Characterisation of Neonicotinoid and Pymetrozine Resistance in Strains of Bemisia tabaci(Hemiptera:Aleyrodidae)from China

Four strains of the Q biotype and one of the B biotype of the whitefly Bemisia tabaci collected from China were characterised for resistance to four neonicotinoid insecticides and pymetrozine.Q biotype strains showed moderate to strong resistance to imidacloprid,thiamethoxam and acetamiprid,but little or no cross-resistance to dinotefuron.Resistance to neonicotinoids was consistently associated with resistance to pymetrozine,despite the latter having a distinct（though unresolved）mode of action.The single B biotype strain proved largely susceptible to all the insecticides investigated.Resistance in the Q biotype strains was associated with over-expression of a cytochrome P450 monooxygenase gene,CYP6CM1,whose substrate specificity presumably accounts for the observed cross-resistance profiles.

Analysis of 80% Pymetrozine·Nitenpyram WG by HPLC

[Objective] The paper was to establish a HPLC method for quantitative determination of 80% pymetrozine·nitenpyram WG. [Method] With the mixture of acetonitrile, water and phosphate buffer （volume ratio 10：80：10） as the mobile phase, pymetrozine and nitenpyram in samples were separated by ODS-2 reversed phase column, and detected by UV detector at 250 nm. In addition, the results were quantified by external standard method. [Result] The linear correlation coefficients of pymetrozine and nitenpyram were 0.9995 and 0.9998; the standard deviations were 0.29 and 0.22; the coefficients of variation were 0.51% and 1.21%; and the average recoveries were 100.7% and 99.1%, respectively. [Conclusion] The method is fast and simple, and can effectively separate pymetrozine and nitenpyram, with high precision and accuracy and good linear relation.

Sublethal effects of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae on rapeseed, Brassica napus L.

Efficiency of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae L. （Homoptera： Aphididae） was determined using demographic toxicology by leaf dip method. At first, bioassay tests were performed. The LC50 value and confidence limit for imidacloprid and pymetrozine were 1.61 × 10^-5 mol/L （0.74 × 10^-5-2.66 × 10^-5） and 2.14 × 10^-4 mol/L （1.24 × 10^-4-3.40 × 10^-4）, respectively. To evaluate the sublethal effect of two insecticides on population growth parameters of cabbage aphid, LC30 concentrations of imidacloprid and pymetrozine were used at 5 mol/L and 30 mol/L. The experiments were carried out in a incubator at 20±1℃, 60% ± 5% RH and 16：8 （L：D） photoperiod on canola seedlings, Brassica napus L. var. ＇PF＇. Net fecundity rate decreased in both insecticide-treated populations. Intrinsic rates of increase （rm） were lower in imidacloprid and pymetrozine treatments than in controls. Intrinsic birth rates also decreased in treated populations. There was a relative increase in intrinsic death rates of treated populations. The mean generation times and doubling time were also lower in populations treated with insecticides than in controls. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different from those treated with imidacloprid and pymetrozine. However, there was no significant differences in aphid life-table parameters between the two insecticide-treated populations （P 〉 0.01）.

Sorption and desorption of pymetrozine on six Chinese soils

Pymetrozine is a selective insecticide with a unique chemical structure and mode to control hemipteran and homopteran. While pymetrozine has brought great benefits to crop production by killing insects, its residues in soil may have a detrimental effect on environment. Therefore, it is of great importance to investigate its behaviors in soil. In this study, the sorption and desorption of pymetrozine on six Chinese soils were investigated using a batch equilibrium approach to understand its mobile behavior in the soils. Both sorption and desorption isotherms ofpymetrozine were in good agreement with the Freundlich model. The sorption coefficient KF varied between 3.37 and 58.32 mL. g-1 and the sorption isotherms were nonlinear, with 1/n ranging from 0.57 to 0.91. A regression equation was proposed to predict the solption of pymetrozine on six different soil samples： log KF = 4.3708 - 4.5709 × log （pH in 0.01mol·L-1 CaC12） ＋ 0.4700 × log OC% ＋ 0.0057 × sand （%） ＋ 0.0022 × CEC（clay）, with R2 = 0.9982. The organic carbon content of soil positively affected the sorption ofpymetrozine, but soil pH had a negative effect on the sorption. Additionally, effects of CaC12 concentration, soil to solution ratio and pesticide form were investigated. The sorption was promoted with an increase in soil to solution ratio and a decrease in CaC12 concentration. The possible variation of the five formulated products of pymetrozine was also investigated.

Effects of a novel mesoionic insecticide,triflumezopyrim,on the feeding behavior of rice planthoppers,Nilaparvata lugens and Sogatella furcifera(Hemiptera:Delphacidae)

The rice planthoppers,Nilaparvata lugens and Sogatella furcifera,are important sap-sucking pests of rice in Asia.The mesoionic insecticide tifumezopyrim was previously shown to be highly effective in controlling both N.lugens and S.furcifera.In this study,electropenetrography(EPG)was used to evaluate the effect of three triflumezopyrim concentrations(LC。LC。and LC)on the feeding behavior of N.lugens and S.furcifera.EPG signals of planthoppes indicated that there were six different waveforms NP,N1,N2,N3,N4,and N5,which corresponded to non-penetration,stylet penetration into epidermis,salivation,extracellular movement of stylet,sap ingestion in phloem,and water ingestion in xylem during feeding.Compared to untreated controls,triflumezopyrim at LC。and LC。prolonged the duration of the non-penetration period by 105.3 to 333.7%.The probing frequencies of N.lugens exposed to tiflumezopyrim at LC1。and LCso were significantly increased;however,the probing frequencies of S.furcifera showed a significant decrease when exposed to triflumezopyrim at all concentrations.Triflumezopyrim exposure prolonged the duration of salivation and shortened the duration of extracellular movement.The duration of phloem sap ingestion decreased from 37.2 to 77.7%in the LCgo and LCgo treatments,respectively.Differences in feeding behavior in response to triflumezopyrim and pymetrozine were minimal.In summary,the results show that the LC。and LCgo concentrations of trflumezopyrim inhibit the feeding activities of N.lugens and S.furcifera mainly by prolonging the duration of non penetration and by shortening the duration of phloem sap ingestion,which may foster more efficient use of triflumezopyrim in Asia.

Occurrence and Chemical Control Techniques of Rice Black-streaked Dwarf Disease in Rongshui County

The chemical control technologies of southern rice black-streaked dwarf disease in hybrid rice were studied in Rongshui County,Guangxi,through a combination of investigation,observation and experiments.Three treatments were set up,namely,no water,shallow water and deep water,and each of which had a treatment area of 67 m^(2).Each treatment was sprayed once with 40 g of 200 million/g Bacillus subtilis wettable powder and 20-30 g of 25%pymetrozine wettable powder per 667 m^(2) in a mixture with 30 kg of water.On the day of spraying,100 diseased rice hills in each treatment were marked for field observation.The test results showed that the control of southern rice black-streaked dwarf disease should be done by draining the field water and spraying the mixture of B.subtilis and pymetrozine evenly,and a better effect can be achieved by keeping the field moist for 6-7 d after spraying.