In order to establish the integrated management of white grubs in ginseng field damages of ginseng plants (Panax ginseng C.A. Meyer) by the larvae of the larger black chamfer (Holotrichia morose Waterhouse) and the Korean black chamfer (Holotrichia diomphalia Bates) were investigated. Most of ginseng damages due to H, morose usually occurred in September through October, mainly on 2nd year plants. However, the damage by H. diomphalia occurred in September through October (usually in odd number of years) on 2nd year plants and in the following May and June on 3rd year plants. Therefore, in the fall of every odd number of years, synchronized occurrence of the two species caused severe damage on ginseng plants. Both of the 3rd instar larvae of the forementioned two species damaged ginseng roots regardless of the age of the plants when ginseng plants were artificially infested with them. Ginseng fields located at the slopes with good drainage are most likely damaged by them.