乐果在茶叶中残留降解动态的研究

本文是介绍有机磷农药乐果及其主要代谢物氧乐果在茶树上的残留降解动态。根据实验结果,在自然条件下,乐果在茶树芽梢上的降解速度中等。喷施800倍和1600倍药液后,芽梢中的乐果含量10天后可降至<0.5ppm和<0.05ppm。干茶中的乐果含量5天后降至<1.0ppm以至0.7ppm,9天后降至<0.1ppm。在喷施乐果的茶树芽梢上可检出其氧化物一氧乐果。喷药后3—5天达最高值,以后渐降,6—9天后即降至

STUDIES ON THE DEGRADATION OF DIMETHOATE IN TEA SHOOTS

Dimethoate has been widely used for the control of tea pests such as jassids,aphids and thrips etc.The present paper deals with the studies on the degradation of dimethoate and dimethoxon in tea shoots.Acording to the results of experiment,it is concluded that under the natural field conditions,dimethoate degrades moderately on the fresh tea-shoots.After the spraying of 40% dimethoate EC at dilution of 1:800 and 1:1600,it decreases to less than 0.5 ppm and less than 0.05 ppm respectively after 10 days.The residue of dimethoate in the made green tea decreases to less than 1.0 ppm and 0.7 ppm respectively 5 days after the application,and decreases to less than 0.1 ppmafter 9 days.Results indicate that the P=0 analoga(dimethoxon)canbe detected in the tea shoots which sprayed with dimethoate.Thereare less than 0.1 ppm to 0.27 ppm initially and increases graduallyand reaches the maximum at the 3-5 days after application then decrea-ses to less than 1 ppm about 6-9 days.The residue of dimethoxon in themade green tea reaches the maximum of about 1 ppm at the 3rd daysafter application and decreases to less than 0.1 ppm at 6th-9th days.The extraction percentage of dimethoate residue in the made tea withthe infusion procedure is relatively high about 41.4%.According to the results of investigation,the authors recommen-ded that the tolerance residue limits in the made tea may be establishedas 1 ppm(expressed as the sum of dimethoate and dimethoxon).According to this,the residue of dimethoate and dimethoxon in the mad etea which manufactured by the teashoots sprayed with 40% dimethoat EC at a dilute of 800 and 1600 may be decreases to less than 1 ppm after 7 days and 5 days after the application.However,owing to the tiants of dimethoate to the made tea,so that the authers recommended that the safety intervals should be delayed to 7 days(40% EC 2000 dilute solution)and 10 days(40% EC 1000 dilute solution).