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<p><i>Brevicoryne brassicae</i> (Linnaeus), the cabbage aphid, is a destructive pest of cruciferous crops worldwide. In Kashmir, management relies heavily on organophosphate insecticides, yet regional susceptibility data are lacking. This study assessed eight field populations for susceptibility to chlorpyrifos, dimethoate, and quinalphos using standardized foliar bioassays with commercial formulations. Probit regression produced reliable dose-response fits, confirmed by <i>χ</i><sup>2</sup> goodness-of-fit tests. Resistance ratios (RRs) were calculated relative to the most susceptible field population in the absence of a laboratory reference strain. LC<sub>50</sub> values ranged from 3.71 mL L<sup>−1</sup> (dimethoate) to 4.61 mL L<sup>−1</sup> (chlorpyrifos), with RRs of 1.0–3.07, all below the resistance threshold (RR ≥ 5). However, LC<sub>50</sub> values in some populations approached or exceeded recommended field doses, indicating early tolerance. Slope comparison revealed horizontal LC<sub>50</sub> shifts for dimethoate and chlorpyrifos, while quinalphos showed significant slope heterogeneity. Principal component analysis and hierarchical clustering demonstrated structured susceptibility, with Baramulla as a distinct cluster. These findings provide the first regional baseline of organophosphate susceptibility <i>in B. brassicae</i> from Kashmir and underscore the need for proactive resistance management through insecticide rotation and integration of non-chemical tactics to sustain field efficacy.</p>

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Evaluation of insecticide susceptibility variation in different field populations of the cabbage aphid, Brevicoryne brassicae (Hemiptera: Aphididae), to selected organophosphate insecticides

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Irfan Ahmad Mir,
  • Bazila Rehman,
  • Barkat Hussain,
  • Tariq Ahmad

摘要

Brevicoryne brassicae (Linnaeus), the cabbage aphid, is a destructive pest of cruciferous crops worldwide. In Kashmir, management relies heavily on organophosphate insecticides, yet regional susceptibility data are lacking. This study assessed eight field populations for susceptibility to chlorpyrifos, dimethoate, and quinalphos using standardized foliar bioassays with commercial formulations. Probit regression produced reliable dose-response fits, confirmed by χ2 goodness-of-fit tests. Resistance ratios (RRs) were calculated relative to the most susceptible field population in the absence of a laboratory reference strain. LC50 values ranged from 3.71 mL L−1 (dimethoate) to 4.61 mL L−1 (chlorpyrifos), with RRs of 1.0–3.07, all below the resistance threshold (RR ≥ 5). However, LC50 values in some populations approached or exceeded recommended field doses, indicating early tolerance. Slope comparison revealed horizontal LC50 shifts for dimethoate and chlorpyrifos, while quinalphos showed significant slope heterogeneity. Principal component analysis and hierarchical clustering demonstrated structured susceptibility, with Baramulla as a distinct cluster. These findings provide the first regional baseline of organophosphate susceptibility in B. brassicae from Kashmir and underscore the need for proactive resistance management through insecticide rotation and integration of non-chemical tactics to sustain field efficacy.