Chemical control, particularly the use of the anticoagulants, will usually form the basis of the control programme in most extant rodent infestations. A good integrated programme will however require that even though chemical control is regarded as the most appropriate control option, there remain a range of decisions that have to be made with regard to the most appropriate chemical control option as well as details relating to the way in which the chemical rodenticide will be presented. The range of available chemical alternatives to the anticoagulants is summarized (see alos Classification and history of rodent compounds and Alternative to anticoagulants:chemical and other control techniques). A good integrated strategy will also require that consideration is given to the following issues
The use of chemical control techniques
Whilst chronic anticoagulant rodenticides are likely to provide the most cost effective control option, consideration should also be given to the use of acute and/or sub-acute rodenticides, where available. These alternatives to the anticoagulants are more likely to provide an appropriate option for control where anticoagulants are not available or are not approved and where there is resistance to the anticoagulants in the rodent population.
Decisions on the most appropriate chemical will also involve consideration of the formulation that is most appropriate to the infestation under control and the environment in which control is being undertaken. Rodenticide baits are now available in a range of formulations including loose grains, bait bags, pellets, blocks, paste baits/soft blocks and gel baits. Not all will be equally palatable to the rodents under control and the different baits will present differing levels of risk depending upon the environment in which control is being undertaken. Selecting the most appropriate combination of chemical and bait formulation is essential and requires careful consideration.
In addition to the bait formulations there are additional techniques for presenting chemical rodenticides. These include contact dusts, contact gels, contact foam and liquid baits. The strengths and weaknesses and risks associated with these techniques need to be an option for consideration in any integrated programme.
Having decided which formulation is appropriate, it is necessary to consider how best to present the rodenticide to both protect it from non-target access, but also to ensure that it is readily available to the rodents being controlled so that rapid and effective control is achieved as safely as possible. The use of bait containers will need to be considered and the options of presenting the baits directly to the rodents themselves (particularly for Norway rats) through burrow baiting.