Since we reported a viral disease extremely fatal to A. dichotoma, had landed on Korea in 2015, we have investigated this disease nationwide and it was turned out the viral disease has spread in the majority of the larva-rearing farms all over the country. The transmission of this disease is most severe when the larvae are harvested and stored for overwintering. During this period, even a few virus-infected larvae can easily transmit the virus and about two hundreds of larvae stored in a container can be killed. In a peroral infection experiment, 80% of infected larvae were killed but survived larvae became adults fully functional physiologically. These survived beetles were confirmed as live virus carrier. Also, about 75% of larvae hatched from the eggs laid by the infected beetles were infected and killed by the virus. This vertical transmission is due to the feeding and secretion activity of the infected parents.

The current market size of insect industry in Korea is estimated at 300 million dollars and more than 500 local farms are related to many insect industry. One of the strong candidates for insect industry is Korean horn beetle, Allomyrina dichotoma. Early this year, we reported a viral disease extremely fatal to A. dichotoma larvae. While we were proceeding a nationwide investigation of this disease, several farmers answered that similar disease symptom has been occurred occasionally during past 10 years. The symptom can be easily confused with early stage of bacterial infection or physiological damage including temperature and moisture. A peroral infection with the purified virus to healthy larvae produced a result that only 21% of larvae survived and became pupae. Although some of the survived adult beetle were deformational, many of them had no abnormal appearance and even succeeded in mating. Later, these beetles were examined if they were carrying the virus, and all except one were confirmed as virus carrier. This implies that these beetle may fly out and spread the disease throughout the country. We found the evidence by collecting wild A. dichotoma larvae which were virus infected, near two local farms rearing the horn beetle. So far, transovarial transmission of this virus to the eggs, or horizontal transmission to other commercially reared insects are not known yet.

In Korea, the value of insect resources has been increased immensely and the insect industry is expected to increase up to 40 billion dollars by 2020. Among them, Korean horn beetle, Allomyrina dichotoma, is one of the strongest candidates for insect industry as medicinal purpose for various liver diseases and diabetes. In many local farms rearing larvae, a few bacterial and fungal pathogens causing disease of A. dichotoma larvae have been identified including Bacillus thuringiensis and Metarhizium anisopliae. For past few years, a disease seemingly due to viral infection has been reported for causing death of larvae en masse. The pathogen of this disease has not been identified so far. In Southeastern Asia, Oryctes rhinoceros nudivirus (OrNV) is known to cause severe disease in coconut palm rhinoceros beetle, Oryctes rhinoceros, and is used as a biological control agent to reduce the pest population. Here, we report for the first time that OrNV may have landed on Korea and may be the major pathogen for the diseased larvae of A. dichotoma. After peroral inoculation with the purified virus extracted from the hemolymph of diseased larvae, we confirmed that over 60% of infected larvae perished in six weeks. This viral disease spreads very fast in many farms nationwide throughout Korea. This threat not only makes economic loss of local farms rearing larvae, but also may disturb the ecosystem by transmitting to wild A. dichotoma.