本研究旨在明确双丙环虫酯对棉蚜的急性毒性和双丙环虫酯亚致死浓度处理对棉蚜生物学特性的影响。结果表明，双丙环虫酯对棉蚜成虫高毒，其72 h的LC₅₀值为1.062 mg L^-1。双丙环虫酯亚致死浓度（LC₁₀）处理能够显著降低了F₀代和F₁代雌成虫的寿命、产蚜量及产蚜天数。同时，LC₁₀浓度处理后，棉蚜F₁代的成虫前期存活率也下降了30%。此外，与对照相比，双丙环虫酯处理后F₁代若虫发育历期、成虫前期、成虫产蚜前期、总产蚜前期均显著延长。双丙环虫酯亚致死浓度处理显著降低了F₁代的净繁殖率（R₀）、内禀增长率（r）和周限增长率（λ）。这些结果表明，双丙环虫酯亚致死浓度能够显著抑制棉蚜的种群增长。本研究结果将有助于科学评估双丙环虫酯对棉蚜的影响。

本文鉴定了一个小菜蛾的羧酸酯酶基因PxαE8，其开放阅读框共1599个核苷酸，编码532年氨基酸残基。对其时空表达谱研究表明，该基因在小菜蛾的不同发育阶段和不同部位或组织均有表达，尤其在幼虫、成虫以及幼虫的脂肪体、马氏管和血淋巴中高表达。进一步研究发现PxαE8在海南（HN）和广东（GD）两个多药抗性种群中的相对表达量分别是敏感种群的24.4-和15.5倍。利用RNAi干扰PxαE8在HN种群中的表达后再用LC₅₀的不同杀虫剂处理，发现用高效氯氰菊酯和辛硫磷处理可使其死亡率分别显著增加25.3%和18.3%。上述结果表明PxαE8的上调表达参与了小菜蛾对高效氯氰菊酯和辛硫磷的抗性，为进一步阐明小菜蛾和其他害虫对杀虫剂多药抗性的分子机制提供了基础。

草地贪夜蛾已扩散蔓延成为非洲和亚洲的重大农业害虫，但在其美洲原生地已通过种植转基因抗虫作物实现了有效控制。我们利用室内盆栽试验和田间小区评价的方法，研究了草地贪夜蛾对转基因抗虫玉米（Bt玉米）、普通玉米以及其它多种寄主植物的产卵偏好性。室内盆栽试验结果表明，和小麦等其它作物相比，草地贪夜蛾偏好在玉米植株上产卵，且普通玉米和Bt玉米产卵量无显著差异；但当幼虫孵化取食为害后，成虫主要在Bt玉米植株上产卵。田间小区试验亦证实，草地贪夜蛾在Bt玉米和普通玉米上的产卵量相近，但显著高于小麦、高粱、谷子、花生和大豆，普通玉米的百株虫量和叶片危害等级或受害株率均显著高于其他寄主植物。此后，因Bt玉米杀死孵化的幼虫而保持极低的受害率，草地贪夜蛾主要集中在Bt玉米植株上产卵，而大幅度减少在受害较重的普通玉米上产卵。本研究表明玉米是草地贪夜蛾嗜好产卵和取食的寄主植物，Bt玉米具有诱杀草地贪夜蛾产卵而减轻其它作物受害的生态学功能。

草地贪夜蛾已成为广泛发生的重大农业害虫，研究明确入侵种群对中国主要农作物的适应性是制定防控策略的基础。本研究构建了草地贪夜蛾取食油菜、大豆和向日葵的实验种群生命表，比较了3种寄主作物对其生长发育和种群增长的影响。结果表明：取食大豆草地贪夜蛾的幼虫存活率明显低于油菜和向日葵，且发育时间长（23.3 d）；取食油菜的蛹体重为0.19 g，显著高于其他两种寄主（取食大豆的蛹重仅为0.15 g）；取食大豆、油菜和向日葵的草地贪夜蛾平均世代周期（T）分别为42.21、39.10和40.44 d，种群内禀增长率（r）分别为0.0844、0.1041和0.1134，周限增长率（λ）分别为1.0881、1.1098和1.1202。总体而言，草地贪夜蛾取食向日葵的适合度高于大豆和油菜，但均能完成生活史并实现种群的快速增长。本研究表明大豆、向日葵和油菜是草地贪夜蛾的适宜寄主，生产上应加强3种作物田间草地贪夜蛾种群发生的监测与防治工作。

