Pesticides: The basics

About pesticides

Pesticides, also known as 'plant protection products' (PPP) are used to control pests, weeds and diseases. Examples include insecticides, fungicides, herbicides, molluscicides, and plant growth regulators.

They can exist in many forms, such as solid granules, powders or liquids and consist of one or more active substances co-formulated with other materials.

Active substances

The active substance or substances within a pesticide has the controlling effect on the pest, weed or disease.

Safeners and Synergists

These are substances added to plant protection products to:

  • eliminate or reduce phytotoxic effects (safeners)
  • substances which can give enhanced activity (synergists)


These are substances in a plant protection product that are neither active substances nor safeners or synergists


An adjuvant is a substance other than water that does not have significant pesticidal properties but which enhances or is intended to enhance the effectiveness of a pesticide product. This could be done by adding the adjuvant to a spray tank containing the pesticide product. They are not pesticides but are subject to regulatory control.


Biocides also combat harmful organisms but are not strictly related to plant protection.

More on biocides

Compliance with the regulations

HSE is the national regulator for the UK, on behalf of the UK government and the devolved administrations.

We aim to ensure that pesticides do not harm human health or have unacceptable effects on the environment by:

  • enforcing the regulations
  • ensuring only authorised products can be marketed
  • ensuring products are used in a sustainable fashion
  • monitoring the impact of the chemicals

Enforcement visits

If you’re in Great Britain an HSE inspector or a pesticide enforcement officer may visit your business to ensure that you’re complying with your duties under plant protection regulations.

Pesticide enforcement officer visits

Register your business with the competent authority

If your work involves pesticides you must comply with the Official Controls (Plant Protection Products) Regulations 2020.

This includes registering with the Competent Authority. This is the Department for Environment, Food & Rural Affairs (Defra) in England and the Scottish and Welsh Governments in Scotland and Wales. Defra will collect this information on behalf of Scottish and Welsh Governments.

More on registering with Defra

Pesticide product authorisation

Before any pesticide product can be used, sold, supplied or stored it must be authorised for use. The pesticides register database lists the pesticide products authorised for use in Great Britain and Northern Ireland.

More on product authorisation

Active substance approval

An active substance must be approved before it can be included in any pesticide product authorised for use in Great Britain. The approvals register lists the approved active substances for Great Britain.

More on active substance approval

Maximum residue levels (MRLs) and import tolerances

A maximum residue level (MRL) is the maximum concentration of a pesticide residue in or on food or feed that is legally tolerated when a pesticide is applied correctly.

MRLs apply to produce both treated and imported into Great Britain.

An import tolerance is a specific MRL set on imported food or feed.

More on MRLs and import tolerances

Adjuvant authorisation

If you wish to market an adjuvant for use with a pesticide in the UK, you must apply for its inclusion on the Official List of Adjuvants. The list gives details of the adjuvant products that may be used with pesticides and the conditions of use that they are subject to.

More on adjuvants

Using pesticides in your garden or allotment

If you use pesticides in your garden, allotment, or on houseplants you are legally responsible for using them correctly and effectively. You must keep your garden and allotment safe for people, pets and wildlife.

More on amateur use of pesticides

Reporting an incident or concern

You should report concerns about non-compliance with the law or incident to the appropriate enforcing authority.

Who you should report an incident or concern to


From 1 Jan 2021 the relevant EU law in relation to the regulation of plant protection products was retained in GB law and kept the same official titles, for example, Regulation (EC) 1107/2009.

Northern Ireland is still subject to existing EU law.

The Plant protection Product Regulations 2011 (PPPR) designates the competent authority in GB and sets out how the duties in Regulation 1107/2009 can be enforced.

The Plant Protection Products Regulations 2011 (

Plant Protection Products (Sustainable Use) Regulations 2012 (PPPSUR) sets out the competence requirements for sale and use of PPPs, the use, handling and storage requirements of PPPs (including Ariel spraying) and requirements for the inspection of PPP equipment. PPPSUR also set out what enforcement action the authorities can take.

The Plant Protection Products (Sustainable Use) Regulations 2012 (

The Food and Environment Protection Act (FEPA) contains statutory powers to control pesticides. The mechanism by which these aims are achieved in Great Britain is set out in the Control of Pesticides Regulations (COPR) 1986.

More about FEPA and COPR

The Official Controls (Plant Protection Products) Regulations 2020:

  • allow regulatory authorities to enforce legal requirements that apply to the placing on the market and use of PPPs throughout the supply chain
  • explain the action enforcement authorities can take where non-compliance is identified or suspected.

The Official Controls (Plant Protection Products) Regulations 2020 on the legislation website

Maximum residue levels (MRLs) are regulated in GB under Regulation (EC) No 396/2005.

Regulation (EC) No 396/2005 on the legislation website

Further help

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Updated 2024-06-21->->->->->