Rats and mice in Netherlands increasingly resistant to toxic pesticides

Rats and mice are becoming increasingly resistant to toxic pesticides in more and more parts of the Netherlands. Researchers from the Foundation for Knowledge and Advice Center for Animal Pests (KAD) and Wageningen University came to this conclusion in a study done for the Ministry of Infrastructure and Water Management.

The study examined over 2,000 rodents, mostly brown rats and house mice. Of the latter group, 38 percent were resistant to poison, and 17 percent of brown rats studied were less sensitive to toxic pesticides.

These figures are national averages, but there are differences at ar regional level. In some regions, only resistant rats were found. In others, none of the tested rats were resistant. The same applies to the mice studied.

The consequence of resistance is that rodents can be controlled less effectively. State Secretary Vivianne Heijnen of Infrastructure and Water Management sent the report to parliament this week and stressed the importance of monitoring, prevention, and control without using chemical agents.

From January 2023, the rules for toxic pesticides will be tightened in the Netherlands, and only certified companies will be allowed to use chemical agents to control rats and mice.