About this guide
This guide provides a comprehensive overview of rodenticides used in the UK for rat and mouse control — including first-generation and second-generation anticoagulants, CRRU regulatory requirements, rodenticide resistance in Yorkshire populations, the differences between professional and consumer products, and safe handling and storage requirements. The page supports Apex Pest Control Ltd's rodent control service by explaining the professional approach to rodenticide selection before users choose a treatment provider.
Rodenticides are chemical compounds used to kill rodents. In the UK, anticoagulant rodenticides are the dominant category used for rat and mouse control in both professional and consumer settings. Understanding the differences between product types, the regulations that govern their use, and the limitations of consumer products helps property owners make informed decisions about pest control.
Anticoagulant rodenticide categories
Anticoagulant rodenticides work by blocking the vitamin K cycle, preventing blood from clotting and causing internal haemorrhage over several days. This delayed action prevents rodents from associating the bait with illness, which would cause bait aversion.
First-generation anticoagulants (FGARs): Warfarin, coumatetralyl, and chlorophacinone require multiple feeds over several days to accumulate a lethal dose. They have lower secondary poisoning risk than SGARs because they are metabolised more quickly in the tissues of poisoned rodents. FGARs are available in consumer products as well as professional formulations. However, their effectiveness is compromised by widespread resistance in UK rat and some mouse populations.
Second-generation anticoagulants (SGARs): Brodifacoum, bromadiolone, difethialone, and difenacoum are considerably more potent — potentially lethal after a single large feed. They are effective against FGAR-resistant populations. SGARs persist in the tissues of poisoned rodents for longer than FGARs, creating higher secondary poisoning risk to predators and scavengers including barn owls, red kites, polecats, and stoats that consume poisoned rodents.
Research by the Rodenticide Resistance Action Group (RRAG) found that approximately 74% of Yorkshire brown rat populations carry a VKORC1 gene mutation that confers resistance to first-generation anticoagulant rodenticides, making FGARs ineffective for the majority of rat populations in the region.
— Rodenticide Resistance Action Group (RRAG), 2022
CRRU regulations and professional use requirements
The Campaign for Responsible Rodenticide Use (CRRU) UK Code governs professional anticoagulant rodenticide use. The revised 2025 Code, which came into force in January 2026, introduced significant changes to outdoor SGAR use:
Outdoor use of any SGAR by a professional pest controller now requires the technician to hold the RSPH Level 2 Award in Rodent Control (or an equivalent recognised qualification) and to be registered with CRRU as a qualified operator. A pre-treatment property survey must be completed, justification for SGAR selection over FGARs must be documented, and treatment records must be maintained and available for inspection. These requirements apply regardless of the individual SGAR product used.
Indoor SGAR use carries fewer restrictions but still requires correct handling, storage according to the product label, and compliance with the Biocidal Products Regulation (BPR PT14) under which all rodenticides are licensed in Great Britain.
Bromethalin is not licensed for use in the UK or EU and must never be used or recommended. Mothballs and naphthalene are not licensed under the Biocidal Products Regulation as rodenticide products and are not effective deterrents — their use as pest control products is not appropriate. Always select products from the approved UK rodenticide register.
Rodenticide resistance in UK populations
Resistance to warfarin and other first-generation anticoagulants is widespread in UK brown rat populations. The VKORC1 gene mutation — which reduces the binding efficiency of the enzyme that anticoagulants target — has been identified in approximately 74% of Yorkshire brown rat populations sampled by RRAG. Similar resistance has been documented in parts of Wales, the Midlands, and southern England.
House mice (Mus musculus) also show resistance to warfarin in some UK populations, though the geographic distribution is less well-documented than in rats. A professional pest controller with knowledge of local resistance patterns will select products accordingly — defaulting to warfarin across Yorkshire, where resistance is widespread, significantly reduces treatment effectiveness.
