High-Altitude Windborne Transport of <Emphasis Type="BoldItalic">Helicoverpa armigera</Emphasis> (Lepidoptera: Noctuidae) in Mid-Summer in Northern China

The high-altitude windborne transport of the second-generation moths of Helicoverpa armigera (Hübner) was observed with radar in July 2001 and 2002 at Langfang, Hebei province, China. Moths of local populations took off at dusk, with area density peaking ca. 0.5 h later. The variation of area density through the night suggested that the maximum flight duration was about 8.5 h. The moths generally ascended to altitudes of up to 1500 m above ground level (AGL) and formed layer concentrations at ca. 300, 500, and 1000 m AGL. Multiple layering was very common and layers were located at zones of maxima in wind speed or in wind shear rather than in temperature inversions. Both the displacement direction and the orientation of the insect were at an acute angle to the downwind direction, rather than being distributed at random, and varied as the wind direction changed. The windborne moths were mainly transported into northeastern China where maize at the silking stage would have provided good hosts for the subsequent (third) generation of H. armigera. These population movements may account for the nondevelopment of resistance to Bt cotton in H. armigera in northern China.     

Influence of transgenic cottons with <Emphasis Type="Italic">Bacillus thuringiensis cry1Ac</Emphasis> gene on the natural enemies of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis>

Transgenic cotton has been released for cultivation in several parts of the world to increase crop productivity. However, concerns have been raised regarding the possible undesirable effects of genetically modified crops on non-target organisms in the eco-system. Therefore, we studied the effects of transgenic cottons with cry1Ac gene from Bacillus thuringiensis Berliner (Bt) on the natural enemies of cotton bollworm/legume pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) under field and laboratory conditions. There was no apparent effect of transgenic cotton on the relative abundance of predatory spiders (Clubiona sp. and Neoscona sp.), coccinellid (Cheilomenes sexmaculatus Fab.), and the chrysopid (Chrysoperla carnea Stephens). However, the abundance of spiders, coccinellids, and chrysopids was quite low in insecticide protected plots towards end of the cropping season. There was a significant reduction in cocoon formation and adult emergence of the ichneumonid parasitoid, Campoletis chlorideae Uchnida reared on H. armigera larvae fed on the leaves of transgenic cottons before and after parasitization. However, no Bt toxins were detected in H. armigera larvae and the parasitoid cocoons with enzyme linked immunosorbent assay. Reduction in cocoon formation was because of early mortality of the H. armigera larvae due to Bt toxins in the leaves of transgenic cotton. There was a slight reduction in adult weight and fecundity, and prolongation of the larval period when the parasitoid was raised on H. armigera larvae fed on the leaves of transgenic cotton before and after parasitization. Survival and development of C. chlorideae was also poor when H. armigera larvae were fed on the leaves of cotton hybrid Mech 184. The adverse effects of transgenic cotton on survival and development of C. chlorideae were largely due to early mortality, and possibly poor nutritional quality of H. armigera larvae due to toxic effects of the transgene.     

Interspecific and intraspecific comparisons of ejaculates in the cotton bollworm <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> and the tobacco budworm <Emphasis Type="Italic">H. assulta</Emphasis>

The evolution of reproductive isolation is a prerequisite in the formation of new species. Although there are numerous studies on ejaculates in lepidopteran insects, ejaculate comparisons among sibling species have not been adequately addressed to understand possible reproductive barriers to hybridization. Here, we examined the interspecific and intraspecific variations of ejaculates in the sibling noctuid moths Helicoverpa armigera and Helicoverpa assulta. We found that there were considerable variations in the number of apyrene and eupyrene sperm and the length of eupyrene sperm. Male pupal mass explained not only a significant proportion of the variation in apyrene sperm number in both H. armigera and H. assulta, but also a significant proportion of the variation in eupyrene sperm number in H. assulta. There was a significant positive relationship between the number of eupyrene sperm and the number of apyrene sperm in both species. No difference in the length of eupyrene sperm was found between them; however, ejaculates of H. armigera had many more eupyrene sperm than H. assulta had. In H. armigera, large males generally mated with large females. The evolutionary consequences of these differences are discussed in this paper.     

