Diagnosing Rodenticide Resistance

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A real-world example of how laboratory resistance testing and a tailored management programme successfully resolved persistent rodent activity across three agricultural sites. 

A. R. Gorringe asked Wilde Pest Control to review the existing rodent management programme after continued rat activity was observed across three operational sites. 

Regular servicing was already taking place, but rodent numbers remained higher than expected. 

Our objective was to identify the factors contributing to the ongoing activity and develop a programme tailored to the site's requirements. 

Our inspection identified several opportunities to improve the existing programme, including bait placement, bait choice and environmental factors that were supporting rodent activity.

One observation suggested that the local rat population could be showing resistance to commonly used anticoagulant rodenticides.

Instead of making assumptions, tail samples were collected and submitted for laboratory analysis.

The results confirmed resistance to two commonly used anticoagulant rodenticides, allowing us to redesign the control programme using the most appropriate treatment.

Laboratory analysis enabled the treatment programme to be tailored to the resistance profile identified on the site. 

 A completely revised rodent management programme was introduced, including:

• Laboratory-guided rodenticide selection. 
• Repositioning bait stations to intercept natural rodent movement. 
• Introducing wheat bait to better match the food sources already available on site. 
• Increased monitoring during the initial control phase. 
• Updated site plans and comprehensive treatment records. 
• Practical proofing and housekeeping recommendations to reduce future risk. 

Every recommendation was tailored specifically to the customer's business rather than following a standard treatment programme.

Within the first three weeks, approximately 4 kg of bait was consumed, confirming the scale of the infestation and the effectiveness of the revised programme.

As rodent numbers declined, bait consumption reduced steadily.

After approximately three months:

• No significant rodent activity was identified. 
• Bait uptake had reduced dramatically. 
• Monitoring stations showed little or no fresh activity. 
• The site transitioned onto a long-term monitoring and prevention programme.

Successful rodent management is rarely achieved by simply increasing the amount of bait used.

Every site presents different challenges, including food availability, harbourage, rodent behaviour and, in some cases, rodenticide resistance.

By identifying the underlying causes of the infestation and adapting the management programme accordingly, long-term control was achieved while supporting the customer's biosecurity and ongoing business operations.

Every rodent infestation has a cause.

Effective rodent management starts with understanding why rodents are present before selecting the most appropriate control strategy.

We don't assume. We investigate.

Every commercial site presents different challenges. Our management programmes are designed around the evidence found during inspection—not a standard treatment schedule.