SGAR resistance in rats is rare but has been reported in some populations. This underscores the importance of professional product selection based on site assessment and local population data rather than a fixed default product.
Rodenticide use for mice vs. rats
While the same anticoagulant compounds are used for both rats and mice, the application differs significantly. House mice are neophilic — curious about new objects — and will readily explore new bait stations within hours of placement, in contrast to the neophobic brown rat that may avoid new objects for several days. This means bait acceptance and early take are typically much faster in mouse infestations.
Mouse-specific bait stations are smaller and positioned differently — mice have a home range of only 3–8 metres and feed at multiple points within this range, so stations can be placed more densely and in locations that would be ineffective for rats. Grain and seed formulations are often preferred over wax blocks for mice due to their natural foraging preference.
Safe use, storage, and disposal
All rodenticides must be placed inside tamper-resistant, lockable bait stations. Loose bait placement is prohibited in professional use and is unsafe in any context. Store rodenticides in their original labelled containers in a locked, dry location away from food, children, and animals. Dispose of unused bait and empty packaging according to label instructions — never pour liquid formulations down the drain. If accidental ingestion by a human or pet is suspected, contact the National Poisons Information Service (NPIS) on 0344 892 0111 or a veterinarian immediately.
Frequently Asked Questions
What is the difference between first-generation and second-generation rodenticides?
First-generation anticoagulants (FGARs — including warfarin) require multiple feeds over several days to kill. Second-generation anticoagulants (SGARs — including brodifacoum and bromadiolone) are more potent and can be lethal after a single large feed. SGARs are effective against FGAR-resistant populations but carry higher secondary poisoning risk to predators. Since January 2026, outdoor professional use of SGARs requires CRRU registration and a Level 2 qualification in rodent control.
Are rodenticides available to buy without professional qualifications?
Consumer rodenticide products containing first-generation anticoagulants such as warfarin are available to the public. Second-generation anticoagulants are restricted to professional use. Note that in Yorkshire, where warfarin resistance is documented in approximately 74% of brown rat populations, consumer FGAR products are often ineffective without a professional product selection based on local resistance data.
What is rodenticide resistance and why does it matter in Yorkshire?
Rodenticide resistance occurs when a genetic mutation allows rodents to survive doses of anticoagulant that would kill a susceptible individual. In Yorkshire, approximately 74% of brown rat populations carry the VKORC1 mutation conferring resistance to warfarin and related first-generation anticoagulants (RRAG, 2022). Using warfarin-based products against resistant populations will not resolve the infestation.
What is the CRRU UK Code?
The Campaign for Responsible Rodenticide Use (CRRU) UK Code governs professional anticoagulant rodenticide use. From January 2026, outdoor SGAR use by professional pest controllers requires a recognised qualification (RSPH Level 2 Award in Rodent Control or equivalent) and CRRU registration. The code aims to reduce secondary poisoning of wildlife from anticoagulant use.
How long do rodenticides take to work?
Anticoagulant rodenticides take 4–7 days to cause mortality after a lethal dose has been consumed. The population reduction is typically not visible until 7–14 days after bait is first placed. This delay is intentional — it prevents rodents from associating the bait with illness and avoiding it (bait aversion).
Are rodenticides dangerous to pets?
Yes. Anticoagulant rodenticides are toxic to all mammals, including dogs and cats. Bait must always be placed inside tamper-resistant, lockable stations. Pets should not have access to areas where stations are deployed. If accidental ingestion is suspected, contact a veterinarian immediately — the antidote is vitamin K1, which is most effective when given promptly.
Can rodenticides be used indoors and outdoors?
Yes, but with different regulatory requirements. Indoor use of both FGARs and SGARs is subject to the Biocidal Products Regulation and must use approved products in correctly labelled, tamper-resistant stations. Since January 2026, outdoor professional use of SGARs additionally requires CRRU registration and a Level 2 qualification. Consumer products are subject to their own label restrictions.