Synergistic interaction between sublethal doses of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> and <Emphasis Type="Italic">Campoletis chlorideae</Emphasis> in managing <Emphasis Type="Italic">Helicoverpa armigera</Emphasis>

Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) is an important solitary larval endoparasitoid of the tomato fruit borer Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in India. The interaction between Bacillus thuringiensis subspecies kurstaki (Btk) HD-1 and C. chlorideae was studied under laboratory condition to explore their compatibility in managing H. armigera. The results had indicated that the growth and development of H. armigera was affected in a dose-dependent manner upon feeding on sublethal doses of Btk HD-1-treated diets. There were no larval survivors in lethal doses of Btk HD-1 (LC₇₀ and LC₉₀). The growth and survival of the parasitoid were normal when the host larvae were fed with sublethal doses or subjected to short time exposure to lethal doses of Btk HD-1. However, the parasitoid offsprings developed slowly and pupal as well as adult period, adult weight and adult emergence rate were reduced significantly if the parasitoid was developing inside a severely Bt intoxicated host larvae. There were no evident differences in longevity of parasitoid adults that were fed on honey solution containing different concentrations of Btk HD-1 as compared to adults fed only on honey solution. This indicates no direct adverse effect of Btk HD-1 on C. chlorideae. Further, the gravid female parasitoid did not discriminate Btk HD-1 intoxicated and normal H. armigera larvae for oviposition. The result implies that spore crystal formulation of Btk HD-1 can be effectively used in a synergistic manner along with existing natural or prereleased population of C. chlorideae in organic farming or as components in biointensive IPM module for managing H. armigera.     

Characterization of directly transformed weedy <Emphasis Type="Italic">Brassica rapa</Emphasis> and introgressed <Emphasis Type="Italic">B. rapa</Emphasis> with Bt <Emphasis Type="Italic">cry1Ac</Emphasis> and <Emphasis Type="Italic">gfp</Emphasis> genes

Crop to weed transgene flow, which could result in more competitive weed populations, is an agricultural biosafety concern. Crop Brassica napus to weedy Brassica rapa hybridization has been extensively characterized to better understand the transgene flow and its consequences. In this study, weedy accessions of B. rapa were transformed with Bacillus thuringiensis (Bt) cry1Ac- and green fluorescence protein (gfp)-coding transgenes using Agrobacterium to assess ecological performance of the wild biotype relative to introgressed hybrids in which the transgenic parent was the crop. Regenerated transgenic B. rapa events were characterized by progeny analysis, Bt protein enzyme-linked immunosorbent assay (ELISA), Southern blot analysis, and GFP expression assay. GFP expression level and Bt protein concentration were significantly different between independent transgenic B. rapa events. Similar reproductive productivity was observed in comparison between transgenic B. rapa events and B. rapa × B. napus introgressed hybrids in greenhouse and field experiments. In the greenhouse, Bt transgenic plants experienced significantly less herbivory damage from the diamondback moth (Plutella xylostella). No differences were found in the field experiment under ambient, low, herbivore pressure. Directly transformed transgenic B. rapa plants should be a helpful experimental control to better understand crop genetic load in introgressed transgenic weeds.     

Cloning and characterization of truncated <Emphasis Type="Italic">cry1Ab</Emphasis> gene from a new indigenous isolate of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>

The insecticidal crystal protein(s) encoded by cry gene(s) of Bacillus thuringiensis (Bt) have been used for insect control both as biopesticides and in transgenic plants. A new 3′-truncated cry1Ab gene was cloned from an indigenous isolate of Bt, A19-31. Nucleotide sequencing and homology search revealed that the deduced amino acid sequence of Cry1Ab toxin of Bt strain A19-31 had a variation of two amino acid residues with the holotype sequence, Cry1Ab1. Expression of the 3′-truncated cry1Ab gene was studied in an acrystalliferous strain of Bt (4Q7). SDS-PAGE and immunostrip analysis of spore-crystal mixture revealed a low level expression of the 3′-truncated cry1Ab gene. Insecticidal activity assay showed that the recombinant 3′-truncated cry1Ab gene product was toxic to larvae of both Helicoverpa armigera and Spodoptera litura.     

Genetic transformation of the codling moth, <Emphasis Type="Italic">Cydia pomonella</Emphasis> L., with <Emphasis Type="Italic">piggyBac</Emphasis> EGFP

Genetic transformation of the codling moth, Cydia pomonella, was accomplished through embryo microinjection with a plasmid-based piggyBac vector containing the enhanced green fluorescent protein (EGFP) gene. Sequencing of the flanking regions around the inserted construct resulted in identification of insect genomic sequences, not plasmid sequences, thus providing evidence that the piggyBac EGFP cassette had integrated into the codling moth genome. EGFP-positive moths were confirmed in the 28th and earlier generations post injection through PCR and Southern blot analyses, indicating heritability of the transgene.     

