Evaluation of selective toxicity of five pesticides against Plutella xylostella (Lep: Plutellidae) and their side-effects against Cotesia plutellae (Hym: Braconidae) and Oomyzus sokolowskii (Hym: Eulophidae)

The toxicities of five pesticides commonly used in vegetable fields to the larvae of the diamondback moth, Plutella xylostella (L) and its two major parasitoids, Cotesia plutellae (Kurdjumov) and Oomyzus sokolowskii (Kurdjumov), were evaluated in the laboratory using several bioassays. When tested at the rates recommended for field application by the manufacturer, fipronil, avermectin and chlorfluazuron produced over 95% mortality on third-instar larvae of P xylostella, but fenvalerate and methomyl did not produce any substantial mortality to such larvae, and over 70% of P xylostella larvae could still pupate normally after feeding on cabbage leaf treated with the two pesticides. In a residual contact assay with adult parasitoids, fipronil and methomyl caused over 93% mortality within 24 h; fenvalerate killed approximately 55% of the adults within 24 h; avermectin and chlorfluazuron showed differential toxicity to the two parasitoids. Avermectin was extremely harmful to O sokolowskii but slightly toxic to C plutellae, while chlorfluazuron was more toxic to C plutellae than to O sokolowskii. In the residue assay with cocoons of C plutellae and pupae of O sokolowskii developed within P xylostella pupae, treatments with pesticides did not reduce adult emergence. However, the mortality of C plutellae adults emerged from the fipronil-treated cocoons increased greatly within 24 h post-emergence; adults from the fenvalerate-treated cocoons parasitized less host larvae. Treatments with fenvalerate and methomyl significantly increased the mortality of O sokolowskii adults within 24 h post-emergence. Recommendations of choosing pesticides for the control of P xylostella are given.     

The joint action of mixtures of insecticides,or of insect growth regulators and insecticides,on susceptible and diflubenzuron-resistant strains of Spodoptera littoralis boisd

The joint action of insecticides, or of mixtures of insect growth regulators and insecticides, on the susceptible (S) strain and diflubenzuron-resistant (R_d) strain of the cotton leafworm Spodoptera littoralis Boisd. was investigated. The joint action of the insecticides and/or insect growth regulator mixtures was determined by mixing them in proportion to their activity equivalents at the LD₂₅ or ED₂₅ levels. A total of 15 mixtures of two synthetic pyrethroids, two organophosphorus, one carbamate and one organochlorine insecticides, were applied to the fourth-instar larvae of the S and R_d strains. The insecticide mixtures cypermethrin/methomyl and cypermethrin/endrin exhibited high and moderate levels of synergism on the S strain, respectively. However the mixtures chlorpyrifos/methomyl, phosfolan/methomyl, and phosfolan/endrin produced antagonism, while the other mixtures showed varying levels of additive effects. The response of the fourth-instar larvae of the S strain, to the joint action of diflubenzuron/juvenoid, diflubenzuron/insecticide, or insecticide/juvenoid mixtures, revealed that diflubenzuron produced high levels of synergism when combined with methoprene and progressively less with fenvalerate, methomyl and cypermethrin. On the other hand, the mixture diflubenzuron/triprene was antagonistic. Fenvalerate with the two juvenoids produced synergism while methomyl showed an additive effect with methoprene. However, the mixtures cypermethrin/methoprene, cypermethrin/triprene and methomyl/triprene produced antagonism. The mixtures that produced potentiation on the fourth-instar larvae of the S strain lost their high potency when tested against the R_d strain. The results also indicated that insecticide/juvenoid mixtures, when applied on 2-day-old pupae of the S strain, were synergistic, except in the case of cypermethrin/methoprene and methomyl/triprene mixtures, for which additive effects were observed. When the mixtures that had synergistic effects on the S strain were tested on the R_d strain, the results revealed that their synergistic effects were apparently reduced. This was attributed to the fact that the generalised levels of tolerance in the R_d strain towards various compounds may have influenced the several defence mechanisms to act against the synergistic action of the chemical mixtures.     

