California ground squirrel field efficacy study using 0.005% chlorophacinone bait

A field efficacy study was completed using Wilco Ground Squirrel Bait (containing 0.005% chlorophacinone) to control California ground squirrels (Spermophilus beecheyi) in Madera County, California. Bait was applied in plastic stations at the rate of 2 lbs. per station. Two plots with buffer zones were treated (about 11.5 acres each). Visual and burrow counts were used as the census indices to determine field efficacy. Pretreatment and posttreatment census observations were conducted over three days pretest and three days posttreatment. Efficacy after 21 days was 94.4% for plot T-1 and 100% on plot T-2 using visual counts. Burrow count data was similar with the T-1 efficacy of 95.1% and T-2 of 95.8%. Tissue residue analysis was completed on muscle, liver and gut remains in recovered ground squirrels and non-target wildlife. Partial carcasses of two cottontail rabbits were found on the plots. Turkey vultures were observed on the study area daily. The numbers and size of vultures observed and the quantity of dead squirrels recorded on the ground surface would tend to indicate no significant impact on the vulture population nor on other wildlife in the treatment area