Mitochondrial DNA analysis of field populations of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Lepidoptera: Noctuidae) and of its relationship to <Emphasis Type="Italic">H. zea</Emphasis>

Background  

Helicoverpa armigera and H. zea are amongst the most significant polyphagous pest lepidopteran species in the Old and New Worlds respectively. Separation of H. armigera and H. zea is difficult and is usually only achieved through morphological differences in the genitalia. They are capable of interbreeding to produce fertile offspring. The single species status of H. armigera has been doubted, due to its wide distribution and plant host range across the Old World. This study explores the global genetic diversity of H. armigera and its evolutionary relationship to H zea.     

<Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Protein Cry6B (BGSC ID 4D8) is Toxic to Larvae of <Emphasis Type="Italic">Hypera postica</Emphasis>

Insecticidal proteins produced by strains of Bacillus thuringenesis are specific toward target pests. One of the Bt proteins, Cry 1Ac has been used successfully for controlling crop predation by polyphagous pests Helicoverpa armigera. Structurally, Bt proteins consist of three domains; domain I and III are fairly homologous in various Bt proteins while domain II is hypervariable. The hypervariable domain II is believed to be responsible for specificity toward target pest. Successful deployment of Bt proteins requires knowledge of its specificity toward the insect. Various Bt proteins have been characterized for activity against coleopteran pests. Some Bt proteins of class Cry6 have been found to be active against potato weevil. We have evaluated the activity of Cry6B protein (BGSC-4D8) against lucerne weevil, Hypera postica, which is a major pest of forage crop Medicago sativa. Results revealed that the purified Cry6B protein is significantly active against the coleopteran pest with LC₅₀ value 280 ng/μl. The leaves coated with the purified Cry6 toxin were three times less damaged as compared with the negative control.     

Effects of climate change and crop planting structure on the abundance of cotton bollworm,Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The interactions between plants and insects play an important role in ecosystems. Climate change and cropping patterns can affect herbivorous pest insect dynamics. Understanding the reasons for population fluctuations can help improve integrated pest management strategies. Here, a 25‐year dataset on climate, cropping planting structure, and the population dynamics of cotton bollworms (Helicoverpa armigera) from Bachu County, south Xinjiang, China, was analyzed to assess the effects of changes in climate and crop planting structure on the population dynamics of H. armigera. The three generations of H. armigera showed increasing trends in population size with climate warming, especially in the third generation. The relative abundances of the first and second generations decreased, but that of the third generation increased. Rising temperature and precipitation produced different impacts on the development of different generations. The population numbers of H. armigera increased with the increase in the non‐Bacillus thuringiensis (Bt) cotton‐planted area. Asynchrony of abrupt changes existed among climate change, crop flowering dates, and the phenology of H. armigera moths. The asynchronous responses in crop flowering dates and phenology of H. armigera to climate warming would expand in the future. The primary factors affecting the first, second, and third generations of moths were T_mean in June, the last appearance date of the second generation of moths, and the duration of the third generation of moths, respectively. To reduce the harm to crops caused by H. armigera, Bt cotton should be widely planted.     

Impact of <Emphasis Type="Italic">cry1AC</Emphasis>-carrying <Emphasis Type="Italic">Brassica rapa</Emphasis> subsp. <Emphasis Type="Italic">pekinensis</Emphasis> on leaf bacterial community

The effects of Chinese cabbage (Brassica rapa subsp. pekinensis) carrying cry1AC derived from Bacillus thuringiensis (Bt) on leaf bacterial community were examined by analyzing the horizontal transfer of trans-gene fragments from plants to bacteria. The effect of plant pathogenic bacteria on the gene transfer was also examined using Pseudomonas syringae pathovar. maculicola. The frequency of hygromycin-resistant bacteria did not alter in Bt leaves, though slight increase was observed in Pseudomonas-infected Bt leaves with no statistical significance. The analysis of bacterial community profiles using the denaturing gradient gel electrophoresis (DGGE) fingerprinting indicated that there were slight differences between Bt and control Chinese cabbage, and also that infected tissues were dominated by P. syringae pv. maculicola. However, the cultured bacterial pools were not found to contain any transgene fragments. Thus, no direct evidence of immediate gene transfer from plant to bacteria or acquisition of hygromycin resistance could be observed. Still, long-term monitoring on the possibility of gene transfer is necessary to correctly assess the environmental effects of the Bt crop on bacteria.     

