Pest control feature | PPC89 November 2017

All UK bat species eat insects and as such do play a part in insect pest control in the UK – a single bat can eat thousands of insects each night. Bats are also considered to be one of our bio-indicator species – where there is a healthy bat population, there is a healthy local environment. 

We’re just beginning to realise what that means not just for plants and wildlife present, but for us too. The health of our surroundings is closely linked with both our physical and mental well-being. 

Sadly all of the UK’s bat populations have declined massively due to habitat loss and persecution. However, populations are starting to stabilise, albeit at much lower levels than originally. This article explores the role awareness and best practice within the pest control industry can have to contribute to their protection.

Speed view:

• The UK’s bat populations have declined massively due to habitat loss and persecution
• It is illegal to damage, destroy or disturb any bats or their roosts
• The law does not prevent pest control occurring in within a property where a bat roost is present
• Controlling wasps, clusterflies and rodents may affect bats or their roost
• Guidance documents are available in our member area

A joint article by the Bat Conservation Trust (BCT), British Pest Control Association (BPCA) and the Property Care Association (PCA).

Which bats use buildings?

Bats are often found using buildings for roosting (somewhere to sleep, raise young etc), particularly as their natural roosting places in tree holes and caves become scarcer as they are destroyed or disturbed. Bats can use all areas of a building, however they are most commonly found in the walls, eaves and roofs. Unlike birds or rodents, bats do not make nests when roosting in buildings or cause structural damage.

Bats can use buildings at any time of year but are most often found in houses between April and September, when female bats give birth to single young. Pipistrelles and long-eared bats are commonly found in houses.

Pipistrelle bats

There are three different species of pipistrelle: the common pipistrelle, soprano pipistrelle and the rarer Nathusius pipistrelle. They sometimes use houses as maternity roosts, choosing confined spaces such as cavity wall voids. However, roosts are usually on the outside of buildings, using features where these crevice dwelling bats can rarely be seen, such as under hanging tiles or fascia boards.

Brown long-eared bat

This species mostly prefers older houses with large roof spaces, and as they roost in the roof void they are the species most frequently seen by householders. Small clusters may be seen at junctions of roof timbers or under the ridge.

Bats can often be found in the same spaces as common pests. However, unlike rodents, wasps and clusterflies, bats are not pests and are in need of your help. Populations of all of our UK bats have declined massively in the last century, some by up to 90%, which is why they are protected under both domestic and international legislation.

Why look out for signs of bats?

There are 18 species of bat in the UK and all bats and their roosts are protected by law, whether the roost is occupied or not, because bats tend to re-use the same roosts year after year. All bats and their roosts are protected under The Wildlife and Countryside Act 1981 (as amended) and The Conservation of Habitats and Species Regulations 2010 (as amended).

Bats should be considered during pest control activities, as it is illegal to damage, destroy or disturb any bats or their roosts without having taken the necessary precautions. In this context ‘damage’ could include such operations as treatment with chemicals found in wood preservatives or leaving open trays of bait within a roost for rodents. If bats make contact with a rodenticide or it gets on their fur, they could then be poisoned when grooming. This can happen when bat droppings are mis-identified as rodent droppings (see above).

The law does not prevent pest control occurring within a property where a bat roost is present, and free advice can be sought via the Statutory Nature Conservation Organisation (SNCO) for your country as to how this may be carried out within the law:

• ENGLAND Natural England via the BCT 0345 1300 228
• NORTHERN IRELAND Northern Ireland Environment Agency 028 9039 5264
• SCOTLAND Scottish Natural Heritage 01463 725 165 batsinhouses@snh.gov.uk 
• WALES Natural Resources Wales 0300 065 3000 (ask for the species team).

Identifying a bat roost: some practical steps

You must take great care when seeking to identify a potential bat roost and it is very important not to disturb any bats. There are a few simple signs to look for:

Bat droppings

Similar in appearance to rodent droppings, bat droppings will be very dry and will crumble to dust under very little pressure. If you notice droppings, a quick crumble test (with gloves or a tissue) is a good way to get an indication of bat presence. On extremely rare occasions there are health risks from allergic reactions, dust inhalation and gastro-intestinal infection, all of which can be avoided by following simple precautions (eg wearing a dust mask and gloves when clearing droppings) and maintaining basic standards of hygiene.

Potential access points

You may see or know of these on or around the property, our smallest bat species can access gaps as narrow as an adults thumb and many species may roost in outside features such as:

• Under weather boarding or
• hanging tiles
• Between timber frames and
• stone work
• Between window frame and
• wall brickwork
• In gaps behind cladding tiles 
• Between underfelt and boards or tiles.

Is there a known history of bats at the property?

Look around before planning your work. Have you or the builders/surveyors seen bats or their signs in the loft space or elsewhere on the property? Inside roof spaces they roost:

• Along the ridge beam
• Around the gable end
• Near the chimney breast.

If you are in any doubt, please visit the BCT website www.bats.org.uk or contact BCT’s National Bat Helpline 0345 1300 228 enquiries@bats.org.uk

How do bats affect pest control?

The control of pests such as wasps, clusterflies, hornets and rodents may unintentionally affect bats or their roosts, so care should be taken when controlling pests in an area where bats are or are known to have been, present.

General advice for avoiding impacts upon bats

To avoid an offence from being committed, if bats are known to be or have been present, or bats or their droppings are discovered at any stage (including after operations have started), work must not commence or must stop immediately and advice be taken from the Statutory Nature Conservation Organisation (SNCO).

In addition, be aware of this pest control best practice to protect bats:

• Rodenticides in an open tray should never be placed below roosting bats
• Spring, cage or sticky traps should never be used in bat roosts
• Ultrasonic deterrents should not be used in a bat roost.

