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PubMed2005

Regional reversion of insecticide resistance in Helicoverpa armigera (Lepidoptera: Noctuidae) is associated with the use of Bt cotton in northern China.

A continuous programme for monitoring resistance of Helicoverpa armigera (Hubner) to commonly used insecticides was undertaken for assessing the impact of Bt cotton planting on the evolution of the pest resistance from 1994 to 2002 in China. The bioassay results showed that the resistance levels per year in field populations of H armigera to lambda-cyhalothrin, phoxim and endosulfan decreased, respectively, to 9-15-fold, 11-14-fold and 6-8-fold in 2001-2002 from 197-262-fold, 52-74-fold and 18-38-fold before the cultivation of Bt cotton in 1997. This significant increase in susceptibility to insecticides is expected to result in a reduction in insecticide application for H armigera control in Bt cotton. It is concluded that Bt cotton is playing an important role in the long-term management of H armigera by increasing the potential for natural and chemical control of the pest.

Animals↗
PubMed1998

Learning in host selection in Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

The effect of experience on pre- and post-alighting host selection in adult female Helicoverpa armigera was tested in an indoor flight cage, and in a large greenhouse. The moths had experienced either tobacco or tomato plants (both are hosts of H. armigera) for 3 days, or were given no experience. Individuals were then released and their host selection assessed. All individuals caught in the greenhouse were identified and tested for post-alighting acceptance on each host. Experience significantly influenced both pre- and post-alighting host selection in ovipositing moths. This modification in behaviour is attributed to 'learning', and presents the first detailed evidence for learning in moths. Possible behavioural mechanisms involved are discussed, and a hypothesis is presented regarding learning in post-alighting host acceptance. The existence of learning in H. armigera, a highly polyphagous agricultural pest, is discussed in the light of current theories on environmental predictability and the advantages of learning. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

Interactions of Bacillus thuringiensis crystal proteins with the midgut epithelial cells of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Binding of different Bacillus thuringiensis insecticidal crystal proteins (ICPs) to the midgut epithelium of Spodoptera frugiperda larvae was characterized by binding experiments with midgut tissue sections and isolated brush border membrane vesicles. Our results show that ICPs interact with the microvilli of epithelial cells of S. frugiperda in two different ways. The first is typical of highly toxic proteins (like CryIC and CryID); this interaction is saturable and specific. In contrast, some nontoxic proteins (like CryIAb) interact nonspecifically with the microvilli, since the binding of this toxin is not affected by the presence of high concentrations of homologous competitor. The CryIC toxin binds to two brush border proteins of 40 and 44 kDa and the CryIAb toxin binds to a single protein of 150 kDa. Immunological detection of ingested B. thuringiensis ICPs on gut sections of S. frugiperda larvae revealed that CryIC and CryID toxins bound along the epithelial brush border microvilli membrane. Binding of the nontoxic protein CryIAb was also observed in the epithelial brush border membrane of fed larvae, but it was extremely weak, implying that this type of interaction occurs also in vivo although it is not related to toxicity.

Animals↗
PubMed1997

Establishment of a cell line from Spodoptera litura (Lepidoptera: Noctuidae) and replication of S. litura nuclear polyhedrosis virus in vitro.

A new cell line, designated IBL-SLO1A, was established from pupal ovaries of the tobacco cutworm Spodoptera litura. Cells were grown in the TNM-FH insect cell culture medium supplemented with 10% fetal bovine serum. The subculture of cells was initiated with 1-3 x 10(5) cells/ml, a split ratio about 1:10. The growth curve of the cells fit the model of exponential growth (Y = e-0.6750 + 0.0317X R2 = 0. 98), the population doubling time during logarithmic growth at 28 degrees C was 21.9 hr. The number of chromosomes was about 140. Cytopathology characteristics of baculovirus infection were observed when the culture cells were infected with SINPV derived from alkali dissolution of occlusion bodies at 24 hr postinfection (pi). The cells lysed and released occlusion bodies into culture medium at 120 hr pi.

