Characteristics of 13 polymorphic microsatellite markers in the corn earworm,Helicoverpa zea (Lepidoptera: Noctuidae)

Thirteen polymorphic microsatellite loci suitable for population genetic studies of Helicoverpa zea were discovered by screening partial genomic libraries enriched for microsatellite sequences. Insects collected (N = 96) in Stoneville, Mississippi were used to characterize these markers. The observed and effective number of alleles per locus ranged from two to nine (average 4.46) and from 1.07 to 2.45 (average 1.81), respectively. Fisher exact tests detected significant deviations from Hardy–Weinberg equilibrium at three loci, probably due to inbreeding, null alleles, or Wahlund's effect. Significant genotypic disequilibrium was not detected between any pair of loci.     

Mycelia and spent fermentation broth of Beauveria bassiana incorporated into synthetic diets affect mortality,growth and development of larval Helicoverpa zea (Lepidoptera: Noctuidae)

Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation.     

Helicoverpa zea males (Lepidoptera: Noctuidae) respond to the intermittent fine structure of their sex pheromone plume and an antagonist in a flight tunnel

Abstract. We investigated the behavioural response of male Helicoverpa zea (Boddie) to the fine-scale structure of an odour plume experimentally modified in a wind tunnel by using an air-pulsing device. Male H. zea flew upwind to pulsed filaments of a binary pheromone blend of (Z)-11-hexadecanal (Z11-16:Ald) and (Z)-9-hexadecanal (Z9-16:Ald) in the ratio of 20:1. Sustained upwind flight in experimentally altered intermittent plumes was dependent on concentration, as well as the frequency of generation of odour filaments. At a loading of 10μg of the major pheromone component, Zll-16:Ald, which gave an emission rate of approximately that released by a female H. zea , sustained upwind flight and source contact correlated positively with filament delivery rate, becoming significant at a minimum filament delivery rate of 2/s. Decreases in upwind progress and source location were recorded at a loading of 1 μg of Z11-16:Ald. At this suboptimal dosage, a high filament generation rate of 10/s was necessary for significant upwind progress and source contact. When an interspecific compound: (Z)-11-hexadecenyl acetate (Z11-16:OAc), was added to the attractive pheromone binary aldehyde blend of H. zea at a proportion of 10% of the major pheromone component, and pulsed from the same source, there was a significant reduction in sustained upwind progress and source location by males, indicating that Z11-16:OAc is antagonistic to the upwind progress of H. zea. However, Z11-16:OAc was less antagonistic when its filaments were isolated and alternated with pheromone filaments, indicating a strong effect of the synchronous arrival of odour filaments on the antenna needed for antagonism of upwind flight.     

Potentialities of methoxyfenozide for the integrated management of Helicoverpa armigera (Lepidoptera: Noctuidae) on cotton in Benin,West Africa

Intensive use of chemical insecticides against Helicoverpa armigera has led to the development of resistance to the major chemical families of insecticides. Consequently, management of H. armigera using conventional chemical insecticides is increasingly difficult. Methoxyfenozide is an agonist of the insect moulting hormone 20-hydroxyecdysone that acts faster than chitin synthesis inhibitors. The present work is aimed to assess the effectiveness of methoxyfenozide for use against H. armigera on cotton in Benin, West Africa. Laboratory tests and field experiments have been carried out. For laboratory studies, topical application of methoxyfenozide was done using L2 and L5 instar larva of H. armigera. Tested methoxyfenozide concentrations varied from 24 μl/ml to 144 μl/ml and the control is water only. For field experiments, a complete randomised block design was used with methoxyfenozide (72 μl/ml) and a control (no spraying). Berthoud Ultra Low Volume sprayer was used to spray methoxyfenozide suspension at 60-l per hectare. Two sprays were applied, 7 days apart. Laboratory tests indicated that 24 h after application of methoxyfenozide, about 100% of treated L2 and L5 larva were morbid or dead compared with 0% for the control larva. There are no significant differences between tested concentrations. Morbid larvae died within 2 days. In field experiments, cotton yield harvested on methoxyfenozide treated plants was double of that obtained on untreated plants (9375 kg and 4875 kg per hectare respectively). Thus methoxyfenozide may be used as component of Integrated Pest Control Programme on cotton in Benin, West Africa.     