鉴于植物花蜜或花粉等补充营养是影响鳞翅目昆虫成虫生殖系统发育和产卵量的重要因素，我们测定了取食不同补充营养（5%洋槐蜂蜜水、5‰玉米花粉水、5‰油菜花粉水、5‰向日葵花粉水、5‰松花粉水、5‰玫瑰花粉水、2.5%洋槐蜂蜜+2.5‰油菜花粉水、2.5%洋槐蜂蜜+2.5‰松花粉水和清水）草地贪夜蛾成虫的内生殖系统发育进度、繁殖和飞行能力。研究结果表明，补充蜂花粉和蜂蜜可显著促进草地贪夜蛾内生殖系统的发育进度，增加产卵量，延长成虫寿命和飞行时间。取食5%洋槐蜂蜜水草地贪夜蛾的产卵前期、产卵期和寿命最长，分别为10.8、6.8和19.2天；而补充2.5%洋槐蜂蜜＋2.5‰松花粉草地贪夜蛾雌蛾的交配率最高，为79.7%，单雌产卵量达644.9粒，卵的孵化率为82.3%。取食蜂蜜可延缓草地贪夜蛾精巢的衰减，2.5%洋槐蜂蜜＋2.5‰松花粉对草地贪夜蛾卵巢发育的促进作用最强。与取食花粉相比，蜂蜜可显著增强草地贪夜蛾的飞行能力，取食5%洋槐蜂蜜水草地贪夜蛾的飞行时间最长（9.5 h），飞行距离最远（29.9 km），飞行速度最大（3.1 km/h）。研究结果对解析环境植被分布对入侵草地贪夜蛾种群消长动态的调控机制，发展成虫取食诱捕和综合治理技术有重要价值。

Received 10 May, 2017 Accepted 9 November, 2017

Aphids are considered as one of the key pests for wheat production worldwide.  Major aphid species that infest wheat in China include Sitobion avenae, Rhopalosiphum padi, Schizaphis graminum and Metopolophium dirhodum.  However, during our wheat field survey in Wenshang County of Shangdong Province, China, we observed that Aphis gossypii can feed on wheat.  The damage risk of A. gossypii on wheat was assessed using host shift method.  A population of A. gossypii collected from a wheat field in 2015 and another population reared on cotton under laboratory conditions for a decade without exposure to insecticides were used in the study.  The results of host shift demonstrated that the A. gossypii colony from wheat has not yet developed wheat specialization.  Moreover, the assessment of A. gossypii fitness on wheat and cotton showed that fecundity and net reproductive rate of A. gossypii population fed on wheat was significantly higher comparing to the population fed on cotton, whether the initial host of A. gossypii population was wheat or cotton.  This study raises a warning that the cotton aphid has potential to establish well on wheat and it may cause significant effects under specific circumstances.  Therefore, future studies are required to evaluate the effects of A. gossypii on wheat production.  

Carmine spider mites (Tetranychus cinnabarinus) and cotton aphids (Aphis gossypii) are both serious pests of cotton, and cause reductions in yields of this key agricultural crop.  In order to gain insights into how plant defense responses induced by one herbivore species affect the behavior and performance of another, we examined how infestation with T. cinnabarinus influences the development of A. gossypii using cotton as a model.  In this study, we measured the activities of several important biochemical markers and secondary metabolites in the leaves of cotton seedlings responding to infestation by T. cinnabarinus. Furthermore, the influences of T. cinnabarinus infestation on the development of A. gossypii in cotton were also examined.  Our data showed that the activities of several key defense enzymes, including phenylalanine ammonia-lyase (PAL), peroxidase (POD), lipoxygenase (LOX), and polyphenol oxidase (PPO), were substantially increased in cotton seedlings responding to spider mite infestation.  Further, the contents of gossypol and condensed tannins, key defensive compounds, were significantly enhanced in leaves of cotton seedlings following T. cinnabarinus infestation.  Moreover, the T. cinnabarinus-induced production of defense enzymes and secondary metabolites was correlated with infestation density.  The developmental periods of A. gossypii on cotton seedling leaves infested with T. cinnabarinus at densities of 10 and 15 individuals cm^–2 were 1.16 and 1.18 times that of control, respectively.  Meanwhile, the mean relative growth rates of A. gossypii on cotton leaves infested with T. cinnabarinus at densities of 8, 10 and 15 individuals cm^–2 were significantly reduced.  Therefore, these data suggested that the developmental periods of A. gossypii were significantly lengthened and the mean relative growth rates were markedly reduced when cotton aphids were reared on plants infested with high densities of spider mites.  This research sheds light on the role that inducible defense responses played in plant-mediated interspecific interactions between T. cinnabarinus and A. gossypii.

