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.

Bow & Arrow


Bow & Arrow Herbicide is the standard for broadleaf weed control in the Australian turf industry providing outstanding control of broadleaf weeds in turf.

DiCamba M


DiCamba M is for the control of broadleaf weeds in couch and kikuyu. Weeds controlled include bindie, clovers, chickweed, creeping oxalis, flatweed, dandelions, portulaca and fleabane. This product is NOT suitable for Buffalo lawns.

Reactor Wetter 600


Reactor Wetter 600 increases the activity and efficiency of pesticides and herbicides. Increases wetting and improves spray coverage. It can also be used to treat hydrophobic soils.