Figures (3)  Tables (7)

    • Figure 1. 

      2024−2026 resistance levels of M. usitatus strains.

    • Figure 2. 

      3D model of M. usitatus VGSC (orange area: Domain I, blue area: Domain II, light blue area: Domain III, purple area: Domain IV).

    • Figure 3. 

      Topological structure diagram of the VGSC M918L/T, T929I and L1014F mutation sites in the M. usitatus.

    • Strains Collection site Year Longitude and latitude Host
      CM-R Chengmai County, Hainan Province 2024−2026 N 20°20'31", E 110°30'11 Cowpea
      LD-R Ledong Li Autonomous County, Hainan Province 2024−2026 N 18°40'03", E 109°30'25" Cowpea
      SY-R Yazhou District, Sanya City, Hainan Province 2024−2026 N 18°23'05", E 109°9'44" Cowpea
      LS-R Lingshui Li Autonomous County, Hainan Province 2024−2026 N 18°31'42", E 110°1'35" Cowpea

      Table 1. 

      Field collection information table of M. usitatus.

    • Primer name Primer sequence Usage
      MuNav-5(F) TTGGCAGTCAATTCCCCGGGGCCACCATGCCGAGTGTCCGGGAGTCG Full-length cloning of VGSC
      MuNav-3(R) AGTCGTAACCAGATCAAGCTTTCAGACATCCGCAAGGGCCGGAG
      Domain II-5(F) ACATTTTCTGCGTGTGGGACTGC Detection of mutation sites in Domain II
      Domain II-5(R) CCAGTTGATAAATCGTGATATTC

      Table 2. 

      Primers for the full-length application and mutation frequency detection of VGSC in M. usitatus.

    • Treatment Strain Sample No. Slope ± standard error Degree of freedom Chi-square LC50 (95% confidence interval) Resistance ratio
      Deltamethrin HK-S 444 1.975 ± 0.239 4 0.279 8.148 (5.853−10.311) 1
      CM2024 461 2.545 ± 0.016 4 4.864 2,489.687 (1,473.860−4,688.216) 305.6
      CM2025 450 5.197 ± 0.571 4 0.173 3,181.355 (2,890.989−3,514.066) 390.4
      CM2026 449 3.920 ± 0.433 4 0.210 3,302.052 (2,945.182−3,755.924) 405.3
      LD2024 445 1.162 ± 0.133 4 7.676 2,579.637 (2,469.245−3,151.628) 316.6
      LD2025 441 1.096 ± 0.217 4 3.294 3,102.792 (1,902.736−5,426.599) 380.8
      LD2026 450 2.947 ± 0.329 4 0.091 3,573.267 (3,090.145−4,270.751) 438.6
      SY2024 438 0.905 ± 0.127 4 0.890 2,409.838 (1,472.794−3,195.164) 295.8
      SY2025 446 1.477 ± 0.073 4 1.011 2,583.096 (1,401.633−5,023.782) 317.0
      SY2026 447 3.102 ± 0.308 4 1.268 2,962.999 (2,131.597−4,757.661) 363.6
      LS2024 443 2.190 ± 0.169 4 3.672 2,699.051 (2,730.686−2,857.614) 331.3
      LS2025 440 2.174 ± 0.228 4 1.806 3,276.117 (1,396.584−6,403.851) 402.1
      LS2026 448 2.952 ± 0.316 4 1.281 3,553.753 (2,280.381−4,217.518) 436.2
      Resistance fold = Field population LC50/Sensitive strain (HK-S) LC50. HK-S is an indoor strain that has not been exposed to insecticides for an extended period, specifically from 2019 to 2025, and its LC50 serves as the fixed benchmark for all comparisons.

      Table 3. 

      Resistance levels of M. usitatus to Deltamethrin.

    • Treatment Strain Sample No. Slope ± standard error Degree of freedom Chi-square LC50 (95% confidence interval) Resistance ratio
      Bifenthrin HK-S 444 2.248 ± 0.293 4 0.461 7.610 (5.501−9.515) 1
      CM2024 446 0.810 ± 0.120 4 2.060 4,642.120 (2,744.790−5,345.450) 610.0
      CM2025 445 2.746 ± 0.386 4 0.704 5,154.927 (4,253.658−6,853.767) 677.4
      CM2026 450 2.233 ± 0.291 4 0.461 5,222.599 (4,167.747−7,257.130) 686.3
      LD2024 441 0.713 ± 0.124 4 0.154 2,710.853 (1,747.671−5,465.877) 356.2
      LD2025 429 1.541 ± 0.155 4 1.045 3,508.291 (2,491.721−7,786.022) 461.0
      LD2026 449 3.409 ± 0.416 4 0.428 3,964.617 (3,461.532−4,705.489) 521.0
      SY2024 438 0.801 ± 0.129 4 0.025 3,602.825 (2,246.790−7,576.970) 473.4
      SY2025 430 1.206 ± 0.022 4 2.964 4,127.643 (2,578.660−7,906.107) 542.4
      SY2026 448 3.059 ± 0.397 4 0.495 4,440.504 (3,790.218−5,507.876) 583.5
      LS2024 446 2.902 ± 0.222 4 7.844 2,999.842 (2,771.627−3,289.249) 394.2
      LS2025 450 1.794 ± 0.067 4 2.454 3,601.884 (2,391.087−6,201.144) 473.3
      LS2026 449 4.741 ± 0.580 4 4.453 3,946.913 (3,371.774−4,824.179) 518.7
      Resistance fold = Field population LC50/Sensitive strain (HK-S) LC50. HK-S is an indoor strain that has not been exposed to insecticides for an extended period, specifically from 2019 to 2025, and its LC50 serves as the fixed benchmark for all comparisons.

