How controlled burning makes herbicides more effective for Australian farmers

Fire is one of Australia’s oldest and most effective land management tools. There’s more to it than just reducing fuel loads – a well-planned, controlled burn can also make herbicides work more effectively.

By altering plant physiology and exposing weed regrowth, fire helps herbicides penetrate deeper and act faster, leading to longer-term control, particularly when dealing with woody weeds.

At Specialist Sales, we work closely with farmers and land managers across Australia who combine controlled burning with targeted herbicide treatments to manage dense shrubs and invasive weeds. This integrated approach is economical, sustainable, and delivers powerful results.

Learn more about controlled burning, including why it works and how to safely incorporate it into your weed management practices. 

Why controlled burning improves herbicide effectiveness

Controlled burning is so effective because it changes the way that plants respond to herbicides. When a woody weed is scorched by a low-intensity burn, its protective bark and leaves are stripped away, forcing the plant to resprout. 

This stress makes the weed much more susceptible to herbicide treatments. Once new shoots emerge, systemic herbicides can move easily through the plant and reach its root zone, which is critical for long-term control. Research from the CSIRO, paired with our customers’ personal weed management experiences, confirms that herbicide application after controlled burning offers longer-lasting, more reliable results compared to just spraying.

Another benefit of burning is the clearing of thick foliage or ground litter that can block herbicide contact. By opening up access to plant stems, burning permits more even spray coverage and precise application, reducing waste and minimising chemical use.

Though controlled burning is extremely effective, ongoing monitoring and follow-up treatments are still essential. Some weed seeds may germinate after fire – reapplication will keep these under control before they’re able to mature into fully-fledged plants.

Navigating legal requirements and fire permits for controlled burning

Before lighting any fires whatsoever, contact your local and state fire authorities. Controlled burning is heavily regulated, and it’s not uncommon to need a permit. Each Australian state has its own regulatory body:

• Queensland: Queensland Fire and Emergency Services (QFES)
• New South Wales: NSW Rural Fire Service (RFS)
• Victoria: Country Fire Authority Victoria (CFA)
• South Australia: South Australian Country Fire Service (CFS)
• Western Australia: Department of Fire and Emergency Services (DFES WA)
• Tasmania: Tasmania Fire Service

Liability for uncontrolled or escaped burns sits with whoever has lit the fire, so confirm local permit requirements and take safety precautions before proceeding. Environmental restrictions may also apply, depending on where you’re located – these are common near waterways and remnant vegetation, or in sensitive conservation zones.

When to burn and when to spray

Controlled burns are the first component of a ‘burn-and-spray’, a program that depends heavily on timing. Burns should always be conducted under stable, mild weather conditions to allow a slow, even burn – do not burn in extreme heat or during periods of rain. This will ensure a low flame height and reduce the risk posed to non-target plants and soil organisms.

After burning, wait until resprouting begins to commence your spray. Spraying too early, before the plant begins to regrow, will be ineffective and waste your chosen herbicide, whereas spraying too late risks missing the most ideal stage for chemical absorption.

The resprouting phase may occur anywhere between a week and six months after burning, depending on the weed species, local climate, and intensity of the fire. Farmers in northern parts of Australia may see regrowth in just weeks, whereas this may take several months in cooler southern regions. To identify resprouting as soon as it begins, conduct regular site visits. 

Once resprouting has started, apply herbicide while stems are still young to ensure the plant’s transport system is active. This will ensure the chemical is drawn into the roots effectively and you can achieve full control.

Recommended approach for combining fire and herbicides

To get the best results from your burn-and-spray program, take note of these tips: 

• Inspect the site regularly for new shoots or stems.
• Apply herbicide as soon as resprouting begins.
• For cut-stump applications, wait until the plants’ stems are completely cool and dry. Avoid applying herbicide while stumps are steaming or moist.
• Always follow the manufacturer’s label instructions and observe any post-fire application constraints. Refer to the APVMA for official guidelines.
• Use low-intensity burns to reduce canopy cover and expose target stems without damaging desirable plants.
• Maintain accurate records of burn dates, herbicide rates, and follow-up inspections and chemical applications.

Choosing the right herbicide after controlled burning

After controlled burning, strike while the iron is hot and administer a herbicide to control weed growth. The herbicide you choose will depend on the weed species, plant size, and location.