Role of chemical cues from cotton in mediating host selection and oviposition behaviour in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

We investigated the role of chemoreception in the host selection and oviposition behaviour of Helicoverpa armigera in the laboratory using five cotton genotypes and synthetic volatile terpenes. Female moths oviposited on substrates treated with methanol, ethanol, acetone and pentane extracts of leaves, squares and flowers of the cotton genotypes. Phytochemicals soluble in pentane were the most efficient in eliciting oviposition behaviour. In a two-way bioassay, pentane extracts of leaves or squares of a Multiple Host-plant Resistance genotype (MHR11), Deltapine commercial (DP90), and Smith Red Leaf (SRL) received significantly more eggs than solvent-treated controls. Extracts of squares of the native genotype Gossypium nelsonii did not receive more eggs. Females preferred DP90 and MHR11 to SRL and G. nelsonii. Female moths also laid more eggs on pentane extracts of MHR11 flowers than MHR11 leaves from preflowering, early flowering and peak-flowering plants. In a flight chamber, female moths used olfactory cues at short range to mediate oviposition and discrimination between host plants. Egg-laying, mated females were attracted at a distance (1.5 m) to volatile compounds released by whole plants and odours emanating from filter papers treated with synthetic volatile terpenes. Individually, the terpenes did not stimulate any significant oviposition response. However, there was a significant oviposition response to a mixture of equal volumes of the terpenes ( trans -β-caryophyllene, α-pinene, β-pinene, myrcene, β-bisabolol, and α-humulene). Conversely, antennectomised (moths with transected antennae), egg-laying, mated females did not stimulate any significant oviposition response. The significance of these findings in relation to H. armigera host-plant selection are discussed.     

棉铃虫卵巢形态与卵子发生过程观察

害虫发生高峰期、 发生量的准确预测和田间防治适期的确定与种群雌虫卵巢结构及卵子发生过程密切相关。为了明确棉铃虫Helicoverpa armigera卵巢结构及卵子发生过程, 本研究利用光学体视显微镜和透射电子显微镜, 对棉铃虫成虫卵巢管和卵子的超微结构进行了研究, 并确定了发育级别划分标准。结果表明: 根据卵巢的形状、 卵的产生过程、 卵黄沉积情况等将棉铃虫卵巢发育程度分为6个级别, 即发育初期(0级)、 卵黄沉积前期(Ⅰ级)、 卵黄沉积期(Ⅱ级)、 成熟待产期(Ⅲ级)、 产卵盛期(Ⅳ级)和产卵末期(Ⅴ级)。根据卵子发生过程中滋养细胞、 卵母细胞的变化, 将卵子发生期分为3个阶段： 卵黄发生前期、 卵黄发生期和卵黄成熟期。本研究首次对棉铃虫的卵子发生进行电子显微观察, 并完善了棉铃虫卵巢发育的分级标准, 为进一步研究棉铃虫的生殖发育机理提供了理论参考, 对田间棉铃虫种群发生期和发生量的预测预报也有重要的实践参考价值。     

Novel polymorphic microsatellite markers developed in the cotton bollworm Helicoverpa armigera （Lepidoptera：Noctuidae）

A novel set of five polymorphic di- or trinucleofide microsatellite loci suitable for population genetic study were developed from an enriched genomic library for the pest insect cotton bollworm, Helicoverpa armigera, and cross-amplifiability of these and other published loci was tested in a closely related species, the tobacco budworm, H.assulta. The expected heterozygosity at these loci ranges from 0.62 to 0.91 in the cotton bollworm. The observed allele numbers varies from 4 to 12 in the limited number of individuals tested. Although a large proportion of cloned microsatellite sequences are present in multi-copy in the cotton bollworm genome, the overwhelming majority of the finalized polymorphic diallelic loci are tri-nucleotide microsatellites - an unexpected outcome, which should facilitate subsequent genotyping analysis.     

棉铃虫蜕皮时期同工酶表达模式

同工酶广泛存在于不同种属生物的组织细胞中,在生物发育的不同阶段有着特定的表达模式和重要的生理功能。昆虫蜕皮是在促前胸腺激素（PTTH）、蜕皮激素和保幼激素共同控制下由一系列基因表达和调控的级联反应。阐明蜕皮发育过程中同工酶的表达模式,可以为研究蜕皮的分子机理提供新的分子靶标,为研制生长调节剂类杀虫剂提供检测的分子标记。该研究分析了棉铃虫Helicoverpa armigera蜕皮时期不同组织中过氧化物酶、乙醇脱氢酶和酯酶的表达模式,找到了3种蜕皮差异表达的过氧化物酶, 2种蜕皮或变态差异表达的乙醇脱氢酶,3种蜕皮差异表达的酯酶。生长调节剂类化学杀虫剂非甾醇类蜕皮激素竞争物RH24-85可以诱导3种酯酶表达上调,可能与蜕皮有关。这些结果为进一步研究棉铃虫蜕皮的分子机理和检测促蜕皮生长调节剂类化学杀虫剂提供了新的分子靶标。     

