Bioassay and field-simulator studies of the efficacy of pymetrozine against peach-potato aphids,Myzus persicae (Hemiptera: Aphididae), possessing different mechanisms of insecticide resistance

Twenty-one clones of the peach-potato aphid, Myzus persicae (Sulzer), carrying various combinations of known mechanisms of insecticide resistance were assessed for their response to the new pyridine azomethine compound, pymetrozine, in leaf-dip bioassays. Pymetrozine was also applied as a foliar spray to populations of four different UK M persicae clones on potato plants in field-simulator chambers. Neither study showed any evidence of cross-resistance to this compound. Pymetrozine, used in conjunction with other effective aphicides, such as pirimicarb and imidacloprid, can therefore play an important role in insecticide resistance-management strategies for M persicae.     

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.     

Insecticide resistance status of Myzus persicae (Hemiptera: Aphididae) populations from peach and tobacco in mainland Greece

The susceptibility of 88 and 38 field samples of Myzus persicae (Sulzer) to imidacloprid and deltamethrin respectively was examined using the FAO dip test bioassay. The field samples were collected from tobacco and peach from various regions of Greece in the period from 2004 to 2006. In addition, 497, 349 and 370 clones originating from peach and tobacco were screened for the three known resistance mechanisms, elevated esterases, modified acetylcholinesterase (MACE) and knockdown resistance (kdr) respectively, using biochemical and DNA diagnostics. Most of the samples assayed with imidacloprid showed low resistance factors (RFs)-39% below 5 and 21% between 5 and 10. However, 9% of the samples (all from tobacco) showed relatively high RF values (24-73). Differences were found between crops, with higher RF values recorded in samples from tobacco than in those from peach. Bioassays with deltamethrin revealed the development of strong resistance in the populations examined. The RFs were mostly higher than 23, and in 29% of the samples they were extremely high (152-436). Finally, the three known resistance mechanisms were found in high frequencies in the populations examined, although some differences between crops and years were detected. The implications of the study for management schemes against M. persicae are discussed.     

我国西南烟区桃蚜Myzus persicae (Sulzer)的抗药性水平

采用毛细管点滴法测定了我国西南烟区云南和贵州省的10个桃蚜Myzus persicae（Sulzer）种群对氰戊菊酯、氧化乐果、灭多威和吡虫啉的抗性。结果表明，云南楚雄种群对氰戊菊酯的抗性高达26．87倍，对氧化乐果、灭多威、吡虫啉的抗性分别为敏感种群的10．02、6．00和5．83倍。云南大理、丽江、石林和曲靖4个种群对氰戊菊酯的抗性分别达24．98、14．94、11．11和10．33倍，抗性水平也较高，但对氧乐果、灭多威和吡虫啉仍较为敏感，应尽早实施抗性治理措施。贵州省的5个种群仍然处在敏感阶段。     

Temporal and spatial dynamics of insecticide resistance in Myzus persicae (Hemiptera: Aphididae)

Advances in understanding insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer), at the genotypic, biochemical and molecular levels have led to rapid and precise methods for the detection of several resistance mechanisms (elevated carboxylesterase, modified acetylcholinesterase or MACE, and knockdown resistance or kdr) in individual insects, and for monitoring their frequencies over space and time. This paper summarises the results of two long-term surveys of resistance dynamics in M persicae in England, based on samples collected directly from field and glasshouse crops or from four 12.2-m suction traps. The study showed marked fluctuations in resistance frequencies that probably reflect the counteracting forces of selection imposed by insecticides for aphids possessing more copies of esterase resistance genes, and selection against these forms when insecticide use is relaxed. There is growing evidence that several different resistance mechanisms in M persicae have associated fitness costs. In the case of esterase and MACE, these costs are apparently strong enough to effect a decline in resistance frequency over winter, and a more prolonged decline over successive cropping seasons when aphid numbers are insufficient to trigger intensive chemical applications. Changes in the overall frequency of resistance genotypes may also be influenced by the predominance of year-round parthenogenesis in M persicae in the UK, leading to non-random associations between mechanisms and selection operating on clonal lineages rather than individual genotypes.     

