Leaf volatiles as attractants for neonate Helicoverpa armigera Hbn. (Lep., Noctuidae) larvae

The 1st instar Helicoverpa armigera larvae were bioassayed in the laboratory to study their orientational responses towards leaf volatiles of four leguminous crops: chickpea, Cicer arietinum L.; pigeonpea, Cajanus cajan Millsp.; blackgram, Vigna mungo L.; and cowpea, Vigna unguiculata L. (Walp.). The gram podborer larvae showed positive orientational responses towards leaves of all four test plants. Whole leaves of chickpea, pigeonpea and blackgram were more attractive for gram podborer larvae than cowpea whole leaves. Larval attraction for crushed (damaged) leaves of chickpea, blackgram and cowpea was significantly higher than the attraction for pigeonpea crushed leaves. The orientational responses of gram podborer larvae for crushed leaves of cowpea were significantly higher compared to whole leaves. However, the whole pigeonpea leaves elicited higher orientational responses than the crushed leaves. Maceration was not observed to affect the attractancy of chickpea and blackgram leaves. Further, the leaves were extracted in n-hexane and methanol. It was observed that the crude extracts of all the test leaves elicited positive orientational responses of larvae. In no-choice tests, the orientational preference of the larvae for the hexane extracts of all the test leaves was statistically equal. Similarly, the methanol extracts of leaves of all the test plants also attracted a greater percentage of larvae in no-choice tests. However, under two-choice bioassays, hexane foliage extract of all the test plants elicited higher orientational responses of larvae compared to the methanolic extracts of same leaves. The results of these bioassays clearly indicate that all the test leaves emit kairomones for gram podborer larvae. Moreover, kairomonal components of these leaves are, at least in part, extractable in hexane and methanol, which are higher in hexane than methanol.     

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.     

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.     

Effect of body size and larval experience on mate preference in Helicoverpa armigera (Hübner) (Lep., Noctuidae)

Abstract:  We studied the mating selection in the cotton bollworm, Helicoverpa armigera (Hübner), in relation to body size and larval diet in the laboratory. When provided with an artificial diet at larval stage, weight, body and forewing length did not affect the probability of a male/female moth being selected for mating, but the abdominal width of selected female moths was significantly wider than that of non-selected female moths. 30 female moths were dissected and number of eggs was counted after mating, and there was a correlation between the abdominal width and egg number. There was also significant difference of weight loss between selected and non-selected male/female moths after the mating. The effect of operational sex ratio on mating latency and copulation duration were tested, and the result indicated that mating latency of male selection was significantly longer than that of female selection, but the difference of copulation duration was not significant. Cotton, corn and peanut plants were provided to larvae to test the effect of larval host plant experience on mate choice. When cotton- and peanut-fed moth severed as potential partners, both female and male of cotton-fed moths significantly preferred cotton- to peanut-fed moths for mating. The possible reasons for mate preference based on larval host plant experience may account for host plants attributes on sex pheromone variation and sexual maturity. These findings may impact Bacillus thuringiensis resistance management.     

Effect of rotational use of insecticides on pyrethroids resistance in Helicoverpa armigera (Lep.: Noctuidae)

Abstract:  To investigate fluctuation in susceptibility to insecticides in the field, natural populations of Helicoverpa armigera were collected from the same field in the region of Multan, Pakistan in 2002 and 2003. The populations were examined against pyrethroids (viz. cypermethrin, esfenvalerate and fenpropathrin) and new insecticides (viz. spinosad, abamectin and indoxacarb). In 2002, the resistance ratio (RR) of cypermethrin and esfenvalerate was significantly higher than fenpropahrin compared with susceptible population. The susceptibility to cypermethrin, esfenvalerate and fenpropathrin increased significantly in 2003; however, the RR for cypermethrin was about half the RR (38) of esfenvalerate (101) and fenpropathrin (89). The toxicity of spinosad, abamectin and indoxacarb was identical in both years. In the field experiments, abamectin was more effective than other compounds tested whereas fenpropathrin, cypermethrin and esfenvalerate had similar toxicity. These results might have important implications in resistance management and suggest that the rotational use of spinosad, abamectin and indoxacarb could help to avoid the development of multiple resistant in H. armigera .     

Effects of Bt-toxin Cry1Ac on Propylaea japonica Thunberg (Col., Coccinellidae) by feeding on Bt-treated Bt-resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract:  Propylaea japonica is an important predatory insect of common cotton pests. To assess the ecological effects of transgenic Bt cotton, expressing Cry1Ac toxin, on this predator, we examined the life history parameters of P. japonica for two generations by feeding them with Bt-resistant Helicoverpa armigera . After ingesting Bt-treated Bt-resistant H. armigera larvae in the third and fourth instar, the body mass and body length of adult P. japonica decreased, a combined effect of poor prey quality and Cry1Ac Bt-toxin may account for these effects. However, larval survivorship and development in these two instars, pupal mortality, fecundity and adult longevity of P. japonica were not affected in both the generations. These results suggest that ingesting Bt-toxin Cry1Ac-treated pests in advanced larval stage might have no significant effect on the fitness of predator P. japonica .     