The red imported fire ant (Solenopsis invicta) is a global major invasive pest, and has caused significant economic, social and environmental impacts since its invasion to mainland of China in 2004. To date, chemical control has been the most effective measure. However, the long-term use of chemicals would lead to an unexpected rebound. To understand the risks and explore the mechanisms of detoxification or induction to insecticides in S. invicta, the O-demethylase activity and expression of cytochrome P450 genes of workers and queens, and the effects of chlorpyrifos and fipronil exposure in workers were investigated. Biochemical assays showed the O-demethylase activity of cytochrome P450 was significantly higher in workers than in queens (1.66-fold), and was significantly induced in workers exposed to chlorpyrifos and fipronil, reaching a maximum (3.00- and 1.95-fold) at 48 h and then decreasing dramatically compared to controls (exposed to acetone counterpart). The relative expression levels of 12 cytochrome P450 expressed sequence tags (ESTs) in workers were significantly higher than in queens (from 2.3- to 36.4-fold). Multiple cytochrome P450 genes (except 9E4) were co-up-regulated (from 1.5- to 2.86-fold) in workers exposed to fipronil. These results indicated that the increased O-demethylase activity may result from the increased transcription levels of cytochrome P450 related to detoxification of insecticides in S. invicta. It appears that cytochrome P450 plays an important role in enhanced metabolic detoxification of insecticides. At the same time, it also provides the theoretical basis for resistance management and rational usage of insecticides to control S. invicta.

    Carboxylesterase is a multifunctional superfamily and can be found in almost all living organisms. As the metabolic enzymes, carboxylesterases are involved in insecticides resistance in insects for long time. In our previous studies, the enhanced carboxylesterase activities were found in the chlorantraniliprole resistance strain of diamondback moth (DBM). However, the related enzyme gene of chlorantraniliprole resistance has not been clear in this strain. Here, a full-length cDNA of carboxylesterase pxCCE016b was cloned and exogenously expressed in Escherichia coli at the first time, which contained a 1 693 bp open reading frame (ORF) and encoded a protein of 542 amino acids. Sequence analysis showed that this cDNA has a predicted mass of 61.56 kDa and a theoretical isoelectric point value of 5.78. The sequence of deduced amino acid possessed the classical structural features: a type-B carboxylesterase signature 2 (EDCLYLNVYTK), a type-B carboxylesterase serine active site (FGGDPENITIFGESAG) and the catalytic triad (Ser186, Glu316, and His444). The real-time quantitative PCR (qPCR) analysis showed that the expression level of the pxCCE016b was significantly higher in the chlorantraniliprole resistant strain than in the susceptible strain. Furthermore, pxCCE016b was highly expressed in the midgut and epidermis of the DBM larvae. When the 3rd-instar larvae of resistant DBM were exposed to abamectin, alpha-cypermethrin, chlorantraniliprole, spinosad, chlorfenapyr and indoxacarb insecticides, the up-regulated expression of pxCCE016b was observed only in the group treated by chlorantraniliprole. In addition, recombinant vector pET-pxCCE016b was constructed with the most coding region (1 293 bp) and large number of soluble recombinant proteins (less than 48 kDa) were expressed successfully with prokaryotic cell. Western blot analysis showed that it was coded by pxCCE016b. All the above findings provide important information for further functional study, although we are uncertainty whether the pxCCE016b gene is actually involved in chlorantraniliprole resistance.