吡虫啉亚致死剂量处理对桃蚜乙酰胆碱酯酶的时间与剂量效应

采用微量滴度酶标板法测定了吡虫啉亚致死剂量对桃蚜乙酰胆碱酯酶(AChE)的影响。结果表明,用不同亚致死剂量吡虫啉处理桃蚜后AChE的活力明显降低,表现为抑制作用,且不同剂量间AChE的活力差异显著;酶动力学分析表明,AChE的K_m值显著降低,而V_max显著升高,表明吡虫啉亚致死剂量处理桃蚜后AChE与底物的亲和力明显增强,且最大反应速度显著加快。用LC₁₀的吡虫啉处理桃蚜后AChE的活力随时间的延长而变化,且表现为明显的抑制作用;AChE的K_m随时间的变化表现为先升高后降低的趋势,但V_max均升高。此外研究了LC₁₀的吡虫啉处理桃蚜后AChE在不同亚细胞层的分布特征,结果表明,AChE比活力的高低次序依次为:微粒体>细胞核与细胞碎片>线粒体>细胞质液;吡虫啉亚致死剂量处理后虽然没有影响AChE在亚细胞中的分布,但是却改变了对底物的亲和力和最大反应速度。     

Apparent Tolerance of a Field-Collected Strain of Myzus nicotianae to Imidacloprid due to Strong Antifeeding Responses

A French strain of the tobacco aphid Myzus nicotianae Blackman (Homoptera: Aphididae), strain FR, showed high tolerance to imidacloprid in short-term (48-h) oral ingestion bioassays when compared to a susceptible reference strain of Myzus persicae, strain NS. The resulting tolerance factors were >50. Measures of the contact activity of imidacloprid by the FAO dip method failed to detect these high factors of tolerance. The tolerance factor was in general <10 when using the dip method. The resulting difference between tolerance factors could be attributed to a behavioural component to fitness between strain FR and strain NS as further experiments revealed. When measuring the effect of systemically applied imidacloprid on honeydew excretion, a 50% reduction occurred in both strain FR and strain NS at nearly the same concentration of imidacloprid, providing evidence for a similar antifeedant response in both strains. Starvation experiments revealed that the French strain was able to survive approximately 24 h longer than a reference laboratory strain of M. persicae. This result coincided with the fact that systemically applied imidacloprid showed the same aphicidal potential against strain FR after three days as against strain NS after two days, i.e. 24 h later. After rearing in the laboratory for six months the French strain of M. nicotianae lost its hardiness and also its apparent ability to tolerate imidacloprid. However, strain FR was a heterogeneous field strain and it is possible that a susceptible variant out-reproduced a more hardy variant. These findings indicate that the type of bioassay is very important when assessing aphid populations for resistance against the chloronicotinyl insecticide imidacloprid, because of its distinct mode of action. It is obvious that an aphid dip test, i.e. FAO dip test, produces more reliable results than the different kinds of short-term oral ingestion bioassays, because of the reversible behavioural changes induced by imidacloprid after oral uptake. Thus a short-term oral ingestion bioassay (≤48 h) is not recommended for precise detection of possible resistance of Myzus sp. to imidacloprid, although this mode of uptake for imidacloprid might be sometimes more realistic in terms of field behaviour. The ideal test to generate most accurate data would be a slightly longer (72-h) feeding bioassay, perhaps used in conjunction with a dip test. The possible influence of the results on resistance monitoring is discussed. © 1997 SCI.     

Use of oils combined with low doses of insecticide for the control of Myzus persicae and PVY epidemics

Experiments were carried out in the laboratory to assess the insecticidal effect on Myzus persicae Sulzer of different oils applied alone or combined with imidacloprid or pirimicarb. The oils tested were a horticultural mineral oil, a refined rapeseed oil, a refined soya oil and a raw fish oil. When the oils were sprayed alone on pepper plants infested with M. persicae, mineral oil caused the highest mortality of aphids (over 80%). Applied before aphid infestation of pepper leaves and in mixture with low doses of imidacloprid (at one-fifth of the dose recommended by the manufacturer) and pirimicarb (at one-tenth of the dose recommended by the manufacturer), the oils did not significantly increase the toxicity of the insecticides alone. However, sprayed on aphid-infested pepper plants, the mortality rates achieved by imidacloprid/mineral oil and imidacloprid/rapeseed oil mixtures were significantly higher than those achieved by imidacloprid alone at 16 and 24 h. In a field experiment the effect on the incidence of the potato virus (PVY) of the oils in combination with imidacloprid was determined. Mineral oil, rapeseed oil and soya oil were sprayed eight times onto seed potato plants treated with imidacloprid before sowing. Mineral oil reduced PVY-infected plants by 60% and rapeseed oil by 40% compared with plots treated with imidacloprid. The oils applied as 10 ml litre-1 emulsions in water did not cause symptoms of phytotoxicity on the potato plants, and yield was not reduced.     

