Winter farm rat levels across the UK have been at their highest level than for at least the past six years and almost certainly for more than a decade, according to national monitoring by rural pest control leader, BASF.

At 860, this year’s winter rat infestation index calculated from rodenticide usage reports across the country is noticeably higher than the modern day peak of just under 790 recorded in the challenging season of 2012/13. Indeed, it stands out as by far the highest since the company started its indexing in 2009 (Figure).

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“Unusually warm weather and good external food availability throughout last winter meant rats were far less evident than usual in and around buildings,” he explained. “This led to a marked decline in treatments. After all, rats only tend to be controlled when they become obvious and troublesome. And unless winter conditions or over-crowding means they have to forage openly for food in the daytime, they can easily remain under the radar.

“Overall then, relatively high rat populations went into last spring to profit from excellent summer breeding conditions. This increased population pressures markedly, so the onset of colder weather this winter meant there were rats all over the place – unprecedented levels on many farms.”

Gavin Wood points out that rat populations at such high levels are very difficult and time-consuming to effectively control.  Under these circumstances he insists no half measures can be taken. Instead, the most palatable rodenticides available have to be widely employed in intensive baiting programmes based on the best possible understanding of rodent behaviour.

“You need to use a rodenticide like Neosorexa Gold that exploits rodents’ natural preferences for variety to give far more rapid and complete uptake than a normal grain bait,” he advised. “Alternatively, choose a modern, high palatability pasta bait designed for situations were large amounts of other foods are readily available.

“Whatever bait you use, it must be put down in the right places, kept well topped-up so all the individuals can consume a lethal dose, and left in place until all signs of rat activity cease. At the same time, particular care must be taken to protect other wildlife and pets by covering and protecting the rodenticide adequately, removing all rodent carcases and clearing any unused bait away thoroughly once control has been achieved.

“With pressures as they are this winter, the most effective control will be essential ahead of the coming spring,” stressed Gavin Wood. “Fail to achieve it and you can look forward to larger rat populations than last year going into the summer to create even greater problems next autumn and winter.”