Let’s explore the most commonly used active ingredients in the Australian context, all of which are available right here at Specialist Sales: 

• Triclopyr, picloram and aminopyralid: Often used alone but most effective when combined, these actives are known as the ‘woody weed specialists’. They’re highly effective on shrubs, trees, and regrowth, and can be used for foliar spraying, basal bark, or cut-stump treatments. They are particularly ideal for the selective control of grasses.

• Fluroxypyr: This herbicide is effective against woody weeds in non-crop settings, pastures, forests, and rights-of-way. Fluroxypyr can be used either as a foliar spray or with cut-stump, basal bark, or brushcutter applications.

• Metsulfuron-methyl: Excellent as a standalone treatment or in combination with other herbicides, metsulfuron-methyl is often used as a ‘spike’ for tough-to-kill shrubs or regrowth. Only small doses of this herbicide are required, and label instructions must be strictly adhered to for environmental safety.
• Tebuthiuron: This residual soil-active herbicide is ideal for large rangeland areas. It prevents regrowth for up to two years without harming established pastures. However, it should only be used where non-target impacts are acceptable, and always following the permitted applications on the Product Label.
• Glyphosate: Glyphosate is a reliable, non-selective systemic herbicide widely used for foliar spraying and cut-stump treatments. It’s absorbed through leaves and stems and moves quickly to the plant’s roots, delivering consistent, long-term results.

How to apply herbicides to weeds after burning

There are several ways to apply herbicides to woody weeds after fire. Consider these options:

1. Cut-stump (cut and paint) application

When to use: On isolated trees and large shrubs, or where selective removal is required (post-burn stems are ideal). 

How to apply: Cut the stem near ground level, then immediately apply your chosen herbicide to the entire cambial surface (the area that produces new wood and inner bark). Use measured doses with a syringe, brush, or knapsack sprayer.

Pros: Low herbicide volume, very selective, minimal drift risk. 

Cons: Labour-intensive, large infestations take time to address.

2. Basal bark or brushcutter application

When to use: In small to medium systems where cutting isn’t practical but bark can be easily penetrated. This method works best on smooth bark and young stems. 

How to apply: Administer a labelled oil-soluble herbicide mixed with diesel (or another recommended product) low on the plant’s stem or on the full circumference of the trunk.

Pros: Good for selective control, effective against many woody species, minimal spray drift. 

Cons: Not always suitable for large stems and trunks, labels vary on allowed oils and rates. 

3. Foliar spraying

When to use: For dense stands of regrowth or small woody plants. Foliar spraying is best when plants are actively growing.

How to apply: Use broadcast or targeted spraying with a boom or knapsack sprayer. Full leaf coverage is essential for systemic uptake. Adding an approved surfactant can help with herbicide efficacy. 

Pros: Efficient for large areas. 

Cons: Drift risk, non-target damage to desirable vegetation. Always observe wind and inversion restrictions when using a foliar spray method. 

4. Aerial, helicopter or drone application 

When to use: For large infestations in remote or rugged areas where ground access is limited. Some states have guidelines or require permits – always check with your local authorities before commencing spraying.

How to apply: Apply using either an aeroplane, helicopter, or drone. This product works best when paired with a spray oil to assist with uptake and mitigate drift. This method is ideal for tebuthiuron pellets in remote or large-scale areas. We recommend working with an experienced contractor to apply all herbicides of this nature, and always reading the product label for directions of use and application rates. 

Pros: Effective for large infestations in remote or inaccessible areas.

Cons: Drift risk and damage to non-target desirable vegetation. Permits may be required from local authorities.

Matching herbicide to application method

Need a recommendation for which herbicide to use based on your chosen application method? Here’s what we suggest:

• Foliar spray: A combination of triclopyr and picloram or triclopyr, picloram, and aminopyralid, mixed with metsulfuron-methyl as a spike. Add a good penetrant or surfactant to address exposed stems and regrowth. 

• Cut-stump painting: A concentrated glyphosate, triclopyr, metsulfuron-methyl, or fluroxypyr formulation applied directly to the exposed cambium. Used small, measured doses to increase efficacy and reduce off-target risk. 

• Basal bark application: For stems under 10-15cm in diameter, use oil-based triclopyr and picloram formulations as labelled. Painting or spraying low on the stem will penetrate the bark and into the cambium. This will be easier after a controlled burn when the bark is more exposed.