Field-simulator studies of insecticide resistance to dimethylcarbamates and pyrethroids conferred by metabolic- and target site-based mechanisms in peach-potato aphids,Myzus persicae (Hemiptera: Aphididae)

A range of insecticides was applied at recommended application rates against populations of Myzus persicae (Sulzer) carrying various combinations of three insecticide resistance mechanisms (carboxylesterase-based metabolic resistance and two target-site mechanisms, known as MACE and kdr), supported on either Chinese cabbage or potatoes in field simulator cages. Patterns of response were similar on both host species. MACE conferred extreme resistance to pirimicarb and triazamate (dimethylcarbamate insecticides). The kdr mechanism was associated with resistance to lambda-cyhalothrin, cypermethrin and deltamethrin (pyrethroid insecticides). A mixture of pirimicarb plus lambda-cyhalothrin was only effective against M persicae not carrying kdr or carrying kdr and low carboxylesterase-based resistance. None of the insecticides tested was effective against M persicae carrying both MACE and kdr resistance. The implications of these findings for the formulation of control strategies, based on regular monitoring of resistance genotype frequencies, are discussed.     

桃蚜高效氯氰菊酯抗药性与乙酰胆碱酯酶的关系

于室内对桃蚜进行高效氯氰菊酯抗药性筛选,选育至10代后抗性倍数增长到49.9倍。生化分析表明,抗性品系乙酰胆碱酯酶(AChE)活性均显著高于敏感品系。比较两个品系乙酰胆碱酶活性个体频率分布发现,更多的桃蚜个体向酶活性高的区域分布。酶动力学测定结果显示,抗性桃蚜酯酶对底物的Vmax、Km显著大于敏感品系。     

Association of MACE-based insecticide resistance in Myzus persicae with reproductive rate, response to alarm pheromone and vulnerability to attack by Aphidius colemani

Reproductive success and response to alarm pheromone, both potentially important components of fitness, were assessed using clones of Myzus persicae (Sulzer) to establish associations with insecticide resistance conferred by insensitive modified acetylcholinesterase (MACE). Both traits showed significant trends that were apparently related to this mechanism. MACE forms appeared to reproduce at slower rates than non-MACE forms expressing moderate (R1) levels of another resistance mechanism based on elevated carboxylesterase. However, MACE forms were more responsive to alarm pheromone than their non-MACE counterparts. The potential implications for parasitoid performance were tested using two clones showing clear differences in alarm response. The level of parasitism of M persicae by the parasitoid Aphidius colemani (Viereck) was significantly lower in MACE forms on pepper crops compared to non-MACE forms. In addition, the distribution of MACE and non-MACE forms differed on the pepper plants, with more MACE forms being found on the growing points. The presence of the parasitoid A colemani did not alter this change in distribution.     

四种杀虫剂对桃蚜和异色瓢虫的选择毒性及 害虫生物防治与化学防治的协调性评价

测定了吡虫啉、鱼藤酮、阿维菌素和印楝素4种杀虫剂对桃蚜及其捕食性天敌异色瓢虫成虫的相对毒力。4种药剂对桃蚜的毒力大小依次为阿维菌素＞吡虫啉＞鱼藤酮＞印楝素,其LC50分别为0.042、1.96、6.54和10.17 mg/L。对异色瓢虫的LC50则分别为1009.42、201.89、8202.90和大于7500 mg/L,益害毒性比分别为24033.81、103.01、1254.27和大于786.63。4种药剂在有效防治桃蚜的前提下对天敌异色瓢虫的安全性依次为阿维菌素＞鱼藤酮＞印楝素＞吡虫啉。阿维菌素、吡虫啉、印楝素和鱼藤酮这4种药剂均可在蚜虫综合治理中发挥有效的作用。     

New developments in insecticide resistance in the glasshouse whitefly (Trialeurodes vaporariorum) and the two-spotted spider mite (Tetranychus urticae) in the UK

A recent survey of insecticide resistance in two of the most problematic pests in UK glasshouses revealed some new developments. At least some individuals in all UK samples of Trialeurodes vaporariorum that were tested resisted the insect growth regulator (IGR) buprofezin. The most strongly resistant strains were unaffected by the field application rate of this compound, and even samples from populations that had never been exposed to buprofezin contained individuals that survived the highest concentration applied (10,000 mg litre-1). The field rate of buprofezin was shown to select for resistance through vapour action alone. The benzophenylurea teflubenzuron, an unrelated IGR, was cross-resisted by buprofezin-resistant individuals. There was no evidence of resistance to imidacloprid, but all T vaporariorum strains tested, regardless of origin, exhibited a high innate tolerance to nicotine, when compared with another whitefly species, Bemisia tabaci. Marked resistance to fenbutatin oxide and tebufenpyrad was found in single glasshouse populations of Tetranychus urticae, but these compounds and abamectin appeared to remain highly effective against all other strains collected.     

