| The two-spotted spider mite,Tetranychus urticae Kochus is one of the most harmful mites in the world.The spider mites are easy to develop resistance to insecticides owing to their little size,fast reproduction,short generation and small range of activity.At present,the control of the two-spotted spider mite in agriculture is primarily depended on chemical methods,however,the irrational use of acaricides,led to the emergence of resistance to various acaricides,which caused its particularly resistant.The mites are widespread in foreign countries and becoming more and more serious in China.Based on this background,three different kinds of acaricides,bifenthrin,bifenazate and cyflumetofen were selected in this paper,the development of metabolic resistance of Tetranychus urticae Kochus and their risk assessment were studied in order to provide scientific basis for rational use of insecticides.The sensitivity of Tetranychus urticae Kochus to bifenthrin,bifenazate and cyflumetofen was determined by leaf immersion method.The results showed that the LC50of the three acaricides to female adult mites of Tetranychus urticae Kochus,larvae and eggs were as follows:the LC50 of bifenthrin were 202.03,264.46 and 6214.85 mg·L-1;the LC50of bifenazate were 24.75,18.55 and 90.33mg·L-1;the LC50 of cyflumetofen were 14.95,11.93 and 18.87 mg·L-1,and the LC50 of the three acaricides against the natural enemy were185.66,>12000 and 952.04 mg·L-1,respectively.The toxicity selection index of bifenthrin,bifenazateandcyflumetofentoTetranychusurticaeKochusandNeoseiulus barkeri?Hughes?were calculated as 0.92,>484.85 and 63.68,respectively.The result could be concluded that the most safe to the Neoseiulus barkeri?Hughes?was bifenazate,and bifenthrin was the most unsafe.Under indoor conditions,through pharmaceutical selected,the results showed that the resistance strains of Tetranychus urticae Kochus to bifenthrin was screened for 16successive generations.The LC50 of female adult mites and larvae of bifenthrin-strain were6321.31mg·L-1 and 5635.70 mg·L-1;The resistance ratio of them were 31.29 and 25.21times.The resistance strains of Tetranychus urticae Kochus to bifenazate was screened for12 successive generations,the LC50 of female adult mites and larvae of bifenazate-strain were 232.12 mg·L-1 and 123.27 mg·L-1;The resistance ratio of them were 9.38 and 6.65times.The resistance strains of Tetranychus urticae Kochus to cyflumetofen was screened for 12 successive generations,the LC50 of female adult mites and larvae cyflumetofen-strain were 86.88 mg·L-1 and 55.24 mg·L-1.The resistance ratio is 5.81 and4.63 times.Determination the cross resistance of screen populations,the results showed that the resistance index of bifenazate and cyflumetofen to the bifenthrin-resistance strains of Tetranychus urticae Kochus were 2.70 and 0.92,respectively;The resistance index of bifenthrin and cyflumetofen to the bifenazate-resistance strains of Tetranychus urticae Kochus were 4.74 and 0.85,respectively;The resistance index of bifenthrin and bifenazate to the cyflumetofen-resistance strains of Tetranychus urticae Kochus were 2.69 and 2.11,respectively.Therefore,there is no apparent cross resistance between of the three acaricides.The metabolic resistance of different strains was studied by using PBO,DEM and DEF as enzyme inhibitors.The result showed that the synergistic ratio of PBO to bifenthrin,bifenazate and cyflumetofen were 22.38,1.70 and 3.44,respectively;that of DEM to the three acaricides were 3.64,1.83 and 3.96;and for DEF,the synergistic ratio to bifenthrin and cyflumetofen were 5.05 and 2.42,however,DEF showed some antagonism instead of synergism.The synergistic effects of three synergists on resistant strains to Tetranychus urticae Kochus showed that the resistance of bifenthrin-resistant strains to bifenthrin was reduced by PBO,DEM,DEF.For the three synergists,PBO showed the best synergism,whose resistance ratio was reduced by 29.89.Synergism of the three synergists to bifenazate were not obvious,and the activity of bifenazate decreased with adding DEF.The three synergists showed different synergistic effect to cyflumetofen-resistant strains,and the synergism ratio was reduced by 3.44,3.96,2.42.The resistance realistic heritability of bifenthrin,bifenazate and cyflumetofen were0.25,0.22 and 0.14,respectively,which was calculated by domain trait analysis on the basis of the population of cultivated resistant strains.Combined with the realistic heritability results,the screening algebras for the rise of resistance to Tetranychus urticae Kochus increased by 5 and 10 times that predicted under the selection pressure of 50%to 90%.The results showed that the algebraic ranges for the resistance of Tetranychus urticae Kochus to bifenthrin,bifenazate and cyflumetofen increased to 5 times were 5.40-2.45,7.67-3.47 and15.67-7.10,respectively.The algebraic ranges for the resistance of Tetranychus urticae Kochus to bifenthrin,bifenazate and cyflumetofen increased to 10 times were 7.73-3.50,10.98-4.97 and 22.42-10.15,respectively.In addtion,the analysis of resistance reality heritability showed that the resistance of Tetranychus urticae Kochus to bifenthrin was higher than that of bifenazate and cyflumetofen,and whether the resistance increased by 5times or 10 times,among the three acaricides,bifenthrin required the least number of algebras and cyflumetofen required the most.The degradation and metabolism trend of bifenthrin,bifenazate and cyflumetofen in cowpea leaves were studied by gas chromatography,high performance liquid chromatograph and high performance liquid chromatography-mass spectrometry with cowpea as the experimental plant.The result showed that the residue of the three insecticides were highest at 2 h after the treatment;their content in cowpea leaves gradually decreased as time went on,and the degradation rates of bifenazate and cyflumetofen were both more than 90%after 14 days.In addtion,the half-life of bifenthrin,bifenazate and cyflumetofen were 4.43 d,1.31 d,1.37 d,respectively.It is speculated that there may be some correlation between the development of resistance and the degradation of acaricides. |
PDF Full Text Request