Solenopsis invicta, known as the red imported fire ant, is an insect native to South America. This species was unintentionally introduced into Australia, New Zealand, several Asian countries, Caribbean countries, and the United States. It shows a high survival rate and settlement potential in human-habitable and non-living areas such as tropical rainforests, disturbed areas, deserts, grasslands, and roads. In Korea, invasions of red fire ants have been reported every year since 2017, and two invasions were discovered in 2023. Quarantine agency analyzing the haplotype and colony social type of S. invicta for surveillance and control. Population genetic analysis using Microsatellite Alleleic data of 66 loci to trace the origin of the invasion. Through research cooperation with the United States Department of Agriculture (USDA), we have received samples and expanded our genetic information database. This study analyzed genetic differences between 15 invasive populations and 44 reference groups. As a result of microsatellite analysis, the domestic invasive population showed a genetic structure similar to those in Guangzhou, China, and Florida, USA.

Origin of the red imported fire ant (RIFA, Solenopsis invicta) is South America, a tropical climate region. It has settled in the invasive area, causing various problems. In recent, colonies of Solenopsis invicta were discovered in Busan in 2017, and then in Busan, Pyongtaek, Incheon, Daegu and Ansan in 2018. This study aims to validate 31 microsatlite loci referred from previous study for tracing origin of Solenopsis invicta colonies. We tried to test previously developed microsatellite loci so that we establish the protocol for molecular epidemiology of RIFA. We applied 31 microsatellite loci to DNA samples from the RIFA colonies found in Texas and Florida, USA. We will present 31 markers were divided into three injections and the amplification rate for each marker was shown as follows.

Two infamous ant species, red imported fire ant (RIFA, Solenopsis invicta) and tropical fire ant (TFA, S. geminata), originated from South America are invading and harming many countries around the world. Among them, RIFA, known as one of the 100 world’s worst invasive alien species, has been discovered in South Korea; in Busan (Gamman CT) in 2017, and subsequently in Busan (Hutchison CT), Pyongtaek, Incheon and Daegu in 2018. With these relentless introduction of RIFA, South Korea is not safe no more from these ants and faces a risk of settlement. Our research goal is tracing the country origin of invasive populations of RIFA and TFA based on molecular epidemiological approach. We are conducting both microsatellite and genome-wide SNP analyses in order to derive a complementary interpretation. These two methodologies are expected to result in improved resolution in population genetics analysis. Nevertheless, this work needs collaboration of many countries belonging to the range of origin and invasion of RIFA and TFA. We will briefly introduce our research project and progress of collaboration research.

The red imported fire ant (RIFA, Solenopsis invicta), an exotic species, detected in Taiwan in 2003 was originally from USA. A program was launched immediately under Bureau of Animal and Plant Health Inspection and Quarantine Council of Agriculture (BAPHIQ) in 2004 for RIFA management. The National Red Imported Fire Ant Control Center (NRIFACC) helps the BAPHIQ to integrate/coordinate the RIFA eradication program which involves every governmental department, however the actual implementation of prevention and control work is the local government. It has made a significant progress in public education, since our general public can recognize RIFA accurately now and succeed to localize RIFA in Northern Taiwan. However, nationwide RIFA eradication is still far from success, the major constraints of the eradication program in Taiwan include (1) RIFA had likely been in Taiwan longer than reported, (2) difficulty to detect incipient infestation, (3) mass reproductive queens that can spread over 10-20 km after nuptial flight, (4) movement control is not easy to perform, (5) man power or company for chemical treatment is not enough, (6) funding is insufficient to allow success, (7) meteorological condition disfavors the control practice. Fortunately, we have developed humidity resistant baits that could enhance the control efficiency of RIFA in humid or wet conditions and resolve the weather constraints of RIFA and other invasive ants control in wet tropical and subtropical habitats. For the success of NRIFACC eradication efforts, participation of all stakeholders would remain a very important strategy in the future. In particular, a centralized team would further facilitate the management of RIFA. Moreover, due to the increasing in international trades and the recent detection of RIFA in Japan and Korea, an international efforts and cooperation on RIFA management is a key issue to control global movements of RIFA.