Carbohydrate chains are the principal antigens by which Bacillus thuringiensis (Bt) identify receptor proteins. The interaction between the antigen and Bt causes a pore in the membrane of midgut epithelial cells of insects. Receptor proteins, such as aminopeptidase N and alkaline phosphatase, are glycoproteins. Cadherin is another cell surface receptor protein which has potential glycosylation sites. Glycosyltransferase is very important for the synthesis and modification of receptor proteins. It can indirectly influence the function of Bt. The 1 950 bp full-length cDNA encoding β-1,3-galactosyltransferase was cloned from the the midgut of Helicoverpa armigera by degenerative PCR combined with RACE techniques (GAL-Harm, GenBank accession no.: GQ904195.1) with two potential N-glycosylation sites (157NNTI160 and 272NKTL275). Protein sequence alignments revealed that H. armigera β-1,3-galactosyltransferase shared high identity with β-1,3-galactosyltransferase in other insect species. The expression level of the β-1,3-galactosyltransferase gene in Cry1Ac-resistant H. armigera larvae was 9.2-fold higher than that in susceptible strain. The function of β-1,3-galactosyltransferase was investigated using RNAi technique. The result showed Cry1Ac enhanced the toxicity against the siRNA-treated larvae compared with non-siRNA-treated ones, which indicated β-1,3-galactosyltransferase played an important role for the insecticidal toxicity of Cry1Ac in H. armigera.

Differential effects of methamidophos and three pyrethroids on ATPase activity and membrane fluidity of mitochondria were investigated between the wolf spider (Pirata subpiraticus (Boes. et Str.)) and the rice stem borer (Chilo suppressalis (Walker)). Based on a comparison of LD50 values, the toxicities of the tested insecticides were higher to the wolf spider than to the rice stem borer. Cyhalothrin at 1×10–4 mmol L–1 caused inhibition of the mitochondrial Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities, and it’s inhibitions on Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities were significantly higher in the wolf spider (44 and 28%) than in the rice stem borer (19 and 11%). Methamidophos at 1×10–4 mmol L–1 decreased Ca2+-Mg2+-ATPase activity by 16 and 27% in the wolf spider and the rice stem borer, respectively, but no significant effect on the specific activity of Na+-K+-ATPase was observed. The DPH (1,6-diphenyl-1,3,5-hexatriene) fluorescence polarization values of mitochondrial membranes were not significantly affected by methamidophos in either species. However, cyhalothrin and alpha-cypermethrin induced the values of DPH polarization of mitochondrial membrane increasing with the concentration of cyhalothrin and alpha-cypermethrin from 20 to 100 μmol L–1 in the rice stem borer and the wolf spider. Effect of ethofenprox on fluidity of the wolf spider and the rice stem borer was contrary. These results suggest that both inhibition of membrane ATPase and changes of membrane fluidity could be appended to the action mechanisms of pyrethroid insecticides.

The insecticide chlorantraniliprole exhibits good efficacy and plays an important role in controlling the diamondback moth, Plutella xylostella Linnaeus. However, resistance to chlorantraniliprole has been observed recently in some field populations. At present study, diamondback moths with resistance to chlorantraniliprole (resistant ratio (RR) was 82.18) for biochemical assays were selected. The assays were performed to determine potential resistance mechanisms. The results showed that the selected resistant moths (GDLZ-R) and susceptible moth could be synergized by known metabolic inhibitors such as piperonyl butoxide (PBO), triphenyl phosphate (TPP) and diethyl-maleate (DEM) at different levels (1.68-5.50-fold and 2.20-2.89-fold, respectively), and DEM showed the maximum synergism in both strains. In enzymes assays, a high level of glutathione-S-transferase (GST) was observed in the resistant moth, in contrast, moths that are susceptible to the insecticide had only 1/3 the GST activity of the resistant moths. The analysis of short-term exposure of chlorantraniliprole on biochemical response in the resistant strain also showed that GST activity was significantly elevated after exposure to a sub-lethal concentration of chlorantraniliprole (about 1/3 LC50, 12 mg L-1) 12 and 24 h, respectively. The results show that there is a strong correlation between the enzyme activity and resistance, and GST is likely the main detoxification mechanism responsible for resistance to chlorantraniliprole in P. xylostella L., cytochrome P450 monooxygenase (P450) and carboxy-lesterase (CarE) are involved in to some extent.

