Western corn rootworm, Diabrotica virgifera virgifera LeConte, neonate susceptibility to clothianidin, a highly effective contact and systemic neonicotinoid insecticide, was determined from both laboratory and field collected populations. Neonates were exposed to filter paper treated with increasing clothianidin concentrations and mortality was evaluated after 24 h. The variation among populations was generally low, (4.44-fold) among populations tested. In general, clothianidin was very toxic to rootworm neonate, with LD₅₀’s ranging from 4.9 to 21.9 ng/cm2. These results show the potential of clothianidin as an effective tool against this corn pest and establish baseline susceptibility levels, which is an essential first step in resistance management. A baseline response provides a reference for tracking shifts in susceptibility following commercial use so that early changes in susceptibility can be detected.