不同地区灰飞虱对吡虫啉的抗性

为了明确全国不同稻区灰飞虱对吡虫啉的抗药性水平及其抗性机制,2012年采用点滴法测定了16个灰飞虱田间种群对吡虫啉的抗性倍数和3种增效剂在10个抗性种群中对吡虫啉的增效作用。结果表明,安徽安庆、合肥、江苏南京、盐城和无锡5个地区种群达到高抗水平(抗性倍数为74.1~91.2);浙江杭州、台州、湖州3个种群达到中等水平抗性(抗性倍数为35.8~47.7),福建福州和广东广州达到低水平抗性(抗性倍数为18.4~21.3),其他地区种群处于敏感性下降阶段。增效剂增效结果表明,氧化胡椒基丁醚(PBO)和磷酸三苯酯(TPP)在5个高抗种群和2个低抗种群中对吡虫啉均具有增效作用,表明P450单加氧酶和羧酸酯酶是抗性产生的主要代谢机制,而3个中抗种群中,仅PBO对吡虫啉表现出显著的增效作用,说明这3个种群仅有P450单加氧酶是其抗性上升的主要代谢机制。顺丁烯二酸二乙酯(DEM)在测定的10个种群中对吡虫啉均没有增效作用,说明谷胱甘肽S-转移酶没有参与其抗性上升。建议在中等水平至高水平抗性地区暂停使用吡虫啉防治灰飞虱。     

抗吡虫啉桃蚜种群的选育及其交互抗性研究

采用浸渍法,在室内用吡虫啉对桃蚜敏感种群进行抗性选育,经过15代的连续汰选,获得抗性指数为14.34倍的抗吡虫啉桃蚜种群。对9种常用杀虫剂的交互抗性测定结果表明,该种群对拟除虫菊酯类如高效氯氟氰菊酯(抗性指数12.76倍)和溴氰菊酯(10.24倍),有机磷类如氧乐果(7.95倍)、辛硫磷(5.44倍)和甲胺磷(5.32倍)以及吡虫啉·高效氯氰菊酯混剂(8.90倍)均产生了不同程度的交互抗性,而对氨基甲酸酯类如灭多威(3.15倍)、有机氯类如硫丹(1.64倍)以及阿维菌素·辛硫磷混剂(2.31倍)等无明显的交互抗性。     

Comparative analysis of neonicotinoid binding to insect membranes: II. An unusual high affinity site for [3H]thiamethoxam in Myzus persicae and Aphis craccivora

Neonicotinoids represent a class of insect-selective ligands of nicotinic acetylcholine receptors. Imidacloprid, the first commercially used neonicotinoid insecticide, has been studied on neuronal preparations from many insects to date. Here we report first intrinsic binding data of thiamethoxam, using membranes from Myzus persicae Sulzer and Aphis craccivora Koch. In both aphids, specific binding of [3H]thiamethoxam was sensitive to temperature, while the absolute level of non-specific binding was not affected. In M persicae, binding capacity (Bmax) for [3H]thiamethoxam was ca 450 fmol mg(-1) of protein at 22 degrees C and ca 700 fmol mg(-1) of protein at 2 degrees C. The negative effect of increased temperature was reversible and hence not due to some destructive process. The affinity for [3H]thiamethoxam was less affected by temperature: Kd was ca 11 nM at 2 degrees C and ca 15 nM at 22 degrees C. The membranes also lost binding sites for [3H]thiamethoxam during prolonged storage at room temperature, and upon freezing and thawing. In A craccivora, [3H]thiamethoxam was bound with a capacity of ca 1000 fmol mg(-1) protein and an affinity of ca 90 nM, as measured at 2 degrees C. Overall, the in vitro temperature sensitivity of [3H]thiamethoxam binding was in obvious contrast to the behaviour of [3H]imidacloprid studied in parallel. Moreover, the binding of [3H]thiamethoxam was inhibited by imidacloprid in a non-competitive mode, as shown with M persicae. In our view, these differences demonstrate that thiamethoxam and imidacloprid, which represent different structural sub-classes of neonicotinoids, do not share the same binding site or mode. This holds also for other neonicotinoids, as we report in a companion article.     

