Helicoverpa armigera (Hubner) Associated Cross Resistance Patterns in South Indian Crop Ecosystem

Aim: To study the cross resistance patterns associated with Mahaboobnagar, Raichur, Nagpur populations of Helicoverpa armigera (Hubner). Study design: Bioassay Place and Duration of Study: The experiment was carried out from February 2010 to May 2011 at Department of Entomology, College of Agriculture, Rajendranagar, Hyderabad, Telangana. Methodology: Helicoverpa armigera was selected for indoxacarb in F1 and F2 continuously then the population subjected to different selected insecticides to know the cross resistance patterns associated. Results: Mahaboobnagar population recorded 1.109 and 0.816 fold resistance at LD50 and LD90, respectively, while Raichur population has developed still higher levels of relative resistance by 1.591 and 0.846 fold when compared with the Nagpur population at LD50 and LD90, respectively. Similarly, the Raichur population has developed 1.435 and 1.037 folds relative resistance at LD50­ and LD90, respectively as compared with the Mahaboobnagar population. The Mahaboobnagar population resistant to indoxacarb at F3, when subjected to selected insecticides like cypermethrin, methomyl, spinosad showed a negative cross resistance ratio of 0.665, 0.830, 0.916 to cypermethrin, methomyl, spinosad respectively, and a positive cross resistance ratio of 1.019 to indoxacarb, while similar trend was displayed by Raichur population showing a negative cross resistance ratio of 0.932, 0.565, 0.803 to cypermethrin, methomyl, spinosad respectively and positive cross resistance of 1.036 indoxacarb further, same trend was shown by Nagpur population by displaying a negative cross resistance ratio of 0.610, 0.735, 0.519 to cypermethrin, methomyl, spinosad and positive cross resistance ratio of 1.026 to indoxacarb. Conclusion: Continuous application of single insecticide belonging to a specific group across the generations increases the resistance from F1 to F3. Alternating the new chemistries with old conventional chemicals resulted in no cross resistance development as it was observed in all test populations.