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.     

The effect of insecticide application sequences on the control and insecticide resistance status of the peach-potato aphid, Myzus persicae (Hemiptera:Aphididae), on field crops of potato

Experiments were done on commercial potato crops in the UK to investigate the effect of different insecticide sequences on the control and insecticide resistance status of Myzus persicae (Sulzer). The work was done to provide field validation of similar laboratory studies done in 'field simulators'. To ensure adequate aphid populations and to influence the initial resistance status of the aphid population, cultured M. persicae from a clone of known resistance status (esterase R1, kdr heterozygote, non-MACE (modified acetylcholinesterase)) were inoculated into both experiments. Two-spray programmes starting with lambda-cyhalothrin (a pyrethroid insecticide) gave poor control in comparison with programmes starting with pirimicarb (a carbamate insecticide) or pirimicarb-containing mixtures. This concurred closely with the results obtained from single applications in field simulator studies. Treatment sequences containing pymetrozine (a pyridine azomethine insecticide) were also effective, though slower-acting. This again concurs with field simulator studies. The proportions of aphids carrying different resistance mechanisms were largely unaffected by treatment in these experiments. The implications of these results for field control strategies are discussed.     

Efficacy of plant metabolites of imidacloprid against Myzus persicae and Aphis gossypii (Homoptera: Aphididae)

The metabolism of the chloronicotinyl insecticide imidacloprid is strongly influenced by the method of application. Whilst in foliar application most of the residues on the leaf surface display unchanged parent compound, most of the imidacloprid administered to plants by soil application or seed treatment is metabolized more or less completely, depending on plant species and time. The present study revealed that certain metabolites of imidacloprid which have been described in crop plants are highly active against aphid pests in different types of bioassays. Some of these metabolites showed a high oral activity against the green peach aphid (Myzus persicae), and the cotton aphid (Aphis gossypii). The aphicidal potency of the metabolites investigated was weaker in aphid dip tests than in oral ingestion bioassays using artificial double membranes. The most active plant metabolite was the imidazoline derivative of imidacloprid. The LC₅₀ values of this metabolite for M. persicae and A. gossypii in oral ingestion bioassays were in the lower ppb-range, i.e. 0·0044 and 0·0068 mg litre^-1, respectively. Most of the other reported metabolites showed much weaker activity. Compared to imidacloprid, the imidazoline derivative showed superior affinity to housefly (Musca domestica) head nicotinic acetylcholine receptors, while all other metabolites were less specific than imidacloprid. It seems possible that, after seed treatment or soil application, a few of the biologically active metabolites arising are acting in concert with remaining levels of the parent compound imidacloprid, thus providing good control and long-lasting residual activity against plant-sucking pests in certain crops. © 1998 SCI.     

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.     

棉蚜抗药性现状及治理策略

棉蚜Aphis gossypii Glover是农业生产上最重要的害虫之一。化学杀虫剂一直以来都是棉蚜综合防治体系中的重要组成部分, 但化学杀虫剂的不合理使用导致棉蚜对多种杀虫剂均产生了高水平抗性。现有研究表明, 靶标位点突变、解毒酶基因的过表达以及某些肠道共生菌丰度的变化是导致棉蚜对杀虫剂产生抗性的主要机制。针对棉蚜抗性发展现状及其抗药性机制, 制定科学合理的抗性治理策略, 是充分发挥化学防治的优势、实现棉蚜可持续治理的关键。本文主要从棉蚜的抗药性现状、抗性机制和抗性治理策略3个方面对近10多年的主要进展进行了综述, 旨在为棉蚜抗药性长效治理和科学施策提供理论依据。     

Monitoring for imidacloprid resistance in the tobacco‐adapted form of the green peach aphid,Myzus persicae (Sulzer) (Hemiptera: Aphididae), in the eastern United States

