Proceedings of the Vertebrate Pest Conference

The Vertebrate Pest Control Research Advisory Committee, through a cooperative agreement with the California Department of Food and Agriculture (CDFA), funded laboratory studies at the National Wildlife Research Center (NWRC). The objective of the studies was to obtain efficacy data for controlling house mice (Mus musculus) and deer mice (Peromyscus maniculatus) that would provide partial fulfillment of the requirements established by the Environmental Protection Agency (EPA) for the re-registration of the CDFA’s 0.01% chlorophacinone and 0.01% diphacinone grain bait labels. Swiss-Webster mice and deer mice from an on site breeding colony were placed on 15- day, two-choice feeding and efficacy trials. The control treatment groups received two dishes each containing the Office of Pesticide Programs (OPP) designated standard rat and mouse challenge diet. The treated groups received one dish of the standard OPP rat and mouse challenge diet and a second dish of the treated grain baits: 0.01% chlorophacinone (two groups of 20 animals, Groups II and III ), or 0.01% diphacinone (two groups of 20 animals, Groups II and III ) grain bait. Results from the treated groups of the four tests are reported. House mice on 0.01% chlorophacinone: female mortality was 100% in Group II and 90% in Group III. Total dietary consumption of treated bait was 23.0% of the total bait consumption. House mice on 0.01% diphacinone: female mortality was 90% in Group II and 100% in Group III. Total dietary consumption of treated bait was 18.2% of the total bait consumption. Deer mice on 0.01% chlorophacinone: female mortality in Groups II and III was 100%. Total dietary consumption of treated bait was 63.1% of the total bait consumption. Deer mice on 0.01% diphacinone: female mortality in Groups II and III was 100%. Total dietary consumption of treated bait was 66.3% of the total bait consumption. In conclusion, the female house mice ate less than the male house mice with the same mortality rate (between 90% and 100%); while the female Peromyscus ate more than the male Peromyscus, they had the same mortality rate (100%). The anticoagulant grain bait test mortality results for both house mice and deer mice met the suggested performance standard for the EPA Pesticide Assessment Guidelines.