Comparative field testing of commensal rodenticides is defined as a side-by-side testing of two or more materials under similar environmental conditions. This differs from comparison of field test data, where information is obtained at different times or under different environmental field conditions.

Comparative testing provides valuable information concerning advantages and limitations of rodenticides, including experience with special uses. This is useful for control operators when planning strategies for chemical and other control techniques in the development of integrated pest management. Comparative testing also may provide information pertinent to labeling instructions.

The design of a comparative field test should permit an unbiased evaluation of the rodenticides. The test site should be relatively homogeneous: a group of similar buildings, several contiguous city blocks, or a building which can be divided into comparable units. The use of isolated areas would be ideal but not essential if precautions are taken to avoid or limit rodent movements between areas. Equivalent pest infestations in all areas, although desirable, also are not essential if the censusing techniques are sensitive to the relative density. Use of two or more censusing techniques is desirable to prevent method limitations from biasing the test results. This permits greater flexibility in data analysis should one of the census methods prove inappropriate or unmanageable.

The test should include a control group or population, if possible. This control area (population) can be an untreated area or, in the case of a warfarin-resistant rat or mouse population, an area treated with a warfarin bait. Use of a control provides baseline information on population patterns within the test environment.

Included for discussion are comparative tests on Norway rats (Rattus norvegicus) in urban habitats and tests on rural resistant house mouse (Mus musculus) infestations. Rodenticides in pelletized and meal formulations were utilized as place pack and bulk baits. Compounds utilized during these evaluations include warfarin (0.025% bait), bromadiolone (Maki) (0.005% bait), brodifacoum (Talon) (0.005% bait), pyriminy (DLP-787) (10% tracking powder), and bromethalin (EL-614) (0.005% bait).