Proceedings of the Vertebrate Pest Conference

Paraffinized rodent baits developed initially for use in control of Norway rats in sewers by Lloyd Plesse of San Jose, California, an experienced bait formulator for Santa Clara County, significantly enhanced longevity and effectiveness of toxic rodent baits. Within a couple of years, this paraffin type molded bait’s moisture resistant qualities and proven efficacy, especially for sewer rat (Norway rat) control, was the subject of several published articles. Those first three articles, 1959-1961, were responsible for rapidly launching this new paraffinized bait formulation into national usage, at first, mostly by health departments. The structural pest control operators and agricultural interests were soon to follow, using them initially for out-of-doors control of rats and indoors where high humidity normally caused bait deterioration. Recognizing the potential of paraffinized rodent baits, along with the published how-to information, commercial bait manufacturers were quick to get into production and distributors eager to market. Paraffinized rodent baits soon came into common usage and literally revolutionized rodent baits by not only making them more moisture and weather resistant but more convenient to use and versatile in applications. This resulted in greatly expanding the conditions under which commensal rodents could be more effectively controlled. The chronology and evolution of paraffinized rodent baits and their practical uses are followed from their beginning throughout much of their early existence, as are the changes in their manufacturing processes. The factors contributing to development and rapid acceptance for rodent control are enumerated, as are their advantages and disadvantages. The greatest emphasis is placed on the first two decades (1960s and 70s) of the existence of paraffinized rodent baits.