A laboratory bioassay was developed to test tarnished plant bug populations for resistance to the neonictinoid insecticides imidicloprid and thiamethoxam. Both of these insecticides are most toxic to plant bugs by ingestion rather than by contact, and traditional bioassays based on contact activity are not as effective for these insecticides. The bioassay developed uses different test doses of the insecticides fed to the plant bugs in honey water to determine LC50 values. These values can be compared over time and location to determine if resistance is increasing or decreasing. Baseline LC50 values for imidicloprid and thiamethoxam are presented along with results from testing several different plant bug populations in the mid-South. Methods for feeding honey water to the tarnished plant bugs are also presented.