桃蚜敏感种群的筛选及其抗药性演化的研究

采用微量毛细管点滴法筛选出比河北廊坊桃蚜相对敏感种群更为敏感的甘肃宕昌桃蚜种群,建立了18种杀虫剂对桃蚜敏感种群的毒力基线,可作为今后国内各地监测桃蚜抗药性水平的敏感基线。用氧乐果、氰戊菊酯及其氧乐果+氰戊菊酯对桃蚜敏感种群进行抗性选育,汰选20次时桃蚜对混剂氧乐果+氰戊菊酯只产生4.85倍的抗药性,比氧乐果单剂(7.39倍)抗性发展速度幔,尤其比氰戊菊酯单剂(87.21倍)更慢,表明桃蚜易对菊酯类药剂产生抗药性,混剂可以延缓产生抗药性。     

Residues of synthetic pyrethroid insecticides on horticultural crops

Foliar applications of synthetic pyrethroids were made to several crops to determine residue levels at various intervals after application. On onions, residues of cypermethrin, permethrin and fenvalerate were negligible > 0.1 mg kg^?1, 7 days after application. On lettuce, residues of fenvalerate and permethrin were 0.8 mg kg^?1. On celery, residues of fenvalerate did not decline and ranged from 0.12 to 0.25 mg kg^?1 during the 14-day period. On green bush-beans, residues of permethrin and cypermethrin did not decline during the 14-day period and ranged from 0.1 to 0.6 mg kg^?1. By day 7, residues of cyfluthrin, cypermethrin, deltamethrin, fenvalerate and permethrin on strawberries were less than the acceptable maximum tolerance of 0.1 mg kg^?1 with the exception of cypermethrin, applied at the rate of 0.14 kg a.i. ha^?1 which gave a residue of 0.14 mg kg^?1.     

Toxicity and sublethal effects of an insecticidal soap on Aphidius colemani (Hymenoptera: Braconidae)

BACKGROUND: The effects of an insecticidal soap on the survival, fitness and behaviour of an aphid parasitoid wasp, Aphidius colemani (Viereck), were studied in the laboratory. The LC(50) (soap concentration causing 50% mortality 24 h after treatment) was determined. The survival of parasitoid larvae (% adult emergence), fitness (tibia length of adults) and number of eggs produced per female parasitoid that survived in third- and fourth-instar aphids treated with insecticidal soap LC(50) were also assessed. The LC(50) for third- and fourth-instar aphids was determined to be 3.25 g L(-1). Acceptance by female parasitoids of aphids that survived their LC(50) was also tested. RESULTS: The soap concentration causing 100% mortality in adult wasps 24 h after treatment was 17.5 g L(-1). The LC(50) was 2.75 g L(-1). Soap did not have any effect on the survival of parasitoid immatures or on the fitness or number of eggs produced per female parasitoid. Wasps that were in contact with treated aphids did not oviposit as much in them as in untreated aphids, indicating that female parasitoids detected aphids treated with insecticidal soap. CONCLUSION: These data suggest that aphid parasitoids released following treatment with insecticidal soap are likely to accept a lower proportion of the surviving aphids. Biological control programmes could be ameliorated by soap applications if the latter were made 1 day before the release of wasps in the greenhouse.     

农药对烟蚜茧蜂的影响

以5种杀蚜农药的田间使用浓度,对烟蚜茧蜂的成蜂和僵蚜体内该蜂的毒杀作用进行了研究。对烟蚜茧蜂成蜂测定的结果,其毒性顺序为:溴氰菊酯>功夫菊酯>氧化乐果>来福灵>杀灭菊酯。在田间实际用药浓度下,来福灵对成蜂影响最小,但喷药后24小时接蜂,48小时后,其存活率亦仅40％。而对僵蚜中的蚜茧蜂均影响较小。其中氧化乐果羽化率达96.6％,杀灭菊酯、来福灵和溴氰菊酯达60.0～66.3％。     

杭州郊区菜蚜寄生蜂初步调查

1985～1986年,在杭州东郊系统调查了13块地5种十字花科蔬菜上蚜虫的寄生性天敌和被寄生率。共发现原寄生蜂两种,即菜小脉蚜茧蜂和烟蚜茧蜂,前者寄生于桃蚜和萝卜蚜,后者仅寄生于桃蚜,寄生率大多在0～3％,很少超过10％,在蚜虫数量上升阶段寄生率一般呈下降趋势,只有在蚜虫数量迅速下降阶段才明显上升,故蚜虫数量变化受寄生蜂影响不大。共发现重寄生蜂5种,重寄生率平均约为50％,高时接近100％。表明重寄生蜂在一定程度上影响了蚜茧蜂对蚜虫的控制效能。     

