Bio-efficacy of Calotropis gigantea plant extracts against H. armigera

The present investigation entitled "Studies on the bio-efficacy of Calotropis gigantea R. Br. Plant extracts against gram pod borer, Helicoverpa armigera (Hubner) (Noctuidae : Lepidoptera)" was carried out during 2005-2007 in the Department of Entomology, Faculty of Agriculture, Annamalai University, Annamalainagar. Some of the important findings made out of the study are presented here under. Among five aqueous extracts of C. gigantea viz., leaf, flower, stem, root and whole plant tested on the eggs of H. armigera, the leaf extract at 10 per cent concentration was found to be very effective causing a maximum of 90.00 per cent inhibition of egg hatching when tested on the 24-48 hrs old eggs. The eggs of 48-72 hrs eggs were less susceptible even when treated with higher dose. When extracted with solvent, leaf extract showed the maximum inhibition (100.00%) of egg hatchability while flower extract recorded 90.00 per cent inhibition in 24-48 hrs eggs at higher concentration of 10 per cent. As the age of the egg increased the effectiveness of the extract got reduced. Aqueous leaf extract caused the maximum mortality (83.33%) of second instar.Other extracts showed low mortality percent.