Tank-mix recommendations on pesticide product labels

1. What is a tank-mix?

You can mix 2 or more plant protection products (PPP) in the spray tank for application together as long as

  • it is within the conditions specified on each label
  • there is not a specific label restriction stating not to carry out that particular mix.

Three specific cases which are unacceptable are:

  1. where 2 or more of the products are anticholinesterase compounds unless the mixture is specifically allowed under the authorised conditions of use on the product label of at least one of the products;
  2. unless there is information to the contrary on the product label, users should not apply Acetolactate synthase (ALS) herbicides in tank mixture or sequence with other ALS herbicides including sulfonylureas.

You may also mix a PPP with an adjuvant (a substance that makes the pesticide more effective) if the adjuvant appears on the Authorised List and use is in line with both labels.

Guidance on the safe use of tank-mixes is given in the 'Code Of Practice For Using Plant Protection Products'.

Authorisation holders may however include specific recommendations for tank-mixes on the product label or other literature. In such cases data must be available to demonstrate physical/chemical compatibility and in some cases biological compatibility (efficacy) of the mix. There are two different types of 'tank-mix' each with their own specific requirements:

Convenience tank-mixes

This is the combination by the user of two or more PPP (or PPPs with an adjuvant) in the same spray tank to reduce the number of spray operations. It is done when the appropriate application timing for the individual PPP coincides, and it is therefore possible to reduce the number of spray operations by applying the products together. A product label 'Compatibility' section may recommend that a product can be mixed with another product. Such tank-mixes must be shown to be physically and chemically compatible. This section of the label may also advise on tank-mixes which are known to be incompatible or on specific mixing instructions to be used with compatible mixes.

Positive tank-mixes

This is the combination by the user of two or more products in the same spray tank to obtain better pest control than if the products were applied alone. A positive tank-mix occurs when a product label recommends a mixture to give an enhanced effect when the tank-mix is used (for example to control additional pests; to reduce the application rate of one or more of the products). In such cases, the mix must be shown to be physically and chemically compatible and biologically compatible (effective and crop-safe). In some circumstances the only use(s) on a PPP product label requires the use of a second pesticide or adjuvant, meaning the tank mix is required to achieve any efficacious use of the product.

In either case you cannot include recommendations for tank mixes containing 2 or more anticholinesterase products unless we have fully assessed the toxicological effects – you should contact us for guidance on the additional data requirement.

2. Convenience tank-mixes

Data requirements for convenience tank-mixes

Any convenience tank-mix recommendation, whether on the product label, or provided to users by the authorisation holder verbally or via websites, advertising or other material must be supported by physical and chemical compatibility data. The ASTM standard method is E 1518-05. If another test method is used then it must be justified.

Applying for convenience tank-mixes on the authorised label

If you are applying for the first authorised label-recommendation of a convenience tank-mix for a product that contains an active substance for which no tank-mixes have been previously authorised in any product, you must submit as part of the application the data and/or reasoned scientific cases demonstrating that the product is physically compatible in the proposed mixture. Full study reports are required.

These data can be considered under the first application to be considered for the active substance (a.s.)  or any subsequent application for a product containing that active substance.

Once the first convenience tank-mixture has been authorised for any product with that a.s., subsequent convenience tank-mixes for any products must also be supported by physical compatibility data. However, we do not need to see these data in full. We will accept a Compatibility Assurance Statement(CAS) - a statement certifying that data or evidence is available to demonstrate that the products in the proposed mixture are physically compatible. The underlying data must be available for submission if requested by HSE. A CAS must be submitted whenever you submit a new label containing new convenience tank-mixes with an application.

The 'convenience tank-mix' section must make it clear that the listed mixes supported only by physical compatibility data are 'physically and chemically compatible'.

Notifying HSE of additional convenience tank-mixtures.

We appreciate that your portfolio of convenience tank-mixtures will increase as new physical compatibility data become available and that it would be difficult to keep updating the authorised label. Therefore, the CAS includes the statement that

We confirm that any additional compatible mixtures that we recommend on the product label, verbally or via websites, advertising or other material will comply with the requirements of paragraphs 2 to 4 above and that these mixtures will be notified to HSE with a new Compatibility Assurance Statement at the next application for this product.

