deliver larger herbicide droplets at higher concentrations and are particularly useful for dense infestations.

When is foliar spray best suited?

Foliar spray is most effective when:

Weeds are actively growing and have sufficient green leaf area for absorption
The target weed is relatively small — ideally under 2 metres in height for best results, though some products can be used on plants up to 6 metres
Large infestations need to be treated quickly and cost-effectively
Selective herbicides can be used safely without risk to neighbouring desirable pasture grasses
Plants can be completely covered

Advantages and disadvantages of foliar spraying

Advantages

Fast and cost-effective over large areas
Suitable for a wide range of weed sizes and species
Can be applied with equipment most landholders already own
Effective at multiple growth stages when weeds are actively growing
Best results occur when used in conjunction with a penetrant or wetter

Disadvantages

Risk of spray drift causing off-target damage to desirable plants
Requires active growth and dry weather conditions (most products are rainfast within one hour)
May require multiple treatments for dense or mature infestations
Less suitable for very large trees, where complete canopy coverage is impractical

The best herbicides for foliar spray application

The most widely recommended and used herbicides for foliar spraying of woody weeds are triclopyr, picloram, and aminopyralid-based products. These actives belong to the pyridine family and work by mimicking plant growth hormones, triggering uncontrolled, abnormal plant growth and eventually causing death.

Grazon Extra contains all three ingredients and is widely regarded as the premium foliar option for woody weeds. It offers the broadest-spectrum control available in a single product, providing both rapid knockdown and residual soil activity to prevent weed seed germination for months after application. Grazon Extra controls the target weeds without harming pasture grasses, making it ideal for grazing contexts.

Other products with the same combination of actives include Hatchet Extra Herbicide, Hatchet Herbicide, and Surefire Raizon Herbicide. They’re cost-effective options for foliar spraying woody weeds and are registered for use in Queensland, New South Wales, Victoria, and Western Australia. Another popular option that contains triclopyr at 600g/L is Garlon 600, which is registered to control woody species like lantana, camphor laurel, and various acacias.

Top tip: When treating woody weeds with these foliar herbicides, always utilise a good penetrant. Combining a penetrant with your herbicide will enhance the herbicide’s efficacy for a more effective eradication strategy.

Basal bark application for woody weeds

What is basal bark application?

Basal bark is a targeted herbicide application method that involves mixing an oil-soluble herbicide in diesel (or another recommended carrier) and applying it around the full circumference of the trunk or stem at the base of the plant. Basal bark spraying is suitable for thin-barked woody plants, undesirable trees, saplings, regrowth, and multi-stemmed shrubs and trees.

After application, the oil carrier penetrates the bark and transports the herbicide directly into the plant’s vascular system, killing it from within without first cutting the plant.

When is basal bark application best suited?

Basal bark is best suited when:

Target plants have a basal stem diameter of less than 5cm (for some products, up to 20cm-diameter plants can be treated with appropriate products)
The bark is thin, smooth, and dry — rough or wet bark reduces penetration significantly
Individual plants or scattered infestations need to be targeted precisely
Working in environmentally sensitive areas where minimising chemical use is a priority
The terrain makes foliar spraying impractical, such as steep creek banks or rocky outcrops
Year-round treatment is required, as basal bark can be applied at any time (provided the bark is not wet, as this can repel the diesel or oil carrier)
Saplings and regrowth are emerging after mechanical clearing

The ThinLine basal mark method

A variation of standard basal bark is the Access™ ThinLine method, which involves applying a more concentrated herbicide-diesel mixture to only the bottom 5cm of the stem. This technique uses significantly less diesel or oil carrier per treatment and is particularly suited to smooth-stemmed species.

Both the basal bark and cut-stump methods should be applied at very low pressure, with the nozzle adjusted to produce a coarse stream instead of a mist, to ensure the mixture dribbles onto the bark rather than spraying into the air.

Advantages and disadvantages of basal bark application

Advantages

Highly targeted with minimal off-target herbicide movement
Can be applied year-round, regardless of plant growth stage, provided the bark is dry
Does not require any cutting or mechanical removal of the plant
Well-suited to environmentally sensitive areas, including creek banks and bushland
Excellent for treating scattered individual plants or regrowth

Disadvantages

Not suitable for thick-barked or wet bark, as diesel or oil carriers cannot penetrate
Limited to smaller-diameter stems (typically under 5 cm for most products)
Requires diesel or an oil carrier that is biosafe when used around or near waterways
More labour-intensive per plant than foliar spraying for large infestations

The best herbicides for basal bark application

Access Herbicide is the leading product for both basal bark and cut-stump applications. It combines 240 g/L triclopyr and 120 g/L picloram in a diesel-or oil-based carrier, delivering selective control of over 50 woody and noxious weed species, including lantana, rubbervine, parkinsonia, brigalow, and prickly acacia.

