噻虫胺等药剂对韭菜迟眼蕈蚊的致毒效应

为了明确新烟碱类药剂对韭菜迟眼蕈蚊的毒力,采用管测药膜法和药液定量滴加法测定了噻虫胺等6种药剂对韭菜迟眼蕈蚊不同虫态的毒力,并研究了噻虫胺、甲氨基阿维菌素苯甲酸盐和辛硫磷亚致死浓度对其4龄幼虫生长发育和繁殖的影响。结果表明,新烟碱类杀虫剂噻虫胺、吡虫啉和噻虫嗪对成虫的击倒毒力均较高,分别是阿维菌素的5.75、3.86和3.51倍;6种药剂对韭菜迟眼蕈蚊卵的毒力均较低;对2龄和4龄幼虫的毒力,均以噻虫胺最高,LC₅₀分别为0.339 mg/L和1.020 mg/L,分别是阿维菌素的27.00倍和25.23倍。用噻虫胺亚致死剂量处理韭菜迟眼蕈蚊4龄幼虫,其发育历期和蛹期延长,蛹重、化蛹率、成虫羽化率、单雌产卵量和卵孵化率均降低。     

Toxicities and sublethal effects of seven neonicotinoid insecticides on survival, growth and reproduction of imidacloprid-resistant cotton aphid, Aphis gossypii

BACKGROUND: Imidacloprid has been a major neonicotinoid insecticide for controlling Aphis gossypii (Glover) (Homoptera: Aphididae) and other piercing–sucking pests. However, the resistance to imidacloprid has been recorded in many target insects. At the same time, cross‐resistance of imidacloprid and other insecticides, especially neonicotinoid insecticides, has been detected. RESULTS: Results showed that the level of cross‐resistance was different between imidacloprid and tested neonicotinoid insecticides (no cross‐resistance: dinotefuran, thiamethoxam and clothianidin; a 3.68–5.79‐fold cross‐resistance: acetamiprid, nitenpyram and thiacloprid). In the study of sublethal effects, imidacloprid at LC₂₀ doses could suppress weight gain and honeydew excretion, but showed no significant effects on longevity and fecundity of the imidacloprid‐resistant cotton aphid, A. gossypii. However, other neonicotinoid insecticides showed significant adverse effects on biological characteristics (body weight, honeydew excretion, longevity and fecundity) in the order of dinotefuran > thiamethoxam and clothianidin > nitenpyram > thiacloprid and acetamiprid. CONCLUSION: The results indicated that dinotefuran is the most effective insecticide for use against imidacloprid‐resistant A. gossypii. To avoid further resistance development, the use of nitenpyram, acetamiprid and thiacloprid should be avoided on imidacloprid‐resistant populations of A. gossypii. Copyright © 2011 Society of Chemical Industry     

Comparative analysis of neonicotinoid binding to insect membranes: I. A structure-activity study of the mode of [3H]imidacloprid displacement in Myzus persicae and Aphis craccivora

Neonicotinoids bind selectively to insect nicotinic acetylcholine receptors with nanomolar affinity to act as potent insecticides. While the members of the neonicotinoid class have many structural features in common, it is not known whether they also share the same mode of binding to the target receptor. Previous competition studies with [3H]imidacloprid, the first commercialised neonicotinoid, indicated that thiamethoxam, representing a novel structural sub-class, may bind in a different way from that of other neonicotinoids. In the present work we analysed the mode of [3H]imidacloprid displacement by established neonicotinoids and newly synthesized analogues in the aphids Myzus persicae Sulzer and Aphis craccivora Koch. We found two classes of neonicotinoids with distinct modes of interference with [3H]imidacloprid, described as direct competitive inhibition and non-competitive inhibition, respectively. Competitive neonicotinoids were acetamiprid, nitenpyram, thiacloprid, clothianidin and nithiazine, whereas thiamethoxam and the N-methyl analogues of imidacloprid and clothianidin showed non-competitive inhibition. The chloropyridine or chlorothiazole heterocycles, the polar pharmacophore parts, such as nitroimino, cyanoimino and nitromethylene, and the cyclic or acyclic structure of the pharmacophore were not relevant for the mode of inhibition. Consensus structural features of the neonicotinoids were defined for the two mechanisms of interaction with [3H]imidacloprid binding. Furthermore, two sub-classes of non-competitive inhibitors can be discriminated on the basis of their Hill coefficients for imidacloprid displacement. We conclude from the present data that the direct competitors share the binding site with imidacloprid, whereas non-competitive compounds, like thiamethoxam, bind to a different site or in a different mode.     