Toxicity of neem to natural enemies of aphids

Neem [Azadirachta indica (A. Juss.)] seed oil (NSO) applied in three concentrations, 0.5%, 1% and 2%, to potted plants infested with green peach aphid,Myzus persicae (Sulzer), totally prevented adult eclosion of larval coccinellids,Coccinella undecimpunctata L., and reduced adult eclosion of syrphids,Eupeodes fumipennis (Thompson), to 11%, 7% and 0%, respectively, of the controls. Under the same conditions, NSO did not reduce the rate of parasitism ofM. persicae byDiaeretiella rapae (Mcintosh), but emergence of parasitoid adults from aphid mummies collected from treated plants was reduced to 35%, 24% and 0%, respectively, of the controls. Although topical treatment of predator larvae with NSO at concentrations of up to 5% did not affect survival, emergence of parasitoids from mummies dipped in aqueous emulsions of NSO at similar rates was reduced significantly. Under field conditions, sprays of NSO and neem seed extract to plants had no significant impact on the number of aphids parasitized. Although total numbers of predators were reduced, numbers of predators relative to aphid numbers were similar to those in controls. Neem insecticides may be suitable for use in integrated pest management programs, as under field use they appear to be relatively benign to aphid predators and parasitoids.     

增效剂对菜蚜茧蜂杀虫剂敏感性的影响

以田间菜蚜茧蜂为试虫,采用药膜法研究了增效剂胡椒基丁醚(PB)、磷酸三苯酯(TPP)和马来酸二乙酯(DEM)对6种杀虫剂的增效作用。结果表明,三种增效剂对6种杀虫剂均有显著增效作用,其大小依次为PB>DEM>TPP。PB对甲胺磷、阿维菌素、氟虫腈、氰戊菊酯、氯氰菊酯和吡虫啉的增效比达5.0～9.6倍。TPP和DEM对甲胺磷、DEM对氟虫腈的增效比达2.6～3.0倍,但TPP和DEM对阿维菌素、氰戊菊酯和氯氰菊酯、TPP对氟虫腈的增效比均在1.9倍以下。PB、TPP和DEM对吡虫啉的增效比分别高达9.6、6.8和8.2倍。体内抑制试验结果显示,PB、TPP和DEM对菜蚜茧蜂AChE活性无明显抑制作用,而PB和TPP对羧酸酯酶(CarE)、DEM对谷胱甘肽S转移酶(CST)活性有显著抑制作用。由此认为,菜蚜茧蜂对所用的6种杀虫剂的耐药性与多功能氧化酶(MFO)、CarE和GST的解毒作用有关。     

The ovicidal action of insecticides and insect growth regulator/insecticide mixtures on the eggs of various ages of susceptible and diflubenzuron-resistant strains of Spodoptera littoralis boisd