BACKGROUND: Imidacloprid is the primary insecticide for controlling the tobacco‐adapted form of the green peach aphid (TGPA), Myzus persicae (Sulzer), a major pest of tobacco worldwide. This study used leaf‐dip bioassays to assess TGPA resistance to imidacloprid in the eastern United States from 2004 through 2007. RESULTS: When combined over the 4 year study, 18, 14 and 3% of the TGPA had imidacloprid resistance ratios (RRs) of 10–20‐fold, 20–30‐fold and 30–90‐fold, respectively, compared with the most susceptible colony tested. This indicates that some colonies have developed moderate levels of resistance to imidacloprid. A colony collected near Clayton, North Carolina, had the highest RR of 91 (LC₅₀ value = 31 mg L^?1). This resistance declined for six tests over a 3 year period in the laboratory culture from >130‐fold RR (LC₅₀ = 48 mg L^?1) to 40‐fold RR (LC₅₀ = 15 mg L^?1). Over the same period, the most susceptible colony and a standard colony not exposed to imidacloprid for over 7 years had consistently low LC₅₀ values. CONCLUSION: Moderate levels of resistance to imidacloprid are noticed among TGPA colonies from the eastern United States. The variation in resistance indicates that the factors responsible are present in the populations at low frequencies and are just not enough to cause field failures yet. Copyright © 2010 Society of Chemical Industry     

Use of the RFLP-PCR diagnostic test for characterizing MACE and kdr insecticide resistance in the peach potato aphid Myzus persicae

The peach-potato aphid Myzus persicae (Sulzer) has developed a number of insecticide resistance mechanisms owing to the high selective pressure produced by world-wide insecticide treatments. Knowledge of the geographical distribution and the temporal evolution of these resistant phenotypes helps to develop suitable pest-management programs. Current understanding of the major mechanisms of resistance at the molecular level makes it possible to diagnose the presence of modified acetylcholinesterase (MACE) or knockdown resistance (kdr). This paper describes a rapid method for the identification of both resistance mechanisms in a single molecular assay by using restriction fragment length polymorphism of PCR products (RFLP-PCR) in individual as well as pooled aphids.     

棉蚜抗药性及其化学防治

棉蚜［Aphis gossypii（Glover）］属半翅目蚜科,是一种世界性的害虫,主要通过取食植物汁液和传播病毒给农业生产造成严重损失。长期以来,棉蚜的防治一直以化学防治为主,棉蚜对有机氯、有机磷、氨基甲酸酯、拟除虫菊酯、新烟碱类等多种杀虫药剂已经产生了抗性。本文主要从棉蚜抗药性发展历史、抗药性机制以及棉蚜的化学防治等方面进行论述,期望能为农业生产上延缓棉蚜抗药性产生、有效治理棉蚜提供指导。     

6种农药对瓜蚜的毒力测定及田间药效

为了筛选防治西瓜瓜蚜的有效药剂,用6种药剂进行了室内毒力测定和田间药效试验。结果表明,1.8%阿维菌素EC对瓜蚜的毒力最高,60g/L乙基多杀菌素SC毒力最低,48hLC50分别为0.38mg/L和2 225.63mg/L。6种药剂毒力大小依次为阿维菌素溴氰虫酰胺氟啶虫胺腈啶虫脒吡虫啉乙基多杀菌素。田间试验结果表明,1.8%阿维菌素EC 3 000倍、10%溴氰虫酰胺OD 2 000倍、22%氟啶虫胺腈SC 4 000倍对瓜蚜速效性及持效性均较好,3~14d防效均达到90%以上,防效差异不显著;20%啶虫脒WP 3 000倍和10%吡虫啉WP 3 000倍速效性及持效性均较差,1d防效分别为31.31%和6.66%,14d防效分别为57.39%和47.80%;60g/L乙基多杀菌素SC 1 000倍防效最差,药后14d的最高防效仅为34.70%。推荐田间轮换使用阿维菌素、溴氰虫酰胺、氟啶虫胺腈防治瓜蚜。     

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.     

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.     

Green peach aphid,Myzus persicae (Hemiptera: Aphididae), reproduction during exposure to sublethal concentrations of imidacloprid and azadirachtin

BACKGROUND: Resurgence of insect pests following insecticide applications is often attributed to natural enemy disturbance, but hormesis could be an alternative or additional mechanism. Green peach aphid, Myzus persicae (Sulzer), is an important insect pest of many crops worldwide that may be exposed to sublethal insecticide concentrations over time. Here, the hypothesis that exposure to low concentrations of imidacloprid and azadirachtin can induce hormetic responses in M. persicae is tested in the laboratory. RESULTS: When insects were exposed to potato leaf discs dipped in sublethal concentrations of insecticide, almost all measured endpoints—adult longevity, F1 production, F1 survival and F2 production—were affected, and a statistically significant (P < 0.05) stimulatory response was recorded for F2 production following exposure to imidacloprid. No other measures for hormesis were statistically significant, but other trends of hormetic response were consistently observed. CONCLUSIONS: Given that variable distribution and degradation of insecticides in the field would result in a wide range of concentrations over time and space, these laboratory experiments suggest that exposure to sublethal concentrations of imidacloprid and azadirachtin could stimulate reproduction in M. persicae. Copyright © 2008 Society of Chemical Industry     