The BCT has been working closely with the pest control industry for a number of years, and BCT can now count a pest control company as a Corporate Member.

In the last year BPCA and BCT have been working on a number of specific advice notes and awareness articles to help promote bat awareness and to liaise on best practice advice.

Wasp nest treatments while protecting bats

In some circumstances, eg where wasps are a health and safety issue, insecticides suitable for use in bat roosts can be used, but advice must be obtained from the appropriate SNCO about when to apply them, particularly if bats and wasps share a common access point or the nest is close to the area used by the bats.

Usually a survey by a bat worker/roost visitor would be required to determine the case-specific advice.

Treating wood destroying insects while protecting bats 

The use of timber treatment chemicals in roofs to control for woodworm used to be responsible for the deaths of whole colonies of bats. Since the problem has been recognised, many products have become available that are more suitable for use in bat roosts to treat the timber and to treat infestations.

Prior to undertaking any form of treatment it is essential to establish if the infestation is active, or historic. All timber should be investigated by a suitably qualified person to determine evidence of current activity to justify any form of treatment. Some timbers may show signs of historic activity. The insect may have already died out due to unsuitability of the timber, decreased moisture content or due to previous treatments – therefore treatment is not justified.

Two of the more notable woodborers found in UK buildings are the common furniture beetle (Anobium punctatum) and the deathwatch beetle (Xestobium rufovillosum).

The common furniture beetle is the most abundant of the wood-destroying insects found in buildings in the UK. It naturally inhabits dead stumps and fallen branches in woods and hedgerows, but is more abundant in building timbers and furniture. One of the most distinguishable indicators of an active infestation by this beetle is trails of fresh bore dust particularly on vertical surfaces. Other indicators include the presence of adult beetles, larvae in the timber, and holes with a fresh cut appearance.

Due to its preference for certain partially decayed hardwoods, principally oak, the deathwatch beetle is most commonly found in historic buildings. The best indicator of an active infestation by deathwatch beetles is the presence of adults, which are typically found on surrounding floors.

Even if bats are absent from the roof space there is still the chance that they will move in in the future. We therefore recommend that only a fluid suitable for use in bat roosts are considered. These treatments have a much lower level of active ingredient, although all insecticides maybe harmful to bats so care must always be taken when using them.

The correct amount of pesticide should be used and treatment should be kept as localised as possible. Since recommendations change regularly, details of insecticides and fungicides can be obtained from SNCOs www.gov.uk/guidance/bat-roosts-use-of-chemical-pest-control-products-and-timber-treatments-in-or-near-them 

No treatment should be undertaken while bats are in the roost.

Not even ‘bat friendly’ emulsion chemicals as there is a danger that bats will come into direct contact with them.

Treating rodents while protecting bats

Always do the crumble test to check droppings are identified correctly.

Where a roost is present or suspected and rodents are also present, it is advisable to lay rodent bait when bats are not present, if at all possible. Care should be taken to minimise any disturbance caused to the bats, particularly during the critical hibernation period (November to February) and breeding season (May to September). Ideally work should be timed for between March and April, or September/October, when any baby bats will have been weaned, and the bats will not have entered hibernation yet.

Provide a copy of BCT’s advice leaflet to the pest control technicians involved for them to follow (available in the BPCA member area or from the BCT directly). Inform them of the presence of a roost and that there is always the possibility of bats being present in loft spaces any time of year.

• Working in line with the CRRU Code of Best Practice and following product label directions:
• Use bait bags or enclosed forms of bait (eg wax blocks in bait stations) only
• Distribute the appropriate number of bait bags/bait stations throughout the roof void at floor level only
• Before embarking on a baiting programme, you should read the product label carefully and follow the instructions given to ensure that the correct, legal and safe procedure for that specific product is followed
• Take care not to disturb any bats when laying fresh bait or when removing old/unused bait and dead rodents. Access the loft only when necessary and allow any bats access to an undisturbed area at all times.

Please do not use:

• Open trays of rodenticide or loose bait – if bats should come into contact with the poison there is a risk they could ingest it
• Spring, cage or sticky traps should not be used in/near bat roosts as there is a risk that bats, particularly babies, may accidentally fall onto them and become injured
• Open trays of bait should not be used – although bats are not attracted to them, there is a possibility that they could fall into one or come into contact with rodenticide and accumulate poison on their fur, which they could ingest upon grooming
• Ultrasonic deterrent devices anywhere near to a bat roost as too little is known about their effect on bats and the use of them may be classified as disturbance.

Treating cluster flies while protecting bats

If bats are present, it may be possible to alleviate the fly problem by blocking the routes that the flies enter the living areas of the house. Alternatively, vacuum cleaners can be used to collect the flies. Bat-friendly fly-traps include an enclosed box containing granules which attracts the flies into it and dispatches them.

Spray treatment is not recommended in bat roosts but can be undertaken (using SNCO approved chemicals) where it can be confirmed by a bat worker/roost visitor that no bats are present.

Spraying should always be a last resort, used only after all non-chemical methods have been considered and deemed unsuitable in that particular situation. If electric fly killers are to be used, advice should be sought from the SNCO beforehand since their operational hours must be monitored and tailored according to the time of year. Any servicing required at intervals must also be agreed with the SNCO. Sticky traps should never be used in the vicinity of a bat roost.

Want more information on bats?

CT has kindly allowed us to share guidance documents for pest controllers. You can download them at bpca.org.uk/member-area

For more information contact BCT Built Environment Officer Jo Ferguson or BPCA Technical Manager Dee Ward-Thompson

For information on bats in general, please go to the BCT’s website or, if you find a bat, please contact the National Bat Helpline immediately on 0345 1300 228.

Parts of this article have appeared in Listed Heritage magazine, the membership Journal for the Listed Properties Club.

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Source: PPC89