The ovicidal action of four insecticides and three insect growth regulators, on eggs of various ages of the susceptible (S) strain of Spodoptera littoralis, was investigated. The results revealed that diflubenzuron was the most toxic compound tested on 0-1-day-old eggs, followed by triprene and then methoprene; chlorpyrifos came next in its toxicity, followed by cypermethrin then fenvalerate; methomyl was the least effective. With the progress of embryonic development, 1-2-day-old eggs showed slight tolerance to the action of the pesticides and juvenoids, but apparently resisted the action of diflubenzuron. Eggs 2-3 days old showed increased tolerance to the insecticides and diflubenzuron and, to a lesser extent, to the action of the two juvenoids. A total of 21 insecticide or insect growth regulator-insecticide mixtures, based on their toxicity equivalents (LD₂₅ + LD₂₅), were applied jointly on 0-1-day-old eggs of the S strain. The mixtures which produced high synergism on this stage could be arranged, according to their decreasing order of potentiation, as follows: fenvalerate/diflubenzuron, cypermethrin/triprene, methomyl/methoprene, cypermethrin/methoprene, fenvalerate/ methoprene, cypermethrin/methomyl, cypermethrin/diflubenzuron, fenvalerate/triprene, diflubenzuron/methoprene and methomyl/triprene. The mixtures that produced synergistic effects on 0-1-day-old eggs were also tested against the 1-2 and 2-3-day-oldeggs of the S strain. Theresults indicated that themixtures fenvalerate/diflubenzuron, and cypermethrin with either triprene or diflubenzuron, when tested on 1-2-day-old eggs, produced levels of synergism nearly similar to those achieved on newly deposited eggs. On the other hand, the mixtures cypermethrin/methomyl, and fenvalerate with methoprene or triprene, showed comparatively lower levels of synergism. However, the synergistic action of the mixture cypermethrin/methoprene, previously detected on newly deposited eggs, became an additive effect on 1-2-day-old eggs. Only the mixtures fenvalerate/diflubenzuron, cypermethrin/triprene and fenvalerate/methoprene showed synergism on 2-3-day-old eggs. The mixtures which showed synergistic effects on 0-1-day-old eggs of the S strain were further tested on eggs of various ages of the diflubenzuron-resistant (R_d) strain. As regards 0-1-day-old eggs, only the combinations cypermethrin/triprene, methomyl/methoprene and fenvalerate/methoprene produced additive effects. The mixture cypermethrin/diflubenzuron was still synergistic against newly deposited eggs of the R_d strain, in a manner similar to that indicated with the S strain. Apparent levels of antagonism were shown to the other insecticide-juvenoid mixtures as well as to the diflubenzuron/methoprene combination. The combinations cypermethrin/methomyl and fenvalerate/diflubenzuron had some effect on the freshly deposited eggs of the R_d strain but produced lower levels of potentiation. With the increase in age of the eggs, the mixture cypermethrin/diflubenzuron showed a lower level of synergism on the 1-2 day-old eggs than was observed in younger eggs. The additive effects, previously detected with some of the mixtures on newly deposited eggs became an antagonistic effect for the 1-2-day-old eggs. The eggs at this stage were more able to resist thejoint action of the other mixtures tested. Moreover, with further increase in the age of the eggs, the combination cypermethrin/diflubenzuron produced a lower level of potentiation on 2-3 day-old eggs, followed by fenvalerate/diflubenzuron at an even lower level, while the other mixtures showed various levels of antagonism.     

Residue behaviour of fenvalerate,tau-fluvalinate,lambda-cyhalothrin and monocrotophos in eggplant (Solanum melongena L.) fruits

The persistence patterns of three synthetic pyrethroids—fenvalerate, tau-fluvalinate, lambda-cyhalothrin—and an organophosphorus insecticide, monocrotophos, on eggplant (Solanum melongena L.) have been evaluated. The extractable residues ranged from 0.05 to 0.45, 0.01 to 0.40, 0.003 to 0.09 and 0.09 to 0.32 μg g^?1 for fenvalerate, tau-fluvalinate, lambda-cyhalothrin and monocrotophos, respectively. Fenvalerate was the most persistent among the four, followed by monocrotophos, lambda-cyhalothrin and tau-fluvalinate. The Maximum Residue Limit (MRL) of these pesticides on S. melongena has not yet been documented. The present data may be useful for establishing MRL and assessing the amount of pesticide residues in this vegetable.     

Evidence for different mechanisms of action of the three pyrethroids,deltamethrin, cypermethrin,and fenvalerate,on the excitation threshold of myelinated nerve

The effects of three α-cyano pyrethroids (deltamethrin, fenvalerate, and cypermethrin) on the electrophysiological function of single myelinated nerve fibers from Rana esculenta were investigated. The time course of pyrethroid-induced changes on the threshold interval, V_s − V_m (V_s: threshold voltage; V_m: membrane potential), as well as stationary membrane parameters determining this interval was measured on the same nerve preparation (membrane potential V_m, stationary transition voltage V_Tr, stationary sodium conductance). The results suggest that the mechanisms of changing the threshold interval are different for the three pyrethroids. Deltamethrin and cypermethrin increase this interval until inexcitability, deltamethrin by increasing the stationary sodium conductance and cypermethrin by blocking the sodium conductance. Fenvalerate, however, insignificantly affects the threshold interval because both V_m and V_s are shifted parallel by about the same amount in the same direction (depolarization). These qualitatively different effects of chemically related substances differentiate the pyrethroids from other classes of substances which are effective on the nerve function and suggests that the molecular mechanisms underlying the pyrethroid effects might have a unique quality.     

