How to control Woody Weeds

Woody weeds are hardy plants of various species that can be incredibly difficult to eradicate. Many species of plant 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. So, 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 that are 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. Because there are so many species of woody weed, though, it can be difficult to immediately classify a plant and take the appropriate action. 

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 is beneficial for farmers to control woody and noxious weeds for a number of 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 both farms and community spaces such as national parks. Removing woody weeds greatly minimises any potential damage to both 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 can be hit and miss, and generally does not provide an effective long-term solution for controlling woody weeds. When paired with other methods, the efficacy of cultivation increases, as it can help to damage the plant’s root system, but this does not reduce the potential for spreading – which means you run the risk of infesting a greater area and being back at square one.

Livestock grazing can reduce woody weed seedlings and prevent them from establishing and growing into mature plants. However, once again this treatment’s effectiveness is sporadic, as seedlings can often grow in areas out of reach of livestock, meaning they have time to mature and spread without intervention from stock. Livestock also tends to target preferable pasture species over woody weeds, which can lead to overgrazing without tackling the issue at hand.

Another method to consider is slashing and burning, which can work well in the first year of growth to reduce the size or area of the woody weed you are dealing with. When used in conjunction with herbicides, slashing and burning is often even more successful. However, be mindful that this technique can also encourage the rejuvenation of many woody weeds. 

Perhaps the most effective way to control and eliminate noxious and woody weeds is through the use of herbicides. When applied at the right time and at the correct rates, herbicides have a significant chance of eradication. It is best to treat weeds when they are in their growth phase. 

Like most things, prevention is better than a cure, so the number one thing to keep in mind when faced with woody weeds is to implement 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 the weeds are still small. 

The best application techniques to control woody weeds with herbicides 

There are a number of ways to control noxious and woody weeds, and the method you choose will also help determine which herbicide to use. Let’s take a look at some of the most popular methods of applying herbicides to control woody weeds. 

 

Stem injection

Stem injection is a suitable technique for woody weed trees that involves making horizontal cuts through the plant’s bark into its sap using an axe. Ideally, cuts should be spaced evenly apart and delivered using a downward motion from approximately waist height. Leaving the axe in the tree, immediately pour the herbicide down the axe blade, making sure the full amount reaches the sap stream of the tree. By doing so, you’ll ensure the tree does not close its sap stream before the herbicide has a chance to properly penetrate. It is best to avoid this type of treatment if the woody weed is stressed, as its sap flow will be low and the effectiveness of the herbicide will consequently be reduced. 

A new form of stem injection with greater benefits has also been developed and involves inserting capsules filled with glyphosate (a non-selective herbicide) into the tree using a special applicator. The applicator in question has been specifically designed to carry and insert these capsules into tree stems and cut stumps. The capsules then are sealed directly into the woody weed, killing the tree from the inside and minimising unintended environmental damage. 

Aerial application

Herbicides in liquid or pellet form can be spread via a helicopter or aeroplane. This is best done when the wind, humidity, and temperature are all low for a more controlled environment. When using an aerial application technique, application and efficacy rates will vary depending on the herbicide used. Liquid or granular herbicides can be used with this method. 

Basal bark

Basal barking is a method to control regrowth and saplings with a diameter of 5cm or smaller and involves mixing a herbicide with diesel or another additive and spraying the woody weed’s circumference or trunk. This method assists with penetration through the bark. It is best to avoid this treatment if the bark is thick or cork-like, or if the stems are charred or wet, as these variables may inhibit the absorption of the herbicide through the bark. 

Brushcutter 

This method uses a brushcutter tool to cut the woody weed as close to the ground as possible, taking the effort out of cutting individual stumps by hand. The herbicide is then sprayed directly onto the newly cut area for maximum absorption. 

Cut stump

Cut stump application is the best method for controlling woody weed regrowth or managing saplings that are too small for stem injection. Cut the stems as close to the ground as possible and thoroughly apply the herbicide immediately after a cut is made. This step is necessary as the tree can seal quickly, preventing the herbicide from optimally penetrating the sap system. 

Foliar spray

This method uses a high volume of herbicide via a hand spray to treat the leaves of the woody weed plant. For the best possible results, it is important that the entire leaf area is covered to the point of run-off and that a good penetrant is used in conjunction with the herbicide

Boom spray

The boom spraying method is best used to control pasture weeds. It is best executed using a boom sprayer with fan nozzles that overlap to ensure all weeds are covered, resulting in better coverage and penetration of the weeds. Spray rates will depend on the type of woody weed in question, and the herbicide being used. 

