Residues and residual toxicity of ethyl parathion and methyl parathion on cauliflower
Attri, B.S.; Lal, R.
Indian Journal of Agricultural Sciences 44(6): 361-365
An investigation was carried out on the residues and residual toxicity of ethyl and methyl parathion on cauliflower (Brassica oleracea var. botrytis). The insecticides were sprayed on the crop 15 days before harvest during Jan.-Feb. 1971 (average temperature 15.degree. C) at 0.325 kg and 0.520 kg ai [active ingredient]/ha. Estimates of the residues by bioassay and chemical assay showed highly significant coefficient of correlation. Ethyl parathion applied at 0.325 kg/ha left residues below the tolerance limit of 1 ppm (FDA of USDA [Food and Drug Administration of USA Department of Agriculture]) after about 6 days on curds and 9 days on leaves, whereas it required about 8 and 11 days, respectively, to reach the tolerance limit when applied at 0.520 kg/ha. Methyl parathion showed less persistence when applied at 0.325 kg/ha, and a period of 4 days on curds and 7 days on leaves was required to degrade to the tolerance limit of 1 ppm; when the dosage was 0.520 kg/ha, the tolerance limit was reached in 7 and 8 days, respectively. The residual toxicity of ethyl parathion to Brevicoryne brassicae and Bagrada cruciferarum with the lower dosage was about 8-10 days, and that of methyl parathion 6-7 days. Nearly 1-1.4 ppm of either insecticide was essential on the plant surface to cause 20% mortality of the pests.