Baseline toxicity of emamectin and spinosad to Helicoverpa armigera (Lepidoptera: Noctuidae) for resistance monitoring

Acute toxicity studies of emamectin and spinosad against Helicoverpa armigera revealed that the pest is highly susceptible to both the insecticides. The median lethal dose (LD₅₀) of emamectin is 3.86 × 10⁻³ µg per larva. The median lethal concentrations (LC₅₀) of emamectin and spinosad were found to be 0.09 and 2.94 ppm, respectively. The discriminating doses were fixed based on the LC₉₅ of the susceptible population of H. armigera as 0.80 ppm for emamectin and 10 ppm for spinosad. Resistance was not observed when the discriminating doses of emamectin and spinosad were applied on field-collected populations of H. armigera from two intensive cotton growing areas, Coimbatore and Madurai, India.     

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.     

Temporal host plant use in three polyphagous Heliothinae,with special reference to Helicoverpa punctigera (Wallengren) (Noctuidae: Lepidoptera)

Abstract Potential host plants of the polyphagous lepidopteran Helicoverpa punctigera (Wallengren) were surveyed in two ways. A broad survey, conducted in southern Queensland and northern New South Wales, indicated that H. punctigera larvae were present on relatively few plant species. A detailed survey of host plant use in a non-cropping area in which H. punctigera was numerous demonstrated restricted host plant use by this species. The density of H. punctigera on its principal host in the area, the indigenous daisy Ixiolaena brevicompta F. Muell., was much higher (as measured per unit of time searched) than on other plant species available. Also, I. brevicompta was used regularly by H. punctigera after rainfall events. Ixiolaena brevicompta represents a new host record and on the basis of the pattern of its use by H. punctigera should be considered a ‘primary host plant’ of this noctuid. In cropping areas sampled, usually more than one plant species hosted H. punctigera regularly and in large numbers. Usually a crop species was included (e.g. cotton and chick pea). Alternative hosts in cropping areas were Sonchus oleraceus L. (sowthistle) and possibly the native legume Sesbania cannabina (Retz.) Poiret. Our results imply that the polyphagy of H. punctigera is probably not as extensive as previously claimed. The criteria for inclusion of a plant species as a primary host for H. punctigera need to include the regularity of use of that species and the relative abundance of eggs and larvae on it. We suggest that an understanding of the host-searching mechanism of this species will be best achieved through study of the interaction of H. punctigera with its indigenous primary hosts. The surveys also yielded information on host plants of two other heliothine noctuids, H. armigera (Hübner) and Australothis rubrescens (Walker), and this is also presented.     

An in vitro method for increasing UV-tolerance in a strain of Helicoverpa armigera (Lepidoptera: Noctuidae) nucleopolyhedrovirus

A method for increasing tolerance to ultraviolet (UV) radiation in a strain of nucleopolyhedrovirus of cotton bollworm, Helicoverpa armigera (Hübner) (HearNPV) using a solar simulator is described. The Coimbatore isolate (CBE I) of HearNPV was subjected to a five-step sequence of selection to increase its UV tolerance. Each step consisted of irradiation of wet deposits of the virus to near UV (at energy level of 300W/m²), bioassay against second instar H. armigera larvae and propagation in early fifth instar larvae. Selection steps carried out at 15, 30, 60 and 90 minutes of exposure revealed that the continuous exposure of HearNPV-CBE I at low doses of UV irradiation (270–540 KJ/m²) did not significantly affect the virus activity as measured by its biological activity against second instar larvae. Selection at higher doses (1620 KJ/m²) led to loss of viral activity in the first two exposure cycles; however, there was retention of virulence coupled with increased tolerance to UV doses from third cycle onwards. Further, studies on the persistence of UV tolerant strain of HearNPV-CBE I in comparison with original strain showed that the tolerant strain had more persistence even after 7 days of weathering both under exposed (18% original activity remaining) and shaded (26% original activity remaining) condition on potted cotton plant.     

飞行过程中棉铃虫对温度的主动选择

为了探讨温度对迁飞性昆虫空中群体聚集成层等行为的作用机制,在室内利用自行设计的连续温度梯度发生装置对棉铃虫Helicoverpa armigera在飞行过程中的温度选择行为进行了研究.结果表明：在存在明显温差的连续温度梯度中,所有棉铃虫飞行个体均对温度具有显著的选择行为.棉铃虫试虫群体表现出对空间最优飞行温度共同的主动选择,选择的温度范围是20~22℃之间;在这一温度范围内棉铃虫的振翅频率最高,持续振翅时间最长.对不同温度梯度条件下各温度区间内试虫的飞行时间进行定量比较发现,在16~22℃温度梯度场中的棉铃虫群体对最适温度的选择比在19~30℃的温度梯度场中的群体更显著,表明在温度较低的迁飞季节中温度对迁飞棉铃虫空中虫群聚集成层的影响要比在高温季节更明显.持续飞行时间对棉铃虫振翅频率的影响明显,表明昆虫迁飞高度与昆虫自身能量的消耗存在联系.     

