Feeding Behaviour of Helicoverpa armigera (Hübner) and Spodoptera litura Fabricius on Bollgard II Bt Cotton

The feeding preference of cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) and leaf eating caterpillar Spodoptera, litura Fabricius (Lepidoptera: Noctuidae) on Bt and non Bt cotton hybrids was studied under laboratory conditions at the Department of Agricultural Entomology, TNAU, Coimbatore. The third instar larvae were allowed to feed on different parts (leaf, squares, flowers and young bolls) of transgenic Bt and non Bt cotton hybrids separately by choice method. Among the different parts of Bt cotton, H. armigera larvae exhibited greater preference towards flower (41.67%) followed by squares (33.33%), bolls (15.00%) and leaves (10.00%) at 24 hr after release, whereas in non Bt cotton, the larvae preferred squares (35.00%) as well as flowers (33.33%) followed by bolls (16.67%) and leaves (15.00%). S. litura larvae showed more preference towards Bt cotton flowers (48.33%) followed by squares (25.00%), leaves (15.00%) and bolls (11.67%) whereas in non Bt cotton, the larval preference was more on flower (38.33%) as well as leaves (35.00%). It can inferred that, both insects exhibited significantly greater preference towards flower than other plant parts, irrespective of the Bt and non Bt cotton hybrids.