| Fenpropathrin is one of the most frequently-used pyrethroid insecticides in the market and has the advantage of low toxicity,high efficiency as well as non-volatile,can prevent pests and mites in a variety of crops,especially when pests occurs or exists concurrently with mites,it produces better control effects.However,in recent years,the resistance of fenpropathrin development rapidly and resistance management must be imperative.As a novel acaricide,cyflumetofen shows excellent efficacy for the control of spider mites and there was no positive cross resistance with the existing ones,but its cost is high.Long-term adoption of one kind of pesticide not only causes the pest resistance but also causes the issues of environmental safety and food safety when used in massive quantities.In this study,Pesticide mixtures can expand controlling spectrum,decrease pesticide dosage and the cost of production,and prolong the service life of insecticides.To a certain extent,nano-emulsion with low energy consumption and good stability can be developed.The effective components of the pesticide can produce biological effects better by pesticide formulation.Therefore,this paper focuses on the following aspects of fenpropathrin,cyflumetofen.the main research methods and results are as follows:1 The screening of fenpropathrin and cyflumetofen optimum ratioToxicities of fenpropathrin and cyflumetofen（two types of insecticide and acaricide）to Tetranychus cinnabarinus were determined by residual contact vial method.And the result showed that the LC50 value of T.cinnabarinus was 711.62 mg·L-1 and 4.32 mg·L-1 respectively.Co-toxicity factor was used to evaluate the formulation synergism and cotoxicity coefficient method was adopted to screen the optimum ratio of pesticides,thus a mathematical model equation was fitted by using the method of optimum ratio and cotoxicity coefficient.Co-toxicity factors method showed that fenpropathrin and cyflumetofen complex had a synergistic effect.Results of the experiment showed that synergism was observed when the ratio of fenpropathrin to cyflumetofen was in range of 18﹕1 to 165﹕1.The synergetic ratio range of fenpropathrin to cyflumetofen is larger and it seems that this pesticide mixtures is feasible.Cotoxicity coefficient method showed the better synergistic interval of fenpropathrin﹕cyflumetofen was 30﹕1 to 50﹕1,cotoxicity coefficients was up to 192.79 to 209.96.The ratio mathematical model of fenpropathrin﹕cyflumetofen is Y=-216.86X2+19201X-424807,R2=0.864,the optimum ratio in theory is 39﹕1,CTC=211.91.Through further cotoxicity coefficient and fitting equation analysis,it showed that toxicity regression equation is y=0.66x+3.8,r=0.9757,LC50=60.96 mg·L-1,the CTC value is 215.36 as the ratio of fenpropathrin to cyflumetofen was 39﹕1.Finally,this ratio of fenpropathrin to cyflumetofen（39﹕1）was selected as the optimum ratio for preparing nano-emulsion.2 Preparation of 8% fenpropathrin·cyflumetofen nano-emulsionAccording to the specific proportion of fenpropathrin and cyflumetofen and their physical and chemical properties,nano-emulsion was formulated through optimization of solvent,emulsifier and water quality,research was made on the preparation of 8% fenpropathrin·cyflumetofen nano-emulsion,and the satisfactory formulation as follows: Fenpropathrin 7.8%（Mass fraction,the same as follows）Cyflumetofen 0.2% Solvent Dosage of solvent 150# solvent naphtha and xylene（4﹕1）10% Emulsifier Dosage of emulsifier Antifreezing agent Calciumalkylaromaticsulfonate and polyoxyethylene aliphatate（2:3）10% 2% Propanetriol Water add to 100% The 8% fenpropathrin·cyflumetofen nano-emulsion was processed by low-energy emulsification method in the laboratory.3 The quality test of 8% fenpropathrin·cyflumetofen nano-emulsionAccording to the characteristics and the FAO standards of nano-emulsion,the quality control indexes of 8% fenpropathrin·cyflumetofen nano-emulsion was developed as follows: Appearance yellow transparent miscible liquids Fenpropathrin ≥0.78% Cyflumetofen ≥0.02% Particle size scope（nm）D（0-50）≈20-500,qualified p H value 4.86-6.13 Residue remaining after dumping（%）2.95%<5%,qualified Residue remaining after washing（%）0.41%<0.5%,qualified Emulsion stability（diluted 200 times）qualified Ageing stability qualified Cold storage stability qualified Thermal storage stability qualified Transparent temperature（℃）0-45,qualified Latherability（1 min）5 m L<15 m L,qualified The experiment of contact angle showed that the 8% fenpropathrin·cyflumetofen nano-emulsion had the smaller contact angle and the 1arger adhesion work which was conducive to the absorption of plant leaves to liquid medicine and thus improve efficacy.4 The field efficacy of 8% fenpropathrin·cyflumetofen nano-emulsionfenpropathrin·cyflumetofen nano-emulsion to Panonchus citri and T.cinnabarinus was conducted in this study.The results showed that 8% fenpropathrin·cyflumetofen nanoemulsion has good control effect on both Panonchus citri and T.cinnabarinus,the sample delt with 40 to 60 mg·L-1 dose had a similar or better control effects of Panonchus citri and T.cinnabarinus than 20% fenpropathrin EC and 20% cyflumetofen SC,but the dosage of sample is obviously smaller than the control agent when they have a similar effect on mites.The nano-emulsion can decrease pesticide dosage and the cost of production,and it generates promising application prospects. |
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