Elevated CO2 may alter pheromonal communication in Helicoverpa armigera (Lepidoptera: Noctuidae)

Carbon dioxide (CO₂) as a greenhouse gas has been increasing in recent decades. Because an elevated atmospheric CO₂ influences insect physiology and behaviour, we hypothesize that pheromone–mediated communication in the moth is affected by an increased CO₂ level. We test the behavioural responses of male Helicoverpa armigera to sex pheromone in a wind tunnel, demonstrating a significant reduction of approaching behaviour to the odour source at a high CO₂ level (1000 ppm). Electroantennogram (EAG) responses of male to the pheromone component are also significantly suppressed in high CO₂ environments (600 and 1000 ppm), indicating that a high CO₂ level inhibits both behavioural and electrophysiological responses of male to the sex pheromone. Interestingly, the EAG response of the whole head preparation of males is influenced more by the elevated CO₂ level than that of the antenna‐cut preparation. A sequential increase of CO₂ levels from an ambient CO₂ level also decreases the EAG response of the whole head but not of the labial palp‐removed head, implying a potential mediation of labial palp in the head where the CO₂ receptor is located. By contrast, sex pheromone production in females reared under or shifted to an elevated CO₂ condition is increased, and the putative underlying mechanism for this is discussed. The present study provides an insight into the adaptive strategy of moth pheromone communication in a changing environment.     

Effects of class-specific,synthetic, and natural proteinase inhibitors on life-history traits of the cotton bollworm Helicoverpa armigera

Herbivorous insects have more difficulty obtaining proteins from their food than do predators and parasites. The scarcity of proteins in their diet requires herbivores to feed voraciously, thus heavily damaging their host plants. Plants respond to herbivory by producing defense compounds, which reduce insect growth, retard development, and increase mortality. Herbivores use both pre- and postdigestive response mechanisms to detect and avoid plant defense compounds. Proteinase inhibitors (PIs) are one example of plant compounds produced as a direct defense against herbivory. Many insects can adapt to PIs when these are incorporated into artificial diets. However, little is known about the effect of PIs on diet choice and feeding behavior. We monitored the diet choice, life-history traits, and gut proteinase activity of Helicoverpa armigera larvae using diets supplemented with synthetic and natural PIs. In choice experiments, both neonates and fourth-instar larvae preferred the control diet over PI-supplemented diets, to varying degrees. Larvae that fed on PI-supplemented diets weighed less than those that fed on the control diet and produced smaller pupae. Trypsin-specific PIs had a stronger effect on mean larval weight than did other PIs. A reduction of trypsin activity but not of chymotrypsin activity was observed in larvae fed on PI-supplemented diets. Therefore, behavioral avoidance of feeding on plant parts high in PIs could be an adaptation to minimize the impact of this plant's defensive strategy.     

Altered mating behaviour in a Cry1Ac-resistant strain of Helicoverpa armigera (Lepidoptera: Noctuidae)

Randomness of mating between susceptible and resistant individuals is a major factor that closely relates to the refuge strategy of resistance management for Helicoverpa armigera (Hübner) to Bacillus thuringiensis cotton. The mating behaviour of Cry1Ac‐susceptible and Cry1Ac‐resistant strains of H. armigera was compared to investigate the randomness of their mating. The percentage of mating was lower for Cry1Ac‐resistant H. armigera compared with that of the susceptible strain under both no‐choice and multiple‐choice conditions. The low percentage of mating in the resistant strain indicates a reduced incidence of successful mating. The percentage of spermatophore‐containing mated female H. armigera in the crossing of susceptible females × resistant males was significantly lower than in the crossing of resistant females × susceptible males, but the observed mating frequencies of these two types of cross were similar to each other. This indicates that resistant males reduce the incidence of mating paternity more than they do their mating frequency. The percentages of heterogametic matings (susceptible females × resistant males, resistant females × susceptible males) in the multiple‐choice experiment were lower than those of homogametic matings (susceptible × susceptible, resistant × resistant) on peak mating nights. However, the difference between heterogametic and homogametic mating was not significant, indicating that there was a random mating between susceptible and resistant strains. The results presented here do not reflect reality in mating associated with Cry1Ac resistance but can provide insight into variable expression.     

