Study On Residue Dynamics Of Dimethachlone In Lettuce And Soil

Lettuce, namely leaf lettuce, has various kinds of appicated species,whose production area has been greatly expanded in recent years in thesoutheast coast of China, especially in big cities, by comparing the suburbanarea. However, Sclerotinia is one of the common plant diseases in Lettuce,which case low yield or get no crop. Dimetachlone is a broad-spectrumfungicide, which has strong penetrability, long duration and so on. It iseffective to prevent Botrytis cinerea, Sclerotinia of tomato, cucumber,strawberry, grape. It can be used to substitute for Dicloran, Topsin,Carbendazim to prevent the pathogens for resistant of these pesticides. Inrecent years, Dimetachlone is widely used to prevent Sclerotinia in lettuce.The residue dynamic of Dimetachlone research report in lettuce and soil wasnot issued in the world.The study used field experiment and laboratory detection to get thecharacteristic on the residue dynamics of Dimetachlone in lettuce and soil. The result of the study can provided a scientific basis for the safe use ofDimetachlone in lettuce.1. It was studied a method to established by gas chromatography-electron capture detector (ECD) and GPC-GCMS to determine theDimetachlone residue in lettuce and soil, which minimum detectableconcentration was0.002mg/kg and0.01mg/kg;2. It was studied a pre-treatment combined with gas chromatography todetermine the Dimetachlone residue in lettuce and soil. The pre-treatmentcontained acetonitrile and acetone ultrasonic extraction, centrifugalstratification, Florisil column cleanup. The method recoveries ranging wasfrom96.0%to106.0%, the coefficient of variation was1.3%~2.8%;3. The half-life of Dimetachlone in lettuce and soil was6.2d,11.4d. Thedispel of7days after applied was86.8%,53.7, and28days after applied was96.7%,82.4%;4. The40%dimethachlone WP were applied with600,1200g/hm~2for3and4times in stage of lettuce initial transplantation, after21daysapplication, the residue of dimethachlone in lettuce and soil was below0.70mg/kg.5. According to NY/T788-2004, it was recommended that the safe usestandard of40%Dimetachlone W.P. in lettuce was application600g/hm2of recommended dose after planted, three times,7d of safety interval.