This product is most effective when applied to weeds that are not stressed due to lack of moisture, excessive heat, or previous herbicide treatment, and are actively growing, as actively growing weeds draw the chemical into the vascular system and transport it down to the roots for maximum efficacy.

Other products like Garlon 600 or Sabakem Triclopyr 600EC Herbicide are also registered for basal bark application for woody weeds, at a rate of 1:60 with diesel distillate. They are suitable for controlling a range of Australian blackthorn, acacia, and eucalyptus species.

Fluroxypyr-based herbicides like Starane Advanced and Neon 400 can be used for basal bark application on plants with a basal diameter above 20cm, when mixed with diesel at 3L/100L.

Note that basal bark products are not registered for foliar application, and must not be interchanged without first checking the product’s registration.

Cut stump application for woody weeds

What is cut stump application?

The cut stump method involves felling or cutting the woody weed as close to the ground as possible (ideally no more than 15cm from ground level), and immediately applying herbicide to the freshly cut stump surface. Once herbicide has been sprayed or painted onto the exposed surface, it will destroy the stump and its root system.

For effective results with the cut stump method, timing is critical — herbicides must be applied within 15 seconds of cutting to maximise uptake. Once the cut surface begins to dry, translocation rapidly decreases and herbicide efficacy drops significantly. Cut stumps should also be horizontal to prevent herbicide runoff.

When treating stumps with a larger circumference, place the solution around the outer edge, as the objective is to target the cambium layer inside the bark. Covering the entire cut surface of a large stump only wastes herbicide. For smaller-diameter stems, however, the entire cut surface should be treated.

When is cut stump application best suited?

The cut stump method is most effective when:

Trees or shrubs are too large for effective basal bark treatment (typically those with stems greater than 5cm in diameter)
The weed must be physically removed from the area (for example, to clear fencing lines or access ways)
Thick-barked species that resist basal bark penetration need to be treated
Working in mixed vegetation where individual trees need to be selectively removed
Preventing regrowth after mechanical clearing operations (e.g., following a dozer push or mulching)

Advantages and disadvantages of cut stump application

Advantages

Immediately removes the physical weed mass, improving land access and appearance
Highly effective on thick-barked or large trees that resist foliar or basal bark methods
Very targeted, with no risk of spray drift or off-target damage
Suitable for use near desirable trees and native vegetation
Prevents regrowth of trees following mechanical control

Disadvantages

Requires mechanical cutting equipment (chainsaw, brushcutter, axe, loppers, or machete)
Labour-intensive and impractical for large-scale infestations
Strict timing requirement as the herbicide must be applied within 15 seconds of cutting
Deciduous plants may be harder to treat outside their active growing season
Cannot be used where standing dead trees pose a safety risk

The best herbicides for cut stump application

Like with basal bark, Access Herbicide is the leading product for cut stump application in Australia. However, other options exist, including glyphosate-based products. Glyphosate at 360g/L is a cost-effective option in contexts where its broad spectrum, non-selective nature is not a concern.

Vigilant II (picloram at 44.7g/L and aminopyralid at 4.47g/L) is a gel-based cut stump herbicide that offers a convenient, no-drip formulation, which is particularly useful when precise application is required for individual stumps. It is applied by cutting the stem close to the ground and applying a 3-5mm layer of gel to the cut surface.

Aerial application for woody weeds

What is aerial application?

Aerial application involves the distribution of herbicide from a manned aircraft — typically a helicopter or fixed-wing aircraft, although drones are also becoming increasingly popular. As a large-scale extension of foliar spraying, aerial application allows operators to treat vast areas of woody weed infestations quickly and efficiently across remote, rugged, and inaccessible terrain where ground-based equipment cannot operate effectively.

Aerial application is particularly popular across Queensland’s vast grazing regions, where infestations of weeds like prickly acacia, brigalow regrowth, rubbervine, and lantana can extend across thousands of hectares. This method can be used to deliver both liquid and granular herbicides via spreader pods mounted on the aircraft.

