Developmental changes in target-pest susceptibility to Bacillus thuringiensis (Bt) toxins matter to resistance management in Bt crops, especially in certain refuge modalities. We determined the cumulative, lethal and sublethal effects of Bt corn hybrids during the larval stages of Bt-resistant populations of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae). The susceptibility to Bt corn traits depended on the fall armyworm population and the developmental stage of the larvae. On Cry1A.105 + Cry2Ab corn, neonate-to-adult survival rates of Cry1F-resistant larvae was 4% when the exposure started in the neonate and 87% when in late instars. Cry1F-resistant larvae feeding on Cry1A.105 + Cry2Ab corn throughout larval development produced viable adults that successfully reproduced without any noticeable disadvantage. In contrast, Bt susceptible larvae had high mortality on Cry1A.105 + Cry2Ab corn, and no adults emerged from the larvae exposed to the toxins, independently of the larval stage. Cry1Ab + Vip3Aa corn killed all larvae in any instar, regardless of the Bt-toxin resistance of the fall armyworm population. These results consistently indicate that Cry1F resistance reduces the susceptibility to Cry1A.105 + Cry2Ab toxins and that Vip3Aa has a high potential to control field populations of Cry-toxin-resistant fall armyworm, even if there was plant-to-plant larval movement to Vip Bt plants in late instars in a scenario seed-mixture refuge. We discuss the implications of our findings for sustainable resistance management.

苏云金芽孢杆菌（Bt）毒素对靶标害虫敏感性的发展变化与Bt作物的抗性管理有关，尤其是在某些避难所中。我们确定了Bt玉米杂交种在秋季粘虫，斜纹夜蛾抗Bt种群的幼虫期的累积，致死和亚致死作用。（鳞翅目：夜蛾科）。Bt玉米性状的易感性取决于秋天的粘虫种群和幼虫的发育阶段。在Cry1A.105 + Cry2Ab玉米上，当从新生儿开始接触时，耐Cry1F的幼虫的新生到成活率是4％，而晚熟期则是87％。在整个幼虫发育过程中，以Cry1A.105 + Cry2Ab玉米为食的耐Cry1F幼虫产生了可存活的成年动物，可以成功繁殖，而没有任何明显的缺点。相反，对Bt敏感的幼虫在Cry1A.105 + Cry2Ab玉米上具有很高的死亡率，并且与幼虫阶段无关，没有幼虫从暴露于毒素的幼虫中出来。Cry1Ab + Vip3Aa玉米杀死了所有幼虫中的所有幼虫，无论秋季粘虫种群对Bt的抗药性如何。这些结果一致表明，对Cry1F的抗药性降低了对Cry1A.105 + Cry2Ab毒素的敏感性，并且即使植物幼虫向Vip移动，Vip3Aa仍具有控制抗Cry毒素的秋季粘虫田间种群的高潜力。转基因植物避难所中处于晚熟期的Bt植物。我们讨论了研究结果对可持续抗药性管理的意义。