      Table 4. 

      Resistance levels of M. usitatus to Bifenthrin.

    • Treatment Strain Sample No. Slope ± standard error Degree of freedom Chi-square LC50 (95% confidence interval) Resistance ratio
      Cypermethrin HK-S 447 1.730 ± 0.222 4 0.566 6.756 (4.387−9.029) 1
      CM2024 425 2.871 ± 0.062 4 2.524 2,380.572 (1,209.860−4,688.216) 352.4
      CM2025 450 2.102 ± 0.219 4 0.425 3,342.027 (2,773.125−4,222.895) 494.7
      CM2026 450 1.651 ± 0.179 4 0.081 3,738.598 (2,939.492−5,142.503) 553.4
      LD2024 445 2.203 ± 0.187 4 1.724 2,461.168 (2,390.935−2,937.372) 364.3
      LD2025 445 2.017 ± 0.884 4 1.027 3,055.231 (1,491.087−4,923.077) 452.2
      LD2026 450 2.250 ± 0.262 4 2.250 3,319.287 (2,828.367−4,040.714) 491.3
      SY2024 437 0.866 ± 0.125 4 0.816 2,459.628 (1,644.078−4,515.853) 364.1
      SY2025 429 2.151 ± 0.017 4 1.739 2,963.782 (1,708.851−4,996.745) 438.7
      SY2026 448 2.970 ± 0.319 4 1.205 3,359.198 (2,913.821−3,984.137) 497.2
      LS2024 441 0.891 ± 0.125 4 0.939 3,652.185 (2,219.346−8,724.188) 540.6
      LS2025 448 2.966 ± 0.693 4 1.831 4,102.857 (3,201.822−7,012.696) 607.3
      LS2026 449 3.874 ± 0.509 4 0.535 4,314.532 (3,795.844−5,094.333) 638.6
      Resistance fold = Field population LC50/Sensitive strain (HK-S) LC50. HK-S is an indoor strain that has not been exposed to insecticides for an extended period, specifically from 2019 to 2025, and its LC50 serves as the fixed benchmark for all comparisons.

      Table 5. 

      Resistance levels of M. usitatus to Cypermethrin.

    • Strain Year M918L Mutation frequency M918T Mutation frequency T929I Mutation frequency L1014F Mutation frequency Total samples
      HK-S 2025 M/L 0 M/T 0 T/I 0 L/F 0 29
      CM2024 2024 M/L 0 M/T 0 T/I 100 L/F 0 29
      CM2025 2025 M/L 0 M/T 0 T/I 93.3 L/F 0 30
      CM2026 2026 M/L 0 M/T 0 T/I 90.0 L/F 0 30
      LD2024 2024 M/L 0 M/T 0 T/I 100 L/F 0 30
      LD2025 2025 M/L 0 M/T 0 T/I 100 L/F 0 30
      LD2026 2026 M/L 0 M/T 0 T/I 96.7 L/F 0 30
      SY2024 2024 M/L 0 M/T 0 T/I 100 L/F 0 29
      SY2025 2025 M/L 0 M/T 0 T/I 100 L/F 0 28
      SY2026 2026 M/L 0 M/T 0 T/I 96.7 L/F 0 30
      LS2024 2024 M/L 0 M/T 0 T/I 100.0 L/F 0 29
      LS2025 2025 M/L 0 M/T 0 T/I 90.0 L/F 0 30
      LS2026 2026 M/L 0 M/T 0 T/I 90.0 L/F 0 30
      To ensure the reliability and accuracy of the experimental data, samples that did not meet quality standards were excluded from the final statistical analysis.

      Table 6. 

      Mutation frequency of M. usitatus M918L/T, L1014F, and T929I mutation sites.

    • Channel Segment
      MuNav1-1 IL45-S5 252VPGLKTIVGA VI ESVKNLRDVI ILTMFSLSVF ALMGLQIY
      IIL45-S5 934WPTLNLLISI MG RTMGALGNLT FVLCIIIFIF AVMGMQLF
      IIIL45-S5 1431MQGMRVVVNA LV QAIPSIFNVL LVCLIFWLIF AIMGVQLF
      IVL45-S5 1749AKGIRTLLFA LA MSLPALFNIC LLLFLVMFIF AIFGMSFF
      IS6 402PWHMLFFIVI IFLGSFYLVN LILAIVAMSY DE
      IIS6 1025WSCIPFFLAT VVIGNLVVLN LFLALLLSNF GS
      IIIS6 1552IYMYLYFVFF IIFGSFFTLN LFIGVIIDNF NE
      IIIS6 1852TIGITFLLSY LVISFLIVIN MYIAVILENY SQ

      Table 7. 

      Amino acid sequences of the Domain II-localized T929I mutation and the pyrethroid-binding site (IIL45-IIS5-IIIS6) in M. usitatus.