Monitoring of insecticide resistance in Helicoverpa armigera (Hubner), from area receiving heavy insecticidal applications in Andhra Pradesh (India)

The diseriminating dose bioassay technique adopted at the Regional Agricultural Research Station, Lam farm, Guntur, Andhra Pradesh (India) for monitoring the insecticidal resistance in Helicoverpa armigera (Hubner) revealed that the mean percent survival of third instar larvae to cypermethrin (0.01 per cent) increased from 46.8 (1991–92) to 95.7 (1994–95). Moreover, at 10 times higher cypermethrin, i.e., 0.1 per cent dose, the survivals averaged 65 per cent during 1993–94 but fell slightly to 55 per cent during 1994–95. Even the plperonyl butoxide suppression was not significant at an average of only 12.0 per cent, indicating that suppression of cypermethrin resistance by PBO was either very low or non-existent. Probably, metabolic resistance mediated by mixed function oxidases was less significant in H. armigera population in this region of Andhra Pradesh. Further, resistance to endosufan (cyclodiene) and quinalphos (organophosphate) was also high with 46 and 45 per cent survival during 1994–95, respectively. This suggests that unrestricted and heavy usage of pesticides was creating conditions favourable for selection of complex multiple resistance mechanism in the Guntur zone of Andhra Pradesh in India.