棉铃虫围食膜的蛋白质组鉴定

【目的】围食膜(peritrophic membrane, PM)是昆虫抵御随食物摄入的病原微生物入侵的第一道天然屏障。本研究旨在鉴定出农业重大害虫棉铃虫Helicoverpa armigera围食膜的总蛋白成分,为进一步揭示昆虫围食膜的形成机制及研发新颖的害虫控制策略奠定基础。【方法】剥离棉铃虫5龄幼虫PM,用三氟甲磺酸(trifluoromethane sulfonic acid, TFMS)处理,采用液质联用技术(LC-MS/MS)鉴定围食膜蛋白质组,然后对鉴定结果进行生物信息学分析。【结果】本研究共鉴定出棉铃虫幼虫围食膜蛋白质169个,是目前鉴定最多的棉铃虫围食膜蛋白。通过GO分析,可以将这些鉴定的蛋白分为细胞组分、分子功能和生物学过程三大类;KEGG富集结果显示,鉴定蛋白可以富集在12条代谢通路中;蛋白互作分析(protein protein interaction, PPI)结果表明,以ACC和CG3011等蛋白为核心可以形成蛋白互作网络。【结论】本研究鉴定了169个棉铃虫幼虫围食膜蛋白质,并对其进行了GO, KEGG和PPI分析,结果有助于人们全面理解昆虫围食膜的分子结构和功能。     

Adaptation of Spodoptera exigua (Lepidoptera: Noctuidae) to barley trypsin inhibitor BTI-CMe expressed in transgenic tobacco

Nicotiana tabacum plants were transformed with the cDNA of barley trypsin inhibitor BTI-CMe under the control of the 35S CaMV promoter. Although the transgene was expressed and the protein was active in the homozygous lines selected, growth of Spodoptera exigua (Lepidoptera: Noctuidae) larvae reared on transgenic plants was not affected. The protease activity in larval midgut extracts after 2 days feeding on transformed tobacco leaves from the highest expressing plant showed a reduction of 25% in the trypsin-like activity compared to that from insects fed on non-transformed controls. The susceptibility of digestive serine-proteases to inhibition by BTI-CMe was confirmed by activity staining gels. This decrease was compensated with a significant induction of leucine aminopeptidase-like and carboxipeptidase A-like activities, whilechymotrypsin-, elastase-, and carboxipeptidase B-like proteases were not affected.     

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.     

棉铃虫酪氨酸羟化酶基因的分子特性及功能分析

【目的】酪氨酸羟化酶(tyrosine hydroxylase, TH)是黑色素形成的关键酶,在昆虫表皮骨化过程中扮演重要角色。本研究旨在获得棉铃虫Helicoverpa armigera TH基因序列,并研究其分子特性、表达模式和功能,为更深入探析该基因作用机理奠定基础。【方法】通过生物信息学和分子生物学技术获得了棉铃虫TH基因序列,利用qRT-PCR分析该基因在棉铃虫不同生长发育阶段的表达模式;利用qRT-PCR技术,分别测定了蜕皮激素20E(400 ng/头)处理不同时间和RNAi成功干扰蜕皮激素受体基因(EcR)前提下再用20E(400 ng/头)处理后,棉铃虫5龄幼虫TH表达量变化;采用生物化学方法检测鞣化激素(30 μg/mg组织)和环腺苷酸(cAMP, 200 ng/mg 组织)处理后棉铃虫幼虫脂肪体中TH活性。【结果】获得了棉铃虫酪氨酸羟化酶基因TH (GenBank登录号: MF440319) cDNA片段,长2 270 bp,开放阅读框1 686 bp,编码561个氨基酸残基。该基因在棉铃虫整个发育期均表达,其中在卵期第3天、2龄幼虫第1天、3-5龄蜕皮期、预蛹期和成虫羽化第1天表达量相对较高。研究还发现,400 ng/头 20E注射能够促进TH的转录;在成功干扰并调低幼虫EcR转录水平的前提条件下(对照仅注射dsGFP)再注射20E,对TH表达量无明显影响;而鞣化激素(30 μg/mg组织)和cAMP(200 ng/mg组织)均显著提高了TH的酶活性。【结论】20E在转录水平参与了TH的表达;鞣化激素和cAMP均能够提高TH活性,在蛋白水平上对TH进行调控。     

Antifeedant and cytotoxic activity of gibberellic acid against Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The present study investigates the effect of gibberellic acid (GA3), a terpenoid and phytohormone, on the digestive physiology and intermediary metabolism of the cotton bollworm Helicoverpa armigera Hübner (Lepidoptera, Noctuidae). Incorporation of GA3 (800 μg g^?1 diet) in an artificial diet results in significant reductions in the rates of diet consumption and the efficiency of conversion of food consumption by by H. armigera larvae. The relative growth rate decreases as the concentration increases. The relative α‐amylase activity in sixth‐instar larvae of H. armigera decreases significantly after ingestion of four concentrations of GA3. Histological studies of the midgut in GA3‐treated larvae (800 μg g^?1 diet) show degeneration of the epithelial cells. The alanine and aspartate aminotransferase activity decreases at the highest concentration. However, acid phosphatase, alkaline phosphatase, γ‐glutamyl transferase and lactate dehydrogenase activity increase significantly compared with the control. The results clearly demonstrate the adverse effects of GA3 on H. armigera via interruption of nutritional physiology and metabolism.     

