Two Location Study on Dissipation of Monocrotophos Residues in Castor (Ricinus communis)

Dissipation of monocrotophos applied @157.32 and 314.64 g a.i. ha⁻¹ on castor (Ricinus communis) leaves and its subsequent levels in castor seed, oil, cake and soil at two different locations at Anand and Thasara in Gujarat, is reported. Initial deposits of monocrotophos at Anand were 24.4 and 40.3mg kg⁻¹ the at the standard and double its dose of application, respectively on castor leaves. The corresponding levels in leaves collected from Thasara were 38 and 50.2mg kg⁻¹. The degradation pattern was similar at both the locations. The insecticide persisted till 15^th day, reaching 2.0 and 8.9 mg kg⁻¹in the samples collected from Thasara and 0.78 and 2.6 mg kg⁻¹ in samples collected from Anand. At harvest (82-day after the last spray) the levels reached below determination limit (BDL) of 0.05 mg kg⁻¹ (limit of quantitation-LOQ) in castor seeds, cake, oil and soil samples collected from both the locations. Hence, monocrotophos can be used on castor taking care of proper waiting period. The decline pattern of the residues at either dose was monophasic and followed 1^st order kinetics. The half life values for residues in leaves were 3.86 and 6.05 days at Thasara and 3.2 and 3.5 days at Anand for the two doses, respectively.