新疆北疆马铃薯甲虫成虫对新烟碱类杀虫剂的敏感性变化

采用点滴法于2009和2010年监测了新疆维吾尔自治区北疆马铃薯甲虫Leptinotarsa decemlineata 9个田间种群成虫对新烟碱类杀虫剂吡虫啉、啶虫脒、噻虫嗪和噻虫啉的敏感性变化,发现其对吡虫啉和噻虫嗪的敏感性逐年降低。2009年监测的6个种群中有3个对啶虫脒和噻虫嗪低抗(抗性倍数5.0~10.0);2010年监测的6个种群全部对噻虫嗪产生了抗性,其中中抗(抗性倍数10.1~40.0)和低抗种群各3个。噻虫嗪与高效氯氟氰菊酯可能存在交互抗性。     

Effect of distribution and concentration of topically applied neonicotinoid insecticides in buffalograss,Buchloe dactyloides,leaf tissues on the differential mortality of Blissus occiduus under field conditions

BACKGROUND: Neonicotinoid insecticides are generally efficacious against many turfgrass pests, including several important phloem‐feeding insects. However, inconsistencies in control of western chinch bugs, Blissus occiduus, have been documented in field efficacy studies. This research investigated the efficacy of three neonicotinoid insecticides (clothianidin, imidacloprid and thiamethoxam) against B. occiduus in buffalograss under field conditions and detected statistically significant differences in B. occiduus numbers among treatments. A subsequent study documented the relative quantity and degradation rate of these insecticides in buffalograss systemic leaf tissues, using HPLC. RESULTS: Neonicotinoid insecticides initially provided significant reductions in B. occiduus numbers, but mortality diminished over the course of the field studies. Furthermore, while all three neonicotinoids were present in the assayed buffalograss leaf tissues, imidacloprid concentrations were significantly higher than those of clothianidin and thiamethoxam. Over the course of the 28 day study, thiamethoxam concentrations declined 700‐fold, whereas imidacloprid and clothianidin declined only 70‐fold and 60‐fold respectively. CONCLUSIONS: Field studies continued to verify inconsistencies in B. occiduus control with neonicotinoid insecticides. This is the first study to document the relative concentrations of topically applied neonicotinoid insecticides in buffalograss systemic leaf tissues. Copyright © 2012 Society of Chemical Industry     

Correlated responses to neonicotinoid insecticides in clones of the peach-potato aphid, Myzus persicae (Hemiptera: Aphididae)

BACKGROUND: Although there are still no confirmed reports of strong resistance to neonicotinoid insecticides in aphids, the peach-potato aphid (Myzus persicae Sulzer) shows variation in response, with some clones exhibiting up to tenfold resistance to imidacloprid. Five clones varying in response to imidacloprid were tested with four other neonicotinoid molecules to investigate the extent of cross-resistance.RESULTS: All four compounds-thiamethoxam, thiacloprid, clothianidin and dinotefuran-were cross-resisted, with ED(50) values ranked in the same order as for imidacloprid. Resistance factors ranged up to 11 for imidacloprid, 18 for thiamethoxam, 13 for thiacloprid, 100 for clothianidin and 6 for dinotefuran.CONCLUSION: This variation in response does not appear to be sufficient to compromise the field performance of neonicotinoids aimed at controlling aphids. However, it highlights the need for careful vigilance and stewardship in all M. persicae populations, and a need to consider neonicotinoids as a single cross-resisted group for management purposes.     

Responses of the cabbage seedpod weevil,Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidacloprid

BACKGROUND: The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new‐generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment. RESULTS: Mean numbers of second‐ and third‐instar larvae were significantly higher in plants seed‐treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new‐generation adults was reduced by 52 and 39% for plants seed‐treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane. CONCLUSION: Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola. Copyright © 2009 Society of Chemical Industry     

