Effect of the timing of applications and amount of 0.01% diphacinone consumed on mortality of California ground squirrels (Spermophilus beecheyi)

Diphacinone, a first-generation anticoagulant rodenticide is used extensively for control of California ground squirrels (Spermophilus beecheyi). The potential for secondary poisoning hazards, has necessitated development of baiting strategies that minimize the amount of bait applied, while still providing a high level of control. Laboratory studies conducted to determine the effect of the amount of bait, number, and timing of 0.01% diphacinone bait applications on mortality rate of California ground squirrels suggest that only 2 applications with 3–5 d between applications are necessary to achieve control. This is contrary to previous beliefs that there must be no more than 48 h between feedings. Reducing the amount of bait per application by 71% had no significant effect on mortality rate.