Toxic effects of insecticides on the life table and development of Earias vittella (Lepidoptera: Noctuidae) on okra

Okra, Abelmoschus esculentus (L.) Moench, is an important vegetable crop grown throughout the tropical and temperate regions of the world. Spotted bollworm, Earias vittella (Fab.), is one of the most important insect pests of okra. The effects of insecticides (cypermethrin, imidacloprid, carbaryl and neem oil) were studied on the fitness of the F1 generation of E. vittella by a demographic method. Life table was constructed from the eggs obtained by the surviving individuals that had ingested insecticides. Survivorship and expectancy was highest with the commencement of age and gradually decreased with the progression of age in the treatment groups and control. However, it was reduced in the treatment groups in comparison to control groups. Highest numbers of unhatched eggs (17%) were recorded with imidacloprid and cypermethrin treatments, whereas all the eggs hatched in control groups. Larval mortality was high in the initial instars as compared to late instars. Potential fecundity was significantly reduced to 94 females/female/generation treated with cypermethrin as compared to 256 in the untreated females. Developmental time of pre-pupa and pupa was significantly decreased with cypermethrin treatment. The intrinsic rate of increase was reduced to 0.0201 females/female/day in cypermethrin groups as compared to 0.046 in the control groups. The generation time was 33.27 days in the control, which was reduced to 26.78 days with carbaryl treatment and was increased to 37.5 days with neem oil. Insecticides cause adverse effect on the surviving generation of E. vittella, and may be incorporated as a valuable component in the integrated management of E. vittella on okra.