The Clarion- International Multidisciplinary Journal

Imidacloprid one of the major components of many widely used insecticides and is relatively persistent in soils. Earthworms are used as indicator species for ecotoxicological evaluation and risk assessment. The effect of Imidacloprid on mortality of a dominant crop field earthworm (Drawida willsi, Michaelsen) was studied under ideal laboratory conditions to rice field soil. Soil and earthworm were collected from a non-irrigated paddy field by hand sorting method. Different concentration of Imidacloprid are prepared in dilution with acetone and sprayed on the soil surface. Five replicate for each concentration of the pesticides were prepared. Earthworm, D. willsi was added to each replicates and 96 h LC₅₀ value of the earthworm were calculated by probit analysis. It was found that the 96 h LC₅₀ value for with their 95% confidence limit of juvenile, immature and adult earthworm was 4.43, 7.96 and 12.45 mg a.i. Imidacloprid/kg dry soil respectively. Although the recommended dose of Imidacloprid was lower the 96 h LC₅₀ values of D. willsi for Imidacloprid, but still it could affect the soil biota by altering its vital rates and metabolism.