How to Help Herbicides Adhere | Surfactants - Lawn Solutions Australia

How to Help Herbicides Adhere | Surfactants

Surfactants (Adjuvants)

An adjuvant is a substance used to modify chemical or physical properties. There are two main categories of adjuvants, but in this article, we are referring to the type known as activator and spray modifiers, specifically the product group known as surfactants.

Why are surfactants sometimes required when applying herbicides or pesticides?

Surfactants are used with herbicide or pesticide solutions in order to reduce the surface tension of the water it is applied with. There is an increase in the ‘spreadability’ of the water, with an increase in the surface area that the solution can cover. In contrast, if you were to apply just water when applied to a waxy surface like that of a weed, it will bead instead of spreading outwards. By adding a surfactant to the water, the molecules are spread outwards as the surfactant molecule is attracted in opposite directions. Rather than being inwardly attracted cohesively it becomes outwards attracted. The surfactant is now the link between what would normally be considered non-compatible materials.

Essentially you end up with a substance that has made water wetter!

Instead of the solution simply beading up and dispersing away, it spreads across the surface of the target material. This will improve the efficacy of the product being applied, ensuring it contacts and adheres to a greater surface area for penetration and improved efficacy.

What is a surfactant?

You can get a better idea of what a surfactant does by breaking down the origins of the word itself. Surfactant is a shortened form of the phrase ‘surface active agent’. Surfactants are soluble in water and are able to reduce water tension. Without going too deep into the science of why this is, the molecules within the surfactant are known as long molecules and have a head and a tail. The head is attracted to water (water-loving or hydrophilic). The tail is attracted to oil, grease and dirt (oil-loving or hydrophobic). So, one end is water-soluble while the other is oil soluble.

The most common types of surfactants are called Carboxylates. These comprise carboxylate salts, like Sodium stearate. Sodium stearate can be found in the most commonly available household ‘surfactant’ item, soap.

What weeds are best to target with the addition of a surfactant?

Target weeds that have a waxy coating or surface that is likely to bead easily upon application are the ideal weed types to look at targeting with a surfactant. Weeds like paspalum, nutgrass or broadleaf weeds like cudweed are ideal candidates for the addition of a surfactant when treating.

What surfactant do I use and how?

In most domestic homeowner situations, the easiest and most accessible surfactant to use is dishwashing liquid. As mentioned earlier, soap contains the surfactant Sodium stearate. Liquid dishwashing liquid can be added to a tank mix of the herbicide or pesticide being applied and mixed with water. A few drops in a 5L pressure sprayer or knapsack should be enough to help ensure that an efficient application is achieved. Many products will advise to use specific surfactants or products designed to achieve the best results with their products. Results after application cannot be guaranteed if using a dishwashing liquid or alternative option with your tank mix that goes against the label instructions.

When determining what surfactant to use it is also important to consider the product that you are tank mixing it with. There are many herbicides that have specific requirements and labels recommend that they be applied with a specifically formulated surfactant or adjuvant to best ensure the success rate of the application. Be sure to read the label thoroughly before applying in case a specific surfactant is required. It is important to consider the effect that any addition to a tank mix will make to the ability for a product to perform as it says it will. If you are unsure, contact the product manufacturer directly for advice.

Some examples of turf surfactant products:

Searles Spredmax

 Spredmax is a concentrated spreader used to maximise spray application. It may also be used to improve foliar applications of soluble and liquid fertilisers. 

Yates Sprayfix

Yates Sprayfix is a non-ionic surfactant that improves the efficiency and effectiveness of garden sprays. Sprayfix can be used with insecticides, fungicides and herbicides.

Agral Spray Adjuvant

Agral is a versatile non-ionic organic surfactant. It is the recommended surfactant to use with the range of products produced by Syngenta.

Pro-Film 904

Pro-Film 904 is a unique, high quality multipurpose surfactant designed to enhance performance of plant protection products. Provides unsurpassed sticking, improves penetration of systemic products. Is soft on turf and forms a film around the plant limiting water loss and helps reduce odour.


Premium surfactant for addition to pesticides to reduce spray drift and to increase rain fastness period.


Activator Surfactant is a premium non-ionic rainfast wetting agent with low foaming qualities.


LI700 Surfactant can be used as an acidifying and penetrating surfactant, reducing alkaline hydrolysis. It will assist with the uptake of systemic herbicides and assists in management of spray droplet size.


Pulse is a non-ionic organo silicone super wetter that improves the spread of spray droplets on leaves by up to 13 times more than standard surfactants. This superior coverage allows thorough penetration and translocation of certain herbicides used for hard-to-control brush and woody weeds.

If you are looking to get the best and most effective use of the products you are using, make sure you read the label thoroughly and add a surfactant if recommended to do so. If you are unsure of best practice, check with the product manufacturer directly for advice specific to their product.

For more lawn care advice, check out our other blogs here.

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