Residues of Spirotetramat and Imidacloprid in Brinjal (Solanum melongena L.) and their Risk Assessment

Persistence of spirotetramat and imidacloprid on brinjal following three applications at 7 days interval of a combination formulation, spirotetramat 12% + imidacloprid 12%, starting first application at fruit initiation stage @ 625 and 1250 mL ha⁻¹ is reported. Average initial deposits of spirotetramat on brinjal fruits were 0.80 and 1.16 mg kg⁻¹ from treatments at single and double dose, respectively. The residues of spirotetramat dissipated with half-life of 1.09 and 1.36 days and reached below its determination limit of 0.03 mg kg⁻¹ after 5 and 7 days, respectively. Average initial deposits of imidacloprid on brinjal fruits were 0.72 and 1.92 mg kg⁻¹ with half-life of 1.39 and 1.25 days, respectively. The residues dissipated below its limit of quantification of 0.01 mg kg⁻¹ after 7 and 10 days, respectively, for the two doses. Acceptable daily intakes of spirotetramat and imidacloprid are 0.05 and 0.06 mg kg⁻¹ body weight day⁻¹, implying that an adult of 55 kg weight can safely tolerate an intake of 2750 and 3300 μg of the two insecticides, respectively. Assuming an average consumption of 80 g brinjal fruit and multiplying it by average residues observed on 0 day both at recommended and double the recommended dosage, the intake of spirotetramat works out to be about 64 and 92.8 μg, respectively, and these values are quite safe in comparison to its ADI. Similarly, intake of imidacloprid was quite low when compared to its ADI.