Feature articles

31 May 2022

PestWatch: Field mice control

Technical | PPC107 June 2022

In this issue of PestWatch, guest author Chris Parmiter from BPCA Consultant Member company Pesttrain clarifies the legal nuances of controlling field mice in the UK.

Field mice control PestWatch BPCA PPC107

Clarification of rodenticide product labels by CRRU UK (Campaign for Responsible Rodenticide Use) in 2020 highlighted that the widely used authorisation phrase of ‘mice’ on the products label should only be interpreted as ‘house mice’ (Mus domesticus). 

As a result of this update, and the more specific wording relating to Mus domesticus only, ‘field mice’ (Apodemus sp.), cannot legally be controlled using any rodenticides on the UK market.

While this change has been rightly welcomed by most and has many environmental benefits, it has led to confusion as to whether it is ever appropriate to control Apodemus sp., even with non-rodenticide methods.

Many professionals are confused with regards to the different meanings of the terms ‘non-target’ and ‘protected’ and indeed whether they can ever be categorised as a pest or be lethally controlled with traps.

Definitions

Pest – widely accepted as any living organism which has the potential to cause harm to humans or human concerns. 

Under this definition therefore, it is feasible that Apodemus sp. can be assessed as a pest - although equally this doesn’t equate that they are always classified as such. If they are in the wrong place at the wrong time, causing a risk to humans then they may be deemed a pest.

Non-target – this term is open to much interpretation but if we use the above definition of a ‘pest’, it would seem fair to assume that a simple classification of a non-target animal would be any living organism which is not causing harm to humans or human concerns.

Under this definition, in the vast majority of situations, Apodemus sp. would be classified as non-target animals, if they are not causing concern to humans and their health

Protected – Certain species of mammals are protected by law, meaning that it is illegal to kill, injure or in many cases, interfere with them, their young or their breeding sites.

Apodemus sp. is not a protected species and therefore, under certain circumstances, can be legally controlled – albeit never deliberately with rodenticides.

Field mouse identification British Pest Control Association PPC107

Controlling field mice internally

Mice indoors in most situations will usually be classified as a pest. However this should still be determined by doing a pest risk assessment. 

Good practice would dictate that, prior to resorting to lethal control, steps should be taken to identify the ‘root cause’– eg how did the rodents enter and what can be done to exclude them?

This is particularly important with Apodemus sp. as they are predominantly an outdoor species (as opposed to house mice which will live for prolonged periods indoors).

Subject to the necessary pest risk assessment, control of Apodemus sp. indoors is likely to be carried out using traps (which can then usually be removed once control is achieved).

Controlling field mice externally

In most situations, Apodemus sp. found outdoors will not be classified as a pest (and would be ‘non-target’) however there will be exceptions, especially in some large and complicated commercial, food or distribution sites.

Again, the justification will come down to a pest risk assessment which should include the potential consequences of not controlling them.

Before adopting any lethal control, an assessment should also be carried out (and ideally documented) to determine if there are other actions which can be carried out to make the site less attractive and deter rodents.

Good practice would dictate that, prior to resorting to lethal control, steps should be taken to identify the ‘root cause’– eg how did the rodents enter and what can be done to exclude them?

Chris Parmiter, Pesttrain

This could be environmental changes (eg reducing vegetation close to the buildings, having a clear buffer to site edges etc) but should also investigate the current pest monitoring strategy. 

If the site is using food-based monitor blocks, these can encourage habitual feeding of rodents close to the building, increasing the pest risk.

With this in mind, your assessment may state that food-based lures should not be used for monitoring purposes.

Once all other reasonable steps have been taken, if there is still a serious risk posed by Apodemus spp. (such as building ingress, damage to stock etc), an assessment can justify external control of the rodents – again using non-rodenticide means.

Once the infestation is controlled, in most cases, lethal control apparatus should be removed.

This article is available as a standalone briefing and guidance document for BPCA member companies. You can download the document at bpca.org.uk/library

Want more?

Pesttrain can help with reducing pest risks, including pest risk assessments, independent pest audits, biologist inspections, training and troubleshooting. For further information contact:

chris@pesttrain.co.uk
07827 917542

An online CPD quiz based on this feature is now available on the BPCA website. BPCA affiliates can take a CPD quiz at any time
bpca.org.uk/cpd-quiz or sign up at bpca.org.uk/affiliate 

Source: PPC107

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