兰州市桃蚜抗药性监测及治理对策研究

以甘肃省宕昌县桃蚜为敏感种群,测定了兰州、永登等地桃蚜对6种杀虫剂抗药性。结果表明兰州市安宁区桃蚜对溴氰菊酯已产生低水平抗性(6.84倍),对氰戊菊酯则处于耐药力增高或敏感性降低阶段,对灭多威、敌敌畏、氧乐果和乐果已显示出早期抗性;永登县桃蚜对溴氰菊酯和氰戊菊酯处于敏感性降低阶段,对灭多威、敌敌畏、氧乐果和乐果仍属敏感阶段;皋兰县和榆中县桃蚜对上述6种杀虫剂则处于敏感阶段。用酶抑制剂进行增效作用测定结果显示,兰州地区桃蚜的抗药性与羧酸酯酶和多功能氧化酶有关。针对兰州市桃蚜的抗药性现状和抗性机制,提出了以建立抗性监测制度、合理用药为主的抗性治理对策。     

Field-simulator study of insecticide resistance conferred by esterase-, MACE- and kdr-based mechanisms in the peach-potato aphid,Myzus persicae (Sulzer)

Insecticide sprays were applied to Myzus persicae (Sulzer) populations carrying various combinations of three insecticide resistance mechanisms (esterase-based metabolic resistance and two target site mechanisms, known as MACE and kdr), supported on host plants growing in field simulator cages. The study showed that MACE confers extreme resistance to pirimicarb and triazamate (carbamate insecticides) but not to deltamethrin + heptenophos (16 + 1) (Decisquick) or dimethoate (an organophosphorus insecticide). Resistance to dimethoate depends solely on levels of esterase-based resistance, while resistance to Decisquick depends on kdr and esterase. None of the four insecticides is effective against aphids carrying MACE combined with extreme esterase-based resistance. This knowledge, in association with current monitoring of the mechanisms, will play an important role in making decisions on insecticide use against M persicae in the UK. © 1999 Society of Chemical Industry     

Evaluation of the biocontrol potential of various Metarhizium isolates against green peach aphid Myzus persicae (Homoptera: Aphididae)

BACKGROUND: Twenty‐three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non‐aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. RESULTS: The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm^?2 and blank control in three leaf‐dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 ± 1 °C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1–95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time–concentration–mortality model well, yielding parameters for the estimates of their LC₅₀ and LT₅₀ that vary with post‐spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC₅₀ values of 44–80 conidia mm^?2 on day 8 and LT₅₀ values of 4.9–6.8 days at 100 conidia mm^?2, with 91–98% of the killed aphids being well mycotised after death. CONCLUSION: The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids. Copyright © 2010 Society of Chemical Industry     

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     

Use of biochemical and DNA diagnostics for characterising multiple mechanisms of insecticide resistance in the peach-potato aphid,Myzus persicae (Sulzer)

The peach-potato aphid Myzus persicae (Sulzer) can resist a range of insecticides by over-producing detoxifying esterase and having mutant-insensitive forms of the target proteins, acetylcholinesterase (AChE), and the sodium channel. Using a combination of bioassays, biochemical and DNA diagnostics, it is now possible to diagnose all three mechanisms in individual aphids, and thereby establish their spatial distributions and temporal dynamics. A survey of 58 samples of wide geographic origin showed that all 46 resistant clones had amplified esterase genes (E4 or FE4) conferring broad-spectrum resistance to pyrethroids, organophosphates and carbamates. These occurred in combination with insensitive AChE (11 clones), conferring resistance to pirimicarb and triazamate, and/or mutant sodium channel genes (25 clones), conferring knockdown (kdr) resistance to pyrethroids and DDT. Amplified esterase genes were in linkage disequilibrium with both insensitive AChE and the kdr mutation, reflecting tight physical linkage, heavy selection favouring aphids with multiple mechanisms, and/or the prominence of parthenogenesis in many M. persicae populations. An ability to monitor individual mechanisms with contrasting cross-resistance profiles has important implications for the development of resistance management recommendations. ©1997 SCI