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。     

Efficacy of new insecticides for management of Helicoverpa spp. (Lepidoptera: Noctuidae) in Australian grain crops

Abstract  Insecticide resistance in Helicoverpa armigera (Hübner) has led to the reduced efficacy of some older insecticide groups (pyrethroids and carbamates) and serious crop losses. Eight small-plot experiments were conducted to evaluate new insecticides for the management of H. armigera in grain crops. Several products showed efficacy equivalent to or better than the commercial standard, thiodicarb. Indoxacarb and spinosad at rates 50% or less of the registered rates for cotton were consistently superior to other tested products across the range of crops treated and provided residual protection for up to 14 d. The insect growth regulator compound, methoxyfenozide, was slower acting than other products tested, but demonstrated potential for H. armigera management. Pyridalyl performed well and warrants further evaluation in grain crops. We discuss the positioning of new compounds in an Insecticide Resistance Management Strategy (IRMS) in relation to a farming system that incorporates both grain and cotton crops. Use guidelines are recommended for indoxacarb, the first new compound to be registered in selected grain crops and cotton in Australia. These guidelines include restricted-use periods and limits on the number of applications per crop. It is anticipated that additional new compounds will be registered in grain crops, leading to the reduced selection pressure on the limited number of efficacious products. Coordinated insecticide use across farming systems and compatibility with developing integrated pest management programs should be fundamental considerations for the future IRMS.     

河北转Bt基因棉田棉铃虫对杀虫剂的抗性及相关酶活性的变化

为明确河北省推广种植植转Bt基因抗虫棉（简称Bt棉）后, 棉铃虫Helicoverpa armigera (Hübner)对常用杀虫剂的抗药性水平及其生化机理, 2011-2012年采用点滴法对保定南郊、 沧州南皮、 邢台巨鹿3个地区的田间种群以及敏感种群进行了室内毒力测定, 并采用生化分析法对4个种群相关的羧酸酯酶（carboxylesterase, CarE）、 谷胱甘肽S 转移酶(glutathione S-transferases, GSTs)和乙酰胆碱酯酶(acetylcholinesterase, AChE)的活性进行了研究。结果表明: 3个田间种群对高效氯氰菊酯和氰戊菊酯处于中至高抗水平, 抗性倍数为20.02~73.70倍; 对灭多威处于低至中抗水平, 抗性倍数为6.27~11.84倍; 对高效氯氟氰菊酯(抗性倍数: 1.07~4.20倍), 辛硫磷、 毒死蜱和马拉硫磷(抗性倍数: 1.00~2.69倍), 以及氯虫苯甲酰胺（抗性倍数: 2.00~3.67倍）均处于敏感水平。3个田间种群的CarE, GSTs和AChE活性分别是敏感种群的1.06~1.23, 1.20~1.63和1.15~1.23倍, 这可能与其对高效氯氰菊酯、 氰戊菊酯和灭多威产生的抗性有关。     

Binding of Cry δ-endotoxins to brush border membrane vesicles of Helicoverpa armigera and Helicoverpa punctigera （Lepidoptera： Noctuidae）

The relatively low susceptibility ofHelicoverpa armigera to CrylAc, its history of resistance to chemical insecticides and the seasonal decline in expression of CrylAc in transgenic cotton necessitated the development of cotton expressing two insecticidal proteins to provide sustainable control of this multinational pest. To manage the resistance issue, it was essential that the second insecticidal protein have a significantly different mode of action to CrylAc. A common feature of resistance to CrylA proteins in several species as well as H. armigera has been a change in the binding site. A study of binding sites for some Cry proteins in the brush border membrane vesicles （BBMV） ofH. armigera and Helicoverpa punctigera was undertaken. The binding affinity for CrylAc was higher than for CrylAb, matching their relative toxicities, and CrylAc and CrylAb were found to share at least one binding site in both I-1. armigera and I-1. punctigera. However Cry2Aa did not compete with CrylAc for binding and so could be used in transgenic cotton in combination with CrylAc to control H. armigera and manage resistance. Variation in the susceptibilities of three different H. armigera strains to CrylAc correlated with the parameter Bmax/Kcom.