Susceptibility Changes in Helicoverpa Armigera (Hübner) (Lepidoptera: Noctuidae) to Bacillus Thuringiensis Cry1Ac Toxin Gonam Suneel Kumar V.1,*, Budime Ram Prasad2 Maharashtra Hybrid Seeds Company Ltd., Hyderabad, Telengana 1Present address: Acharya N. G. Ranga Agricultural University, Agricultural Research Station, Darsi, Prakasam District, Andhra Pradesh. 2Acharya N. G. Ranga Agricultural University, District Agricultural Advisory and Transfer of Technology Centre, Warangal, Andhra Pradesh *E-mail: suneelkumar.gonam@gmail.com
Online published on 15 March, 2016. Abstract The susceptibility of Helicoverpa armigera to the Cry1Ac was monitored during three seasons. The LC50 and LC90 values ranged from 0.018 to 0.040 and 0.344 to 0.462 μg per ml in 2005–06; 0.012 to 0.154 and 0.345 to 1.673 μg per ml in 2006–07; 0.016 to 0.112 and 0.159 to 0.711 ìg Cry1Ac per ml of diet in 2007–08, respectively. Similarly, the IC50 values ranged from 0.001 to 0.004; 0.002 to 0.005 and 0.003 to 0.009 Mg per ml; IC90 values ranged from 0.007 to 0.017; 0.008 to 0.017 and 0.017 to 0.038 μg per ml in 2005–06, 2006–07 and 2007–08, respectively. The EC50 ranges were 0.0002 to 0.001; 0.0001 to 0.0017, 0.0004 to 0.0016 μg per ml and the range of EC90 values were 0.0013 to 0.0044; 0.0017 to 0.01 and 0.003 to 0.01 μg of Cry1Ac per ml in 2005–06, 2006–07 and 2007–08, respectively. The overall variability in susceptibility level indicated by larval mortality was to an extent of 2.2, 13 and 7-fold to Cry1Ac, respectively in 2005–06, 2006–07 and 2007–08 populations compared to baseline estimates of 5 and 5.5fold in 1999 and 2001 cropping seasons. Top Keywords Cry1Ac, Bt cotton, monitoring, Helicoverpa armigera, larval mortality. Top |