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.

The disadvantage of the current Red imported fire ants (RIFA) diagnostic is that it takes at least two days, because it is subjected to PCR amplification and DNA sequence identification process using an arthropod universal mitochondrial cytochrome oxidase I prime pair after genomic DNA extraction. In order to overcome this drawback, two RIFA specific genes were confirmed and used to develop techniques for identifying the species using various PCR methods. The conventional PCR method can be confirmed by the presence of amplified DNA, but additional time is required to confirm whether the PCR products are present or not. In contrast, SYBR green Real Time (RT) PCR or TaqMan probe RT PCR method has the advantage of confirming the results immediately after the reaction is completed. The new molecular diagnostic method has the advantage of shortening the time of two days, which is the biggest disadvantage of RIFA molecular diagnostic method, to 3 hours or less.

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.

The red imported fire ant (RIFA, Solenopsis invicta Buren) is defined as invasive species and one of 100 most threaten alien species in world by IUCN. In Korea, RIFA has been first detected at September 28th, 2017 in Busan Port during surveillance by Animal and Plant Quarantine Agency (APQA). The RIFA colony was revealed as a polygyne and H5 type through epidemiological analysis on Gp-9 gene and mt-DNA haplotype. APQA has developed eradication program for RIFA with enhanced surveillance in all nationwide Ports and Internal Container Depots. There are subsequently 7 times more invasions of RIFA in Ports (Busan, Pyongeaek, and Incheon) including 2 times of inlands (Daegu and Ansan) and completely eradicated so far. International trade and climate change increases possibility of establishment and spreading of RIFA in Korea. Therefore, it must be required an international cooperation for prevention of global spreading of RIFA between countries.

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.

붉은불개미는 세계 100대 침입외래 해충 중의 하나로 우리나라에서는 관리 해충으로 1996년도에 지정되었다. 2017년 9월28일 부산항 감만 부두에서 국내 최초로 발견된 후, 2018년에 부산항, 평택항 과 인천항에서 발견이 되었고, 9월18일에 대구의 아파트 공사장에서 내륙에서는 처음으로 발견이 되었다. 대구에서 발견된 붉은불개미도 아파트 건설을 위하여 중국에서 수입한 석재에 혼합되어 수입된 토양과 식물체와 같이 혼입된 것으로 추측이 된다. 그러므로, 현재까지 국내에서 붉은불개미가 번식을 하여 토착화되었다는 증거는 없다. 현재까지 붉은불개미에 대한 종 판명은 전문가에 의한 형태적인 분류가 대부분이다. 그래서, 붉은불개미에 대한 확증을 위해서는 채집된 개체를 검역기관으로 이송하여 분자진단을 실시해야 하므로, 최소 이틀의 시간이 필요하다. 현재 항원항체 반응을 이용한 붉은불개미 진단 키트가 해외에서 개발되어 판매되고 있지만, 낮은 민감도로 최소 3~5개의 충체가 필요한 실정이다. 현재 판매되고 있는 진단키트가 가지는 문제점은 이를 대신할 새로운 키트의 개발이 필요함을 보여주고 있다. 신속한 붉은불개미의 검역현장에서 진단을 가능하게하기 위한 노력 중의 하나로 우리는 붉은불개미의 복부에서 발현되는 유전체에 대한 연구를 수행하였다. 본 발표에서는 그에 대한 현재까지의 연구 진행과 결과를 설명하도록 하겠다. (본 연구는 농림축산 검역본부의 연구비 지원으로 이루어졌음).