Animals↗
PubMed1999

Development and use of a PCR assay for detection of the reproductive virus in wild populations of helicoverpa zea (Lepidoptera: noctuidae)

Helicoverpa zea reproductive virus (HzRV) is a nonoccluded bacilliform virus that affects both female and male moths of the corn earworm H. zea. In order to study the biology and host range of HzRV, a bioassay was previously developed to detect the presence of this virus in infected insects. A drawback of this bioassay is that it is time consuming and requires more than a month to complete. Here we describe the development of a polymerase chain reaction (PCR) assay for the rapid detection of HzRV in infected corn earworms. The genome of HzRV was digested with PstI and cloned into a plasmid vector. Sequences from two different clones, P4 and P13, were selected for designing two sets of primers. These primers were used for PCR and their sensitivity and specificity in detecting HzRV DNA were examined. Both sets of primers produced the expected amplification product in samples containing HzRV DNA but not in uninfected corn earworm samples, Spodoptera frugiperda (Sf-9) cells, or samples from the Autographa californica nuclear polyhedrosis virus. In addition, the primer pair of the clone P13 was sensitive enough to detect approximately 175 copies of viral DNA. We then used this assay to examine feral populations of H. zea from seven geographical locations in the United States. HzRV was detected primarily in the Mississippi populations and to a lesser extent in Iowa and Georgia, but none in Maryland, Missouri, and Texas populations. This PCR assay provides a highly specific, sensitive, and rapid way of detecting the presence of HzRV and will be useful in further studying the host range, tissue specificity, and incidence of this virus in wild populations of the corn earworm.

Journal Article↗
PubMed1999

A noda-like virus isolated from the sweetpotato pest spodoptera eridania (Cramer) (Lep.; noctuidae)

A small isometric virus has been isolated from larvae of the sweetpotato pest Spodoptera eridania (Cramer) collected near Pariacoto, Ancash province, Peru. It is designated the Pariacoto virus (PaV). In addition to its high pathogenicity on its natural host Spodoptera eridania, PaV was found to replicate in Spodoptera ochrea (Hampson) larvae but not in Spodoptera frugiperda (Smith) larvae. The size of the viral particle was estimated to be about 30 nm in diameter. Polyacrylamide gel electrophoresis showed a protein of approximately 40.5 kDa. After agarose gel electrophoresis, the viral genome appeared to be bipartite RNA. Gel immunodiffusion tests showed no serological relationship between PaV and Nodamura virus, the type species for insect nodaviruses. Electron microscopy confirmed that viral replication occurs in the cytoplasm. These properties are similar to those of other members of family Nodaviridae, to which the virus is currently assigned. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Biological activity of SeMNPV, AcMNPV, and three AcMNPV deletion mutants against Spodoptera exigua larvae (Lepidoptera: noctuidae).

Virulence and speed of action, as related to dose, are important effectiveness-determining properties of insect-pathogenic biocontrol agents. We used the droplet-feeding bioassay to compare dose responses between two wild-type baculoviruses, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) and Spodoptera exigua MNPV (SeMNPV), and three deletion mutants of AcMNPV in S. exigua larvae. In each mutant one gene was deleted by genetic engineering: pp34, coding for the polyhedral membrane; egt, coding for ecdysteroid UDP-glucosyltransferase; or p10, coding for fibrillar structures in infected insect cells. SeMNPV had the lowest median lethal dose (LD(50)) as well as the highest speed of action (LT(50)) of all viruses investigated. In our comparative bioassays the only significant effect of gene deletions in AcMNPV was a slightly lower speed of action for the p10 deletion mutant. Otherwise, wild-type and recombinant AcMNPVs had similar biological activities. Our results suggest, in contrast to what is generally assumed, that gene deletions in AcMNPV for improved insecticidal activity should be critically assessed in each host system prior to further implementation as a control agent. Insertion of foreign genes coding for entomotoxins is less questionable and more promising in this respect.

Animals↗
PubMed1996

Insensitive Acetylcholinesterase and Resistance to Thiodicarb in Australian Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Thiodicarb resistance was diagnosed in a field strain of Helicoverpa armigera from Tamworth, New South Wales in March 1993. This is the first record of H. armigera resistance to thiodicarb. Bioassays after selection in the laboratory indicated that the thiodicarb resistance factor was greater than 40-fold and was associated with cross resistance to methomyl. Insensitive acetylcholinesterase was identified as a resistance mechanism. Potential resistance management tactics and opportunities for biochemical resistance monitoring are discussed.

