Triclopyr, Picloram & Aminopyralid: Top Solutions for Woody Weeds

Noxious woody weeds can pose significant challenges to Australia’s agricultural and natural landscapes. These invasive species not only impact the productivity of farmland, but they also threaten native ecosystems.

To control these insidious weeds, you’ll need a herbicide that features a potent active ingredient. Triclopyr, picloram, and aminopyralid are by far the most effective and popular actives, which is why they’re our top recommendations to customers looking to eradicate woody weeds.

Keep reading as we explore the effectiveness of these powerful ingredients in controlling noxious woody weeds.

Using pyridines for weed control

Triclopyr, picloram, and aminopyralid all fall under the same chemical classification: they are all ‘pyridines’. Let’s explore each of these three compounds, understand how they work as herbicides, and determine how to make the best use of them to rule out unwanted noxious woody weeds.

What is triclopyr?

Triclopyr is a synthetic herbicide chemically classified as a ‘pyridine’. It’s predominantly used as a foliar herbicide, and occasionally as a fungicide.

Triclopyr works by mimicking the natural plant hormone auxin, which regulates plant growth. When triclopyr is absorbed by the plant, it over-stimulates its growth processes, which leads to uncontrolled and abnormal growth, and subsequently, death.

Triclopyr is great for targeting broadleaf and woody plants, and is particularly effective against infestations of species like lantana, gorse, and blackberry.

What is picloram?

Like triclopyr, picloram is a pyridine – but as a herbicide, it has a different mode of action.

Picloram works by disrupting a plant’s ability to transport nutrients. It is absorbed through the leaves, stems, or roots, and moves systematically through the plant to inhibit its growth. Due to its long residual activity in the soil, picloram is especially effective at eradicating deep-rooted and perennial woody weeds like prickly acacia and blackberry.

Why are triclopyr and picloram so effective in Australia?

Australia’s climate, soil conditions, and diverse ecosystems make it an unfortunate hotspot for the proliferation of noxious woody weeds. These weeds can be very aggressive, with deep root systems that make removal by hand difficult.

Herbicides from the pyridine family have proven particularly successful at eliminating noxious woody weeds for a number of reasons:

Selective targeting: Both triclopyr and picloram target broadleaf weeds and leave grasses and other monocots relatively unaffected. This is crucial in pastures, where farmers want to protect grasses whilst eliminating harmful weeds.

Systemic action: These herbicides travel through the plant to target both the foliage and the root system. This systemic action ensures a thorough kill and prevents regrowth.

Residual effects: Picloram in particular has a long-lasting residual effect in the soil, which can prevent weed regrowth over extended periods. This is ideal for controlling perennial species that can return year after year.

How to use triclopyr and picloram on noxious woody weeds

These pyridine herbicides are typically applied as either foliar sprays or basal bark treatments. Use one of these methods to ensure best results.

Foliar spray

Foliar spray herbicides are ideal for young, actively growing weeds with adequate leaf surface for herbicide absorption. Both triclopyr and picloram can be mixed with water and sprayed directly onto the leaves, where they will then be absorbed and translocated throughout the plant.

Basal bark treatment

The basal bark treatment method is effective at controlling mature woody plants, and combines both chemicals – triclopyr and picloram – for best results. A mixture of these ingredients is diluted in an oil carrier and applied to the lower stems or trunk of the plant, which allows the herbicides to penetrate the bark and kill the plant from within.

When to use triclopyr and picloram herbicides

The best time to apply herbicides will depend on the season and the growth stage of the weed species you’re trying to target. Here are some guidelines to consider:

- Growing season (spring to summer): Foliar applications will be most effective when weeds are actively growing, as the plants will be more capable of absorbing the herbicides during this time.

Dormant season (autumn to winter): Opt for basal bark treatments during winter, when plants are dormant but more susceptible to herbicides applied to their bark and stems. The dormant season is also a good time for targeting mature woody weeds, as foliar treatments may be less effective on these plants.

What is aminopyralid?

Aminopyralid is also a pyridine-based herbicide that’s effective against a wide range of broadleaf weeds including woody perennials. Just like triclopyr, it mimics auxin, which means it can take control of a plant’s growth processes and send them into overdrive, causing plant death.

Why combine aminopyralid with triclopyr and picloram?

While aminopyralid can be used on its own, when combined with triclopyr and picloram, it creates a powerful synergistic effect that will supercharge the overall efficacy of your herbicide treatment.

Including aminopyralid in your herbicide treatment will:

Broaden the spectrum of activity: Aminopyralid works on hard-to-kill weeds that triclopyr and picloram alone aren’t potent enough to control. It is especially effective against thistles, capeweed, and other major pasture-damaging broadleaf species.

Increase soil activity: Like picloram, aminopyralid has residual soil activity, which means it provides extended control over regrowth and suppresses the establishment of seedlings. However, its residual effects are more targeted towards broadleaf species, making it the perfect compound to combine with picloram.

Provide synergistic action: Combined, these three active ingredients offer a comprehensive and long-lasting weed control solution. This is particularly beneficial for land managers who need to tackle a range of invasive species at once while minimising the need for frequent reapplication.

Our top tips for using triclopyr, picloram, and aminopyralid

To maximise the effectiveness of any herbicide, you should always adhere to best practices for application and management. Let’s break down a few of the most important guidelines to follow.

Choose the right herbicide

Always select a herbicide or combination of herbicides to suit the weed species you’re trying to eradicate. If you’re unsure, most product labels or descriptions will outline the target species.

Use a wetting agent

Utilising a wetting agent such as a penetrant surfactant, or a spreading agent like a surfactant, is always recommended when mixing sprays for hard-to-kill weeds.

Time your application correctly

Apply herbicide during the plant’s growth season for foliar treatments, or during the dormant season for basal bark application.

Follow the label directions

Always adhere to the dosage rates, mixing ratios, and safety precautions outlined on your chosen product’s label to ensure effective and environmentally responsible use.

Monitor weather conditions

Avoid applying herbicides on windy or rainy days, as this can reduce efficacy and increase the risk of damage to non-target plants.

Reapply as needed

For large or heavily infested areas, follow up with a second application the following year for comprehensive control.

While they are all effective herbicides in their own right, combining triclopyr, picloram, and aminopyralid offers an exceptionally powerful solution for managing noxious woody weeds in Australia.

By understanding how these active ingredients work and following best practices for application, landowner and farmers can significantly reduce the spread of invasive weeds and protect both their agricultural productivity and native ecosystems.

Shop herbicides for woody weeds, including triclopyr, picloram, and aminopyralid, with Specialist Sales, your friendly partner in all things Australian agriculture.