新烟碱类杀虫剂在韭菜中的内吸性及其对韭菜迟眼蕈蚊幼虫的毒力比较

通过药剂水培法,研究比较了不同培养条件对7种新烟碱类杀虫剂在韭菜中的内吸性及其对韭菜迟眼蕈蚊Bradysia odoriphaga(Diptera:Sciaridae)4龄幼虫的毒力。结果表明:随着水培时间的延长,韭菜中7种杀虫剂对供试幼虫的毒力均呈增强的趋势,其中在100 mg/L下,噻虫胺和吡虫啉产生毒力作用较快,水培72 h时对幼虫的致死率分别为32.38%和36.50%,168 h时,呋虫胺的致死率最高,达96.35%;同一药剂在相同浓度下处理,内吸至韭菜叶部产生的致死作用快于内吸至假茎所产生的作用,并且致死率更高;水培温度及药液浓度越高,内吸后毒力产生越快,且致死率越高。表明新烟碱类杀虫剂可以通过韭菜根部处理防治咀嚼式口器害虫韭菜迟眼蕈蚊。     

七种新烟碱类杀虫剂对韭菜迟眼蕈蚊幼虫及蚯蚓的选择毒力

为筛选出高效安全的韭蛆防治药剂,室内采用胃毒触杀联合毒力法比较了吡虫啉、啶虫脒、噻虫嗪、噻虫胺、呋虫胺、烯啶虫胺、噻虫啉与毒死蜱和高效氯氟氰菊酯等6种对照药剂对韭菜迟眼蕈蚊幼虫的毒力,同时用人工土壤法测定了13种药剂对蚯蚓的急性毒性,并通过盆栽试验验证了其对韭蛆和蚯蚓的选择毒力。结果表明,吡虫啉、噻虫胺、呋虫胺、噻虫啉、噻虫嗪对韭菜迟眼蕈蚊4龄幼虫的毒力明显高于6种对照药剂,对虫酰肼的相对毒力倍数分别为101.6、55.0、32.9、27.2、13.6;13种供试药剂中,除吡虫啉、啶虫脒、噻虫胺、呋虫胺对蚯蚓中等毒性外,其余均为低毒;盆栽试验中,吡虫啉、噻虫嗪、毒死蜱、噻唑膦、高效氯氟氰菊酯的防虫效果和保苗效果均分别高于其它药剂,但其中只有噻虫嗪对蚯蚓没有明显致死作用。     

Investigating nicotinic acetylcholine receptor expression in neonicotinoid resistant Myzus persicae FRC

The peach–potato aphid Myzus persicae is a pest of many commercial crops due to its polyphagous nature of feeding and has a well-documented history of acquiring resistance to insecticides. In 2009 a strain (M. persicae FRC) emerged in southern France with a point mutation (R81T) at the nicotinic acetylcholine receptor (nAChR), the target site for neonicotinoids such as imidacloprid. This point mutation was associated with the loss of the high affinity imidacloprid binding site (pM Kd), with the single remaining binding site (low nM Kd) highly overexpressed compared to laboratory controls (Bass et al., 2011 [1]). Here we report that after 2 years of continuous selection in the glass house environment with neonicotinoids, the total level of IMD-sensitive nAChRs (low nM Kd) in M. persicae FRC is now comparable to laboratory controls (pM and low nM Kd). Interestingly, despite this large reduction in IMD-sensitive nAChRs, this was not associated with any significant alteration in NNIC-lethality. Additionally, sustained absence of neonicotinoid-selection did not alter nAChR protein levels. We suggest that alterations in nAChR protein expression level described in the original characterisation of the field-isolated M. persicae FRC is unlikely to have been a direct consequence of the R81T mutation. Rather, we speculate that nAChR expression in aphids is likely influenced by as yet unknown conditions in the natural field environment that are absent in the laboratory setting.     

Neonicotinoid insecticides imidacloprid and clothianidin affect differently neural Kenyon cell death in the cockroach Periplaneta americana

The intracellular toxicity of the neonicotinoid insecticides imidacloprid and clothianidin was studied on cockroach Periplaneta americana Kenyon cells using the trypan blue exclusion test and the adenylate kinase (AK) detection reagent. To evaluate cytotoxicity, Kenyon cells were exposed to different concentrations (1, 5, 10, 50 and 100 μM) of both imidacloprid and clothianidin at different delays (1, 3, 5, 8 and 24 h). Our data show that both imidacloprid and clothianidin decreased cell viability, with a more pronounced effect following imidacloprid exposure. Indeed, a significant decrease of cell viability was observed for 50 and 100 μM imidacloprid at 8 and 24 h, with trypan blue exclusion test. Study of the AK activity revealed that 50 and 100 μM imidacloprid induced an increase of AK activity, except for 50 μM at 24 h whereas at the same concentrations, clothianidin induced a transient effect at 5 and 8 h. According to previous studies showing that imidacloprid was a partial agonist and clothianidin a full agonist of insect nicotinic acetylcholine receptors, we demonstrated that both imidacloprid and clothianidin were also able to induce distinct intracellular toxic effects.     

