Persistence of Pyrethroid and Nicotiriyl Insecticides on Okra Fruits

Beta-cyfluthrin @ 12.5, 18.75, 25, 37.5 and 75 g a.i. ha⁻¹, lambda-cyhalothrin @ 37.5 g a i ha⁻¹ and imidacloprid @ 40 g a.i. ha⁻¹ were sprayed at the fruiting stage of the okra crop. In a separate experiment, okra seeds were treated with imidacloprid (Gaucho 600 FS) @ 3, 5.4, 10.8 and 21.6 g a.i. kg⁻¹ seeds and were sown. Residues of the insecticides from okra declined progressively with time and became non detectable on 7th d from beta-cyfluthrin and on 10th and 15th d from imidacloprid and lambda-cyhalothrin spray treatment, respectively. Residues of imidacloprid in okra fruits were found to be 0.08, 0.10, 0.14 and 0.24 mg kg⁻¹ from 3, 5.4, 10.8 and 21.6 g a.i. kg⁻¹ seed treatments, respectively, after 55 d of sowing (i.e. nearly 7–10 d after fruiting started) and became non-detectable after 60 d of sowing (ca 12–15 d after fruiting)