In this extensive review, we note that brodifacoum has been successfully evaluated against most small mammal pests around the world, and in a variety of both commensal and agricultural situations. Brodifacoum offers reduced rodenticide requirements to lower costs and hazard, and makes new baiting strategies, such as pulsed baiting, practical for large-scale use. Broad spectrum activity enables effective control with mixed-species infestations and against those normally tolerant of other anticoagulants, such as house mice. Useful against warfarin-resistant commensal rodents, brodifacoum gives effective control in urban and other situations where first-generation anticoagulants have previously been extensively used. It has the same mode of action and antidote (vitamin K) as other anticoagulants, providing the advantages of delayed action. We include exhaustive appendices of brodifacoum’s toxicity to a wide diversity of rodents worldwide, as well as listings of previous published research on this new compound.

The development of second-generation anticoagulant rodenticides for commensal rodent control arose from the need to overcome genetic resistance to earlier anticoagulants, to improve efficacy, and to reduce hazard over older acute rodenticide materials. Over the past three decades, the second-generation anticoagulant products have become the principal commensal rodenticides used in the U.S. and elsewhere. During this long usage, individual cases of human and nontarget wildlife exposure have been documented, and the significance has been debated. Following a lengthy re-registration and review process, the U.S. Environmental Protection Agency in January 2007 proposed restrictions on the use of second-generation anticoagulant rodenticides for commensal rodent control. The proposed restrictions would shift emphasis to other rodenticides, including those with inherent problems that were the basis for developing second-generation anticoagulants. Reduced efficacy, prolonged public exposure to rodents, limitations in bait formulations and placements, increased genetic resistance, and greater application rates (exposure) are anticipated if these restrictions are adopted. Various nontarget concerns will remain with alternative products and use patterns by professional users and consumers, including use of products without specific antidotes. These impacts would occur amidst increasing rodent problems in many U.S. municipalities with declining management resources and aging infrastructure. Alternative measures should include use of human taste deterrents in baits and revised label statements to limit the use of all commensal rodenticide from sensitive areas, including placement along fence lines, and bordering natural habitats.

Vertebrate pest management characteristically focuses on research and development of control tools and their application. Similarly, integrated pest management (IPM) principles focus on control methods and habitat alteration to reduce risks from pest species. Organizational structure, administrative elements, and program management are rarely identified as key components of IPM or the development and execution of vertebrate pest strategies; however, they should be included when seeking sustainable and costeffective programs. In urban areas, rodent control programs typically are reactionary and uncoordinated rather than preventative and systematic, resulting in short-term results that cannot be sustained. Use of an environmental management system (EMS), as described by ISO 14001 standards, establishes program structure and priorities for improvement. As part of the EMS, an Aspect Register can be used to identify risk factors and specific mitigation measures; for example, this can be done on a national scale to rank cities at greatest risk of rodent infestations or for program development and execution within an individual city block or building. Emphasis on program and systems management, organizational skills, risk factors, multi-disciplinary training, and prevention is needed as part of vertebrate pest management. Technology often is not the limiting factor; rather it is administrative and management elements for sustainable and effective program execution.

A method for the evaluation of mouse control using tamper-proof mouse bait stations was developed and efficacy trials conducted to determine if house mice (Mus musculus) would visit and consume rodenticidal baits located within these stations. All stations were rapidly investigated by mice. Variation seen between the individual stations related to animal variation and did not appear to be related to differences in the stations themselves. Station placement was more critical to mouse investigation and subsequent bait consumption from the station than were the various features used to prohibit nontarget access.

Brodifacoum, a new rodenticide, is described. This anticoagulant is shown to be of exceptional potency and capable of controlling resistant rodents as well as several non-commensal species. Results demonstrate that, in contrast to first generation anticoagulants, a bait concentration of only 50 ppm is adequate to give control and in only a single feeding for most species. In common with other anticoagulants, vitamin K1 is an effective antidote. In contrast with other acute rodenticides, symptoms are delayed and no bait shyness is observed. The results of laboratory and field trials from many parts of the world are summarized and comparisons of efficacy and specificity with other rodenticides are made. In all cases, brodifacoum is shown to be an exceptional rodenticide, the single feeding action of which offers novel rodent control applications.

While the problem of anticoagulant resistance in commensal rodents has been well-documented from certain areas of northern Europe in recent years, this paper describes its first known occurrence in North America in 1971. Over a rural area of about 5 square miles in Johnson County, North Carolina, it was noted that attempts to control Norway rats using typical warfarin rodenticide bait were increasingly ineffective. Diphacinone was alternated with warfarin with no success. On one farm, 200 lbs of bait had been used in bait boxes in a single month. Laboratory trials on rats captured at this location demonstrated resistance. It was concluded that at this location, intensive use of anticoagulants (mostly warfarin) over a decade, in the absence of adequate sanitation and building maintenance, provided the selective agent to develop resistant populations. This likely will be repeated elsewhere in the U.S.

Aversive agents are proposed as potential additives to rodenticides to increase selectivity to the target species. Examples of various aversive agent categories are given, including odorants, tastants, and emetics, with examples of evaluations. Tastant additives have been found that do not interfere with rodenticidal efficacy. Denatonium benzoate (commercially available as Bitrex®) is an intensely bitter but non-toxic substance, being increasingly used to adulterate common household materials to reduce the potential risks involved with accidental exposures. No known prior research results have been published concerning the incorporation of Bitrex in rodenticides. Rate determination studies utilizing different rodenticidal formulations were conducted. A Bitrex level of 10 ppm was well accepted by wild commensal rats and mice in laboratory tests of brodifacoum pellet and wax block formulations (TALON®, KLERA T® rodenticides). Bait samples with this level of Bitrex (without anticoagulant) were evaluated in a human taste panel study. Samples with Bitrex were found to show significantly greater average rejection by the panel than similar samples without Bitrex. Field trial results are reviewed, which verified the efficacy of Bitrex-containing commensal rodenticides. The potential role of Bitrex or similar taste deterrents as rodenticide additives is considered opposite accidental toxicant exposure statistics, and perceptions relating to rodenticides and other pesticides.