Insecticide susceptibility studies of Fenthion and temephos (Organophosphate) in thirty strains of Anopheles stephensi - Liston, a malaria mosquito

The baseline susceptibility studies were carried out in thirty strains of laboratory maintained strains of Anopheles stephensi Liston, one of the important malaria vectors in the Indian subcontinent. The studies were carried out by taldng late third instar larvae for two organophosphate insecticides i.e, Fenthion and Temephos by applying standard larval test procedure of World Health Organization. The data dearly showed that the lowest LC50 value of 0.00063 mg/l was observed in Papareddypalya (PRP) strain, whereas highest LC50 value of 0.0145 mg/l was recorded in Mangalore (MNG) strain for Fenthion. Similarly the lowest LC50 value of 0.0004 mg/l was observed in Jnanabharathi Campus (JBC) strain and the highest LC50 value of 0.0088 mg/l was recorded in Shimoga (SHM) Strain for Temephos. The resistance ratio of LC50 ranges between 1.00 - 22.94 and 1.00 - 22.00 for Fenthion and Temephos respectively. The value of LC50, LC50 regression equation correlation of coefficient χ2 and resistance ratio of insecticides on each strains were calculated and presented