Persistence of Acephate and Cypermethrin on Cotton Leaves, Cottonseed, Lint and Soil

Abstract

Following foliar applications of combination formulation (cypermethrin 5% + acephate 45% DF) at 850 and 1,700 g ha⁻¹, resulting in active application of acephate at 382.5 and 765 g a.i. ha⁻¹ whereas active application of cypermethrin at 42.5 and 85 g a.i. ha⁻¹, the average initial deposits of acephate on cotton leaves were found to be 13.45 and 27.73 mg kg⁻¹, at single and double the doses of application, respectively. Residues of acephate declined below detectable level of 0.02 mg kg⁻¹ after 15 days of applications at application rates with t _½ values of 1.56 and 0.68 days, respectively. Similarly, the average initial deposits of cypermethrin were found to be 22.31 and 32.45 mg kg⁻¹, respectively. Cypermethrin residues reached below its detectable level of 0.02 mg kg⁻¹ after 21 days of its application at both the dosages of application. The half-life values for cypermethrin were observed to be 0.71 and 0.69 days, corresponding to single and double the dose of application, respectively. Interestingly, none of the samples of cottonseed, lint and soil showed presence of acephate or cypermethrin at the detection limit of 0.02 mg kg⁻¹ at first pick of the harvest time of the crop.