Dimethoate belongs to organophosphate (OP) group of insecticides, used worldwide against several economic insect pests. This study was done to evaluate the fitness costs and stability of dimethoate resistance in a previously selected strain of dusky cotton bug, Oxycarenus hyalinipennis Costa (Hemiptera: Lygaeidae), a serious sucking pest of cotton. Previously, dimethoate selected (Dimeth-SEL) strain was developed after selecting O. hyalinipennis for six generations in the laboratory. The selected strain expressed resistance ratios (RRs) of 157.76-, and 14.13-fold to dimethoate when compared with Lab Pop, and Unsel Pop, respectively. Data on fitness traits of selected strain reveal that the relative fitness (Rf) of Dimeth-SEL was 0.77 along with significant decrease in nymphal survival, hatchability, net reproductive rate (R0), intrinsic rate of natural increase (r_m), and biotic potential (Bp). The Rf evaluated for Cross₁ and Cross₂ was 1.02 and 0.91, respectively. For resistance stability, Dimeth-SEL (G₆) was left unexposed to dimethoate for five generations (G₇-G₁₁) and the bioassay results at G₁₁ showed that removal of selected strain from selection pressure resulted in a significant decline in dimethoate resistance. It can be inferred from these results that resistance to dimethoate was developed in O. hyallinipennis at the expense of very high energetic costs and that these costs might also contributed in lowering the resistance levels towards susceptibility after stopping the selection for several generations. These results have practical implications in managing the dimethoate resistance against O. hyallinipennis by implementing the insecticide rotation strategy and also by delaying the dimethoate spray in the field for some generations.

乐果属于有机磷 (OP) 类杀虫剂，在世界范围内用于对抗多种经济害虫。本研究旨在评估先前选定的暗色棉虫Oxycarenus hyalinipennis Costa（半翅目：Lygaeidae）（一种严重的棉花吸食害虫）的适应性成本和乐果抗性的稳定性。此前，乐果选择（Dimeth-SEL）菌株是在实验室选择O. hyalinipennis六代后开发的。与 Lab Pop 和 Unsel Pop 相比，所选菌株对乐果的抗性比 (RR) 分别为 157.76 和 14.13 倍。所选品系的适应度性状数据表明，相对适应度 ( Rf）Dimeth-SEL的是，在若虫存活率，孵化率，净生殖率（显著减少而0.77 R0）的自然增长（内禀增长率[R_米），和生物潜能（BP）。对交叉₁和交叉₂评估的Rf分别为 1.02 和 0.91。对于抗性稳定性，Dimeth-SEL (G ₆ ) 未暴露于乐果五代 (G ₇ -G ₁₁ ) 和 G ₁₁的生物测定结果表明从选择压力中去除选择的菌株导致乐果抗性显着下降。从这些结果可以推断，在O. hyallinipennis中产生了对乐果的抗性，代价是非常高的能量成本，并且这些成本也可能有助于在停止选择几代后降低对易感性的抗性水平。这些结果对通过实施杀虫剂轮换策略以及通过将乐果在田间喷洒数代延迟来管理对O. hyallinipennis的乐果抗性具有实际意义。