Pattern of cross-resistance in pyrethroid-selected populations of Helicoverpa armigera Hübner (Lep., Noctuidae) from India

Abstract:  In Helicoverpa armigera , withdrawal of selection pressure resulted in a two- to fourfold increase in susceptibility to synthetic pyrethroids and continuous selection enhanced the resistance level by four- to fivefold to the respective pyrethroids at the end of the 14th generation. Populations selected for resistance to one pyrethroid showed positive cross-resistance to all other pyrethroids, but no cross-resistance to endosulfan and thiodicarb. There was a significant increase in mixed-function oxidase activity with advancing generation suggesting its possible role in the positive cross-resistance among the pyrethroids. The induction of carboxyl esterases in pyrethroid-selected populations may have resulted in the activation of indoxacarb, thereby accounting for the observed negative cross-resistance.     

Relationship between oviposition preference and offspring performance in Australian Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract We investigated the oviposition preference and larval performance of Helicoverpa armigera under laboratory conditions to determine if the oviposition preference of individual females on maize, cowpea and cotton correlates with offspring performance on the leaves of the same host plants. The host-plant preference hierarchy of females did not correlate with their offspring performance. Female moths chose host plants that contributed less to their offspring fitness. Plant effects accounted for the largest amount of variation in offspring performance, while the effects of female (family) was low. The offspring of most females (80%, n  = 10) were broadly similar, but 20% (two out of 10), showed marked difference in their offspring performance across the host-plant species. Similarly, there was no relation between larval feeding preference and performance. However, like most laboratory experiments, our experi-mental design does not allow the evaluation of ecological factors (for example, natural enemies, host abundance, etc.) that can play an important role in larval performance in the field. Overall, the results highlight the importance of carrying out preference performance analysis on the individual or family level, rather than pooling individuals to obtain average population data.     

Active compounds in Populus nigra L. wilted leaves responsible for attracting Helicoverpa armigera (Hübner) (Lep., Noctuidae) and new agaropectin formulation

Abstract:  The leaf extracts of Populus nigra were collected and identified by steam distillation, air entrainment and gas chromatographic–mass spectrometric analysis. Electroantennograms were recorded from Helicoverpa armigera adults in response to the chemicals identified. Both aromatic compounds and green-leaf volatiles elicited strong responses. Field experiments revealed that the active compounds responsible for attracting H. armigera moths are mainly short-side-chain aromatic alcohols and aldehydes. We, for the first time, used agaropectin as the controlled-release matrix of insect attractants. A five-component lure containing all the aromatics without phenolics, mixed in the proportions as found in the steam distillate of the leaves collected in August, produced the best trap catch. The results showed that the volatiles of wilted leaves of P. nigra can attract H. armigera adults by feeding attraction.     

Impact of males on the progeny sex ratio of Campoletis chlorideae (Hym., Ichneumonidae), a parasitoid of Helicoverpa armigera (Hübner) (Lep., Noctuidae)

Abstract: The endoparasitoid Campoletis chlorideae and its host Helicoverpa armigera were reared in the laboratory to determine the progeny sex ratio of C. chlorideae in the presence and absence of male parasitoids. It was observed that the presence of male parasitoids affects the progeny sex ratio by decreasing the number of females in the offspring population, i.e. a significant increase in the proportion of males was observed in united sexes. Therefore, while constructing the life table of the parasitoid, the effect of presence of male parasitoids, should be considered together with other factors, which decreases the efficiency of the parasitoid.     

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.     

Partial purification of Cytochrome P450 from Helicoverpa armigera (Hübner)

Abstract The cytochrome P450 (Cyt‐P450) proteins from the fat body and midgut of the cotton bollworm, Helicoverpa armigera, were respectively partially purified by a set of purification procedures including differential centrifugation, solubilization of CHAPS, protein precipitation by PEG precipitation and DE‐32 column chromatography. The Cyt‐P450 was detected by methods of CO difference spectrum and SDS‐PAGE. Fraction of detergent solubilized microsomes from the fat body of H. armigera was purified more than 17‐fold. Three protein bands were detected by SDS‐PAGE with molecular masses of 70 600, 63 300 and 571 200Da. It is possible that the proteins with molecular mass of 63 300 and 571 200Da were the isozymes of Cyt‐P450.     