棉铃虫漆酶2基因的分子鉴定

【目的】黑化反应在昆虫表皮骨化以及免疫防御过程中起着重要作用, 酚氧化酶是黑化反应中的关键酶类, 漆酶2 (laccase2, LAC2)是酚氧化酶的一种, 在昆虫变态发育和免疫系统中起着重要的作用。本研究旨在探讨LAC2在棉铃虫Helicoverpa armigera表皮骨化中表达模式及激素调控作用。 【方法】采用PCR及RACE的方法, 从棉铃虫5龄幼虫中得到了lac2 cDNA全序列。利用荧光定量PCR、 激素处理及RNA干扰方法, 对LAC2的表达模式差异和激素调控作用进行分析。【结果】序列分析表明, lac2 cDNA全长3 221 bp, 编码框长度为2 268 bp, 编码756个氨基酸残基。发育时序表达分析发现, lac2在幼虫各龄期表达规律相似, 均在蜕皮期高水平表达, 在5龄96 h转录水平达到最高峰。组织表达结果分析, lac2基因在幼虫表皮和成虫卵巢以及触角表达量较高。激素处理实验发现, 保幼激素类似物（methoprene）对lac2基因转录有抑制作用; 蜕皮激素（20-hydroxyecdysone）则促进其表达。进一步利用RNA干扰蜕皮激素受体EcR （ecdysone receptor）和USP （ultraspiracle isoform）基因发现, 干扰后蜕皮激素受体的表达明显受到抑制, 同时lac2基因的表达也显著受到抑制, 表明蜕皮激素调控lac2基因转录。【结论】这些结果为进一步研究漆酶在昆虫表皮的骨化以及免疫防御等方面不同的生理功能提供理论依据。     

光温条件明显影响棉铃虫的滞育强度

为了探明不同地理种群棉铃虫Helicoverpa armigera滞育强度的地理变异, 本研究系统地比较了光温条件（光照时数 11～16 h, 恒温20, 22, 25, 28和31℃及变温）对来自中国的4个地理种群（广东广州、 江西永修、 山东泰安和辽宁喀佐）棉铃虫滞育强度的影响。结果表明： 滞育诱导的光周期对继后棉铃虫的滞育强度有明显影响。在光照时数11～14 h范围内, 各地理种群的滞育持续期均随着光照时数的增加而延长。滞育强度也受到滞育诱导的温周期影响, 当光期温度相同时, 低纬度的GZ种群温周期比恒温有更强的诱导效应; 中纬度的YX种群温周期与恒温具有相同的滞育诱导强度; 高纬度的KZ和TA种群温周期所诱导的滞育强度一般低于恒温。滞育解除过程中的温度也显著影响到滞育的解除, 在20~31℃下, 温度愈高滞育解除愈快; 滞育持续期同时受到滞育诱导温度的影响, 对于北方的泰安种群和喀佐种群, 较高的滞育诱导温度能诱导更强的滞育。     

Possible effect of genetically modified cotton on foraging habits of early instar Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae

Abstract  We estimated survival and final location of neonate Helicoverpa armigera after 72 h on both genetically modified (GM) and conventional cotton at the squaring stage. On average, about 2.5% out of a total of 1620 initial larvae survived on two gene GM cotton (CS × 450, 289BGII®) compared with 39.5% out of a total of 810 initial larvae on Sicot 189, a conventional cotton variety. A disproportionate number of larvae were collected on squares of GM cotton, assuming they behave the same way on GM plants as on conventional plants but suffer higher rates of mortality. Our results imply that the behaviour of neonates on GM plants in terms of finding squares (and/or better survival on squares) may be contributing to the continued pest status of Helicoverpa on GM cotton from time to time. Experiments to determine if selection for changed behaviour in the field has or is occurring are urgently required.     