Biochemical and physiological changes on Bacillus thuringiensis cotton after imidacloprid foliar spray

Bacillus thuringiensis cotton is a variety of cotton genetically modified to contain a gene derived from B. thuringiensis bacteria; which results in expression of toxin protein that confers resistance to bollworm complex (the most destructive pest of cotton). Introduction of Bt cotton lowered the need of insecticides, but still a number of insecticides are used for other insects like jassids, whitefly, aphids and tobacco caterpillar to which Bt gene does not provide effective control. Imidacloprid (tradename Imidacel 17.8 SL) is an insecticide designed for control of these major sucking/piercing insects that affect cotton. So in the present work we studied the post effect of imidacloprid insecticide on plant health of three Bt cotton hybrids (RCH-134, JKCH-1947, NCEH-6R) as there are reports of this insecticide causing growth and yield enhancements in absence of insect pests. Imidacloprid was first sprayed at recommended concentration (40 ml/acre) on 3 months old plants sown in randomly designed plots with three replications of each hybrid. The spray was repeated three times at 10 days interval. The level of B. thuringiensis gene expression, peroxidase activity and total phenols was measured on third day after every spray in leaves along with growth and yield of plants. The insecticide has shown to increase the level of B. thuringiensis protein, peroxidase enzyme activity, total phenols, height, number of bolls retained on plants and yield. These observations suggested that the imidacloprid treated plants showed better growth and development, thereby imidacloprid has growth enhancing effect on Bt cotton plants in addition to its insecticidal properties.     

Resistance and cross-resistance to imidacloprid and thiamethoxam in the Colorado potato beetle Leptinotarsa decemlineata

One of the major challenges in managing the Colorado potato beetle, Leptinotarsa decemlineata (Say) is its remarkable ability to develop resistance to virtually every insecticide that has ever been used against it. Resistance is particularly common throughout northeastern USA as far north as Maine. The first instances of resistance to imidacloprid have already been reported from several locations in New York, Delaware and southern Maine. Rotating insecticides with different modes of action may delay insecticide resistance, but successful implementation of this technique depends on a good understanding of resistance and cross-resistance patterns in populations of target pests. LC(50) values were measured for imidacloprid and thiamethoxam in Colorado potato beetle populations from a variety of locations in the USA and Canada using diet incorporation bioassays. The field performance of imidacloprid, thiamethoxam and clothianidin against imidacloprid-resistant beetles on a commercial potato farm in southern Maine was also evaluated. Correlation between LC(50) values for imidacloprid and thiamethoxam was highly significant, even when populations previously exposed to thiamethoxam were excluded from the analysis. There was no statistically detectable difference in the LC(50) values between populations exposed to both insecticides and to imidacloprid alone. Applications of neonicotinoid insecticides at planting delayed build-up of imidacloprid-resistant beetle populations on field plots by 1-2 weeks but failed to provide adequate crop protection. Consistently with bioassay results, there was also substantial cross-resistance among the three tested neonicotinoid insecticides. Results of the present study support the recommendation to avoid rotating imidacloprid with thiamethoxam as a part of a resistance management plan.     

Influence of pesticides and application methods on pest and predatory arthropods associated with cotton

Incidence of sucking pests was studied in a transgenic (Bt) and non-transgenic cotton (non-Bt) agro ecosystem in 2008 and 2009. Simultaneously, the influence of different pesticides applied in two different methods on sucking pests and generalist predators was investigated on transgenic cotton. In stem application, the insecticides solutions prepared were painted directly on the middle portion of the plant stem but in foliar application the recommended dosages of the insecticides were sprayed on the cotton plant. The transgenic and non-transgenic cotton did not differ significantly in the population of sucking pests. The different pesticides when applied by foliar sprays reduced significantly more sucking pests than stem application. Among the different insecticides used, imidacloprid caused the maximum reduction of the leaf hopper population, acetamiprid caused the maximum whitefly reduction, and clothianidin caused the maximum thrips reduction under foliar application. Via stem application, acetamiprid and thiomethoxam were found better in suppression of the sucking pests?? population, but the population of predators was significantly less disrupted by the stem application method. The foliar application was in general more effective; stem application may be more applicable early in the season when its efficacy was higher and when foliar sprays were particularly destructive to beneficial pests. In foliar application, all the systemic neonicotinoids like imidacloprid, clothianidin, admire, thiamethoxam and acetamiprid were found highly toxic to natural enemies in comparison with spirotetramat, buprofezin and fipronil.     

