BACKGROUND: In an effort to control the most devastating cotton pest, Helicoverpa armigera (Hübner), in Qiuxian County (Hebei, China), Bt cotton has been planted almost exclusively since 1998 in this area. Owing to the high insecticidal selection pressures in this region, monitoring of Bt resistance in H. armigera is necessary so that proactive actions can be implemented before field control measures fail. From 2003 to 2005, an F(2) screen was conducted in order to monitor Bt resistance in H. armigera populations collected from this area. RESULTS: The F(2) screen showed that 15 out of 278 isofemale lines carried resistance alleles to Bt cotton. The resistance allele frequency in field populations of H. armigera ranged from 0.0119 to 0.0297, with an overall frequency of 0.0146 and a 95% confidence interval of 0.0084-0.0225 for the 3 year period. This value is greater than the value reported from 1999 (P < 0.05). CONCLUSION: A fluctuating but overall increase in resistance allele frequency was detected in the field populations of H. armigera in Qiuxian County from 1999 to 2005. To prevent further increases in Bt resistance frequency in this pest, it is necessary to introduce Bt cotton expressing multiple Bt toxins and integrate this technology with other tactics for management of this key pest. Copyright (c) 2009 Society of Chemical Industry.
BACKGROUND: In an effort to control the most devastating cotton pest, Helicoverpa armigera (Hübner), in Qiuxian County (Hebei, China), Bt cotton has been planted almost exclusively since 1998 in this area. Owing to the high insecticidal selection pressures in this region, monitoring of Bt resistance in H. armigera is necessary so that proactive actions can be implemented before field control measures fail. From 2003 to 2005, an F(2) screen was conducted in order to monitor Bt resistance in H. armigera populations collected from this area. RESULTS: The F(2) screen showed that 15 out of 278 isofemale lines carried resistance alleles to Bt cotton. The resistance allele frequency in field populations of H. armigera ranged from 0.0119 to 0.0297, with an overall frequency of 0.0146 and a 95% confidence interval of 0.0084-0.0225 for the 3 year period. This value is greater than the value reported from 1999 (P < 0.05). CONCLUSION: A fluctuating but overall increase in resistance allele frequency was detected in the field populations of H. armigera in Qiuxian County from 1999 to 2005. To prevent further increases in Bt resistance frequency in this pest, it is necessary to introduce Bt cotton expressing multiple Bt toxins and integrate this technology with other tactics for management of this key pest. Copyright (c) 2009 Society of Chemical Industry.
Authors: Karlos Diogo de Melo Chalegre; Tatiany Patrícia Romão; Daniella Aliny Tavares; Eloína Mendonça Santos; Lígia Maria Ferreira; Cláudia Maria Fontes Oliveira; Osvaldo Pompílio de-Melo-Neto; Maria Helena Neves Lobo Silva-Filha Journal: Appl Environ Microbiol Date: 2012-07-06 Impact factor: 4.792
Authors: Jeff Fabrick; Cris Oppert; Marcé D Lorenzen; Kaley Morris; Brenda Oppert; Juan Luis Jurat-Fuentes Journal: J Biol Chem Date: 2009-05-05 Impact factor: 5.157