Impact of Cheiracanthium pelasgicum (Araneae: Miturgidae) and Chrysoperla carnea (Neuroptera: Chrysopidae) intraguild predation on the potential control of cotton pest Helicoverpa armigera (Lepidoptera: Noctuidae)

Antagonist interactions such as intraguild predation (IGP) or cannibalism among predatory arthropods can reduce the impact of these invertebrates on pest limitation in agroecosystems. Here, the effects of IGP between two major natural enemies of cotton pests, the cursorial spider Cheiracanthium pelasgicum (C.L. Koch) and the common green lacewing Chrysoperla carnea (Stephens), were studied under laboratory conditions. First, a feeding preference test was carried out to determine the degree of C. pelasgicum preference for lacewing larvae, using second-instar Helicoverpa armigera larvae as alternative prey. In a second bioassay, the effects of predator interactions on potential predation of H. armigera larvae were analysed using three treatment combinations (plus a control with no predator): (1) spider alone, (2) lacewing larvae alone, (3) spider + lacewing larvae. Potential predation by C. pelasgicum on lacewing eggs was also studied. C. pelasgicum showed no significant preference for either of the two species, indicating that this spider may impact negatively on the green lacewing population. Findings revealed no additive effects and an antagonist interaction between C. pelasgicum and green lacewing larvae, which adversely affected H. armigera suppression; both predators displayed lower predation rates when kept together than either predator alone. However, presence of lacewing larvae and subsequent unidirectional IGP did not affect the predation capacity of C. pelasgicum. Finally, predation rates of C. pelasgicum on lacewing eggs were very low (mean 2.35 ± 0.71 eggs, 24 h after offering) indicating that the impact of C. pelasgicum on lacewing populations may be limited.     

光强度对棉铃虫交配行为的影响

【目的】为阐明光强度对棉铃虫Helicoverpa armigera (Hübner)交配行为的影响。【方法】本实验设置4个光照强度(0,0.5,5.0和50.0 lx),观察记录不同光照强度下棉铃虫雌蛾的求偶行为;分别通过单个腺体性信息素提取法和解剖雌虫受精囊的方式,检测不同光照强度下棉铃虫的雌蛾性信息素滴度和交配率。【结果】在强光(50.0 lx)下,棉铃虫雌蛾求偶起始时间最长,求偶持续时间最短,求偶次数最少,雌蛾性信息素滴度始终处于较低水平,交配率也属于最低。在微光(0.5 lx)下,雌蛾求偶起始时间最短,求偶持续时间最长,求偶次数最多;雌蛾性信息素始终处于较低水平,但暗期后段求偶率高达40%。【结论】强光(50.0 lx)可以抑制棉铃虫雌蛾的求偶行为、性信息素的合成及交配;微光(0.5 lx)可以促进棉铃虫雌蛾的求偶行为;相对黑暗环境(0 lx),微光(0.5 lx)还可以促进棉铃虫快速(1 h)完成交配,微光(0.5 lx)对棉铃虫的交配行为具有重要意义;求偶和性信息素的合成没有必然联系。本研究可为探讨光对夜蛾交配行为的影响提供一定的理论基础,也可为利用物理、化学通讯信息调控夜蛾行为提供一定的参考。     

Effects of climate change on different geographical populations of the cotton bollworm Helicoverpa armigera (Lepidoptera,Noctuidae)

The effects of climate change on pest phenology and population size are highly variable. Understanding the impacts of localized climate change on pest distribution and phenology is helpful for improving integrated pest management strategies. Here, the population dynamics of cotton bollworms (Helicoverpa armigera) from Maigaiti County, south Xinjiang, and Shawan County, north Xinjiang, China, were analyzed using a 29‐year dataset at lower latitudes and a 23‐year dataset at higher latitudes to determine the effects of climate change on the population dynamics of H. armigera. The results showed that all generations of H. armigera at both sites showed increasing trends in population size with climate warming. Abrupt changes in phenology and population number occurred after abrupt temperature changes. Climate change had a greater effect on the phenology of H. armigera at higher latitudes than at lower latitudes and led to a greater increase in population size at lower latitudes than at higher latitudes; the temperature increase at higher latitudes will cause a greater increase in the adult moth population size in the future compared to that at lower latitudes; and abrupt changes in the phenology, temperature increase, and population size at lower latitudes occurred earlier than those at higher latitudes. Thus, it is necessary to develop sustainable management strategies for Helicoverpa armigera at an early stage.     

