title: Survival and Development of Spodoptera frugiperda and Chrysodeixis includens (Lepidoptera: Noctuidae) on Bt Cotton and Implications for Resistance Management Strategies in Brazil.
abstract: In Brazil, Spodoptera frugiperda (J. E. Smith) and Chrysodeixis includens (Walker) are important cotton pests and target of control of Bollgard II (Cry1Ac/Cry2Ab2) and WideStrike (Cry1Ac/Cry1F) cotton technologies. To subsidize an insect resistance management program, we conducted laboratory studies to evaluate the toxicity of these Bt cotton plants throughout larval development of S. frugiperda and C. includens. In bioassays with leaf disc, the efficacy of both Bt cotton plants against neonates was >80% for S. frugiperda and 100% for C. includens. However, S. frugiperda larvae that survived on Bt cotton had >76% of growth inhibition and stunting. In bioassays with S. frugiperda and C. includens larvae fed on non-Bt near-isoline during different time period (from 3 to 18 d) and then transferred to Bollgard II or WideStrike leaves showed that larval susceptibility decreased as larval age increased. For Bollgard II cotton, in all S. frugiperda instars, there were larvae that reached the pupal and adult stages. In contrast, on WideStrike cotton, a few larvae in fifth and sixth instar completed the biological cycle. For C. includens, some larvae in sixth instar originated adults in both Bt cotton plants. In conclusion, Bollgard II and WideStrike cotton technologies showed high efficacy against neonates of S. frugiperda and C. includens. However, the mortality of these species decreases as larval age increase, allowing insect survival in a possible seed mixture environment and favoring the resistance evolution.
authors: Department of Entomology and Acarology, "Luiz de Queiroz" College of Agriculture (ESALQ), University of São Paulo (USP), Av. Pádua dias 11, Piracicaba, São Paulo 13418-900, Brazil.
authors: Rodrigo J
authors: RJ
authors: Sorgatto
authors: Department of Entomology and Acarology, "Luiz de Queiroz" College of Agriculture (ESALQ), University of São Paulo (USP), Av. Pádua dias 11, Piracicaba, São Paulo 13418-900, Brazil.
authors: Oderlei
authors: O
authors: Bernardi
authors: Department of Entomology and Acarology, "Luiz de Queiroz" College of Agriculture (ESALQ), University of São Paulo (USP), Av. Pádua dias 11, Piracicaba, São Paulo 13418-900, Brazil. Corresponding author, e-mail: celso.omoto@usp.br.
authors: Celso
authors: C
authors: Omoto
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001938:Brazil; D004731:Endotoxins / Q000235:genetics*; D003368:Gossypium / Q000235:genetics* / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics*; D007300:Insect Control / Q000379:methods; D007814:Larva / Q000254:growth & development; D009036:Moths / Q000254:growth & development*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D018411:Spodoptera
chemical_list: D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins
keywords: fall armyworm; insect resistance management; soybean looper; transgenic cotton