Distribution Of Dinotefuran In Rice Field And Its Efficacy On Chilo Suppressalis

Stem borer(Chilo Suppressalis)is one of the important pests which damage rice growth.Dinotefuran is a new type of neonicotinoid insecticide with high efficient,broad-spectrum and low toxicity,which is currently used mainly for controlling rice planthopper.To clarify the distribution characteristics of dinotefuran in the paddy field and its efficacy on stem borer,an analytical method using high performance liquid chromatograph(HPLC)was established for determination of dinotefuran residues in the paddy field,and the distribution characteristics of five formulations of dinotefuran in the paddy field of Jiangxi were determined,and its efficacy on stem borer was evaluated after the photodegradation of five formulations of dinotefuran in different water environment were tested.The result could provide reference for reasonable application of different formulations of dinotefuran in the paddy field.The results were as follows:1.The photodegradation characteristics of dinotefuran were measured under UV lamp.The results indicated that photodegradation rates of dinotefuran were positively correlated with the initial concentration.When the initial concentrations of dinotefuran were 5,10 and20 mg?L-1,its half-lives were 11.36,13.28 and 18.89 h,respectively.The pH value had a great effect on the photodegratation of dinotefuran.When pH values were 4,7 and 10,the half-lives of dinotefuran were 10.83,12.06 and 11.53 d,respectively.There were a significant difference among photodegradation rates of the five formulations of dinotefuran,which were in sequence of SC>SG>WG>GR>WP.The hardness of water had little effect on the photodegradation of dinotefuran.The NO3-and NO2-had the promoting effect on the photodegradation of dinotefuran.When the concentration of NO3-and NO2-reached 20mg?L-1,promoting photodegradation rates of dinotefuran were 16.84% and 30.04%,respectively.The effects of Fe3+ and Fe2+ on the photodegratition of dinotefuran were positively correlated with its concentrations.The photodegratition rate of dinotefuran were144.79% when the concentration of Fe3+ reached 20 mg L-1.2.A method for the determination of dinotefuran residues in the paddy field was developed using high performance liquid chromatograph(HPLC).The average recovery rates of dinotefuran reached 89.1%-113.52% and 88.37%-121.92% at the fortifying concentrations of 0.5 and 2 mg?kg-1 in the paddy water and soil samples,respectively,and80.28% ~ 101.30%,76.60% ~ 100.04% and 80.68% ~ 92.10% at the fortifying concentrations of 0.5-5 mg?kg-1 in the rice husk,rice and rice plant samples,respectively.The average recovery rates at fortifying concentrations of 0.05-5 mg?kg-1 in differernt samples were from 76.60% to 121.92% with relative standard deviations of 0.75% ~11.22%.The results indicated that the mothod was simple and feasible,accord with thestandard of pesticide residue detection.3.The distribution characteristics of five formulations of dinotefuran in the paddy field were determined using HPLC method.The results showed that degradation dynamics of five formulations of dinotefuran in the paddy field accorded with the first-order kinetics equation,and its degradation trends in paddy water,soil and rice plants were similar.The degradation half-life of dinotefuran in the paddy water was 3.11-3.79 d with the original deposition amount of 0.2228-0.5622 mg?kg-1.The initial deposition amounts and half-lives of SC and GR were higher than that of the other three formulations.The degradation rate of SG was the fastest with degradation half-life of 3.35-4.60 d,and its degradation dynamic trend first increased and then decreased.The degradation half-life of SG in rice plants was 0.83-1.86 d,and its initial deposition amount was 0.6489-15.1810 mg?kg-1,larger than those in the paddy water and soil samples.The degradation rates of dinotefuran in the rice plants were consistent with those in the paddy soil,showed sequence of SG>SC> WG>WP >GR.The final residue test showed that the residues in rice and rice husk samples were 0.0421-0.1542 mg?kg-1 7 d after treatment,and 0.0100-0.1163 mg?kg-114 d after treatment,and lower than the maximum residue limit in rice(Japan).4.The efficacy of five formulations of dinotefuran on Chilo Suppressalis was tested in paddy field by method of foliar spray and granule application.The efficacy of dinotefuran applied during early tillering stage of rice and peak stage of eggs hatching on Chilo Suppressalis increased with using dose increased.The efficacy of 50% dinotefuran SG and 20% dinotefuran WG with the dosages of 90-150 g?ha-1 and 2% furosemide GR with the dosages of 150-180 g?ha-1 on Chilo Suppressalis of early and late rice was better than or equivalent to that of control insecticide 24% methoxyfenozide SC with the dosage of 90 g?ha-1.There was not significant difference between the effects of 25% dinotefuran WDG with the dosage of 150 g?ha-1 and that of control insecticide on protecting seedling of early rice and killing insect of late rice,and the efficacy of other treatments was significantly lower than that of control insecticide.The efficacy of 20% dinotefuran SC with the dosage of 90-150 g?ha-1 on Chilo Suppressalis of early and late rice was significantly lower than that of control insecticide.The efficacy of different formulations of dinotefuran on Chilo Suppressalis performed sequence of WG > SG > GR > WP ?SC under the same using dose.WG,SG and GR of dinotefuran with high dose are suitable for controlling Chilo Suppressalis.