Biochemical identification and comparative insecticidal activity of nucleopolyhedrovirus isolates pathogenic for Heliothis armigera (Lep., Noctuidae) larvae

Three Nucleopolyhedrovirus (NPVs) originally isolated from Heliothis armigera larvae, collected from Portugal (HearNPV-PO) and two places in Spain (HearNPV-SP1 and HearNPV-SP2), and three previously described NPVs were compared biochemically and biologically. Restriction endonuclease analysis of the virus genome with several enzymes revealed that isolates HearNPV-SP1 and HearNVP-SP2 are unique but closely related genotypes which represent two new strains of the NPVs of H. armigera. The DNA fragment profiles of HearNPV-PO were distinct from those of the HearNPV-SP1 and HearNPV-SP2, with all the enzymes used, while they were identical to the Mamestra brassicae NPV strain present in the commercial product MAMESTRIN^®. Bioassays in third-instar H. armigera larvae showed that the LD₅₀ value obtained for HearNPV-SP1 (68 occlusion bodies/larva) was about two- and six-times lower than those of HearNPV-SP2 and a Russian isolate, HearNPV-RU, respectively. The corresponding LT₅₀ values were not found to differ significantly between these three virus isolates at comparable doses.     

Comparison of Metarhizium isolates for biocontrol of Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea

Metarhizium isolates from soil (53) and insect hosts (10) were evaluated for extracellular production of cuticle degrading enzyme (CDE) activities such as chitinase, chitin deacetylase (CDA), chitosanase, protease and lipase. Regression analysis demonstrated the relation of CDE activities with Helicoverpa armigera mortality. On basis of this relation, ten isolates were selected for further evaluation. Subsequently, based on LT₅₀ of the 10 isolates towards H. armigera, five isolates were selected. Out of these five isolates, three were selected on the basis of higher conidia production (60–75 g/kg rice), faster sedimentation time (ST₅₀) (2.3–2.65 h in 0.1% (w/v) Tween 80) and lower LC₅₀ (1.4–5.7×10³ conidia/mL) against H. armigera. Finally, three Metarhizium isolates were selected for the molecular fingerprinting using ITS sequencing and RAPD patterning. All three isolates, M34412, M34311 and M81123, showed comparable RAPD patterns with a 935G primer. These were further evaluated for their field performance against H. armigera in a chickpea crop. The percent efficacies with the three Metarhizium isolates were from 65 to 72%, which was comparable to the chemical insecticide, endosulfan (74%).     

Entomopoxvirus of cotton bollworm,Helicoverpa armigera (Hbn.)

Occurrence of an Entomopoxvirus (EPV) from a lepidopteran insect viz;. cotton bollworm, H. armigera (HaEPV) along with gross pathological symptoms is reported for the first time in India. Histopathological study revealed that the fat body being the most favoured site of infection followed by haemocytes and gut epithelium. HaEPV was found to be not cross infective to six of the agricultural lepidopteran insect pests except for the potato black cutworm, Agrotis segetum registering 100% mortality showing typical symptom. Further, safety of HaEPV was shown against beneficial insect like mulberry silkworm, Bombyx mori and an useful insect general predator, Chrysoperla carnea.     

Calling behaviour of adult female Helicoverpa armigera (Hübner) (Lep., Noctuidae) of overwintering generation and effects of mating

The calling behaviour of overwintering generation females of Helicoverpa armigera and the effects of mating were studied in the laboratory at 24 ± 1°C and under reversed light-dark cycle (16 h light : 8 h dark). Age had a significant influence on calling patterns. Based on calling age, mean number of calling bouts and total calling length of virgin females increased significantly, and mean onset time of calling advanced significantly from calling day 1 to subsequent calling days. Females of the overwintering generation exhibited more short bouts in calling, and some females that initiated calling on a previous day did not call on subsequent days. Mating had no effect on the overall patterns, but did affect calling behaviour. Mated females did not resume calling after mating during the same scotophase and, on the day following mating, mated females called less frequently and for a shorter duration, but thereafter increased to the same level of virgin females of the same calling age. Furthermore, as the moth aged, the percentage of mated females calling was lower than that of virgin females.     

Effects of environmental factors on virulence of the entomopathogenic fungus, Nomuraea rileyi, against the corn earworm, Helicoverpa armigera (Lep., Noctuidae)

The effects of environmental factors on infection of the entomopathogenic fungus, Nomuraea rileyi , isolated from the corn earworm, Helicoverpa armigera , in Taiwan, to its host insect were studied in the laboratory. The fungus caused higher larval mortality at 20°C than at 30°C when 5 × 10⁶ conidia/ml were sprayed on the fourth instar. However, mortality of the fifth instar injected with 1 × 10³ conidia/larva was not significantly different when the inoculated larvae were incubated from 15 to 30°C. The fungal development in inoculated larvae was best at 20 and 25°C after shifting from 20°C to either lower or higher temperatures. The germination rate was higher at 20 and 25°C than at 30 or 35°C. Conidial germination was better on the wash-off of insect cuticle than on Sabouraud maltose agar with yeast extract. Sporulation on chill-dried cadavers was maximal at 95 or 100% relative humidity than at lower levels of relative humidity. The time required for sporulation was 2 days less at 100% than at 95% relative humidity. Although photoperiod did not affect fifth instar mortality caused by N. rileyi , the median lethal time (LT₅₀) values were shorter upon incubating under light than in darkness. Incubation of infected cadavers under 12 or 24 h light resulted in 20-fold more conidial production than under full darkness. Therefore, illumination is necessary for development of this isolate on insect cadavers.     

