INSECTICIDE USE PATTERN, POSTHARVEST PROCESSING AND MONITORING OF RESIDUES ON CASHEW NUT

Abstract

A survey was conducted on insecticide use pattern adopted in cashew cultivation by selecting 30 progressive farmers in each of Cuddalore, Pudukottai and Perambalur districts of Tamil Nadu. The information on insecticides used, application interval and knowledge on compatibility of insecticides and number of application of insecticides were collected and expressed in percentage. The survey indicated endosulfan, monocrotophos, cypermethrin, lamdacyhalothrin and fenvalerate as the common insecticides. On the whole cashew farmers were found to have apparent knowledge on the quantity of insecticide/dosage (55.6%) and spray fluid requirement (32.2%) when compared to other details of insecticide usage like name of the pesticide, compatibility and spray interval. Among these monocrotophos, endosulfan and lambdacyhalothrin were selected for monitoring studies. The cashew nut samples were collected for three months at 20 samples/month from processing unit and multi-residue analysis was performed. None of the samples collected had detectable level of residues. A laboratory study was conducted on the impact of commonly followed processing steps on resulting residues of monocrotophos (720 ppm), endosulfan (700 ppm) and lamdacyhalothrin (50 ppm) on cashew nut. The initial deposit detected after an hour of treatment was 36.16, 67.79 and 31.39 mg/kg. The shelling process has resulted in 93.58, 96.2 and 97.13% reduction of initial deposit and the residues were found to be 2.32, 2.63 and 0.90 mg/kg, respectively. The insecticide residues reached below detectable limit (BDL) after roasting of the nuts and removal of testa layer.