When is aerial application best suited?

Aerial application is the preferred method when:

Infestations are large, typically hundreds to thousands of hectares, making ground-based spraying impractical or uneconomical
Terrain is steep, rugged, or inaccessible to vehicles and ground based equipment
Weeds are established in remote areas, and road access is limited
The speed of treatment is critical as the woody weed is about to set to seed
Granular herbicides like tebuthiuron need to be broadcast across vast areas

Advantages and disadvantages of aerial application

Advantages

Covers very large areas quickly, ideal for extensive infestations across hundreds, if not thousands, of hectares
Accesses terrain that is inaccessible or unsafe for ground based equipment
Reduces labour requirements significantly for large scale operations
GPS guided aircraft ensures precise, repeatable coverage with accurate swath management
Granular aerial application of tebuthiuron offers long-lasting residual control with minimal treatment and no impact on grass
Allows treatment during periods when ground conditions are too wet for vehicle access

Disadvantages

Can be costly (depending on area) when considering aircraft hire, fuel and operating fees
Risk of spray drift, particularly with liquid applications, therefore requiring careful attention to wind speed, temperature, and atmospheric conditions
Requires licensed and accredited aerial operations — landholders cannot conduct herbicide application without appropriate licences
Not suitable for the selective treatment of individual plants among desirable vegetation
If using a granular herbicide like tebuthiuron, cannot be applied to or near 100m of waterways
Tebuthiuron granules cannot be used on land with a slope greater than 20% (11 degrees)
Tebuthiuron granules cannot be used under conditions that could cause pellets to move to non-target areas during application

The best herbicides for aerial application

Products containing triclopyr, picloram, and aminopyralid are registered for aerial application across Queensland and other states for control of woody weeds like lantana and blackberry. Options include Grazon Extra and Hatchet Extra, both of which are registered for aerial application.

Tebuthiuron granular herbicides like Tebulex 200GR are preferred for aerial broadcast granular application across large-scale brigalow, tea tree, and mixed woody weed infestations on grazing lands.

Selecting the right application method for controlling woody weeds

Choosing the correct application method for controlling woody weeds will come down to the species, the plant’s size, the scale of infestation, your available equipment, and the surrounding environment. Here’s how each stacks up.

Foliar spraying

Best for: Small to medium actively growing plants, large-scale infestations

Plant size: 2-6m, depending on species

Time of year: Spring to autumn during active growth periods

Key products: Grazon Extra Herbicide, Hatchet Extra Herbicide, Surefire Raizon Herbicide, Garlon 600

Basal bark

Best for: Saplings, regrowth, multi-stemmed shrubs, environmentally sensitive areas

Plant size: Stems under 5cm in diameter (thin-barked species)

Bark condition: Must be dry and relatively smooth

Time of year: Year-round, provided bark is not wet

Key products: Access Herbicide, Garlon 600, Sabakem Triclopyr 600EC Herbicide, Starane Advanced, Neon 400

Cut stump

Best for: Large trees, thick-barked species, site clearing, selective removal

Plant size: Any, but primarily larger trees where basal bark is insufficient

Time of year: Year-round, but most effective during active growth

Key products: Access Herbicide, Vigilant II, glyphosate-based herbicides at 360g/L

Aerial application

Best for: Large-scale, remote, or inaccessible infestations across grazing lands

Plant size: Any

Time of year: During active growth for liquid spray, or any time for granules (rain required for activation)

Key products: Grazon Extra, Hatchet Extra Herbicide (for liquid foliar spray), Tebulex 200GR (for granular application)

In practice, the most successful woody weed management programs use a combination of all of the methods we’ve detailed. A large-scale foliar spray program may be used to knock back the bulk of an infestation, with cut-stump treatment applied to mature trees that escaped foliar coverage and basal bark applied to regrowth and saplings emerging in the months after the initial treatment.

With any application method, always read the product label before use to ensure it is registered for your target weed species and state, and to confirm the correct dilution rate. Contact an agronomist or refer to your local agriculture or primary industries department for species-specific advice.

While woody weeds can be challenging to control, with the right knowledge, herbicides, and application techniques for your own specific circumstances, there’s a fantastic chance of successful eradication. At Specialist Sales, we offer a range of woody weed herbicides, no matter your budget or the area you are treating. If you need expert advice on eliminating woody weeds, please get in touch with our experienced customer care team.