Acta Entomologica Sinica ›› 2020, Vol. 63 ›› Issue (5): 590-596.doi: 10.16380/j.kcxb.2020.05.008

• RESEARCH PAPERS • Previous Articles     Next Articles

Comparison of bioassay methods for the toxicities of chemical insecticides against Spodoptera frugiperda (Lepidoptera: Noctuidae)

LÜ Sheng-Lan, WANG You-Bing, GU Shao-Hua, LIANG Pei, ZHANG Lei*, GAO Xi-Wu*    

  1. (Department of Entomology, China Agricultural University, Beijing 100193 China)
  • Online:2020-05-20 Published:2020-06-08

Abstract: 【Aim】 This study aims to identify the most repeatable and convenient bioassay method to assess the toxicities of chemical insecticides of different types against larvae of the fall armyworm, Spodoptera frugiperda. 【Methods】 The toxicities of seven insecticides of different types (chlorantraniliprole, emamectin benzoate, acephate, lambda-cyhalothrin, spinetoram, chlorfenuron and lufenuron) against the 3rd instar larvae of S. frugiperda were detected with topical application method, diet incorporation method and leaf dipping method, respectively. 【Results】 Detected with topical application method, emamectin benzoate showed the highest toxicity to the 3rd instar larvae of S. frugiperda among the seven insecticides, with the LD50 value of 0.375 μg/g at 24 h after treatment, and lufenuron showed the lowest toxicity, with the LD50 value of 261.107 μg/g at 72 h after treatment. Detected with diet incorporation method, emamectin benzoat showed the highest toxicity and acephate showed the lowest toxicity to the 3rd instar larvae of S. frugiperda, with their LC50 values of 0.061 and 9 426.217 μg/g, respectively, at 24 h after treatment. Detected with leaf dipping method, emamectin benzoate showed the highest toxicity and lambda-cyhalothrin showed the lowest toxicity to S. frugiperda larvae, with their LC50 values of 0.062 and 471.343 mg/L, respectively, at 24 h after treatment. The bioassay data obtained in topical application method had the smallest chi-square value and the largest P-value. At the same time, S. frugiperda populations showed higher genetic consistency in topical application method and leaf dipping method than in diet incorporation method. 【Conclusion】 Topical application method is the optimal bioassay method for all the tested insecticides except for lufenuron, including chlorantraniliprole, emamectin benzoate, acephate, lambda-cyhalothrin, spinetoram, and chlorfenuron. Compared with diet incorporation method and leaf dipping method, topical application method can not only accurately reflect the genetic purity of S. frugiperda populations, but also show the highest repeatability of bioassay results. However, diet incorporation method and leaf dipping method are recommended in lufenuron bioassay.

Key words: Spodoptera frugiperda, insecticides, toxicity, topical application method, diet incorporation method, leaf dipping method