大灰食蚜蝇幼虫饲养及温室释放试验

在室内用桃蚜、蔷无网蚜、桃粉大尾蚜、菊花蚜虫4种蚜虫饲养大灰食蚜蝇幼虫取得比较满意的结果,幼虫成活率76～80％,蛹羽化率92～94％,子代卵孵化率84～91％。用豌豆修尾蚜饲养,幼虫成活率仅48％,蛹羽化率50％,子代卵孵化率无明显差异。在大灰食蚜蝇幼虫发育期中,前期用桃蚜饲养,后期改用修尾蚜饲养,对幼虫成活率及蛹羽化率仍有影响.食物(蚜虫)充足时,幼虫自残程度低,可以集体饲养。以1:10的益害比释放大灰食蚜蝇3日龄幼虫,防治非洲菊上的蚜虫,3天后蚜虫下降85.9％,效果显著。     

Effect of azadirachtin applied systemically through roots of plants on the mortality,development and fecundity of the cabbage aphid (<Emphasis Type="Italic">Brevicoryne brassicae</Emphasis>)

The effect of low concentrations of azadirachtin applied systemically through root tissues of rape plants (Brassica napus subsp.napus) on the mortality, period of development, longevity and fecundity of the cabbage aphid (Brevicoryne brassicae L.) (Sternorrhyncha: Aphididae) was studied. The concentrations of azadirachtin A tested were: 0.25, 0.05, 0.005, 0.0005 and 0.00005 mg ml⁻¹. The mortality of cabbage aphid nymphs, particularly during the period of ecdysis, increased significantly with increasing concentrations. Azadirachtin had no effect on the length of the development period of the respective immature stages of cabbage aphids. The average longevity of the cabbage aphids decreased with increasing azadirachtin concentration and time spent feeding. The fecundity of aphids decreased after the application of azadirachtin. http://www.phytoparasitica.org posting May 6, 2004.     

油菜品种抗蚜性多目标模糊综合决策

作者采用模糊统计回归法，建立了油菜品种的自然感蚜量、蚜虫在品种上的“累积存活率”，平均发育历期、平均产仔量、内禀增长率及品种耐害性、干扰效应等抗性指的模糊隶属函数，建立了品种抗蚜性的模糊综合决策模型。结果表明，１２个品种抗性强弱为：红叶芥＞咸阳７４－１＞甘油５号＞８８６３１＞７２１１＞７５－１＞波力木耳＞８８６３８＞德国１５选株＞华油９号＞秦油３号＞秦油２号。同时作者提出的一套衡量品种抗性的指禁     

南方小花蝽对三种蚜虫的捕食能力和喜好性

南方小花蝽Orius similis是我国南方农田生态系统中一种对小型害虫极具控害潜力的重要捕食性天敌昆虫.为了明确天敌南方小花蝽对云南小春作物上常见蚜虫的捕食能力和喜好性,本文在实验室条件下研究了南方小花蝽5龄若虫、雌雄成虫对不同组猎物的捕食喜好性.选取云南小春作物上3种主要蚜虫种类:烟蚜Myzus persicae...     

4种寄主植物的繁蚜－繁蜂能力和子代烟蚜茧蜂的寄生潜力比较

为比较不同寄主植物繁蚜,继而繁育烟蚜茧蜂Aphidius gifuensis的潜力,促进烟蚜茧蜂扩繁,从烟田采集供试烟蚜与烟蚜茧蜂,比较了烟草、萝卜、油菜和小白菜共4种常用寄主植物的繁蚜-繁蜂能力和繁育的子代烟蚜茧蜂的寄生潜力。结果显示:(1)烟草和萝卜的单株繁蚜速率较快、繁蚜量大,表明两者的繁蚜能力强于小白菜和油菜;(2)4种寄主植物上的僵蚜羽化率没有显著差异,烟蚜茧蜂对烟草和萝卜繁育烟蚜的寄生率显著高于小白菜和油菜,表明在烟草和萝卜上繁蜂能力强于油菜和小白菜;(3)烟草上繁育的子代蜂寿命及其后足胫节长度均显著大于在其他3种寄主植物上繁育的寄生蜂的相应参数,表明烟草上繁育的子代烟蚜茧蜂的营养状态优于在其他3种寄主植物上得到的烟蚜茧蜂。总体而言,烟草的繁蚜-繁蜂能力和子代烟蚜茧蜂的寄生潜力均强于其他3种寄主植物,更适用于烟蚜茧蜂扩繁;萝卜上繁育的子代烟蚜茧蜂的寄生潜力不及烟草,但明显优于小白菜和油菜,可作为一种烟蚜茧蜂繁育的替代寄主植物,用于提纯、复壮烟蚜和烟蚜茧蜂。     

