Role of chemical cues from cotton in mediating host selection and oviposition behaviour in Helicoverpa armigera (Hubner) (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-beta-caryophyllene, alpha-pinene, beta-pinene, myrcene, beta-bisabolol, and alpha-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 hostplant selection are discussed.

Characterization of a Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae) - derived chitinase and its potential for pest control

The larval endoparasitoid Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae) has a toolbox of biological weapons to secure for host colonization and the successful parasitization of its host Heliothis virescens (F.) (Lepidoptera: Noctuidae). The cDNA of a putative chitinase has been previously isolated and initially characterized from teratocytes of this parasitoid among the plethora of molecules available in the venom and calyx fluids injected by females, oral and/or anal secretions released by the parasitoid larvae and/or produced by the expression of genes of the symbiotic associated polydnavirus. This putative chitinase has been initially associated with the host cuticle digestion to allow for parasitoid egression and with the asepsis of the host environment, acting as an antimicrobial. As chitinases are commonly expressed in plants against plant pathogens, the chitinase derived from the teratocytes of T. nigriceps is a potential tool for the development of insect pest control methods based on the disruption of the perithrophic membrane of herbivores. Therefore, we aimed to characterize the activity of the putative chitinase from teratocytes of T. nigriceps (Tnchi) produced using the Escherichia coli expression system and its potential to control H. virescens larvae when expressed into transgenic tobacco plants. The purified E. coli-produced Tnchi protein showed no chitinolitic activity, but was active in binding with colloidal and crystalline chitins in water and with colloidal chitin in buffered solution (pH = 6.74). Transgenic tobacco plants showed no enhanced chitinolitic activity relative to control plants, but survival of three-day old larvae of H. virescens was severely affected when directly fed on transgenic tobacco leaves expressing the recombinant Tnchi protein. Some properties of the Tnchi protein and the potential use of Tnchi-transgenic plants to control plant pests are discussed. (c) 2012 Elsevier Inc. All rights reserved.

Distribuição vertical e temporal de ovos de Alabama argillacea e de Heliothis virescens (Lepidoptera: Noctuidae) e parasitismo natural por Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Genetic variability and demographic history of Heliothis virescens (Lepidoptera: Noctuidae) populations from Brazil inferred by mtDNA sequences

Intra-and inter-population genetic variability and the demographic history of Heliothis virescens (F.) populations were evaluated by using mtDNA markers (coxI, coxII and nad6) with samples from the major cotton-and soybean-producing regions in Brazil in the growing seasons 2007/08, 2008/09 and 2009/10. AMOVA indicated low and non-significant genetic structure, regardless of geographical scale, growing season or crop, with most of genetic variation occurring within populations. Clustering analyzes also indicated low genetic differentiation. The haplotype network obtained with combined datasets resulted in 35 haplotypes, with 28 exclusive occurrences, four of them sampled only from soybean fields. The minimum spanning network showed star-shaped structures typical of populations that underwent a recent demographic expansion. The recent expansion was supported by other demographic analyzes, such as the Bayesian skyline plot, the unimodal distribution of paired differences among mitochondrial sequences, and negative and significant values of neutrality tests for the Tajima's D and Fu's F-S parameters. In addition, high values of haplotype diversity ((H) over cap) and low values of nucleotide diversity (pi), combined with a high number of low frequency haplotypes and values of theta(pi)<theta(W), suggested a recent demographic expansion of H. virescens populations in Brazil. This demographic event could be responsible for the low genetic structure currently found; however, haplotypes present uniquely at the same geographic regions and from one specific host plant suggest an initial differentiation among H. virescens populations within Brazil.

Inorganic elements in the fat bodies of Diatraea saccharalis (Lepidoptera: Crambidae) larvae parasitized by Cotesia flavipes (Hymenoptera: Braconidae)

Koinobiont parasitoids use several strategies to regulate the host`s physiological processes during parasitism. Although many aspects of host-parasitoid interactions have been explored, studies that attempted to assess the effects of parasitism on the availability of inorganic elements in the host are virtually nonexistent. Therefore, we aimed to evaluate the effects of parasitism on the concentrations of inorganic elements in the fat bodies of larvae of Diatraea saccharalis (Lepidoptera: Crambidae) during the development of the parasitoid Cotesia flavipes (Hymenoptera: Braconidae), by using total reflection X-ray fluorescence (TXRF). TXRF analysis allowed comparisons of the changes in the availability of the elements P. S. K, Ca, Cr, Fe, Ni, Cu, and Zn in the fat body tissues of D. saccharalis larvae parasitized by C. flavipes. Overall, the concentration of inorganic elements was higher early in parasitoid development (1 and 3 days after parasitism) compared to non-parasitized larvae, but much lower towards the end of parasitoid development (7 and 9 days after parasitism). Ca, K, and S were reduced after the fifth day of parasitism, which affected the total abundance of inorganic elements observed in the fat bodies of the parasitized hosts. The regulatory mechanisms or pathological effects related to the observed variation of the host inorganic elements induced by the parasitoid remain unknown, but there might be a strategy to make these elements available to the parasitoid larvae at the end of their development, when higher metabolic activity of the host fat body is required to sustain parasitoid growth. The observed variation of the host`s inorganic elements could also be related to the known effects of parasitism on the host`s immune response. (C) 2010 Elsevier Inc. All rights reserved.

