Differential susceptibility of field population of gram Podborer (Helicoverpa armigera) to insecticides in Tamil Nadu

Abstract

An experiment was conducted during 1990-91 to study the susceptibility of gram podborer [Helicoverpa armigera (llubner)] to 4 insectcides. Tbeir reaction to field populations of gram podborer from 3 areas in Tamil Nadu growing upland cotton (Gossypium hirsutun L) and gram (Cicer arielinum L.) was studied. The populations from field at Udumalpet, Andipatti and Coimbatore recorded higher LD_50M (10.6-31.24) to all the insecticides, followed by those from Andipatti and Coimbatore. Differences in LD₅₀ values within population were noticed for individual insecticides. The differential susceptibility of these field-collected population may be attributed to frequent application of insecticides, leading to the development of resistance.