Impact of neonicotinoid insecticides on natural enemies in greenhouse and interiorscape environments

The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant‐feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation. Copyright © 2010 Society of Chemical Industry     

Comparison of foliar and soil formulations of neonicotinoid insecticides for control of potato leafhopper, Empoasca fabae (Homoptera: Cicadellidae), in wine grapes

BACKGROUND: The potential of systemic neonicotinoid insecticides to control potato leafhopper, Empoasca fabae (Harris), a damaging pest of wine grapes in the eastern United States, was investigated. Soil or foliar applications were made to potted or field‐grown vines, and the response of leafhoppers was determined in clip cages over the following month on young or mature leaves. RESULTS: Foliar application of imidacloprid caused immediate and long‐lasting reductions in E. fabae survival on both leaf ages, whereas the activity of soil‐applied imidacloprid was delayed. Clothianidin, imidacloprid and thiamethoxam all provided long‐lasting reduction in leafhopper survival on young and mature foliage when applied through either delivery route. However, the percentage of moribund nymphs was significantly greater on foliar‐treated vines and increased over time in mature and immature leaves compared with soil‐treated vines. Residue analysis of foliar‐applied imidacloprid showed an 89% decline in mature leaves from day 1 to day 27, and a 98% decline in immature leaves over the same time period. Comparison of soil‐applied clothianidin, imidacloprid and thiamethoxam in field‐grown vines showed significant reduction in E. fabae only on mature leaves of vines treated with thiamethoxam. CONCLUSIONS: Neonicotinoids can control E. fabae in small vines, even in rapidly expanding foliage where this pest causes greatest injury. Soil application provides superior long‐term vine protection because declining residues on foliar‐treated vines lead to suboptimal activity within 2–3 weeks. Vineyard managers of susceptible cultivars may take advantage of this approach to E. fabae management by using foliar applications of the three neonicotinoids tested here, or by using soil‐applied thiamethoxam. Copyright © 2011 Society of Chemical Industry     

四种新烟碱类杀虫剂对蜜蜂的急性毒性及初级风险评估

采用饲喂管法和点滴法,分别测定了吡虫啉、噻虫嗪、噻虫胺、啶虫脒4种原药及其制剂对意大利蜜蜂成年工蜂的急性毒性,并采用危害商值(HQ)法进行了初级风险评价。结果表明:饲喂管法测得97.3%吡虫啉原药、25%吡虫啉可湿性粉剂、96%噻虫嗪原药、30%噻虫嗪悬浮剂、97%噻虫胺原药、5%噻虫胺可湿性粉剂、96%啶虫脒原药及40%啶虫脒可溶性粉剂的经口毒性48 hLD50值分别为有效成分8.04×10-3、9.46×10-3、7.04×10-3、4.64×10-3、11.8×10-3、5.25×10-3、5.22和6.31μg/蜂;点滴法测得各药剂的接触毒性48 h-LD50值分别为有效成分2.46×10-2、1.33×10-2、3.63×10-2、9.27×10-3、1.52×10-2、2.21×10-2、5.82和5.07μg/蜂。按《化学农药环境安全评价试验准则》的毒性等级划分标准,啶虫脒原药及其可溶性粉剂对蜜蜂的急性毒性均为中等毒,其他6种药剂对蜜蜂的急性毒性均为高毒;根据危害商值(HQ),啶虫脒对蜜蜂为低风险,吡虫啉、噻虫嗪和噻虫胺对蜜蜂均存在高风险。     

Comparative acute toxicity of neonicotinoid and pyrethroid insecticides to non‐target crayfish (Procambarus clarkii) associated with rice–crayfish crop rotations

