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By Dr Brian de Villiers
August 2025
Adjuvants are applied with various crop protection products (CPPs) to increase and stabilise weed, pest and disease control. Some companies include the adjuvant in the CPP formulation, while others prefer to recommend an adjuvant that is added to the
spray solution. Both approaches have advantages and disadvantages. Villa uses a combination of the in-can and tank-mix methods, depending on the specific situation and label recommendations. It is important to understand the benefits and limitations of both approaches to ensure the optimal efficacy of CPPs.
Tank-mix approach
The major advantage of the tank-mix approach is flexibility, because the adjuvant type and rate can be changed depending on the situation. CPP labels sometimes list more than one adjuvant, and the product is selected based on the specific tank mixture, environmental conditions, plant morphology and other factors. This approach also affords flexibility with regard to the adjuvant rate, enabling the user to add the highest recommended rate for marginal situations. The rate of surfactants and oils, which are frequently recommended on a percentage basis, can be altered depending on the water volume. The major disadvantage of this approach is that the CPP registration holder has
little control over how the end-user selects the type and rate of adjuvant. With this comes the risk of mistakes that can impact efficacy, compatibility, and crop damage.
In-can approach
The major advantage of the in-can approach is that the registration holder has control over the type of adjuvant that is used with their CPP. This ensures that the built-in adjuvant will always be used and that the end-user cannot replace it. However, this approach offers less flexibility. The type of adjuvant cannot be adapted to make provision for tank mixtures, environmental conditions, and other relevant factors. The adjuvant rate in CPPs will also vary with different CPP rates. Furthermore, when
CPPs are applied on a per area basis, the adjuvant rate is fixed, and it cannot be adapted for different water volumes. This is acceptable if the adjuvant’s function is only related to its ratio to the CPP. However, if the adjuvant is also used to reduce droplet bounce, increase retention and droplet spreading, the ratio of adjuvant to the water volume is important.
Villa’s stance
It is important to stick to label instructions regarding adjuvant choice, regardless of whether it is the tank mix or in-can option. Although both methods have benefits and limitations, we feel that the flexibility provided by the tank-mix option is best suited to
the Villa approach. We can recommend adjuvants that are tailor made for specific situations to ensure optimal efficacy. However, it is important that the label instructions are followed to ensure the success of this strategy. Contact your Villa agronomist for more information about adjuvants and water quality.