Popillia quadriguttata (F.) has caused extensive damage to ≈20 families and 25 species of plants in Asia, especially in China and Korea. Adult feeding causes serious damage to soybean leaves, and larvae develop on the roots of soybean, turf, and horticultural crops. As Japanese beetle (Popillia japonica Newman) lures have been used for trapping P. quadriguttata in a previous study, mass trapping this pest with various densities of the Japanese beetle pheromone, Japonilure, and floral lure, alone and in combination, were carried out during 2012–2013 in a northeastern China soybean field. Mass trapping in 2012 with Japonilure gave the best results with 72 and 75% adult and larval reduction, respectively. In 2013, mass trapping (30 traps per hectare) with Japonilure, floral lure, or the combination resulted in a 93, 70, and 74% reduction of adults trapped, and a 90, 77, and 93% reduction of overwintering larvae, respectively. In addition, field tests showed that almost twice as many beetles approached the lure combination compared with the floral lure alone, and the pheromone residual was ≈80% of the initial dosage after 30 d. Because reduction of overwintering larvae is the most critical parameter indicating treatment efficacy, the results here indicate that the lure or lure combinations can be recommended for use by Chinese soybean farmers.