单宁酸对棉铃虫谷胱甘肽S转移酶的影响

通过培养基混药法,研究了植物次生物质单宁酸对棉铃虫Helicoverpa armigera（Hübner）谷胱甘肽S-转移酶活性的影响。谷胱甘肽S-转移酶活性随棉铃虫发育期的进程而变化,在卵期最低,5龄、6龄幼虫和成虫期最高。用含0.005%单宁酸的饲料饲喂棉铃虫后,5龄和6龄幼虫的谷胱甘肽S-转移酶活性明显降低,分别为对照的59%和67%。单宁酸低剂量、短时间处理棉铃虫幼虫,可诱导中肠和脂肪体中的谷胱甘肽S-转移酶的活性增加,高剂量或低剂量长时间处理没有诱导增加作用,甚至还有抑制作用。单宁酸连续处理4代,对棉铃虫6龄幼虫中肠谷胱甘肽S 转移酶均有抑制作用,对脂肪体谷胱甘肽S-转移酶活性无明显影响或有抑制作用。单宁酸处理的第4代幼虫对溴氰菊酯的敏感度有增加的趋势,对甲基对硫磷的敏感度没有明显改变。     

Determinants of male ejaculate investment in the cotton bollworm Helicoverpa armigera: mating history,female body size and male age

Many studies demonstrate that ejaculate size may be influenced by male condition, female quality and the risk or intensity of sperm competition. In the present study, the effect of male and female conditions, male mating history and female mating status on ejaculate sperm numbers in the polyandrous moth Helicoverpa armigera is examined. A large variation in ejaculate size is found and, although female body size and male age influence ejaculate size, female age and copula duration do not. Both male and female mating histories have significant effects on ejaculate sperm numbers. Males reduce ejaculate expenditure in successive matings but deliver significantly more apyrene and eupyrene sperm to nonvirgin than to virgin females.     

Genetic differentiation of Helicoverpa armigera (Hübner) and H. assulta (Guenée) (Lepidoptera: Noctuidae) based on AFLP markers

Abstract Here we use amplified fragment length polymorphism (AFLP) to assess genetic differentiation of Helicoverpa armigera and H. assulta . The results indicated that both species-specific fingerprints and cluster analysis showed the ability of AFLP technique to discriminate the two sibling species; among a total 1963 AFLP markers amplified from nine primer combinations: 777 (39.6%) were H. armigera -specific, 602 (30.7%) were H. assulta -specific, and 584 (29.7%) were common bands. The mean number of H. armigera -specific bands was significantly more than that of H. assulta -specific bands for nine primer combinations ( P < 0.05); the intraspecific distance of H. armigera and H. assulta was 0.123 0 and 0.110 7 respectively, and the interspecific distance was 0.178 3. In addition, the percentage of polymorphic loci and estimated average heterozygosity were used to estimate genetic diversity of the two species. This study therefore demonstrates that AFLP analysis is a sensitive and reliable technique to study genetic differentiation and genetic relationships between species and provides sufficient molecular markers for future linkage map construction, location and eventual cloning of genes involved in traits differentiation.     

Biology of Campoletis chlorideae (Uchida) (Hym., Ichneumonidae) developing in Bt-treated, Bt-resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract:  Life history parameters in two generations of endoparasitoid Campoletis chlorideae (Uchida) were examined using Bacillus thuringiensis (Bt)-resistant Helicoverpa armigera (Hübner) larvae feeding on B. thuringiensis toxin Cry1Ac. In the laboratory, Bt toxin was fed to Bt-resistant host larvae continuously in case of Bt treatment and only before or after the host larvae were parasitized in Bt–P and P–Bt treatments, respectively. C. chlorideae pupae developed faster in Bt treatment than non-Bt treatment. The shortened pupal stage duration was mainly because of the feeding of host larvae on Bt-diet before being parasitized. Body length of adult male C. chlorideae developed inside Bt-treated Bt-resistant (Bt–Bt) H. armigera larvae significantly decreased, especially in host larvae feeding on Bt-diet after being parasitized. However, survival, pupal mortality and adult longevity of C. chlorideae were almost unaffected in Bt-resistant H. armigera larvae feeding on Bt-toxin. Furthermore, Bt-treated host larvae had the same effect on the F₁ progeny of C. chlorideae as the previous generation, and there was no significant difference between generations. This experiment suggests that there is very limited effect on the life history parameters in two generations of C. chlorideae parasitizing Bt–Bt H. armigera larvae. But both generations of C. chlorideae are affected when Bt-resistant H. armigera larvae fed on Bt toxin for different durations.     