*these relate to confirmation that the tank mix partners are authorised for use on the crops on the product label, evidence of physical and chemical compatibility will be made available on request and belief that none of the hazards of the product will be increased by mixing with the tank mix partners.

Therefore, whilst your authorised label may include a certain number of convenience mixtures it is acceptable to:

  1. Add new convenience tank-mixes to the label without applying for a new authorisation as long as you have physical compatibility data. Instead, the next time you submit an application for a change to the product label, it should include the additional tank-mixes with a CAS to confirm the data are available.
  2. Refer the user to another source (the company itself or their website/ other literature) to obtain details of the most up-to-date list of convenience-mixes. You may therefore include general phrases on product labels rather than specific lists, such as;
    • 'for up to date details of compatible tank-mixes contact the manufacturer/distributor',
    • 'product x may be tank-mixed with a variety of plant protection products providing that the application timing is correct for both product x and the partner(s) in the mixture. For further information on the authorisation status of mixture partners, consult the manufacturer'
    • 'Consult manufacturer for details of tank mixes'

Again, the next time you submit an application, you must submit a CAS with a list of all the convenience tank-mixes that you are currently recommending that do not appear on the label itself.

3. Positive tank-mixes

Data requirements for the authorisation of positive tank-mixes?

In addition to the physical and chemical compatibility data required for convenience tank-mixes (see above), where a positive tank-mix recommendation is being made, additional biological compatibility (efficacy) data will be required to support the proposed positive tank-mixes. This also applies to positive tank-mix recommendations made with adjuvants.

Efficacy testing must be conducted in line with the requirements for 'positive tank-mixtures' in Efficacy Guideline 604: Efficacy Data Required for Tank Mixtures and Sequences of Pesticides.

The proposed recommendations must be within the authorised conditions of use of the product to be included in the positive tank-mix recommendation. Otherwise you will also need to submit the appropriate safety data, to amend the authorised conditions of use for the product to be included in the positive tank-mix recommendation.

Where all uses on the label require the use of a second PPP or adjuvant to achieve efficacy, the impact of the tank-mix on all areas of the risk assessment must be considered.  As such it may be necessary for certain formulation studies (for example dermal absorption or ecotoxicology) to also include the adjuvant. This is to allow HSE to assess the risk from the use of the PPP under realistic, normal, or proposed practical conditions of use. Under these circumstances it is advised to discuss the testing requirements with HSE prior to commissioning studies.

Applying for positive tank-mixes on the authorised label

Positive tank-mix recommendations may only be added to the product label following evaluation of the above data as part of an application to HSE. All data must be submitted in full.

Positive tank mixes may not be recommended in any company literature etc.

4. How to specify a tank-mix on the product label?

The products recommended for 'convenience' or 'positive' tank-mixes on your product label should only be specified in one of the following formats:

  1. Product name (with the appropriate MAPP number if you wish);
  2. MAPP number;
  3. Active substance name with a list of appropriate MAPP numbers;
  4. For certain products that are simple salt formulations and contain the same active substance, one formulation is considered to be similar to another in terms of physical and biological characteristics. It is therefore not necessary to test each individual product for compatibility. The following active substances fall under this criteria and products may be referenced as detailed below:
    • for 2,4-D, dichlorprop-P, MCPA, MCPB and mecoprop-P only:
    • authorised salt formulations containing [active substance]
    • for products that are simple salt formulations of chlormequat (ie not those containing metal chelates or di-1-p-menthene) with or without choline chloride:
    • authorised salt formulations containing [active substance] or Authorised salt formulations containing only chlormequat or chlormequat and choline chloride'

5. Tank-mix recommendations containing withdrawn partner products

In order to provide accurate advice to the user it is essential that any pesticide product recommended as a tank-mixture partner or as a sequential treatment is authorised (refer to HSE's Pesticide Register database). Any reference to products that are no longer authorised must be removed from the product label. For convenience tank mixtures, HSE do not need to be informed, and it is normally acceptable for the changes to be made at the next label reprint. Where authorisation holders become aware that a positive tank-mixture partner or sequence treatment has been withdrawn, they must notify HSE as soon as possible, as this is likely to affect the label recommendations, and possibly the authorisation status of the whole product. HSE will then consider whether a formal application together with a revised label is necessary.

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Updated 2024-01-30