Group of brown rats foraging in barn© FLPA/REX/Shutterstock

Rat populations across UK farms are at their highest level this winter for at least the past six years, a survey on pest control shows.

The 2014-15 index of winter rat infestations, calculated by BASF from sales of its top-selling rodenticides through selected distributors in a four-month period, reached 860 – noticeably higher than the peak of just under 790 recorded in the challenging season of 2012-13.

See also: Rabbit and rodent pest control laws changing

“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.”
Gavin Wood

And it stands out as by far the highest since the company started its indexing in 2009.

BASF rural hygiene specialist Gavin Wood said: “This season’s dramatic surge in rat problems almost certainly has its roots in a failure to get on top of populations in last year’s exceptionally mild winter.

“Unusually warm weather and good external food availability throughout last winter meant rats were far less evident than usual in and around buildings.”

Overall then, relatively high rat populations went into last spring and profited from excellent summer breeding conditions, he added.

See also: Take our free online course on rat control

“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.”

Mr Wood said rat populations at such high levels are difficult and time-consuming to control. 

“You need to use a rodenticide 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,” added Mr 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.”