Feeding inhibition of Helicoverpa armigera （HiJbner） by Eucalyptus camaldulensis and Tylophora indica extracts

Crude leaf extracts of Eucalyptus camaldulensis and Tylophora indica were evaluated for their antifeedancy against Helicoverpa armigera larvae in no-choice bioassays. Cabbage leaf-disc dipped in different concentrations of leaf extracts was used for feeding fifth instars of H. armigera for 24 hours. Ethanol extracts from both the plant species exhibited significant feeding inhibition, activity. The effective concentrations of ethanol extracts that caused 50% reduction in larval feeding （EI50） were 6.9% for E. camaldulensis and 2.8% for T. indica, while these values of hexane extracts were 9.3% and 5.2%, respectively. Compared to the crude leaf extracts, crude alkaloids from T. indica and crude tannins from E. camaldulensis were more potent in reducing larval feedings.     

棉铃虫化学感受蛋白HarmCSP6二聚体的组织表达分析及气味结合特征

为了研究棉铃虫Helicoverpa armigera (Hübner)化学感受蛋白（chemosensory proteins, CSPs）在嗅觉识别过程中的功能, 本研究克隆并在原核细胞中表达了棉铃虫化学感受蛋白HarmCSP6, Western blot和快速液相色谱（fast protein liquid chromatography, FPLC）检测证实该HarmCSP6蛋白以二聚体的形式表达。实时荧光定量PCR检测发现HarmCSP6基因在雌雄虫触角中表达量很高, 在雌虫足及翅中也有一定程度的表达。该二聚体蛋白与22种气味分子的荧光竞争结合实验结果表明, 该蛋白与醛类及萜烯类等气味小分子具有较强的结合能力。通过研究该蛋白与小分子的结合, 筛选出合适的气味, 从而为开发棉铃虫引诱剂及驱避剂提供理论依据。     

球孢白僵菌不同感染方式侵染棉铃虫幼虫的毒性比较及组织病理变化

为明确球孢白僵菌在不同感染方式下对棉铃虫的侵染能力, 采用饲喂法和浸渍法测定了球孢白僵菌HFW-05对棉铃虫Helicoverpa armigera (Hübner) 2龄幼虫的致病力, 并通过组织切片显微技术、 扫描电镜技术观察了球孢白僵菌HFW-05对棉铃虫的致病方式。结果表明: 白僵菌HFW-05可通过消化道（饲喂法）成功侵染2龄棉铃虫, 接种感染6 d后的校正死亡率为75.8%。经由体表（浸渍法）接种白僵菌HFW-05的试虫, 试验中体重的变化和取食量与对照相近（6 d校正死亡率仅为17.3%, 不能通过体表达到致病效果）。组织病理学变化表明: 26±1℃条件下, HFW-05菌株对棉铃虫以消化道侵染为主, 侵染后可导致寄主中肠微绒毛脱落严重, 肠壁组织溶解并最终只剩余底膜; 马氏管变形萎缩, 边缘向外突出隆起, 管径变大; 脂肪体萎缩解体, 结构松散; 表皮下的细胞被菌丝侵染破坏。浸渍法接种的试虫, 切片观察处理6 d后试虫, 体内未发现菌丝, 肠壁组织正常完整。扫描电镜观察, 浸渍法接种的分生孢子未能穿透棉铃虫表皮, 而是贴于寄主表皮表面生长, 在湿度合适的条件下, 菌丝生长到一定时间后断裂成为芽生孢子。白僵菌HFW-05可经由消化道对棉铃虫达到较高的致病效果, 在一定程度上弥补外界环境对白僵菌侵染的不利影响, 对今后应用白僵菌进行生物防治具有重要意义。     

在转Bt基因棉压力下棉铃虫和异色瓢虫的波动性不对称

以取食转Bt基因棉的棉铃虫和取食转Bt基因棉上的蚜虫的异色瓢虫为研究对象,结合各自的适合度参数考察了波动性不对称（fluctuating asymmetry, FA）在不同种群中各对称性状间的表现情况。结果表明： 处理组棉铃虫种群的前、中、后足腿节,前翅肘横脉,前翅副室短径,后翅翅长均表现出FA;与对照种群比较,前足腿节与后翅翅长的FA值较高。 适合度参数测定结果显示,棉铃虫卵孵化率与成虫寿命显著低于对照种群,而成虫产卵量和幼虫发育历期与对照种群差异不显著。异色瓢虫取食了转Bt基因棉上的蚜虫后对其适合度各参数及各虫龄的捕食功能反应均无不良影响,其后翅翅长表现出FA,但与对照种群的FA值无显著差异。FA的大小与种群适合度间存在一定的联系,尚需做进一步的分析。     

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。