萝卜蚜对氰戊菊酯的抗药性汰选及其交互抗性

将田间采回的萝卜蚜种群分成两部分,一部分用氰戊菊酯连续汰选13次,另一部分不用药汰选,连续饲养作对照。汰选前及每汰选3～4次测定1次氰戊菊酯对两种群的毒力。结果表明,对照种群对氰戊菊酯的敏感性增加3.76倍,而汰选种群对该农药的抗药性与汰选前比较增长了163.25倍,与同期饲养对照种群比较,抗性已达613.62。该汰选种群对不含氟的溴氰菊酯和氯氰菊酯存在明显的交互抗性(分别达360.7和53.9倍),对含氟的三氟氯氰菊酯、氟氰菊酯和氟胺氰菊酯也存在交互抗性,但只有7倍左右;而对马拉硫磷、氧化乐果、杀螟松、久效磷和灭多威及菊马混剂没有表现出交互抗性,为进一步探讨萝卜蚜的抗药性治理措施提供了试验依据。     

Pharmacokinetics of pyrethroids in twospotted spider mites

The penetration and degradation of six pyrethroids were examined in the twospotted spider mite, Tetranychus urticae Koch, and the results were related to their toxicity as measured by inhibition of respiration using the Warburg technique and mortality using the slide-dip bioassay. FMC-54800 [1,1′-biphenyl-3ylmethyl cis-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate] was the most toxic pyrethroid to the mites based on both respiration and mortality studies. It and flucythrinate had the highest pharmacokinetic efficiency as determined by delivery and maintenance of internal levels of parent compounds. Permethrin, fenvalerate, and fluvalinate were intermediate in pharmacokinetic efficiency, whereas cypermethrin was significantly lower. The highest intrinsic activity, as estimated by the percentage inhibition of respiration per microgram of internal parent, was possessed by cypermethrin and FMC-54800. Fenvalerate and fluvalinate had intermediate levels, while permethrin and flucythrinate had significantly lower capacities to inhibit respiration. The combination of relatively high pharmacokinetic efficiency and intrinsic activity of FMC-54800 appeared to be responsible for its high toxicity. In addition to these findings, differences in the kinetics for cis and trans isomers were observed for permethrin but not cypermethrin. This study has yielded evidence that acaricidal activity of pyrethroids can be enhanced by optimizing the structure for increased pharmacokinetic efficiency and increased intrinsic activity.     

Differential efficacy of three commonly used pyrethroids against laboratory and field‐collected larvae and adults of Helicoverpa zea (Lepidoptera: Noctuidae) and significance for pyrethroid resistance management

BACKGROUND: Helicoverpa zea (Boddie) pyrethroid resistance monitoring programs typically utilize cypermethrin in the adult vial test. Here we investigated if differences in insect growth stage and pyrethroid structure affect resistance ratios and discuss implications for pyrethroid resistance management. RESULTS: Vial bioassays with cypermethrin, esfenvalerate and bifenthrin were conducted on H. zea third instars and male moths from a susceptible laboratory colony and the F1 generation of a pyrethroid‐resistant field population. In the susceptible population, both growth stages were most sensitive to bifenthrin and adults were more sensitive to esfenvalerate than cypermethrin. LC₅₀ resistance ratios for the larvae and adults of the resistant population were approximately two times higher for bifenthrin than cypermethrin or esfenvalerate. CONCLUSION: For the resistant population, vial assays using either growth stage gave similar resistance ratios for each of the three pyrethroids, respectively, proving the adult vial test accurately reflects larval resistance. However, as resistance ratios varied considerably depending on the pyrethroid used, resistance ratio values obtained with one pyrethroid may not be predictive of resistance ratios for other pyrethroids. Our results suggest that carefully chosen pyrethroid structures diagnostic for specific mechanisms of resistance could improve regional monitoring programs. Copyright © 2009 Society of Chemical Industry