It is always best to try and avoid a rodent infestation before it starts, but sometimes a baiting programme is necessary. This 6 step plan sets out a straightforward roadmap to achieve, and maintain, effective control.
Step 1 – Site survey
On a map of the property mark out:
- signs of rodent activity including actual sightings, footprints, earthworks and runs, fresh droppings, grease smears, urine trails, gnawing, chewing and any other evidence.
- primary and alternate sources of food and water.
- harbourage points for sleeping, hiding, eating and breeding.
- the degree of public access to the site and especially the presence of any children.
- the presence of non-target animals such as pets, farm livestock and wildlife.
- evidence of poor housekeeping and hygiene.
- obvious building defects such as broken pipes, defective sewer chamber covers, bad construction, surface water gullies and so on.
- environmental factors including soil and water courses that could be contaminated by chemical baiting.
This survey is your baseline for proofing work and will also map the bait station placement, so that you can record results and adjust as necessary.
Step 2 – Tidy up
Like all animals, rodents need the triangle of food, water and harbourage to survive. By reducing the availability of any one of these (ideally all 3) you immediately curtail an infestation and also encourage rodents to feed on the selected bait.
- Remove all spilled and spoiled foodstuffs and ensure fresh foods are stored in rodent proof bins and containers.
- Remove all sources of standing or pooled water and any access to running water – rats need to drink once per day to survive but mice do not.
- Remove all materials and habitats that provide easy harbourage in and around buildings, including all rubbish. Store straw off the ground and away from the wall. If you can, clear vegetation around buildings to give an open perimeter for natural predators.
Step 3 – Proofing and exclusion
Mice can squeeze through a hole the size of your little finger and rats through a hole the size of your thumb. Some points of ingress will be obvious, especially around doors and windows, but pay special attention to parts of the building where joists, pipes, cables and drains enter and leave as these are easy access for rodents. Fit metal kick plates, grilles, or wire mesh to doors and windows and seal any holes and gaps in wood, brick, or PVC to stop entry. If you are tackling a large infestation consider leaving a well-used, easily accessible rodent ingress point available to make baiting easier.
Step 4 – Selecting the correct bait
There is no such thing as a universal rodenticide that you can use effectively in every situation. Faced with an array of baits there are two important considerations:
- Active ingredient
British rodenticides are based on second generation anticoagulants which lead to internal haemorrhaging. The toxicity of these active ingredients is measured using an LD50 calculation, enabling the lethal dose to be compared as below:
Based on a typical 250g rat and 25g mouse, daily consumption based on 25g/3g respectively. LD50 data taken from a variety of sources.
In most general situations difenacoum is more than twice as effective on mice as bromadiolone, which is more effective for rat control. Brodifacoum is by far the most effective on both rats and mice but is also considerably more toxic to non-target species such as birds and dogs.
Pellet and grain baits are designed to match existing food sources; high calorie pasta baits are effective in cold weather and during breeding season; wax block baits are formulated to withstand humid and wet conditions and contact gels, ingested through grooming, are effective where feed baits have been resisted or are not practical. To achieve good ‘bait take’ use baits with high quality ingredients to tempt rodents away from their existing food sources.
Select the combination of active ingredient and formulation to best suit the pest and the environment you are dealing with, whilst considering any non-target children, pets and wildlife around. Remember to always check the label for regulations and directions for use.
Step 5 – Follow a sound baiting regime
Securely place bait stations at points of ingress and along well used rodent routes and mark them on your site survey. Camouflage their plastic smell by rubbing them down with dirt, debris, leaves etc from the site. Try to ensure rodents cannot simply go around them by using things on the site to ‘direct traffic’ and block alternative routes. Make sure wildlife, farm animals, pets and children cannot reach the bait.
For a low infestation, where rodents are only seen at night, place bait stations every 10 metres for rats or every 5 metres for mice. For a high infestation, where rodents are seen in the daytime, place them every 5 metres for rats and every 2 metres for mice. With a high LD50 bait such as difenacoum use 200g per bait station for rats (40g for mice), for brodifacoum use 60g (20g for mice). It is best to tackle large populations by increasing the number of bait points, not the amount of bait within them.
Service the bait points regularly – ideally every 2 to 3 days but at least once per week. Check they remain secure, replenish busy ones, remove any spoiled bait and relocate any that are untouched. Routinely hunt for dead rodents and dispose of them, so that they do not pose a risk to non-targets. Note all of this on your plan so that you can identify patterns of activity and resolve any issues.
Once activity has stopped collect up all spoiled and uneaten bait and dispose of it according to the label instructions. Store any unused bait and associated equipment out of the reach of children and non-targets.
Step 6 – Remain vigilant
Don’t give up once the resident population has been eliminated; there will always be new colonies waiting to take advantage of the site and so follow-up treatments may be needed two to three weeks after the initial baiting.
Most immigrant rats will travel down recognised and identifiable routes such as hedges, drainage channels and property boundaries. You can anticipate their movements and cut off entry to the site as part of your ongoing proofing and exclusion work.
Rodent control programmes often fail because the wrong type of product is selected, not enough bait is used, baiting stops too soon or more rodents move in. By following these 6 steps you should be able to quickly gain control – and keep it!