Changes in the law on rodenticides use means farmers have more options to tackle rats effectively this autumn. We discuss how the law changes affect farmers and offer practical tips and advice on integrated pest management.

Second-generation anticoagulant rodenticides (SGARs) have been used for rodent control since the 1970s and now provide more than 90% of control.

They have overtaken warfarin and first-generation anticoagulants after growing resistance problems.

See also: Find out more about rat control

SGARs fall into two types based on their potency:

• Single-feed baits are highly potent and give both rats and mice a lethal dose from just one feed (about 2g for a rat). No resistance has been found against these.
• Multiple-feed baits require larger amounts of intake for a lethal dose (about 7g for a rat).

How has the law changed with regards to rodenticides and baiting and when did these rules come into force?

Until January 2015, UK law prevented single-feed SGARs being used outside buildings, effectively confining these rodenticides to mainly controlling mice, which live almost entirely indoors.

However, all SGARs must be used within the stewardship regime, developed by the Campaign for Responsible Rodenticide Use (CRRU), to manage non-target species risks.

From June 2016 the regime states only people who hold certificates of competence in rodent control will be able to buy more than 1.5kg of rodenticides at a time for professional use.

There is, however, a derogation until December 2017 for those in farm assurance schemes with a rodent control requirement.

Farm inspectors will expect to see good record-keeping of regular rodent monitoring along with details of the locations of bait points and amount of bait used.

How do I comply with the stewardship regime?

The ERRU stewardship sets out a clear three-step approach to integrated pest management, which must first include measures to prevent infestation, then monitoring for signs of activity and finally eradication.

Exclusion

Eliminate what makes rodents want to live there.

• Clear up feed spillages.
• Store grain and feed securely behind closed doors if possible.
• Block up obvious rodent access points.
• Fit metal strips to the base of gnawed doors.
• Keep buildings’ immediate surroundings free from weeds and clutter to discourage rats from entering and increase the likelihood of predation.
• Stack silage clamp tyres neatly and keep hosepipes off the ground so burrows and rat runs are more visible.
• Remove scrap materials.
• Dispose of potential nesting materials (old insulation/feed bags).

Monitoring

Look closely at your surroundings.

• Every month walk round and check for signs of damage or faeces in hotspots, for example grain stores.
• Put small patches of sand around the farm on the edges of doorways and on rat runs to assess numbers of footprints and faeces.
• If it has been raining, check the mud for rodent activity.
• Use a torch to look for pairs of eyes at night.
• Use motion-sensitive cameras to capture images overnight.
• Seeing rats in the day indicates a large infestation.
• Clear up droppings regularly for accurate assessment of the population.

Eradication

A detailed risk assessment should identify if infested areas can be accessed by non-target species, as this influences bait type and positioning. Consider physical, non-chemical controls first.

• Killing traps are useful if a small amount of activity has been identified, but will require checking and resetting regularly.
• Traps where the rodents remain alive should only be used where non-target species are also present and must be checked daily.
• Baiting active rat burrows is the most effective control method. By stringing the bait on to a wire, inserting it inside the burrow and securing the wire to the outside of the burrow, it can be easily checked and not dragged in or away. The closer the bait is to the rats’ home, the more likely they are to eat it instead of looking for other food.
• Plastic bait boxes discourage rats from feeding. Use natural materials (preferably those already on the rat runs) to place bait in, as long as they are covered and protected from non-target species.
• Avoid placing bait stations in the open or along the perimeter fences of rural properties as these are the preferred habitats of field mice and voles.
• Place bait boxes in yards close to buildings where non-target species are less likely to forage.
• Loose baits must be used with a bait station and are recommended for indoor use only to minimise exposure to non-target species.
• Farmers need to understand rodent behaviour for an effective baiting strategy.
• Mice take small amounts of feed from up to 100 places every night, whereas rats return to the same place to feed, so a single bait point for a mouse infestation is useless.
• Rats are neophobic – they don’t like new things in their environment, so will take a while to adjust to a bait box. Natural materials will result in quicker bait uptake.
• Mice spend most of their time in the fabric of a building, so use a 3D baiting strategy, not just on ground level.
• Rats can become pregnant again from the day they give birth – one breeding pair of rats can increase to a population of 2,000 in 27 weeks.
• Mice don’t drink, but can use moisture from feed, so an oily seed bait is more attractive.

What bait should I use?

Only use single-feed SGARs where necessary, for example if the infestation has not been controlled by a multifeed or if there is known resistance to the multifeed bait.

SGARs are more costly and as they are highly potent, a more detailed risk assessment is needed. But smaller amounts of single-feed bait will be needed, along with fewer top-up visits, resulting in less bait in the environment.

Only use SGARs outside buildings if they can be secured to safeguard non-target species. Ensure all baits are topped up according to the label. More frequent top-ups and with larger amounts will be required for the multifeed baits.

How do I become certified?

There are several options available depending on your level of existing knowledge.

You can attend a workshop and sit a test of 20 multiple choice and 10 yes/no answer questions at the end.

A shorter top-up workshop is also available with the same test at the end. Find details of course venues at www.rodentcontrolonfarms.co.uk.

You can also complete the full or top-up workshop and test online at farmtrainecademy.co.uk.

Those wishing to just sit the test are advised to read AHDB’s Rodent Control User Guide.

Costs vary from £50-£150 depending on the route taken and the certificate is valid for life.

Once the farm holding has a certified and registered bait user, anyone may purchase the bait for that user.