Hand or spreader application 

Finally, controlling woody weeds is possible through hand distribution or a spreader. Simply apply granules to the soil ensuring the root area of the woody weeds are covered evenly. Application rates will depend on the granule selected. 

The best herbicides for treating woody weeds

There are many herbicides that can be effective in the pursuit of treating woody weeds, including liquid, granular and gel herbicides.

 

Liquid herbicides 

Liquid herbicides are a popular choice for controlling woody weeds. There are many herbicides that can support the elimination of woody and noxious weeds, including commonly known herbicides like glyphosate and 2-4-D. However, the most impactful herbicides tend to include the active ingredients of triclopyr and picloram. The third ingredient of aminopyralid makes this mix even more effective – you can add it manually, or you might find it is already included in your herbicide of choice. There are several excellent herbicides on the market that combine these three potent ingredients for optimal control of woody weeds. 

Many woody and noxious weeds have waxy or hairy leaves, which can be difficult to wet as the herbicide just runs off the leaves or is held away from the leaf surface. To tackle this problem, we recommend a good quality premium penetrant to enable the herbicide to penetrate the foliage and encourage uptake into the sap system. These penetrants are different to a general-purpose wetter, as they include a highly-penetrating surfactant that is ideal for treating hard-to-kill weeds. Premium penetrants also strip away the top layer of the leaf to allow the herbicide to enter the plant’s sap flow and effectively translocate it from the leaf to the roots. 

Granular herbicides

Effective using a number of application techniques, there are several granular herbicides that can combat hard-to-kill woody and noxious weeds. Some even provide ongoing residual control without impacting your pastures. Granular herbicides can be distributed by hand, with a hand spreader or electric spreader, or through aerial application.

If you are considering stem-injecting woody weeds, new technology makes it easier than ever to get to the root of the problem using encapsulated granular herbicides. The Di-Bak G Herbicide capsules can be inserted directly into the trunk of the woody weed using the Injecta 400, a specialised applicator. Di-Bak G capsules are made of glyphosate (700g/kg) and kill the tree without having any adverse effects on the environment. 

Another very effective – and economical – herbicide choice for removing woody weeds on grazing land is tebuthiuron. This product has no negative impact on pastures and has a residual effect that slows regrowth. The beauty of this product is that it can be applied at any time of the year – treatment only becomes effective once sufficient rainfall breaks down the clay-based pellet, allowing the chemical into the root zone where it is absorbed by the woody weed plant. Herbicidal activity occurs at this point and will continue for several seasons after application. During this time, the woody weeds may undergo repeated defoliation and regrowth until death occurs. Soil type, the amount of rainfall, root depth, plant species, plant density, and the rate of tebuthiuron used can all affect how long this takes. When using tebuthiuron, a single application is normally effective for several years. Depending on rainfall and grazing management practices, you may see more forage grass production during this time period as woody weed competition declines. 

Finally, another effective granular herbicide to consider is metsulfuron. Metsulfuron can be mixed with water and used as a standalone liquid treatment for controlling broadleaf weeds in cereal crops and brush species, like woody weeds in pastures. It can also be added as a ‘spike’ to other liquid herbicides when controlling weeds. Metsulfuron has a residual impact, with a systemic compound that impacts foliar and soil activity and works rapidly after it is taken up by the plant. It works by inhibiting cell division in the shoots and roots of the plant and is biologically active at very low rates – meaning you only need to use a very small amount of this powerful herbicide. It controls more than 40 different species of woody and broadleaf weeds and is very effective in particular when there’s a mixture of weed species to manage. Due to its synergistic effect (‘spike’), metsulfuron works best when added to other woody weed herbicides to boost the ‘killing power’ of the spray mix. 

Gel herbicides

Gel herbicides are ready to use and have been specifically developed to control a wide range of woody weeds and trees, scrambling weeds, and vines like broadleaf weeds. They also provide a non-spray alternative to controlling invasive weed species. Gel herbicides should be applied directly to a fresh-cut stump or system, and can be used in sensitive areas like native bush, conservation areas, farms, lifestyle blocks, gullies, parks, and reserves. 

Vigilant II Herbicide Gel contains the powerful and proven ingredient aminopyralid, which causes immediate brownout and knockdown of weeds, and eradicates many common weed problems. 

 

Conclusion

While woody weeds can be challenging to control, with the right knowledge, herbicides, and application techniques for your own specific circumstances, there is a fantastic chance of successful eradication. At Specialist Sales, we offer a range of woody weed solutions, 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.