The efficacy of rodent bait containing the insecticide imidacloprid was evaluated for controlling fleas on the California ground squirrel, Spermophilus beecheyi. The bait was designed to deliver an oral dose of insecticide resulting in flea mortality when obtaining a blood meal. During the five-week trial, performed at Vandenberg Air Force Base, Santa Barbara County, CA, a spot-baiting technique was used to apply bait to ground squirrel burrows. Bait was applied six times throughout the trial. Results indicated that the use of a host-targeted bait was effective in significantly reducing the flea burden on S. beecheyi. Efficacy at reducing flea abundance was near 100% at both day 15 and day 29 of the trial. Use of the bait also reduced the prevalence of flea-infested S. beecheyi. Our results indicate that the use of rodent bait containing insecticide could provide an effective, economical method of controlling the fleas of S. beecheyi, the primary vectors of human plague in California.