• Soil residual application: Tebuthiuron in targeted corridors where long-term suppression is desired and non-target damage is acceptable. Always review the Product Label and any environmental requirements before applying. 

Why cut-stump treatments are more effective after burning

The cut-stump application method works exceptionally well after a controlled burn because fire exposes the plant’s stems and reduces moisture content. By cutting the stem close to the base and immediately applying herbicide to the exposed cambium, the chemical can be rapidly absorbed and translocated throughout the plant.

Simply put, after fire:

• There’s less foliage, making stems easier to locate and treat.
• Outer bark and leaves are charred, improving herbicide penetration.
• The plant directs nutrients to regrowth points, helping the herbicide travel directly to the roots.

When using a cut-stump method, always ensure stems have cooled before applying herbicide. Some species, such as those with lignotubers or epicormic buds, may resprout even after treatment, which means follow-up applications will be necessary.

Personal and environmental safety after burning

Safety is non-negotiable when using herbicides after a burn. Adhere to these recommendations to ensure both environmental and personal safety:

• Follow label directions: These are a legal requirement for any herbicide application.

• Spray during suitable weather conditions: Avoid high winds or still air, as these can cause drift and inversion. The ideal conditions for applying herbicide after a burn are 3-20km/h winds and mild temperatures.

• Protect waterways and desirable vegetation: Maintain buffer zones to ensure no off-target damage or pollution occurs.

• Take personal safety precautions: Use the recommended PPE, and never apply herbicides while standing near smouldering logs or hot ground.

• Record every treatment: Take note of dates, products, and rates for compliance and monitoring. 

Addressing the limitations of burn-and-spray programs

The use of a slow-burning fire coupled with follow-up herbicide spraying is powerful, but not a silver bullet solution. Make these considerations when employing the burn-and-spray method to ensure safe, effective control.

• Monitor and follow up: Vigilance when treating woody weeds is essential for total eradication, as fire often stimulates germination or can release buried seeds. Always administer follow-up herbicide treatments to control new sprouts and seeds.

• Avoid off-target impacts: If using a residual herbicide, be cautious not to impact non-target species and desirable plants. Some herbicides, especially those that are soil-activated (e.g., tebuthiuron) can remain in the soil for two years or more, depending on the soil type. Use a buffer at all times to prevent unwanted damage.

• Calculate your costs: Some recommended herbicide application methods for after a burn are labour-intensive and costly. Because monitoring and retreating is imperative, this should always be factored into your costs before proceeding.

Employing integrated management practices for best results

The most effective program combines fire and herbicide with integrated management practices.  For best results:

• Combine fire and herbicide programs with rotational grazing and strategic revegetation.
• Track all treated areas and schedule follow-up checks at three, six, and twelve months post-application.
• Integrate residual herbicides cautiously to protect desirable vegetation.
• Maintain detailed property records for long-term planning and compliance.

FAQs about controlled burning

Which types of weeds respond best to fire and herbicide?

Woody weeds such as lantana, prickly acacia, gorse, African boxthorn, and rubber vine will respond particularly well to burn-and-spray programs.

Can I use the burn-and-spray method near conservation zones?

Yes, it’s safe to burn and spray near conservation zones, but you must hold the correct permits and maintain wide buffer zones to protect native vegetation.

How long should I wait before spraying after a burn?

After a burn, wait until visible resprouting occurs before spraying. This is when herbicides are most effectively absorbed and translocated to the roots of a plant.

Do I need to keep livestock off treated areas?

Yes, you must keep livestock away from treated areas and follow the withholding period stated on the Product Label before reintroduction.

Is burning before spraying more cost-effective?

 Typically, yes. Controlled burning reduces foliage density, meaning less herbicide is required for the same level of control.

What are the safest conditions for controlled burning?

The safest conditions for controlled burning are mild temperatures, low winds (between 5-15 km/hr), and moderate humidity.  Always check with your local fire authority before proceeding with a burn.

When planned and executed responsibly, the combination of controlled burns and targeted herbicide treatments is one of the most effective and sustainable methods for managing woody weeds in Australia. By following proper timing, product selection, and safety measures, farmers can achieve cleaner paddocks, healthier pastures, and lower long-term costs.

At Specialist Sales, we’re proud to support Australian farmers with expert advice and a comprehensive range of herbicide products suited to post-burn conditions. Explore our range now, or contact our team for tailored guidance.