Lethal and Sublethal Effects of Imidacloprid on Nicotine-Tolerant Myzus nicotianae and Myzus persicae

Bioassays of nicotine and imidacloprid against clones of Myzus persicae (Sulzer) and Myzus nicotianae (Blackman) from around the world demonstrated that some had low levels of resistance to both compounds. This was expressed not only as a reduced mortality, but more markedly as differential inhibition of feeding by imidacloprid concentrations in the parts per billion range. Such concentrations also reduced aphid fecundity by inhibiting the production and viability of nymphs, and this effect was more marked for susceptible aphids than for those showing reduced direct lethal and antifeedant effects.     

吡虫啉与三种拟除虫菊酯杀虫剂对马铃薯桃蚜的联合毒力

本文探讨了吡虫啉分别与氰戊菊酯、高效氟氯氰菊酯和联苯菊酯复配对马铃薯桃蚜的防治效果,为合理有效地应用复配剂对其进行化学防治提供依据。应用共毒因子法和共毒系数法分别确定了最佳药剂配伍和最佳复配比例。采用共毒因子法测定结果表明,吡虫啉与氰戊菊酯混配对马铃薯桃蚜防治有明显增效作用。进一步采用共毒系数法测定表明,吡虫啉与氰戊菊酯复配比例为2∶3时,增效作用最显著,共毒系数达276.82;吡虫啉与氰戊菊酯以6∶1复配时,表现出拮抗作用。     

桃蚜对噻虫嗪代谢抗性机制研究

对桃蚜进行室内噻虫嗪抗性品系筛选,选育至15代后抗性倍数达到75.6倍。对噻虫嗪敏感品系(THI-S)和抗性品系(THI-R)桃蚜的谷胱甘肽S-转移酶(GSTs)、酸性磷酸酯酶(ACP)、碱性磷酸酯酶(ALP)、羧酸酯酶(CarE)、多功能氧化酶(MFO)O-脱甲基活性进行了比较,结果显示:敏感品系(THI-S)和抗性品系(THI-R)的谷胱甘肽S-转移酶比活力分别为3.127 5和3.215 9,差异不显著,桃蚜抗性品系体内酸性磷酸酯酶、碱性磷酸酯酶、羧酸酯酶和多功能氧化酶O-脱甲基活性均显著高于敏感品系,分别达到了1.57、2.10、6.12、2.03倍。表明桃蚜对噻虫嗪抗性的产生与酸性磷酸酯酶、碱性磷酸酯酶、羧酸酯酶和多功能氧化酶O-脱甲基的活性相关。     

Antifeedant effect,biological efficacy and high affinity binding of imidacloprid to acetylcholine receptors in Myzus persicae and Myzus nicotianae

It is known from laboratory studies that tobacco-associated forms of Myzus persicae (Sulzer) and the closely related tobacco aphid Myzus nicotianae (Blackman) are often somewhat less susceptible to imidacloprid than non-tobacco strains of M. persicae. Choice tests (floating leaf technique) showed that tobacco aphids were also less susceptible to the antifeedant potential of imidacloprid in contact bioassays. Synergists like piperonyl butoxide or DEF did not enhance the susceptibility of tobacco-associated morphs of Myzus ssp. to imidacloprid, thus providing evidence that neither oxidative detoxication nor hydrolytic metabolization took place. However, in an attempt to study the influence of endosymbiotic bacteria on the efficacy of imidacloprid, we allowed small populations of tobacco aphids to feed on diets containing the antibiotic chlortetracycline prior to imidacloprid treatment. While the effectiveness of imidacloprid, i.e. lower LC₅₀ values, could be improved in all strains, including the susceptible reference strain, there was no change in overall tolerance factors. In order to investigate any possible alteration of the target site, the affinity of imidacloprid and nicotine to nicotinic acetylcholine receptors in whole-aphid homogenates was measured. All strains (and clones) showed the same high-affinity binding sites and no detectable difference. Studies using the FAO dip method revealed that the lower susceptibility of M. nicotianae is not restricted to chloronicotinyls like imidacloprid or acetamiprid, because other insecticides with different modes of action such as pymetrozine and fipronil were also affected in laboratory studies. It is considered that the observed tolerance to chloronicotinyls in certain strains of Myzus ssp. is a natural variation in response, probably not coupled with any known mechanism of resistance in this species complex. © 1998 SCI