![]() Farmers have to spray insecticide even in Bt crops for effective control of S. However, Bt cotton expressing only CrylAc proteins are unable to provide effective control against Spodoptera spp. 2012), and armyworms including the beet armyworm that becomes one of the major pests in Bt cotton fields (Arshad and Suhail, 2011). The widespread adoption of Bt cotton has led to several non-target insect pests such as mirids (Lu et al. exigua attacks the cotton plants throughout the whole growing season causing yield losses (Osoria et al. ![]() The beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a polyphagous pest of various field crops including vegetables, cotton, and ornamentals. The trend in lethal concentration and its respective resistance level was higher in 2016 than in 2015. The molt inhibitory concentration (MIC 50) ranged from 0.04 to 0.56 μg ml −1, 0.08 to 0.99 μg ml −1, and 0.10 to 1.42 μg ml −1 for the three instars, respectively. The Bahawalpur population was highly resistant and showed 5.63, 5.30, and 3.89 variations than the susceptible population, followed by Multan 3.01, 3.71, 3.10, and Faisalabad 1.93, 2.41, 2.31 population for first, second, and third larval instars, respectively. The LC 50 ranged from 0.45 to 2.52 μg ml −1, 1.08 to 5.74 μg ml −1, and 2.01 to 7.85 μg ml −1 for first, second, and third larval instars, respectively. exigua, collected from Faisalabad, Multan, and Bahawalpur, compared with susceptible laboratory population was carried out in 20. The baseline susceptibility bioassay test for first, second, and third larval instars of S. The efficacy of Bt technology depends on stage, age, and susceptibility of the tested population to Cry proteins. Transgenic Bacillus thuringiensis ( Bt) cotton is engineered to express delta endotoxin (Cry toxin) proteins in lepidopteran midgut when ingested by lepidopteran larvae such as the beet armyworm, Spodoptera exigua (Hübner).
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