Pesticide adjuvants and the Official List of Adjuvants

Definition of an adjuvant

Adjuvants are authorised under Regulation (EC) 1107/2009 which defines 'adjuvants' as being:

'substances or preparations which consist of co-formulants or preparations containing one or more co-formulants, in the form in which they are supplied to the user and placed on the market to be mixed by the user with a plant protection product and which enhance its effectiveness or other pesticidal properties, referred to as 'adjuvants'.

Adjuvants are not plant protection products (PPPs); but, as they influence the way PPPs behave and the effects they have, they are subject to regulatory control.

The Official List of Adjuvants

The 'Official List' provides details of the adjuvant products that may be used with PPPs and the conditions of use to which they are subject.

Each officially listed adjuvant product is issued with an individual 'list entry' which specifies the identity of the adjuvant and the conditions that a user must comply with. At any point in time there will only ever be one extant list entry for each individual adjuvant product.

The Official List is published in full on the adjuvant database located on the HSE website. Any additions and amendments are updated regularly on the website. A copy of the list entry is sent to the applicant upon issue.

To add a new product to the Official List, or to amend the conditions of an existing list entry, an application must be submitted with all the necessary data to show that the adjuvant itself is safe to use, and is also safe to use when mixed with the proposed PPPs. All applications are processed in a similar way to plant protection products.

List entry

The list entry specifies:

  • the 'identity' of the product (for example tradename, ADJ (registration) number, applicant and formulation details)
  • the conditions of use with which a user must comply when using the adjuvant with an authorised plant protection product. These are in addition to complying with the conditions of use as specified on the plant protection product label
  • the expiry date(s) for the conditions of the previous list entry where a new list entry has superseded the former, or where a product has been withdrawn from the list

Each list entry has a unique list entry number, issued following evaluation of an application. A new list entry number is allocated each time a new list entry is issued.

The list entry will be sent to the applicant at the successful conclusion of the evaluation and published as part of the Official List.

Identity of an adjuvant

Product tradename

Any change to the tradename requires an application to amend the list entry.

Unique registration (ADJ) number

Every adjuvant product carries a unique product registration number, prefixed by 'ADJ', which we allocate upon issue of the first list entry for a new product.

This number will remain with this specific adjuvant product, unless there is a subsequent change to its identity such as a change in product tradename, applicant, classification or a major change to its formulation.

The applicant

The applicant, as specified in the Official Listing, has a different definition to that used for authorisation of plant protection products. The role of the applicant company is:

  • the party making the application to include an adjuvant on the list
  • the party responsible for meeting any data requirement
  • the party responsible for any literature produced directly on their behalf
  • the party who may request to have an adjuvant removed from the list

Any change of the applicant requires an application to amend the list entry.

It should be noted that there are no legal controls over companies marketing adjuvants (unless they are also the applicant company). Marketing company details are not included on the list entry and notification of changes to these companies are not required.


The formulation details referenced on the list entry will refer to the specification of the 'effective adjuvant component' (as detailed in Appendix 1 of the application form) and the 'recipe' of the formulation (as detailed in Appendix 2 of the application form – unacceptable co-formulants).

Any changes to the formulation must be the subject of an application to HSE.

Effective adjuvant component

The applicant must propose which constituent(s) in the formulation are the 'effective adjuvant component(s) or EAC. This is the constituent which is/are primarily responsible for giving the product its adjuvant properties, or in other words, the main active component of an adjuvant. Their identity and quantity will be the only part of the (otherwise confidential) formulation details which will be specified in the published list entry.

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Updated 2024-01-30