Rodenticides 101: A Guide for Pest Controllers and Farmers

Of the 2,500 rodent species worldwide, only 16 are present in the UK and just three associated closely with humans. These three are considered serious pests: the Mus musculus (House mouse), Rattus rattus (Black Rat) and Rattus norvegicus (Norway rat).

These rodents can damage property and food, as well as pose a threat to human health by transmitting diseases through cross contamination of products and surfaces via their faeces, urine and via bites.

Alongside good hygiene practices, environmental management, physical barriers and traps, rodenticides are crucial for controlling target rats and mice, particularly where populations are high and speed is important. But to ensure they are effective, it’s important to understand what they are, how they work, and the different types available.  In this blog, we'll delve into the fundamentals of rodenticides, both for pest controllers and farmers.

 

What are rodenticides?

Rodenticides are chemicals that kill rodents. In the UK, their target is House Mice, Black Rats and Norway Rats, but in other parts of the world, they may be used against squirrels, chipmunks, voles and other rodents.  There are different types of rodenticides and numerous strategies for using them.

Most rodenticides in the UK are anticoagulants and prevent rodents from producing blood clotting factors. What makes them effective is their gradual onset of action. Rodents don't immediately associate their consumption of the bait with its lethal effects. Instead, it takes several days – sometimes even weeks – of continuous feeding for the poison to have its full effect. Death typically occurs between two to 14 days after the rodent starts consuming the bait.

Rodenticides are often delivered with bait – a food source that is designed to lure the rodents into consuming the active ingredient. These can be produced as pellets, pastes, pastas, blocks, grains and gels. 

There are also contact preparations, such as Racumin foam, which stick to the rodents' fur and are consumed when the rodent grooms itself. This is particularly useful in locations where traditional baiting methods are not possible.

 

Rodenticides and safety

Today, thanks to advances in technology, rodenticides are formulated with lower toxicity levels and are designed to prevent the poisoning of non-target organisms. Harmonix® Rodent Paste, for example, has a stop-feeding effect which is proven to reduce bait use by 50% in comparison with other formulations. It contains cholecalciferol which has a different mode of action to anticoagulants as it causes hypercalcification of the target rodent. It is non-persistent and doesn’t accumulate in the environment.

Professional pest controllers use other tools to minimise risk, such as securing the bait inside fixed and locked tamper-resistant bait stations and using their expertise and knowledge to strategically select sites for bait placement.

Professionals rarely use rodenticides in isolation. Instead, they are part of an integrated pest management (IPM) strategy that provides long-term prevention and maintenance of rodent populations.

We, for example, have developed Harmonix® Monitoring Paste. It is a non-toxic monitoring bait that enables you to assess rodent activity and if there is a need to implement control strategies. It has full traceability day and night, is free from the big eight food allergens including wheat, and is also HACCP certified, making it suitable for use within the food industry. It is the first essential step in a dynamic IPM program for early detection of rodent activity and to encourage bait acceptance before treatment.

In the UK, the production and use of rodenticides is well regulated and controlled. Professionals from across the industry have voluntarily agreed to a Rodenticide Stewardship Regime run by the Campaign for Responsible Rodenticide Use (CRRU) UK to ensure continued safe and effective use.

 

Choosing the right rodenticide

When it comes to choosing a rodenticide, it is important to consider a variety of factors, such as location, population size and presence of non-target species. Good rodenticides are formulated for specific circumstances. 

Rodilon Soft Block, for instance, uses high-food grade ingredients, texture and blending to make it extremely palatable. It’s designed for use where other food sources are available and therefore it’s important to choose a highly palatable bait.

Likewise, Rodilon Wheat Tech uses the highest quality wheat which increases rodent consumption, even in the most difficult treatment environments. This, combined with the “turbo impregnation” technology – the coating and impregnation of each grain – means Rodilon Wheat Tech is extremely palatable and has superior performance.

Rodenticides are indispensable tools for pest control, but understanding the different types, their mode of action, formulation and features is key to optimising their performance. The most effective rodenticides are those which have been designed for the circumstances in which they are being used. Whether it’s palatability, speed of efficacy, or environmental profile, different formulations have different strengths.

Choosing the right rodenticide and adhering to best practice ensures a successful and sustainable approach to rodent control, safeguarding crops, livestock, and public health. To conclude, Richard Faulkner, Envu’s National Account and Technical Manager, UK & Ireland says, “Rodenticides are an important part of integrated rodent treatment strategy. It is of the upmost importance to carry out an Environmental Risk assessment in order to determine which rodenticide and formulation should be used and is most suited to the situation at hand. Aways follow the product label instructions. These will tell you your target rodents, safe areas of use, quantity of bait per bait point, minimum follow up requirements, and also the areas where the product cannot be used and is not suitable.”