Journal Article↗
PubMed1981

The fine structure of the compound eye of the African armyworm moth, Spodoptera exempta Walk. (Lepidoptera, Noctuidae).

The morphology of the compound eye of the noctuid moth Spodoptera exempta was investigated by electron microscopy. This eucone superposition eye is composed of about 8000 ommatidia. Each ommatidium is surrounded by six secondary pigment cells showing pigment movement according to the state of adaptation. It contains four crystalline cone cells forming together a crystalline cone and tract, two primary pigment cells, which encompass the crystalline cone, and usually eight retinula cells. On the basis of their rhabdomeric structure, three types of retinula cells can be distinguished. According to the structure of the rhabdom, two types of ommatidia are found in different regions of the eye. The rhabdom of the lobed type, providing more than 80% of ommatidia, is composed of V-shaped rhabdomeres with fanwise arranged microvilli. The rhabdom of the square type, found in a small area in the dorsal region of the eye, consists of triangular rhabdomeres with parallel microvilli. The functional significance of this difference is discussed.

Animals↗
PubMed1983

The influence of larval maturation on responses of Mamestra brassicae L. (Lepidoptera: Noctuidae) to nuclear polyhedrosis virus infection.

Responses of mature Mamestrae brassica larvae, in the fifth and sixth instars, to nuclear polyhedrosis virus (NPV) have been quantified. There was an 86 fold decrease in susceptibility to virus, related linearly to increasing body weight, for the larval weight range tested. Although the rate of decreasing response to weight was constant, three phases of susceptibility were identified by shifts in the positions of the regression line of log LD50 on log body weight. Larvae above 700 mg were proportionately less susceptible than those between 250 and 700 mg which were, in turn, proportionately less susceptible than those below 250 mg. LT50 responses were inversely related to virus dosage but increased with larval age. This was accompanied by an increase in the proportion of infected larvae that eventually died in the pupal stage. The ratio of LT50 to time remaining for larval development provided a good predictor of the time course of NPV infection for all larval stages. Extensive comparison with a previous study on responses of immature M. brassicae larvae to NPV infection (6) have been included.

Insect Viruses↗
PubMed2001

Primary and continuous midgut cell cultures from Pseudaletia unipuncta (Lepidoptera: Noctuidae).

Midgut epithelial cells were isolated from fifth-instar Pseudaletia unipuncta larvae by collagenase treatment of midgut tissue, and cultured in TNM-FH medium. Long-term continuous culture and maintenance of midgut cells were achieved with P. unipuncta armyworm intestinal cells. Several cells lines were obtained from these P. unipuncta primary cultures, and they have been subcultured and maintained for over 24 mo. The three major midgut cell types were present in the cultures, including stem (regenerative), columnar, and goblet cells. In vitro morphogenesis and differentiation of columnar and goblet cells from stem cells were observed. There appeared to be a cycle of cell death of goblet and columnar cells followed by their replacement from stem cells every 7-8 wk. After approximately six passages, the cell density in T-flasks appeared to be somewhat constant, reaching 10(3)-10(4) cells per milliliter of medium. The columnar cells are round to rectangular in shape and possess a brush border, while the goblet cells have a classic flask-like shape with a central cavity. Peritrophic membrane-like secretions were observed in all the culture flasks. Infection of these cells with multiply embedded nucleopolyhedrovirus was confirmed, and we conclude that these midgut cells can be used as an in vitro model system to study early events in baculovirus infection.

Animals↗
PubMed1998

Characterization and comparative pharmacological studies of a functional gamma-aminobutyric acid (GABA) receptor cloned from the tobacco budworm, Heliothis virescens (Noctuidae:Lepidoptera).