表皮碳氢化合物分析用于棉铃虫与烟青虫幼虫分类鉴别

本文利用ＧＣ－ＭＳ技术分析了棉铃虫与烟青虫幼虫的表皮碳氢化合物,并与亚洲玉米螟幼虫表皮碳氢化合物进行了比较。结果表明,棉铃虫与烟青虫幼虫表皮碳氢化合物的组分与含量均有显著差异,与玉米螟相比,这二者之间的差异明显小于它们与玉米螟的差异,其表现与三者之间自然的系统发育关系相一致。     

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.     

Incidence and within field dispersion pattern of pod borer,Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea in Ethiopia

Podborer is a major pest of chickpea in Ethiopia. Field surveys were conducted in 2013/2014 and 2014/2015 in central and northwestern Ethiopia to assess the prevalence and within field distribution of the pest. Although podborer was prevalent throughout the surveyed areas, there was a significant difference in larval density (0.10–3.75 larvae per m²) among zones and districts within zones. This variation was attributed to cropping history, cropping patterns, chickpea-crop adjacency, and weather (rainfall and temperature) conditions before and during the season as well as control measures applied. The optimum sample size required for precision ranged from 98, when podborer density was 10/m², to 1045, when podborer density was ≤1/m². Within field distribution of the larvae fitted a negative binomial distribution indicating that the larvae had a clumped/aggregated dispersion pattern. These results will enable chickpea stakeholders to develop and apply appropriate integrated crop management techniques for the control of podborer.     

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.     

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。     

Comparative life history and fecundity of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) on different soybean varieties

The effect of different soybean varieties ( Glycine max 356, M4, M7, M9, Clark, Sahar, JK, BP, Williams, L17, Zane, Gorgan3 and DPX) on the life history and fecundity of the gram pod borer Helicoverpa armigera (Hubner) (synonym Heliothis armigera (Hubner), also known as the American or African bollworm) was determined at 25 ± 1°C, 65 ± 5% r.h. and a light : dark cycle of 16:8 h. The larval period ranged 17.30 to 26.20 days on M7 and L17, respectively. The longest development time was on L17, BP and Sahar (42.71, 40.29 and 39.20 days, respectively) and the shortest was on M7, M9, Williams and Clark (34.21, 36.06, 36.60 and 36.82 days, respectively). The development index of overall immature stages varied from 1.39 to 2.41, with the minimum on L17 and BP and the maximum on M7. The highest daily fecundity and total fecundity (118.92 and 582.70 eggs, respectively) and the lowest (37.88 and 177.10 eggs, respectively) were observed on DPX and 356, respectively. Cluster analysis of the biological parameters of H. armigera on different soybean varieties demonstrated that BP, Sahar and L17 were partially resistant to H. armigera . Knowledge of the extent of susceptibility or resistance of crop varieties and biology of a pest on that crop are fundamental components of integrated pest management (IPM) programs for many crops. Such information can help to detect and monitor pest infestation, variety selection and crop breeding.     

Effects of constant and changing temperature conditions on diapause induction in Helicoverpa armigera (Lepidoptera: Noctuidae)

The effects of photoperiod and temperature on the induction and termination of facultative pupal diapause in Helicoverpa armigera (Lepidoptera: Noctuidae) were investigated under laboratory conditions. Exposing H. armigera larvae to both constant and fluctuating temperature regimes with a mean of 25°C and 20°C resulted in a type-III photoperiodic response curve of a short-long day insect. The long-day critical daylengths for diapause induction were ten hours and 12 hours at the constant temperatures of 25°C and 20°C, respectively. Higher incidences of diapause and higher values both for the longer and the shorter critical photoperiods for diapause induction were observed at fluctuating regimes compared with the corresponding constant ones. At alternating temperatures, the incidence of diapause ranged from 4.2% to 33.3% and was determined by the temperature amplitude of the thermoperiod and by the interaction of cryophase or thermophase with the photoperiod. Helicoverpa armigera larvae seem to respond to photoperiodic stimuli at temperatures >15°C and <30°C; all insects entered diapause at a constant temperature of 15°C, whereas none did so at a constant temperature of 30°C under all the photoperiodic regimes examined. Although chilling was not a prerequisite for diapause termination, exposure of diapausing pupae to chilling conditions significantly accelerated diapause development and the time of adult emergence. Therefore, temperature may be the primary factor controlling the termination of diapause in H. armigera.