Effects of Different Pesticides,Application Rate and Dosage Used Before and After Rice Heading on Pesticide's Residue in Rice

The variety of pesticide,the date and dosage and frequency of employing pesticides were connected with the security of rice grain.Among the pesticides for experiments,besides dichlorovos,others were all detected in the rice grain and the pesticicde residues of triazophos were the most,that of acephate and methamidophos were next and that of chlorpyrifos was the least.When pesticides were employed two times in the period before heading,residues of methamidophos and triazophos were beyond the national standard of maximum residue limit in food and when three times,that of chlopyrfos was equivalent to the national standard and that of acephate didn't meet the national standard.The dosage of above-mentioned pesticides doubled with a residues increase of 30%-50%and besides chlorpyrifos,other were all beyond the national standard after they were employed two times.When pesticides were employed in the period after heading,pesticide residues rose remarkably.The residues of methamidophos,triazophos and chlorpyrifos were beyond the national standard except acephate when they were employed two times at the normal dosage and all of them were beyond the national standard when the dosage doubled.The residues of imidacloprid,one kind of neonicotinoid pesticide,were all below the maximum residue limit in food whenever it was employed in the period before or after heading.The pesticide residues in rice grain were connected with the storage life.The rice which had been stored for 90 days all met the national standard.The authors considered that it was very important in the production of innocuous rice to reduce the using frequency and dosage of pesticides and employ high-effective,safe and less-residual pesticides.