This paper reports the functional expression and pharmacological characterization of a full length complementary deoxyribonucleic acid (cDNA) (pIVY12) cloned from a Heliothis virescens fertilized egg cDNA library that encodes for a gamma-aminobutyric acid (GABA) receptor subunit (HVRDL-Ser 285). Two electrode voltage clamp recordings of Xenopus oocytes expressing the HVRDL GABA-gated chloride channel revealed robust chloride ion conductance in response to GABA and the GABAA receptor agonist, muscimol. Baclofen, a GABAB agonist had no effect. Phenobarbital showed a positive dose-dependent allosteric modulatory effect, whereas the benzodiazepine, flunitrazepam, had no effect. Chloride conductance was depressed by the novel insecticide, fipronil ((+/-)-5-amino-1-(2,6 dichloro-alpha, alpha, alpha-trifluoro-p-tolyl)-4-trifluoromethyl-sulfinylpyrazole-3-carb onitrile) and the GABAA antagonist, picrotoxinin. The HVRDL GABA receptor was insensitive to blockage by dieldrin and the GABAA antagonist, bicuculline. The comparative actions of fipronil, picrotoxinin and dieldrin were examined on oocytes expressing the H. virescens wild-type (HVRDL-Ser 285), the site-directed mutant (HVRDL-Ala 285), the Drosophila melanogaster Rdl wild-type (DMRDL-Ala 302) and the Rdl dieldrin resistant (DMRDL-Ser 302) homo-oligomeric GABA receptors. HVRDL-Ala 285 was 15-fold more sensitive to blockage by fipronil than HVRDL-Ser 285. DMRDL-Ala 302 and DMRDL-Ser-302 showed a similar level of sensitivity to blockage by fipronil. HVRDL-Ser 285 and DMRDL-Ser 302 exhibited a similar level of insensitivity to picrotoxinin. HVRDL-Ala 285 and DMRDL-Ala 302 showed a similar range of picrotoxinin sensitivity. DMRDL-Ala 302 and HVRDL-Ala 285 showed some sensitivity to blockage by dieldrin. Fipronil sensitivity was significantly altered by the serine to alanine mutation at position 285 in the M2 region of the HVRDL subunit, whereas no difference was observed between the DMRDL-Ser 302 and DMRDL-Ala 302 receptors.

Amino Acid Sequence↗
PubMed1977

The establishment of two cell lines from the insect Spodoptera frugiperda (Lepidoptera; Noctuidae).

The history and characteristics of two cells lines developed from primary explants of pupal tissue from the insect, Spodoptera frugiperda (J.E. Smith), are described. One cell line, IPLB-SF 21, was developed with hemolymph-supplemented medium and has been maintained continuously on the medium. The second cell line, IPLB-SF-1254, was developed with a medium containing a combination of vertebrate sera plus hemolymph and was adapted to hemolyphn-free medium at the 6th passage. The IPLB-SF-21 cell line has a population doubling time of 26 to 30 hr; the doubling time of the IPLB-SF-1254 line is 36 hr. The chromosomal morphology and distribution was typical of other lepidopteran cell lines. Serological studies showed that both cell lines have at least one antigen which also is common is tissue antigens from pupae of Spodoptera frugiperda.

Animals↗
PubMed1997

Evidence for gene conversion between tandemly duplicated cytoplasmic actin genes of Helicoverpa armigera (Lepidoptera:Noctuidae)

Tandemly duplicated actin genes have been isolated from a Helicoverpa armigera genomic library. Sequence comparisons with actin genes from other species suggest they encode cytoplasmic actins, being most closely related to the Bombyx mori A3 actin gene. The duplicated H. armigera actin genes, termed A3a and A3b, share 98.3% nucleotide sequence identity over their entire putative coding region. Analysis of the distribution of nucleotide differences shows the first 763 bp are identical between the two coding regions, with the 18 nucleotide changes occurring in the remaining 366 bp. This observation suggests a gene conversion event has taken place between the duplicated H. armigera A3a and A3b actin genes. Translation of the open-reading frames indicates the products of these genes are identical, apart from a single amino acid difference at codon 273. Polymerase chain reaction and northern blot analysis have shown both H. armigera A3a and A3b genes are expressed during pupal development and in the brain of newly enclosed adults. A region 5' of the H. armigera A3a actin gene start codon has been identified which contains regulatory sequences commonly found in the promoter region of actin genes, including TATA, CAAT, and CArG motifs.

Actins↗