Reports suggest rodent infestations in feed stores and general farm buildings have been slower to build this year, but this situation could change drastically as the current higher than normal temperatures drop and natural food supplies diminish.

The key to keeping on top of any rodent issue is to have procedures in place to prevent rodents from utilising their efficient reproductive capabilities.

For example, a female rat can produce five to six litters per year with a gestation period of just 21 days. Litter sizes are commonly between five to 10 rats and as high as 12 to 14. Newborn rats can reach sexual maturity anywhere from five to eight weeks of age.

Another reason for swift action is that rats can pose a serious risk for human health (Weil’s disease) and cause significant damage in a short space of time to equipment, wiring etc.

A task force made up of Government departments and agencies, NGOs and product manufacturers, developed a campaign for responsible rodenticide use (CRRU) in recent years.

The campaign aims to promote the responsible use of chemical rodent controls and best practice techniques to manage an infestation while also minimising any risk of exposure to non-target species such as birds, other predators and farmyard dogs or pets.

CRRU code

A seven point CRRU code was also established to provide concise recommendations. The seven points are as follows;

  • Always have a planned approach.
  • Always record quantity of bait used and where it is placed.
  • Always use enough baiting points.
  • Always collect and dispose of rodent bodies.
  • Never leave bait exposed to non-target animals and birds.
  • Never fail to inspect bait regularly.
  • Never leave bait down at the end of the treatment.

    • The code advises farmers to carry out an assessment of the site to see where rodents are entering the yard or buildings, and in particular to assess where they are seeking out cover. This should not be altered before the infestation is addressed, as it will make treatment more difficult.

    Remedial action, such as removing or trimming back weeds, shrubs, bushes etc that provide cover, or rodent proofing entry points to feed stores, sheds etc, should be undertaken following treatment.

    Rodenticides should be placed alongside areas where rodents travel or congregate and should only be used as long as is necessary to achieve satisfactory control. Removing access to other food sources such as spilled grain will help to encourage higher consumption of bait. The CRRU code advises that any bait should have achieved control within 35 days and that where satisfactory control is not achieved, then a more potent anticoagulant should be considered.

    If intake is low relative to the size of the infestation, then revisiting of bait points or the type of bait box used should also be considered.

    Removal of rodents

    The bodies of dead rodents can carry residues of rodenticides and as such, if eaten by scavengers, predators or pets, may be a source of wildlife exposure. Rat bodies may be found several days after rats have eaten bait and it is common for rats to die up to 100m or more away from baited sites.

    A wildlife aware training course was established in recent years by CRRU, in cooperation with the Irish Agricultural Supply Industry Standards (IASIS), with the course targeted at professional pest control technicians and other competent users of rodenticides.

    A list of accredited professionals are available on www.iasis.ie. This is also a good source of more detailed information regarding rodent control.

    Note that it is a requirement under the Bord Bia sustainable beef, lamb, dairy and other quality assurance schemes to record rodent/pest control strategies and also the presence of bait points on a farmyard sketch.