BACKGROUND: Most insecticides used to control rice water weevil (Lissorhoptrus oryzophilus Kuscel) infestations are pyrethroids. However, pyrethroids are highly toxic to non‐target crayfish associated with rice–crayfish crop rotations. One solution to the near‐exclusive reliance on pyrethroids in a rice–crayfish pest management program is to incorporate neonicotinoid insecticides, which are insect specific and effective against weevils but not extremely toxic to crayfish. This study aimed to take the first step to assess neonicotinoids as alternatives to pyrethroids in rice–crayfish crop rotations by measuring the acute toxicities of three candidate neonicotinoid insecticides, clothianidin, dinotefuran and thiamethoxam, to juvenile Procambarus clarkii (Girard) crayfish and comparing them with the acute toxicities of two currently used pyrethroid insecticides, lambda‐cyhalothrin and etofenprox. RESULTS: Neonicotinoid insecticides are at least 2–3 orders of magnitude less acutely toxic (96 h LC₅₀) than pyrethroids to juvenile Procambarid crayfish: lambda‐cyhalothrin (0.16 µg AI L^?1) = etofenprox (0.29 µg AI L^?1) ? clothianidin (59 µg AI L^?1) > thiamethoxam (967 µg AI L^?1) > dinotefuran (2032 µg AI L^?1). CONCLUSION: Neonicotinoid insecticides appear to be much less hazardous alternatives to pyrethroids in rice–crayfish crop rotations. Further field‐level neonicotinoid acute and chronic toxicity testing with crayfish is needed. Copyright © 2009 Society of Chemical Industry     

长翅型与短翅型褐飞虱对杀虫剂的敏感性比较

采用稻苗浸渍法测定了长、短翅型褐飞虱对烯啶虫胺、环氧虫啶、呋虫胺、噻虫嗪、噻虫胺、吡虫啉、毒死蜱、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性，并对其体内解毒酶活力进行了比较分析。结果表明:长翅型与短翅型褐飞虱若虫对新烟碱类杀虫剂呋虫胺、噻虫嗪、噻虫胺和吡虫啉的敏感性存在显著差异，长翅型比短翅型更敏感；相反，对于有机磷类杀虫剂毒死蜱，短翅型褐飞虱则更敏感；2种生物型对烯啶虫胺、环氧虫啶、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性无显著差异。解毒酶相对比活力测定结果表明，长翅型褐飞虱若虫酯酶比活力显著高于短翅型，细胞色素P450单加氧酶比活力显著低于短翅型，而谷胱甘肽S-转移酶比活力无显著性差异。本研究结果可为褐飞虱的有效防控提供科学参考。     

Effects of insecticides on plant-growth-promoting activities of phosphate solubilizing rhizobacterium Klebsiella sp. strain PS19

In this study, four technical grade insecticides, fipronil, pyriproxyfen, imidacloprid and thiamethoxam were applied at the recommended and the higher doses to investigate their effects on plant growth-promoting activities of phosphate-solubilizing Klebsiella sp. strain PS19, isolated from mustard rhizosphere. All tested insecticides displayed a concentration-dependent inhibition in plant growth promoting traits, like, inorganic phosphate solubilization, biosynthesis of phytohormones and siderophores, of rhizobacterial strain PS19. For example, the phosphate-solubilizing activity of Klebsiella sp. PS 19 was reduced maximally by 95%, at 3900 μg l⁻¹ pyriproxyfen over control. At the recommended rate, the magnitude of toxicity of insecticides to plant growth promoting traits was less severe compared to the higher doses. The sequence of insecticide-toxicity expressed as percent decrease, determined at highest dose rate of each insecticide, over control was: pyriproxyfen (95) = imidacloprid (95) > thiamethoxam (94) > fipronil (85), for phosphate-solubilizing activity while for salicylic acid (SA) it was: thiamethoxam > pyriproxyfen = imidacloprid > fipronil. The impact of the highest dose rate of insecticides on 2,3-dihydroxybenzoic acid (DHBA) was almost equal to those observed for SA. Thiamethoxam decreased the indole acetic acid (IAA) synthesis maximally by 86% whereas fipronil had least toxicity and reduced it by 67% relative to the control. Among the experimental insecticides, pyriproxyfen at 3900 μg l⁻¹ in general, had the greatest toxic effects for plant growth promoting activities of the test strain. The study inferred that insecticides affect the plant beneficial activities of rhizobacteria adversely. These findings are likely to add a new insight into the pest management practices.