Preliminary Studies On Combination Of Reduced Chemical Pesticides For Controlling Rice Insect Pests

Field experiments in three sites in Zhejiang province were carried out for evaluation of efficacy and economic efficiency of formulation and dosage of pymetrozine in controlling rice planthoppers, by economic threshold model-based simple judgment rule of chemical control. In Haiyan county trial, water dispersal granule (WG) of pymetrozine was as effective as suspension emulsion (SE) in same rate of75g a.i./hm2in controlling the small brown planthopper Laodelphax striatellus in rice panicle. In Linhai county trial,50%pymetrozine WG in rates of75g a.i./hm2and112.5g a.i./hm2had efficacies of60～97%from1to21days after treatment (DAT) for controlling SBPH and the white-backed planthopper Sogatella furcifera in mid-season of rice growing. In Jinhua trial, same sates of50%pymetrozine WG obtained the efficacies of77%～98%for the brown planthopper Nilaparvata lugens from4to21DAT. The trends of control efficacies for the three species planthoppers in the two experimental sites were similar and could be well-fitted by Logistic models against DAT and reached the final maximum value of98%, suggesting both the rates of the WG formulation of pymetrozine have fast and sustainable controlling effect for at least21days. The economic threshold model-based simple judgment rule of chemical control indicated that50%pymetrozine WG in a rate of75g a.i./hm2is the optimal selection in control of the three species of rice planthoppers in both japonica rice and indica hybrid rice.The combined application of pesticides in the overview of crop seasonal progfile indicated that such pest monitoring-based combinations reduced numbers of application and amount total pesticides, increased the efficacies and efficientcies and saved the total cost and raised the final income.The main principles, objectives and technical packages in the frame of ecological engineering for rice pest management were emphased.