Cry toxins produced by Bacillus thuringiensis (Bt) are effective biological insecticides against certain insect species. However, there are potential risks of the evolved resistance of insects to Cry toxin owing to decreased binding of toxins to target sites in the brush border membranes of the larva midgut. The Cry toxins with different binding sites in the larval midgut have been considered to be a good combination to deploy in delaying resistance evolution. Bioassay results demonstrated that the toxicity of different Cry toxins ranked differently for each species. The toxicity ranking was Cry1Ac>Cry1Ab>Cry2Ab for Helicoverpa armigera, Cry1B>Cry1C>Cry2Ab for Spodoptera exigua, and Cry2Ab>Cry1B> Cry1C for S. litura. Only Cry2Ab was toxic to Agrotis ipsilon. Binding experiments were performed with 125I-Cry1Ab, 125ICry1Ac, 125I-Cry1B, 125I-Cry1C, 125I-Cry2Ab and the brush border membranes vesicles (BBMV) from H. armigera, S. exigua, S. litura and A. ipsilon. The binding of Cry1Ab and Cry1Ac was shown to be saturable by incubating with increasing concentrations of H. armigera BBMV (Kd=(45.00±2.01) nmol L-1 and (12.80±0.18) nmol L-1, respectively; Bmax=(54.95±1.79) ng and (55.44±0.91) ng, separately). The binding of Cry1B was shown to be saturable by incubating with increasing concentrations of S. exigua BBMV (Kd=(23.26±1.66) nmol L-1; Bmax=(65.37±1.87) ng). The binding of 125ICry toxins was shown to be non-saturable by incubating with increasing concentrations of S. litura and A. ipsilon BBMV. In contrast, Cry1B and Cry1C showed some combination with the BBMV of S. litura, and a certain amount of Cry2Ab could bind to the BBMV of A. ipsilon. These observations suggest that a future strategy could be devised for the focused combination of specific cry genes in transgenic crops to control target pests, widen the spectrum of insecticide effectiveness and postpone insect resistance evolution.

The 7-ethoxycoumarin O-deethylase (ECOD) activities of cytochrome P450s and differential expression of six cytochrome P450 genes induced by the volatiles from both damaged and undamaged maize plants were investigated in the cotton bollworm, Helicoverpa armigera (Hübner). The ECOD activity changed with time of exposure to maize volatiles. At 36 h after cotton bollworm larvae exposure to maize volatiles, the ECOD activities in cotton bollworm damaged and artificially damaged groups were 2.36 and 4.53 times higher than the control group respectively. The relative expression levels of CYP4S1, CYP6B2 and CYP6B7 in the cotton bollworm were significantly increased in artificially damaged plant group, which was 2.93, 5.09 and 10.66 times higher than that in the control group, respectively. The expression levels of CYP6B2, CYP6B6, CYP9A12, and CYP9A14 were much lower in the larvae exposure to volatiles from both healthy and pest damaged maize seedlings than in the control group at 12 h after larvae exposure to maize volatiles. For the cotton bollworm damaged maize group, the expression of CYP4S1 and CYP9A14 increased.

Metaflumizone is a novel sodium channel blocker insecticide, which has been registered for controling the diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae) in China. It is unavoidable for DBMs to be exposed to sublethal dose of metaflumizone in brassicaceous vegetable field. Sublethal effects of metaflumizone at LC15 (1.06 mg L-1) and LC25 (2.03 mg L-1) on the biological characteristics were investigated. Pupation rate, pupal period and pupal weight were significantly declined comparing with the control (P=0.05) when third instar larvae were exposed to LC15 and LC25 of metaflumizone. Comparing the control group to LC15 and LC25 treatment groups, there were significant differences in the development periods of eggs, first instar larvae, pupae and total preoviposition period. The peak of age-specific fecundity in LC15 and LC25 treatment groups was lagged behind control group. Mean values of intrinsic rate of increase (rm), net reproductive rate (R0) and finite rate of increase (λ) observed from the LC15 and LC25 treatment groups were lower than those from the control group. But mean values of gross reproduction rate (GRR) was not different. The mean generation time (T) of the treatment groups was prolonged. Whether sublethal doses of metaflumizone could stimulate reproduction in the long term needs further investigation on continuous generations.