Changes in the hemolymph and fat body metabolites of Diatraea saccharalis (Fabricius) (Lepidoptera : Crambidae) parasitized by Cotesia flavipes (Cameron) (Hymenoptera : Braconidae)

The koinobiont Cotesia flavipes responds to and is influenced by biochemical changes in the host hemolymph composition, Diatraea saccharalis. Changes in the composition of macronutrients may occur due to the hosts own development or by changes induced after parasitization. These changes occur to facilitate parasitoid invasion and to make the host internal environment suitable to parasitoid immature development. Therefore, changes in the availability of stored and circulating nutrients may correlate with the nutritional requirements of specific parasitoid immature stages. In here, we describe changes in the biochemical composition of parasitized and control larvae at different stages of parasitoid development to gain information on C flavipes host regulation and on its quantitative immature nutritional requirements. Total proteins, lipids and carbohydrates free in the hemolymph or stored in host fat bodies, and the SDS-PAGE protein profile of the hemolymph were evaluated in control and parasitized 6th instar during the whole parasitoid development. Changes in the total protein available in the host hemolymph were detected soon after parasitization, but carbohydrate and lipids were observed to differ only towards parasitoid larvae egression. Although C. flavipes affected the availability of all macronutrients observed in the host hemolymph, lipids and proteins stored in the host fat bodies were unaffected. However, carbohydrate concentration at the end of parasitoid larval development was much lower in parasitized than in control larvae at the same stage of development. SDS-PAGE analysis indicated C flavipes up-regulated two host proteins (125 and 48 kDa) and released two parasitism-specific proteins towards the end of parasitoid larval development. We provide a discussion on the role these changes may have on the process of host regulation and their possible requirement to sustain parasitoid development. (C) 2007 Elsevier Inc. All rights reserved.

Ecology and behavior of first instar larval Lepidoptera

Neonate Lepidoptera are confronted with the daunting task of establishing themselves on a food plant. The factors relevant to this process need to be considered at spatial and temporal scales relevant to the larva and not the investigator. Neonates have to cope with an array of plant surface characters as well as internal characters once the integument is ruptured. These characters, as well as microclimatic conditions, vary within and between plant modules and interact with larval feeding requirements, strongly affecting movement behavior, which may be extensive even for such small organisms. In addition to these factors, there is an array of predators, pathogens, and parasitoids with which first instars must contend. Not surprisingly, mortality in neonates is high but can vary widely. Experimental and manipulative studies, as well as detailed observations of the animal, are vital if the subtle interaction of factors responsible for this high and variable mortality are to be understood. These studies are essential for an understanding of theories linking female oviposition behavior with larval survival, plant defense theory, and population dynamics, as well as modern crop resistance breeding programs.

Desenvolvimento dos estágios imaturos de Palmistichus elaeisis Delvare & LaSalle (Hymenoptera, Eulophidae) em pupas de Lepidoptera

Palmistichus elaeisis Delvare & LaSalle, 1993 é um endoparasitóide coletado de pupas de Sabulodes sp. (Lepidoptera, Geometridae). Os estágios imaturos deste parasitóide foram estudados em laboratório (25 ± 1ºC; 70 ± 10% UR; fotofase 14 h) em pupas dos seguintes lepidópteros: Diatraea saccharalis (Fabricius, 1794) (Crambidae), Anticarsia gemmatalis Hübner, 1818, Heliothis virescens (Fabricius, 1781), Spodoptera frugiperda (J. E. Smith, 1797) (Noctuidae) e Thyrinteina arnobia (Stoll, 1782) (Geometridae). Observou-se que os ovos e as larvas de 1º ínstar são hialinas e himenopteriformes; as larvas dos 2º, 3º e 4º ínstares são esbranquiçadas e 12 segmentadas. A espécie de hospedeiro não influenciou o número de ínstares.

Proteínas Cry1 e Vip3A de Bacillus thuringiensis: sinergismo e efeito sub-letal no controle de Heliothis virescens

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synergism and Antagonism between Bacillus thuringiensis Vip3A and Cry1 Proteins in Heliothis virescens, Diatraea saccharalis and Spodoptera frugiperda

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Assessment of the high-dose concept and level of control provided by MON 87701 x MON 89788 soybean against Anticarsia gemmatalis and Pseudoplusia includens (Lepidoptera: Noctuidae) in Brazil

