Investigation on chemistry and residual fate of some synthetic and botanical pesticides

Abstract

Sugarcane cultivation is one of the most important agricultural activities in India for production of alcohol, sugar and derived foods. Insect infestation in sugarcane crops in the world is a serious problem. In India 292 pesticides are registered for use in agriculture (CIBRC, 2020). For Sugarcane crop 10 insecticides and 8 herbicides are registered for use in India. Fipronil insecticide is widely used as foliar applications in a number of crops including sugarcane. To understand the dissipation of fipronil residues in sugarcane (variety: CO 1148), a field experiment was conducted in Nadia, West Bengal following thrice application of Fipronil 5% SC at 100 g (T1) and 200 g (T2) a.i./ha along with untreated control (T3). Residue analysis of fipronil in sugarcane (juice, cane, baggase, leaf and soil) was conducted using GC-ECD and GC-MS/MS detector at 5 and#956;g/kg (LOQ). The recovery of fipronil and its metabolite from fortified sugarcane sample was obtained in the range of 80.7 to 98.5% (for juice, bagasse, cane and leaf) and for soil it was 81.9 to 86.2% at LOQ and upper two levels of LOQ (10 and 100 and#956;g/kg). newlineThe initial residues of fipronil were found to be 293 and#956;g/kg to 789 and#956;g/kg in sugarcane and 127-223 and#956;g/kg in soil. Total fipronil was dissipated by 10.4 to 21.9% in sugarcane and 9.9% to 10.2% in cropped soil at 1 day after application (DAA) following 1st order reaction kinetics. Fipronil dissipated with half-life (T1/2) of 2.8-4.3 days while for total fipronil (with metabolites) it was 3.7-6.0 days. Estimated pre-harvest intervals (PHI) for fipronil were 20.3-27.0 days in sugarcane plant while for total fipronil the corresponding values were 28.2-37.8 days. No dietary risk was observed due to fipronil (RQd lt 1) 5 DAA. Potential risk exists towards algae and soil macro-organism (RQs gt 1), but for earthworms it was safe (RQs lt 1).