Oryctes rhinoceros nudivirus (OrNV) has been known to cause severe disease in coconut palm rhinoceros beetle, Oryctes rhinoceros, in Southeastern Asia and is used as a biological control to reduce the pest population. Here, we report for the first time that the OrNV may have landed on Korea and may be the major pathogen for diseased larvae of Korean horn beetle, Allomyrina dichotoma. After peroral inoculation, over 60% of infected larvae perished in 6 wk. This viral disease spreads very fast in several locations throughout Korea. This threat not only makes economic loss of local farms rearing A. dichotoma larvae but also may disturb the ecosystem by transmitting to wild A. dichotoma.