Cry toxins produced by Bacillus thuringiensis (Bt) are effective biological insecticides against certain insect species. In this study, bioassay results indicated that Cry1B and Cry1C were toxic to Spodoptera exigua. We also identified a cadherin-like gene in S. exigua that could enhance the toxicity of Cry1B and Cry1C. The cadherin-like gene identified from the larvae midgut tissue was cloned by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The full-length cDNA of the gene consisted of 5 220 bp encoding 1 740 amino acid with a predicted molecular mass of 196 kD. BLAST search analysis showed that the predicted amino acid sequence had a high sequence identity to the published sequences of cadherin-like proteins from other Lepidoptera insects. Spatial expression of the cadherin-like gene detected by qRT-PCR analysis revealed that the cadherin-like gene was mainly present in the gut of 4th instar larvae and during different life stages. The results suggested that the commercial development of this synergist has the potential to enhance Cry1B and Cry1C toxicity against Lepidoptera insects.

The whitefly Bemisia tabaci are considered as a taxonomically complex that contained some destructive pests. Two of the most prevalent cryptic species are B. tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED). In an extensive field survey of the B. tabaci complex present throughout part of China from 2004 to 2007, we obtained 93 samples of B. tabaci from 22 provinces. We determined that these Chinese haplotypes included 2 invasive species (MEAM1 and MED), and 4 indigenous cryptic species (Asia II 1, Asia II 3, China 3 and Asia II 7) by sequencing mitochondrial cytochrome oxidose one gene (mtCOI). The diversity and genetic differentiation of a subset of 19 populations of B. tabaci were studied using cDNA amplified fragment length polymorphism (AFLP). Prior to 2007, MEAM1 was a dominant species in many provinces in China. By 2007, MED was dominant in 11 provinces. Both invasive and indigenous species were simultaneously found in some regions. Indigenous species of B. tabaci were found in six provinces in southern China. MED and MEAM1 have broad ranges of host plants, and indigenous species appeared to have much narrower host ranges. All Asia II 3 samples were found on cotton except one on aubergine. China 3 has more host plants than Asia II 3. Twelve samples of China 3 were collected from sweet potato, Japanese hop, squash and cotton. A total of 677 reproducible bands amplified with 5 AFLP primer combinations were obtained. The highest proportion of polymorphic bands was 98.7% and the lowest was 91.9%. Unweighted pair-group method analysis indicated that the clustering was independent of the different species. MED showed the lowest degree of similarity than the other species. The data indicate that both MEAM1and MED were rapidly established in China.

The gene expression and activity of (+)-d-cadinene synthase during cotton development and in response to stress, as well as the spatial and temporal pattern of sesquiterpene biosynthesis, constitute one of chemical defense mechanisms in cotton plants. In order to explore the effects of omethoate on the cotton defense in relation to (+)-d-cadinene synthase and gossypol, effects of omethoate treatments on activity of (+)-d-cadinene synthase and gossypol content in cotton seedlings were investigated. Cotton seedlings treated with 400 mg L-1 omethoate exhibited a significant decrease in the specific activity of (+)-d-cadinene synthase from 12 to 120 h after treating when compared to the untreated control; significantly lower (+)-d-cadinene synthase activity was also observed in cotton seedlings treated with 200 mg L-1 omethoate from 72 to 120 h after treating; but for cotton seedlings treated with 100 mg L-1 omethoate, from 12 to 120 h after treating, no significant changes were observed for activity of (+)-d-cadinene synthase. The gossypol content in cotton seedlings treated with 100, 200 or 400 mg L-1 omethoate for different time periods showed no significant changes compared to that of the control. These results indicated that the activity of (+)-d-cadinene synthase in cotton seedlings in responses to exposure of omethoate at three concentrations for different time periods followed dose- and time-dependent responses to omethoate exposure. With omethoate as a chemical stress factor for cotton seedlings, the cotton defense in relation to the activity of (+)-d-cadinene synthase in cotton seedlings may be affected by omethoate application.