Investigation of kdr and super-kdr target-site mutations in suspected pyrethroid-resistant Bathycoelia distincta (Hemiptera: Pentatomidae) in South Africa

Bathycoelia distincta (Hemiptera: Pentatomidae) is one of the most economically important stink bug pests of macadamia in South Africa. Recent field bioassays have indicated reduced efficacy of synthetic pyrethroids in certain pest populations. Target-site resistance associated with mutations in the voltage-gated sodium channel gene, particularly at the knockdown resistance (kdr) and super-kdr loci, is widely documented in other insect taxa. This study investigated whether mutations at these loci occur in South African populations of B. distincta. Species-specific primers were developed using comparative sequence data from Halyomorpha halys and Musca domestica to amplify regions spanning the putative kdr (L1014) and super-kdr (M918) positions. A susceptible reference sequence was generated, and 104 field-collected individuals from major macadamia-producing regions were screened using Sanger sequencing. No amino acid substitutions corresponding to the canonical kdr or super-kdr mutations were detected in the individuals analysed. These findings indicate that target-site mutations at these loci were not detected in the sampled populations and suggest that alternative resistance mechanisms may contribute to reduced pyrethroid efficacy. This study provides the first molecular characterisation of these loci in B. distincta and establishes molecular tools for future resistance monitoring.