Effect of Cadmium on Biology of Tobacco Caterpillar Spodoptera litura Fabricius (Lepidoptera:Noctuidae)

The present study was conducted to investigate the impact of cadmium on biology of Spodoptera litura F. and its accumulation in three consecutive generations. The influence of Cd on fecudinty, fertility, incubation period, larval period, adult longevity and total development period was studied at seven different concentrations viz., 1, 5,10,15, 20, 30 and 40 mg/kg apart from control. Pure culture of S. litura from field collected adult was maintained under laboratory conditions on castor leaves. Fecundity and fertility was low in the highest dose of 40 mg/kg which decreased with generations. Incubation period prolonged with increasing cadmium concentration and generations. The variable doses of cadmium had significant influence on total larval period of the insect. Longest mean larval period of 23.39 days was recorded at 40 mg Cd/kg which differed statistically from its lower concentration. The duration of pupal period decreased with increasing Cd doses as well with generations. Thus, increased cadmium concentrations resulted in prolongation of total developmental period of the insect. Irrespective of generations, total developmental period was 33.97 days in the highest concentration (T₇) as compared to control (28.61 days). The accumulation of cadmium in the sixth instar larvae of S. litura increased with increase in dose of heavy metals in artificial diet and with increase in generations. The accumulation of cadmium in agroecosystem might influence the growth and development of S. litura through host plants to some extent.