Proceedings of the Vertebrate Pest Conference

Valley pocket gophers (Thomomys bottae) cause considerable damage each year to a variety of crops. In the fall of 1997, efficacy data were collected after the hand placement of anticoagulant grain baits into underground burrows of Valley pocket gophers in northern California. Twenty-four Treatment Units (TUs) were divided into one of four treatment groups: 1) 0.01% diphacinone; 2) 0.005% diphacinone; 3) 0.01% chlorophacinone; and 4) 0.005% chlorophacinone grain baits. Each treatment group contained five treated TUs and one control TU. Active burrow systems were hand baited with the respective baits. Efficacy was determined through use of the open-hole index and radio telemetry. Neither the 0.005% or 0.01% chlorophacinone or diphacinone grain baits met the Environmental Protection Agency’s 70% standard for verifying efficacy of rodenticides. Potential reasons for the low efficacy of less than 10% for the four treatment groups are discussed.