The red imported fire ant, Solenopsis invicta, first arrived in Texas in 1956 and quickly spread, where it now occupies more than half the state. The ecological and economic impact of this invasive ant has been well-documented in the state. Ecologically, it reduces native arthropod fauna and has a big effect on ground nesting birds. Economically, it’s estimated that this pest ant costs the state $1.2B dollars annually, affecting both urban and agricultural areas. After failed federal efforts to eradicate the fire ant, the state of Texas invested in its own research and management program, as did several other states. However, the Texas program, the Imported Fire Ant Research and Management Program, was the largest state program with $1.25 M invested annually since 1997. Several important developments arose out of this program including research on the biology and management of fire ants as well as treatment recommendations. Results of these research and management efforts will be discussed.

Incursions of red imported fire ant (RIFA), Solenopsis invicta into Korea have been increasing. After a first interception of a colony of S. invicta on Gamman pier, Pusan port while intensive surveillance by Animal & Plant Quarantine Agency (APQA) in September 2017, three more RIFA colonies have been found in sea port piers of Pyeongtek, Incheon and Pusan cities. The social forms and mitochondrial DNA haplotypes of the intercepted RIFA colonies were analysed by allelic discrimination assay (peptide nucleic acid probe based RT-PCR) of Gp-9 gene and mt-DNA fragment of 768 bp, which is part of the Cytochrome oxidaseⅠ gene. The colony on Gamman pier, intercepted in Sep. 2017 was previously reported as a haplotype 5 (H5) of mitochondrial DNA and a social form of polygyne. The colony on Hutchison pier of Pusan port, intercepted in June 2018 were confirmed as a H22 haplotype and a monogyne. Those different social forms show different origins of each colonies. Those on piers of Pyeongtek and Incheon ports, also found in 2018 were confirmed samely as H22 and monogyne. However, it could be putatively assumed that those two colonies were differently introduced via different container cargoes, considering those colonies were found in container yards of distantly located different sea ports. More genetic variation analyses using diverse sets of molecular markers such as microsatellites, genome-wide single nucleotide polymorphisms, etc. in nuclear gens are being proceeded for more exact introduction routes (origins).

The red imported fire ant (Solenopsis invicta) is a species of ant native to South America. The fire ant was inadvertently introduced into USA, Australia, New Zealand, and other Asian countries including China and Taiwan. Since the first report of the fire ant in port city of Busan, Korea in 2017, it was found in many other cities of Korea in following year. To obtain the molecular information of this invasive species, total RNA was extracted from the abdominal segment of the ants collected in Incheon, and subjected to transcriptome sequencing. By using Illumina sequencer platform, 101 base pared-end sequencing generated 2 × 50,064,081 of raw reads to obtain 2 × 45.95 Gbase of quality filtered nucleotide sequences. The in silico cDNA library was constructed by Trinity de novo assembler followed by TransDecoder ORF finder and CD-HIT clustering program to streamline the library. The final version of cDNA library contains 20,442 contigs with protein coding capability. To survey the virome of this ant, these contigs were searched against the viral reference sequences from NCBI RefSeq database with BLASTN program. As a result, contigs which showed high sequence identities with several RNA viruses including previously reported SINV-2 were found from the fire ant. This virome information might give an idea of a shift of virological environment of this newly found ant isolate or population in Korea.

A colony of Solenopsis invicta was first intercepted on Gamman pier, Pusan port in Korea at September, 2017 by Animal and Plant Quarantine Agency. The mitochondrial DNA (mt-DNA) of workers was analyzed and compared with vary libraries of mt-DNA haplotypes to elucidate the origin of the introduced colony with the trade pattern of the Gamman pier. The mt-DNA fragment of 768 bp, which is part of the Cytochrome oxidae I gene, was amplified and sequenced. The results showed that the mt-DNA was in the clade of haplotype 5, which is endemic in southern USA, China, Taiwan, and Australia. More than 60% of containers are imported from China into Gamman pier, it may be possible to assume that the colony was inadvertently invaded through containers from China.

벌목 개미과 두마디개미아과(Hymenoptera: Formicidae: Myrmicinae)의 Solenopsis invicta Buren, 1972가 국내 부산항에서 처음 발견되 어 농림축산검역본부에 의해 신속하게 제거되었다.