What Is a Weed Wiper and How Does It Work?

Blanket spraying covers ground quickly, which is why most people default to it. The cost is everything else it hits. Overspray lands on pasture you paid to establish, and you end up treating an entire paddock to deal with weeds growing across a fraction of it.

A weed wiper resolves that issue. It applies herbicide to the weeds standing above your pasture and leaves the grass below untouched.

What Is a Weed Wiper?

A weed wiper is a towed machine with a herbicide tank and a set of wicks running the width of the frame. You set those wicks at the height that suits your paddock.

As the machine travels, weeds growing above that height brush against the wet wicks and pick up chemical. Anything shorter passes underneath untouched.

There are no nozzles and no spray, so the chemical moves only when a leaf touches a wick. Wind no longer decides which days you can work. You will also see these machines called wick wipers or wick applicators, which were the common names in the early years.

How a Weed Wiper Works

Mixing and filling the tank

Add herbicide and water at the rate your label sets for wiper application. Wiper rates run well above boom spray rates. Glyphosate is commonly wiped at around 1:10, and some products are diluted further still. Always work to the rate printed on your own product's label.

A sprayer coats the leaf, while a wiper only touches it briefly, so the concentration has to make up the difference. Mixing at boom spray strength is the most common reason a wiping job disappoints.

Wetting the wicks

You should flush the system with water to wet the wicks and ensure good flow before adding chemicals to the tank. Once the chemicals are added, the wicks should not be soaking wet. They should be wet enough to wipe the chemical onto the weeds without dripping.

Wicks that are too dry will not transfer enough chemical, while dripping wicks can leave chemical on the pasture and cause strip damage. Machines vary in how they control the flow, so check the soaking system before you buy.

Bruising the weed before contact

Some machines carry a bar in front of the wicks that knocks the weed about immediately before the wick reaches it.

Many pasture weeds have hard, waxy leaves that resist chemical uptake, and damaging the surface first gives the herbicide a way in. On the tough species, it lifts your strike rate.

Setting the wiping height

Set the wicks low enough to make solid contact with the weeds and high enough to clear the grass you want to keep. Set them too low, and you burn a strip through your pasture; too high and you miss the tops of the weeds.

Do this in the paddock rather than the shed, and check it again after the first few passes. A hand winder makes the adjustment quick when you move between paddocks with different pasture heights.

Travelling at the right speed

Most operators settle on about 10 km/h, which covers ground while holding the contact time that moves chemical onto the leaf. Manufacturers quote coverage of around 4.5 hectares an hour for their larger machines at that speed. Pushing faster leaves the contact patchy.

On stemmy or clumping weeds, run a second pass in the opposite direction to reach the side of the plant the first pass missed. Most operators treat this as standard on the harder species.

Which Weeds Suit Wiping

Wiping suits the weeds your stock leave behind and the ones a normal spray program keeps missing. They fall into three groups:

• Problem pasture grasses, including giant rat's tail, Parramatta grass, African love grass, serrated and Poa tussock, blady grass and setaria
• Upright broadleaf weeds such as thistles, silverleaf nightshade, fireweed, Bathurst burr and ragwort
• Rushes, bracken and woody regrowth like gum shoots and wattle

Each grows clear of the pasture around it, and each is expensive to control any other way.

You can also create that height difference yourself. Slash or hard graze a paddock, then let it come back. The weeds recover faster and grow taller than the grass. That lifts them clear and gives you a window to wipe.

Where weeds sit level with your pasture or below it, wiping is the wrong tool. Spot spraying or a selective herbicide will do a better job.

Choosing a Machine That Suits Your Property

Redback Weedwipers come in different sizes and configurations, so the right setup depends on your paddocks, terrain and the vehicle you plan to use.

• Working width: Match it to your paddocks and your tow vehicle. A narrow unit behind a ride-on or quad suits a lifestyle block, house paddocks and fence lines. Bigger country justifies more width.Ensure your machine wings fold up to easily navigate farm gates and raceways.
• Wiping height range: Check how high and low the wicks can be adjusted. The machine needs to go high enough to protect taller pastures while still making good contact with the weeds. This is important when wiping weeds such as rat's tail grass through tall pastures.
• Ground contour: On undulating country, a rigid frame lifts off the weeds on one side and drags through pasture on the other. Pivoting wings and wing wheels let the frame follow the ground. That keeps the wiping height even across the full width. It is a common feature on weed wipers built for Australian paddocks.
• Frame and wheel arms: Compare how machines are built before you compare prices. Hot-dipped galvanised box section is heavier than folded sheet metal. A heavier frame generally holds its shape better in rough country. Check how the wheel arms are braced, since that affects alignment over time.
• What is included: Two rows of wicks give more contact than a single row. Rigid and rotating wipers also behave differently. Cheaper machines often omit the tank, pump and wiring loom. Check whether you are buying a complete setup or just the frame.
  
  

What to Expect After Wiping

Wipe while the weeds are actively growing. A stressed plant will not translocate chemical down to the roots. Operators often see the first signs within a week during the growing season, though this varies with species, product and conditions. The full result takes longer.

Perennials rarely die from a single pass. Watch treated areas for regrowth and plan a follow-up. Wiping works best alongside rotational grazing and competitive pasture, not on its own.

Is Wiping Right for Your Paddocks?

Three things decide the result. Get the mix rate, the wiping height and the timing right, and a wiper will clear the weeds your spray program has been missing without setting your pasture back.