Skip to main content
Last reviewed:

About inhibitor substances

There is no common definition used around the world to describe inhibitors. Therefore, the Ministry for Primary Industries (MPI) has defined inhibitor substances as having the purposes of mitigating the adverse environmental, sustainability, or climate change impacts of an agricultural activity if it is:

  • used or intended for use in the direct or indirect management of plants or animals, or
  • to be applied to a place on or in which there are plants or animals, or
  • to be applied to the feed or water of plants or animals.

For the purposes of this definition, the "inhibitor substance" is the active ingredient in the product that achieves the inhibitor effect.

Your guide to the new rules for inhibitors pamphlet [PDF, 734 KB]

ACVM Act and inhibitors

In 2021, the Government agreed after public consultation that regulatory oversight of inhibitors needed strengthening to manage:

  • residues in primary produce
  • risks to trade in primary produce
  • food safety.

Read about the consultation on the regulation of inhibitors used in agriculture

A number of substances that can be used as active ingredients in inhibitor products are on a list of substances declared to be agricultural compounds by an Order in Council (OIC) under the ACVM Act. The OIC came into effect on 18 July 2022.

Agricultural Compounds and Veterinary Medicines (Inhibitor Substances) Order 2022 – NZ Legislation

Any inhibitor product containing one or more of the substances on the OIC list can only be imported, manufactured, sold, or used if it has an authorisation under the ACVM Act.

What you need to do to sell your product as an inhibitor

This will depend on whether the substance in the product is listed in the OIC or not. Only those products containing substances on the OIC list are subject to the ACVM Act and regulations when used as an inhibitor.

List of inhibitor substances declared to be agricultural compounds – NZ Legislation

What to do if your inhibitor product contains a substance on the OIC list

If your inhibitor product contains a substance on the OIC list, it must be authorised under the ACVM Act before it can be imported, manufactured, sold, or used.

The 2 main types of authorisation required are:

  • registration (for sale on the market), or
  • an approval to conduct research trials of the inhibitor product. This can be done by either a provisional registration or research approval. A requirement for either option is the inhibitor product cannot be sold on the market.

If you are unsure which type of authorisation is required, email approvals@mpi.govt.nz

If your inhibitor was on the market at the time the OIC commenced (18 July 2022), it can continue to be marketed as you have a period of 2 years to obtain its registration. You can apply for registration at any time before 18 July 2024. We encourage companies to apply for registration as soon as they are ready within this period. After the 2-year period, if not already registered, the product cannot be imported, manufactured, sold, or used until it is registered.

How to apply for an authorisation for your inhibitor product

Inhibitors have been categorised as either agricultural chemicals or veterinary medicines based on how the inhibitor is to be used.

Agricultural chemical-based inhibitors: These are inhibitors applied to pasture or feed crops, or crops that may be used as animal feed. This would include the situation where animals would graze the treated crop or forage.

Veterinary medicine-based inhibitors: These are inhibitors administered directly to the animal, such as a vaccine, in-feed or in-water treatment, or bolus.

For guidance on authorisation requirements (registration and research) for an inhibitor product, see:

Agricultural chemicals: making, selling, and using

Veterinary medicines and the ACVM Act 1997

Guidance documents cover such matters as general requirements, chemistry and manufacturing, residues, target animal and plant safety, and efficacy.

If you are unsure of which category an inhibitor falls within, email approvals@mpi.govt.nz

What you need to do if your inhibitor product does not contain a substance on the OIC list

It is the intention to make all inhibitor products subject to the ACVM Act and require registration. An amendment to the ACVM is being sought to enable this.

Inhibitor products containing substances that are not on the OIC list are not subject to the ACVM Act and its regulations when used solely as an inhibitor. If a product contains a substance used as both an agricultural compound and an inhibitor and is not on the OIC list, they will remain subject to the ACVM Act and its regulations for the agricultural compound purpose only.

Other legislation inhibitors must comply with

Whether or not the inhibitor is on the OIC list, there may be other legislation the inhibitor needs to comply with. This includes the Hazardous Substances and New Organisms Act 1996 (HSNO Act). The HSNO Act is administered by Environmental Protection Authority (EPA).

Hazardous substances – Environmental Protection Authority

If you have questions relating to inhibitors and the HSNO Act, email the EPA at HS.Applications@epa.govt.nz

Proving your product works (efficacy)

Efficacy information is required to support the label claim as part of the registration process for inhibitors.

On 30 November 2022, New Zealand Food Safety published 2 efficacy guidance documents:

Efficacy data generated from trials before 18 July 2022 may not align with the guidance documents. MPI will take this into account when assessing such trial work, and assess the efficacy data case by case. You should explain this in your application summary when applying.

If you have any doubts about efficacy data requirements and trial design, email approvals@mpi.govt.nz

Relation between the ACVM regulatory process and the Greenhouse Gas (GHS) Inventory

Registration of an inhibitor product under the ACVM Act does not mean it will be incorporated into the National GHG Inventory.

While both ACVM and GHG Inventory require the effectiveness of a proposed mitigation be proved by robust peer-reviewed research conducted in New Zealand conditions, the GHG Inventory approval processes are different. This is because the Inventory has different objectives such as ensuring changes to emissions reporting meet international reporting requirements under the UNFCCC. The inventory also needs to be confident that accurate data on the use of an inhibitor product can be obtained in the future and that this data will be detailed enough to estimate emissions reductions from the use of the product.

Manufacturers should discuss Inventory requirements with the GHG Inventory team at MPI.

Find out about greenhouse gas reporting

Who to contact

If you have questions about inhibitors and the ACVM Act, email approvals@mpi.govt.nz

MPI business units