BACKGROUND: Genetically modified MON 87701 X MON 89788 soybean (Glycine max), which expresses the Cry1Ac and EPSP-synthase proteins, has been registered for commercial use in Brazil. To develop an Insect Resistance Management (IRM) program for this event, laboratory and field studies were conducted to assess the high-dose concept and level of control it provides against Anticarsia gemmatalis and Pseudoplusia includens. RESULTS: The purified Cry1Ac protein was more active against A. gemmatalis [LC50 (FL 95%) = 0.23 (0.150.34) mu g Cry1Ac mL-1 diet] than P. includens [LC50 (FL 95%) = 3.72 (2.654.86) mu g Cry1Ac mL-1 diet]. In bioassays with freeze-dried MON 87701X MON 89788 soybean tissue diluted 25 times in an artificial diet, there was 100% mortality of A. gemmatalis and up to 95.79% mortality for P. includens. In leaf-disc bioassays and under conditions of high artificial infestation in the greenhouse and natural infestation in the field, MON 87701X MON 89788 soybean showed a high level of efficacy against both target pests. CONCLUSIONS: The MON 87701X MON 89788 soybean provides a high level of control against A. gemmatalis and P. includes, but a high-dose event only to A. gemmatalis. Copyright (c) 2012 Society of Chemical Industry

Molecular cloning and insecticidal effect of Inga laurina trypsin inhibitor on Diatraea saccharalis and Heliothis virescens

Native Inga laurina (Fabaceae) trypsin inhibitor (ILTI) was tested for anti-insect activity against Diatraea saccharalis and Heliothis virescens larvae. The addition of 0.1% ILTI to the diet of D. saccharalis did not alter larval survival but decreased larval weight by 51%. The H. virescens larvae that were fed a diet containing 0.5% ILTI showed an 84% decrease in weight. ILTI was not digested by the midgut proteinases of either species of larvae. The trypsin levels were reduced by 55.3% in the feces of D. saccharalis and increased by 24.1% in the feces of H. virescens. The trypsin activity in both species fed with ILTI was sensitive to the inhibitor, suggesting that no novel proteinase resistant to ILTI was induced. Additionally, ILTI exhibited inhibitory activity against the proteinases present in the larval midgut of different species of Lepidoptera. The organization of the ilti gene was elucidated by analyzing its corresponding genomic sequence. The recombinant ILTI protein (reILTI) was expressed and purified, and its efficacy was evaluated. Both native ILTI and reILTI exhibited a similar strong inhibitory effect on bovine trypsin activity. These results suggest that ILTI presents insecticidal properties against both insects and may thus be a useful tool in the genetic engineering of plants. (c) 2012 Elsevier Inc. All rights reserved.

Intra-specific variation for host plant use in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae): Implications for management

The polyphagous moth Helicoverpa armigera (Hubner) is one of the world's most important agricultural pests. A number of existing approaches and future designs for management of H. armigera rely on the assumption that moths do not exhibit either genetically and/or non-genetically based variation for host plant utilization. We review recent empirical evidence demonstrating that both these forms of variation influence host plant use in this moth. The significance of this variation in H. armigera in relation to current and future pest management strategies is examined. We provide recommendations on future research needs and directions for sustainable management of H. armigera, under a framework that includes consideration of intra.-specific variation for host use relevant in this and other similar pest species. (C) 2004 Elsevier Ltd. All rights reserved.

Discrepancy between antennal and behavioural responses for enantiomers of -pinene: electrophysiology and behavior of Helicoverpa armigera (Lepidoptera)

The ability of adult cotton bollworm, Helicoverpa armigera (Hubner), to distinguish and respond to enantiomers of alpha-pinene was investigated with electrophysiological and behavioral methods. Electroantennogram recordings using mixtures of the enantiomers at saturating dose levels, and single unit electrophysiology, indicated that the two forms were detected by the same receptor neurons. The relative size of the electroantennogram response was higher for the (-) compared to the (+) form, indicating greater affinity for the (-) form at the level of the dendrites. Behavioral assays investigated the ability of moths to discriminate between, and respond to the (+) and (-) forms of alpha-pinene. Moths with no odor conditioning showed an innate preference for (+)-alpha-pinene. This preference displayed by naive moths was not significantly different from the preferences of moths conditioned on (+)-alpha-pinene. However, we found a significant difference in preference between moths conditioned on the (-) enantiomer compared to naive moths and moths conditioned on (+)-alpha-pinene, showing that learning plays an important role in the behavioral response. Moths are less able to distinguish between enantiomers of alpha-pinene than different odors (e.g., phenylacetaldehyde versus (-)-alpha-pinene) in learning experiments. The relevance of receptor discrimination of enantiomers and learning ability of the moths in host plant choice is discussed.

Replication of Heliothis virescens ascovirus in insect cell lines

Ascoviruses (AVs) infect larvae of various insect pests belonging to the family Noctuidae. The result of AV infection in the hosts is cleavage of infected cells into vesicles, a unique feature of AV infection. Since insect cell lines facilitate the study of virus life cycles, attempts were made to analyze Heliothis virescens AV (HvAV3e) infection in several cell lines and compare cell pathology to larval infection. In this study, replication and cytopathological effects of HvAV3e on four different cell lines were investigated. HvAV3e replication was confirmed in three noctuid cell lines from Spodoptera frugiperda (Sf9) and Helicoverpa zea (BCIRL-Hz-AM1 and FB33). However, the virus did not replicate in the non-noctuid insect cell line from Pieris rapae (Pieridae). Despite replication of the virus in the three permissive cell lines, the cytopathological effects of the virus were significantly different from that of larval infection.