We report 37 mitochondrial genome (mitogenome) sequences of Bombyx mori strains (Lepidoptera: Bombycidae) and four of B. mandarina individuals, each preserved and collected, respectively, in South Korea. These mitogenome sequences combined with 45 public data showed a substantial genetic reduction in B. mori strains compared to the presumed ancestor B. mandarina, with the highest diversity detected in the Chinese origin B. mori. Chinese B. mandarina were divided into northern and southern groups, concordant to the Qinling–Huaihe line, and the northern group was placed as an immediate progenitor of monophyletic B. mori strains in phylogenetic analyses, as has previously been detected. However, one individual that was in close proximity to the south Qinling–Huaihe line was exceptional, belonging to the northern group. The enigmatic South Korean population of B. mandarina, which has often been regarded as a closer genetic group to Japan, was most similar to the northern Chinese group, evidencing substantial gene flow between the two regions. Although a substantial genetic divergence is present between B. mandarina in southern China and Japan, a highly supported sister relationship between the two regional populations may suggest the potential origin of Japanese B. mandarina from southern China instead of the Korean peninsula.

This study was conducted to evaluate the insecticidal effects of ethyl formate (EF), methyl bromide (MB), and phosphine (PH₃) fumigants against PH₃-susceptible and -resistant strains of the rice weevil (Sitophilus oryzae), a major rice pest. The highest lethal concentration time 50 (LCt₅₀) values of the PH₃-susceptible strains were 255.797, 21.104, and 6.171 mg h L⁻¹ for EF, MB, and PH₃, respectively, at pupal stage. The highest LCt₅₀ values of the PH₃-resistant strains were 149.028 and 48.170 mg h L⁻¹ for EF and PH₃, respectively, at late larval stage, and 43.520 mg h L⁻¹ for MB at pupal stage. In comparison to the susceptible strains, the PH₃-resistant strain collected in South Korea had a resistance level 4 to 56 times higher. Use of the major quarantine fumigants EF, MB, and PH₃ indicated the existence of PH₃-resistant rice weevils in South Korea for the first time.

The complete mitochondrial genomes (mitogenomes) of two DNA barcode-defined haplotypes of Metcalfa pruinosa and one of Salurnis marginella (Hemiptera: Flatidae) were sequenced and compared to those of other Fulgoroidea species. Furthermore, the mitogenome sequences were used to reconstruct phylogenetic relationships among fulgoroid families. The three mitogenomes, including that of the available species of Flatidae, commonly possessed distinctive structures in the 1702–1836 bp A+T-rich region, such as two repeat regions at each end and a large centered nonrepeat region. All members of the superfamily Fulgoroidea, including the Flatidae, consistently possessed a motiflike sequence (TAGTA) at the ND1 and trnS₂ junction. The phylogenetic analyses consistently recovered the familial relationships of (((((Ricaniidae + Issidae) + Flatidae) + Fulgoridae) + Achilidae) + Derbidae) in the amino acid-based analysis, with the placement of Cixiidae and Delphacidae as the earliest-derived lineages of fulgoroid families, whereas the monophyly of Delphacidae was not congruent between tree-constructing algorithms.

The flatid planthopper, Metcalfa pruinosa (Hemiptera: Flatidae), which is an invasive species, is widespread in Korea. We sequenced a fragment of the COI from 536 individuals collected mainly in Korea and the European countries and combined these sequence data with the public data, totaling 830 individuals worldwide. The identification of one shared haplotype only between Korea and the USA, the presence of this haplotype only in the North-West region of Korea, and the highest haplotype diversity in this region suggested that the North-West region is another point of entry in addition to the South-East region, which is the presumed sole point of entry to Korea. Furthermore, it suggested that North-West entry involves the M. pruinosa originating from the USA. In an effort to find further variable regions in the mitochondrial genome, one region provided substantially increased variability compared to that of the fragment of COI. F_ST estimation, PCoA, and BAPS analysis, using the concatenated sequences of COI and the newly detected variable region to infer the expansion pattern in Korea, indicates that the main highway, running obliquely between the North-West and South-East regions, appears to be responsible for the current population genetic structure of M. pruinosa in Korea, facilitating gene flow through this highway traffic.

Mitochondrial genome sequences have been used in diverse fields of biology. In this study, we sequenced the complete mitochondrial genomes (mitogenome) of two pear pests: Cacopsylla jukyungi, the most damaging insect pest to commercial pears in South Korea, and Cacopsylla burckhardti (Hemiptera: Psyllidae). The two mitogenomes were compared to confamilial species to accumulate genetic information and understand evolutionary characteristics of the family Psyllidae. The 15,438 bp-and 14,799 bp-long complete mitogenomes of C. jukyungi and C. burckhardti, respectively, had many features typical of insect mitogenomes; however, at 1283 bp, the C. jukyungi mitogenome had an unusually long A+T-rich region, which was composed of two identical 540-bp repeat sequences. Among the intergenic spacer regions, the one located at the ND1 and trnS₂ junction was relatively well conserved in length (mostly within 23–36 bp). This region had a high sequence identity in all Psyllidae, possessing a 5-bp consensus sequence (CGGTA), which is speculated to have a functional role. Though the A+T-rich region in available Psyllidae mitogenomes varied substantially in length (662–1430 bp) and sequence divergence, all species had a conserved sequence stretch at the 3′-end of srRNA, which is also speculated to have a functional role. Genetic divergence among genes indicated the lowest variability in srRNA, lrRNA, and COI, whereas ATP8 and ND6 showed the highest variability at both family and genus (Cacopsylla) levels. Our data provide evidence that the family Psyllidae, including current C. jukyungi and C. burckhardti, have evolutionary unique features that were previously undetected, along with the unique A+T-rich region structure in C. jukyungi.

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is native to tropical and subtropical regions of the Western Hemisphere, but is now regularly appearing in crop fields across South Korea, particularly in corn fields. Therefore, it is crucial to promptly and accurately identify the presence of FAW in crop fields to effectively eradicate it as a regulated quarantine species. We developed a loop-mediated isothermal amplification (LAMP) assay, which allows for rapid in-filed identification. To develop the LAMP assay, we selected FAW-specific genomic regions from the whole-genome sequences of one FAW and 13 other lepidopteran species and validated five primer sets that consistently produced positive reactions in ten FAW samples collected from eight different locations in four countries. The assay successfully identified FAW in a maximum of 45 min, starting from crude DNA extraction (~15 min) to diagnosis (30 min) from the following samples, which were deposited outdoors for 30 days: a 1st-instar larva, an adult leg, an adult antenna, and 1/16 and 1/8 of an adult thorax. The five assays can be used selectively or in combination to cross-check and provide further confidence in the in-field diagnosis of FAW.