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Control of Rodent Pests on Farms over the Winter Period

09 December 2019
Type Media Article

By Eamonn Dempsey, Teagasc Advisor, Kerry/ Limerick Region

Coming into the winter months, food and water sources for rodents tend to become scarce, leading to a rise in rodents turning up around farmyards. Rodent control is essential to ensure food hygiene and for the protection of human and animal health. Rodents if not controlled can cause serious economic losses on farms through consumption, contamination and spoilage of food and feed, spread of pathogens which are damaging to human and animal health, damage to buildings and equipment and loss of quality assurance accreditation e.g. Bord Bia.

A farm rodent control strategy must consider the concept of ‘Risk Hierachy’ whereby the least severe methods in terms of risk to humans and wildlife must always be considered first. If using rodenticides, information on the product label must be adhered to, which includes application details, manner and area of use and risk and safety information. Relying on rodenticides alone does not guarantee the successful elimination of rodent’s, it is important to concentrate on improving hygiene and proofing as well as maintenance and repair of buildings. Farms should be cleared of rubbish, old machinery and equipment, unwanted stores of hay and straw etc. vegetation and scrub clearance on farms should be carried out, outside the nesting season between 1st March and 31st August. It is desirable to provide an open area of 20 metres or so around buildings so that harbourage is removed and predators can take rodents. Rodent predators e.g. Barn Owl can be exposed to rodenticides by feeding on rodents that have died of rodenticide poisoning, or catching and feeding on live rodents which have these toxins in their system.

Rodent predators include red kite, barn owl, pine marten, buzzard, long eared owl, kestrel and Irish stoat. Farm cats and dogs are more effective in preventing the re-establishment of a rodent pest infestation than in eliminating an infestation as they are better able to catch and kill an invading rodent that does not know any escape routes. Cats are effective predators of mice, but usually will not attack an adult rat.

Trapping has several advantages, any rodents taken can be removed from the site and there are no chemical residues. However if not done properly, trapping may have a detrimental impact on non-target animals e.g. Rabbits. The bait used should be appropriate to the conditions and circumstances of the infestation, such biocidal products include meals, cut or whole grain, pellets, wax blocks, edible lards/gels/pastes and foam. The average farm has a range of buildings including grain storage facilities and animal accommodation, infestations maybe found in all these places as well as in outdoor locations in the immediate vicinity. Rodent infestation can also occur in open countryside where food availability is high.

The Campaign for Responsible Rodenticide use recognised the need to address the concerns surrounding the responsible use of rodenticides and the protection of wildlife. The CRRU Code involves an integrated pest management plan in which the site is surveyed and alternative food sources removed. On the site plan the quantity of bait used and where the bait is placed is recorded. It is important to ensure enough baiting points and rodent bodies are collected and disposed of as dead rodents carry rodenticide residues. Never leave bait exposed to non-target animals and birds. It is important to inspect bait points regularly and do not leave rat bait down continuously for more than 35 days. Once the infestation is controlled, records should be updated to signify that the infestation has been controlled. If precautionary measures are rigorously implemented, re-infestations will be infrequent, limited in scale and easy to control with farm dogs and cats or by using traps.

From the 1st January 2018, new rules have been agreed by the European Union, farmers will only be allowed to use specific types of rodenticides (Anticoagulants) in and around buildings and only in tamper-resistant bait stations unless they complete additional training.