Molecular analysis of insecticide resistance mutation frequencies in five cockroach species from Korea.

Cockroaches are major urban pests that pose public health risks due to their ability to transmit pathogens and develop insecticide resistance. In the Republic of Korea (ROK), resistance monitoring has traditionally relied on bioassays, with limited studies on resistance-associated mutations. This study examined the prevalence of kdr and rdl mutations, conferring resistance to pyrethroids and fipronil (a phenylpyrazole insecticide), respectively, in five cockroach species (Blattella germanica, Blattella nipponica, Periplaneta americana, Periplaneta japonica, and Periplaneta fuliginosa). A total of 1278 cockroaches from 243 regional samples were analyzed using quantitative sequencing. Results showed widespread resistance in B. germanica, with an overall frequency of 57.1 % for the kdr mutation (L993F) and 94.2 % for the rdl mutation (A302S) across 169 regional samples. No evidence of other kdr mutations, E434K or C764R, was found. Notably, B. nipponica, despite its recent emergence in indoor environments, exhibited no detectable resistance mutations, likely due to lower insecticide exposure in rural areas. Similarly, no kdr mutations were found in Periplaneta species, and the rdl mutation was detected in only a single P. americana regional sample, marking the first documented case. Given the increasing resistance to fipronil, alternative insecticides are needed for effective cockroach management. Dinotefuran, a neonicotinoid with limited prior use in cockroach control, is a promising candidate, as its toxic bait products are already available in the ROK. Broflanilide and isocycloseram also show potential but require regulatory approval. These findings highlight the need for ongoing resistance monitoring and proactive pest management strategies.