中红侧沟茧蜂对不同龄期棉铃虫幼虫及其为害棉株的趋性反应

研究中红侧沟茧蜂Microplitis mediator Haliday对棉铃虫Helicoverpa armigera Hübner幼虫及其为害棉株的趋性行为, 可为高效应用中红侧沟茧蜂控制棉铃虫提供理论依据。本研究在实验室内以中红侧沟茧蜂雌蜂、1~5龄棉铃虫幼虫及其为害棉花植株（去虫或未去虫）为试验材料, 采用“Y”型昆虫嗅觉仪测定了中红侧沟茧蜂雌蜂对1~5龄棉铃虫幼虫及其为害棉株的趋性行为反应。结果表明: 中红侧沟茧蜂对3龄、4龄和5龄棉铃虫幼虫均没有明显的趋向行为反应, 1龄和2龄棉铃虫幼虫对中红侧沟茧蜂有显著的引诱作用。此外, 1~5龄棉铃虫幼虫为害后去虫棉株与健康棉株均对中红侧沟茧蜂有吸引作用。在未去虫的处理中, 虫害诱导棉株比健康植株更能吸引中红侧沟茧蜂, 与健康植株差异显著, 而且不同龄期棉铃虫幼虫为害处理间差异较大, 对中红侧沟茧蜂引诱作用的相对顺序为: 5龄为害植株>2龄和4龄为害植株>1龄和3龄为害植株 (2龄和4龄为害处理间差异不显著; 1龄和3龄为害处理间差异不显著)。本研究结果可为中红侧沟茧蜂在生物防治上的应用提供一定的理论指导和实践依据。     

棉铃虫幼虫自相残杀习性与其龄期和食物营养的相关性（英文）

【目的】 昆虫自相残杀行为可以促进特定病原体的传播,这在利用昆虫病原体防治害虫方面有潜在的应用价值。本研究旨在探究棉铃虫 Helicoverpa armigera 幼虫自相残杀习性与其龄期及食物营养之间的相关性。【方法】 分别饲喂室内品系和野外品系的棉铃虫幼虫含不同Na⁺浓度的人工饲料,并在饲养至3龄、4龄、5龄和6龄时,将取食相同饲料的10头幼虫为一群组移入同一培养皿中,通过测定各处理幼虫存活率,评估幼虫龄期和饲料中的Na⁺含量对自相残杀行为的影响。【结果】 当以3龄和4龄为群组的起始龄期时,棉铃虫幼虫存活率显著低于起始龄期为5龄和6龄的群组。此外,取食正常人工饲料的幼虫存活率最高,取食缺钠饲料时,幼虫存活率明显下降。最后,幼虫群组起始龄期和食物Na⁺含量对幼虫化蛹率无明显影响。【结论】结果说明,棉铃虫4和5龄幼虫与3和6龄幼虫相比,自相残杀行为发生的概率更大,而Na⁺含量较低的食物在一定程度上促进自相残杀行为发生的可能性。本研究为在这一领域的进一步工作提供了基础。     

Detection and evolution of resistance to the pyrethroid cypermethrin in Helicoverpa zea (Lepidoptera: Noctuidae) populations in Texas

The bollworm, Helicoverpa zea (Boddie), is a key pest of cotton in Texas. Bollworm populations are widely controlled with pyrethroid insecticides in cotton and exposed to pyrethroids in other major crops such as grain sorghum, corn, and soybeans. A statewide program that evaluated cypermethrin resistance in male bollworm populations using an adult vial test was conducted from 2003 to 2006 in the major cotton production regions of Texas. Estimated parameters from the most susceptible field population currently available (Burleson County, September 2005) were used to calculate resistance ratios and their statistical significance. Populations from several counties had statistically significant (P < or = 0.05) resistance ratios for the LC(50), indicating that bollworm-resistant populations are widespread in Texas. The highest resistance ratios for the LC(50) were observed for populations in Burleson County in 2000 and 2003, Nueces County in 2004, and Williamson and Uvalde Counties in 2005. These findings explain the observed pyrethroid control failures in various counties in Texas. Based on the assumption that resistance is caused by a single gene, the Hardy-Weinberg equilibrium formula was used for estimation of frequencies for the putative resistant allele (q) using 3 and 10 microg/vial as discriminatory dosages for susceptible and heterozygote resistant insects, respectively. The influence of migration on local levels of resistance was estimated by analysis of wind trajectories, which partially clarifies the rapid evolution of resistance to cypermethrin in bollworm populations. This approach could be used in evaluating resistance evolution in other migratory pests.