A major upsurge in rodent infestations this year on farms and agri-businesses has been blamed on the mild wet winter and more restrictive baiting regulations.
Pest control professionals report a 40-60pc increase in incidents of infestation, with the relatively mild wet weather over the last two months resulting in the latest spike in activity.
The weather this winter wasn't cold enough to reduce numbers, but the heavy rains of the last two months has forced more rats into the open, pest control technicians report.
"The rats' burrows have been flooded, and so are the sewers and drains, so rodents are moving indoors and looking for suitable nesting sites," said Chris Izart of the National Pest Technicians Association (NPTA).
Mr Izart said that NPTA members have described the last three months as extremely busy, with many businesses experiencing serious rodent infestations for the first time.
Farmers have also been in the firing line. One cereal grower in the southeast who stores a lot of grain said this winter has been the "worst one ever".
'Coming in waves'
"It was a full time job keeping bait down. The rats were just coming in waves. You'd get the problem under control, then you'd realise you had a problem again, and it was back to baiting," he said.
One of the difficulties highlighted by pest control technicians is the tighter regulations which only permit toxic baiting with rodenticides when there is evidence of an infestation.
The new guidelines were introduced to protect what are described by the Department of Agriculture as "non-target" rodents, such as field mice and shrews. And also to prevent the secondary poisoning of birds of prey or other mammals.
However, Eugene Slowey of Pest Proof, who are based in Galway and Monaghan, said these restrictions mean that rodents are always "a step ahead" of the farmer or business owner as preventative baiting is heavily restricted.
The Department regulations stipulate that toxic baiting is only allowed for a maximum of 35 days.
In addition, long-term toxic baiting is only permitted using specific products in situations where trained pest control professionals certify that all other alternatives have not worked.