Japanese beetle, Popillia japonica Newman, is an invasive insect, native to Japan. The species was detected in the United States in New Jersey in 1916, and then first confirmed in Minnesota in 1968. Since their arrival, P. japonica has become a major pest in turfgrass and several crop agroecosystems. As P. japonica continues to spread throughout the U.S., it's important to discover more efficient ways to monitor adult populations. In 2018–2020, due to the high volume of P. japonica beetles collected in traps, a comparison of weight and volume calibration methods was conducted in Minnesota. Each method yielded a strong goodness of fit with counts of beetles captured. However, with a goal of cost-effective use of traps and in-field estimates, the volume-based approach was the preferred, most efficient method. In addition, a comparison of monitoring systems was conducted to observe differences in trap type, lure age, and check interval. Results from these studies indicate a standard green/yellow trap, and multi-component, semiochemical-based lure used for the duration of the P. japonica flight period, and a weekly check interval will minimize sampling time and resources, while providing accurate population estimates. In addition, results from these studies will benefit growers and researchers as they continue to explore integrated pest management (IPM) strategies for P. japonica. More importantly, by reducing the time required to quantify trap catches and rebait traps, these results may also facilitate area-wide tracking of P. japonica populations in newly invaded regions.