酶抑制分光光度法检测蔬菜上有机磷和氨基甲酸酯类农药残留的方法的研究

为了缩短用于蔬菜上有机磷和氨基甲酸酯类农药残留检测的酶抑制分光光度法的检测时间对抑制时间为10分钟时的最适条件进行了研究。提出了新的最适条件确定标准,即保证酶的活性保持在一定的水平的基础上（0.1333 min-1 ≤k1 ≤0.2667min-1 [ 1 ]）,选择抑制率(以甲胺磷为抑制剂)最高时的温度和pH值作为最适条件。确定了抑制时间为10分钟时的最适条件为：抑制温度47.0℃,pH值为7.7。进而在此最适条件下确定了新的检测结果判断标准：当酶抑制率≥58％时,蔬菜中含有某种有机磷或氨基甲酸酯类农药残留为阳性。     

Synthesis and molluscicidal structure-activity relationships of some novel 1,2,4-triazole N-methyl carbamates

A new series of 1,2,4-triazole derivatives and their corresponding carbamates have been synthesized and screened for their molluscicidal activity against two types of terrestrial snail, Helix aspersa and Theba pisana, by two methods of application, either as contact or as bran baits. Several of the tested compounds exhibited good molluscicidal activity, and T pisana was more sensitive than H aspersa. Substitution at the o- and/or p-positions of the phenyl ring with chlorine or bromine gave higher molluscicidal activity than the unsubstituted compound, with o,p-dichloro substitution being optimum. In addition, compounds containing two triazole moieties showed higher molluscicidal activity, particularly as stomach poisons, than the contact toxic effect of the corresponding compound with one triazole ring. In general, carbamate derivatives were more active than their corresponding 1,2,4-triazole derivatives.     

Terbufos biodegradability and efficacy against Radopholus similis in soils from banana cultivation having different histories of nematicide use,and the effect of terbufos on plant growth of in vitro-propagated Musa AAA cv. Grande Naine

The aims of this investigation were to: (1) determine whether there is enhanced biodegradability of terbufos in soils of banana plantations infested with Radopholus similis; (2) whether nematicide use history affects the degree of biodegradation; and (3) establish whether terbufos has phytotoxic side-effects on banana root growth. A greenhouse bioassay, using soils collected from different banana fields in Costa Rica, revealed that terbufos underwent enhanced biodegradation in the soil of a plantation having a long history of terbufos use. In the soils of two other plantations, where terbufos had never been used, and in another where the most recent terbufos application had occurred over a year before soil collection, high nematicide activity against R. similis was obtained even 60 days after application. Our study demonstrated that terbufos efficacy lasted longer in soils with no or low history of terbufos than in soils that had been treated several times. Terbufos did not reduce root fresh weight of in vitro-propagated bananas, and its positive effect was related to a control of R. similis.     

Insecticide resistance in Egyptian populations of the cotton whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae)

Three collections of Bemisia tabaci were taken from cotton and vegetable crops at the beginning of the growing season in Egypt. These displayed marked resistance to the carbamates carbosulfan (ca 20- to 50-fold) and aldicarb (ca 40- to 80-fold) and moderate resistance to the pyrethroids cypermethrin (ca 10- to 30-fold) and lambda-cyhalothrin (ca 10- to 25-fold). They displayed no resistance to the organophosphates profenofos and pirimiphos-methyl, or to imidacloprid. Another population, collected at the end of the growing season, differed markedly in its response. In this population, resistance to carbosulfan remained high (ca 40-fold), resistance to profenofos and cypermethrin was increased (ca 20- and 50-fold respectively) and a slight resistance to imidacloprid was detected (ca 6-fold). Resistance to cypermethrin and profenofos was shown to be similar among adults and nymphs. Irrespective of collection date, none of the populations showed resistance to pyriproxyfen. These Egyptian populations were compared with two representative Israeli populations. The differences between their resistance profiles is discussed in terms of their collection date, their geographical proximity and the patterns of insecticide use at their sites of collection.     

Organophosphate insecticides and acaricides antagonise bifenazate toxicity through esterase inhibition in Tetranychus urticae

BACKGROUND: Bifenazate is a carbazate acaricide known for its potency, particularly against tetranychid mite species such as the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). It was recently shown that the compound needs to be activated by an S,S,S-tributyl-phosphorotrithioate (DEF)-sensitive mechanism in spider mites to display full acaricidal efficacy. The ability of well-known organophosphates and carbamates to inhibit the activation of bifenazate and thus compromise its acaricidal potential was tested.RESULTS: Esterase activity determined in vivo after pre-exposure of mites with organophosphates and carbamates revealed--depending on the compound--varying esterase inhibition nicely correlated with the ability of the individual compound to antagonise bifenazate action on mites.CONCLUSIONS: The findings illustrate that organophosphates and carbamates interfere with bifenazate efficacy, most probably by inhibiting carboxylesterases responsible for the activation of the pro-drug. As a result of the strong antagonism, mixtures of bifenazate with carbamates or organophosphates should not be used under field conditions. Moreover, there exists a real threat in repeatedly applying organophosphates and bifenazate. The present study again illustrates how important mode of action information is for the proper planning of resistance management strategies.     

QuEChERS-超高效液相色谱-QDa质谱法快速测定白菜与油菜中15种氨基甲酸酯类农药及代谢物残留

基于QuEChERS方法,采用乙腈提取目标物,采用新型净化装置多功能针式过滤器净化,以CORTECS? T3色谱柱 (3.0 mm × 150 mm, 2.7 μm) 进行液相分离,通过超高效液相色谱-QDa质谱 (UPLC-QDa MS) 单离子扫描模式进行快速测定分析,建立了白菜与油菜中15种氨基甲酸酯类农药及其代谢物残留的快速分析方法, 单个样品处理分析过程不超过30 min。结果表明:在0.001~0.1 mg/L范围内,白菜与油菜中15种氨基甲酸酯类农药及代谢物的质量浓度与对应的峰面积间线性关系良好 (r > 0.99) 。在0.01~0.2mg/kg添加水平下,回收率处于68%~120%之间,相对标准偏差均小于15% (n = 3) ,方法检出限范围 (LOD,S/N≥3) 为0.001~0.004 mg/kg,定量限 (LOQ,S/N≥10且回收率处于60%~120%之间) 处于0.005~0.01 mg/kg之间。该方法准确、快速、稳定,适合基层实际检测需要。     

Multiple Resistance in the Larger House Fly Musca domestica in Germany

Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37- to >10000-fold for organophosphates and 150- to >6600-fold for pyrethroids. The constituent enantiomer pairs of the α-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers II and IV had the best activity, with LD₅₀ values of 0·012 and 0·014 μg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum (‘Grimm’) in comparison to the susceptible strain (‘WHO-N’). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3·5-fold) and mixed-function oxidase (2·3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.