Construction of a Promoter-probe Vector for <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>: the Identification of <Emphasis Type="Italic">cis</Emphasis>-acting Elements of the <Emphasis Type="Italic">chiA</Emphasis> Locus

The expression and application of Bacillus thuringiensis (Bt) chitinase genes have been extensively investigated. However, little information is available regarding the regulation of chitinase gene expression in Bt. In this study, a shuttle promoter-probe vector was constructed incorporating the thermostable β-galactosidase gene bgaB of B. stearothermophilus as the reporter for the study of Bt promoters. Using this plasmid, the activity of the chiA gene promoter in Bt was investigated. Deletion analysis of the putative chiA promoter region revealed that the sequence located ~75 bp DNA from positions −116 to −42, with respect to the translation start site, is the core promoter of chiA gene. Furthermore, a site for chitin induction was identified near position −36. This site for negative regulation was indicated downstream of the RNA polymerase binding sites of the promoter of chiA. The expression of chiA started in cell grown for about 6 h and reached the maximum after 60 h of incubation. Induction of chiA expression by chitin was demonstrated by an increase in β-galactosidase activity of ~2.5-fold.     

Gene cloning and expression of cadherin in midgut of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> and its Cry1A binding region

Cadherins belong to one of the families of animal glycoproteins responsible for calcium-dependent cell-cell adhesion. Recent literatures showed that the cadherin-like in midgut of several insects served as the receptor of Bt toxin Cry1A and the variation of cadherin-like is related to insect’s resistance to Cry1A. The full-length cDNA encoding cadherin-like of Helicoverpa armigera is cloned by degenerate PCR and RACE techniques and the gene was designated as BtR-harm, which is 5581 bp in full-length, encoding 1730 amino acid residues (BtR-harm was deposited in GenBank and the accession number is AF519180). Its predicted molecular weight and isoelectric point were 195.39 kDa and 4.23, respectively. The inferred amino acid sequence includes a signal sequence, 11 cadherin repeats, a membrane-proximal region, a transmembrane region and a cytoplasmic region. Sequence analysis indicated that the deduced protein sequence was most similar to the cadherin-like from Heliothis virescens with 84.2% identity and highly similar to three other lepidopteran cadherin from Bombyx mori, Manduca sexta and Pectinophora gossypiella, with the sequence identities of 60.3.6%, 57.5% and 51.0%, respectively. The cDNA encoding cadherin gene was expressed successfully in E. coli and the recombinant proteins can bind with Cry1Ac. Truncation analysis and binding experiment of BtR-harm revealed that the Cry1A binding region was a contiguous 244-amino acid sequence, which located between amino acid 1217 and 1461. Semi-quantitative RT-PCR analysis showed that BtR-harm was highly expressed in midgut of H. armigera, very low expressed in foregut and hindgut and was not expressed in other tissues. After H. armigera producing resistance to Cry1Ac, the expression quantity of BtR-harm significantly decreased in midgut of H. armigera. It is the first confirmation that BtR-harm can function as receptor of Cry1Ac in H. armigera and the binding region was located on a contiguous 244 amino acid sequence, suggesting that the decrease of expression quantity of BtR-harm is one of the main reasons for H. armigera resistance to Cry1Ac.     

<Emphasis Type="Italic">Wolbachia</Emphasis> and bacteriophage WO-B density of <Emphasis Type="Italic">Wolbachia</Emphasis> a-infected <Emphasis Type="Italic">Aedes albopictus</Emphasis> mosquito

Wolbachia are maternally inherited symbiotic bacteria capable of inducing an extensive range of reproductive abnormalities in their hosts, including cytoplasmic incompatibility (CI). Its density (concentration) is likely to influence the penetrance of CI in incompatible crosses. The variations of Wolbachia density could also be linked with phage WO density. We determined the relative density (relative concentration) of prophage WO orf7 and Wolbachia (phage-to-bacteria ratio) during early developmental and adult stages of singly infected Aedes albopictus mosquito (Wolbachia A-infected) by using real-time quantitative PCR. Phage WO and Wolbachia did not develop at the same rate. Relative Wolbachia density (bacteria-to-host ratio) was high later in development (adult stages) whilst relative prophage WO density (phage-to-bacteria ratio) was low in the adult stages. Furthermore, 12-d-old adults of singly infected female mosquito had the highest Wolbachia density. In contrast, the larval stage 4 (L4) contained the highest prophage WO-B orf7 density. The association of hosts-Wolbachia-phage among diverse species is different. Thus, if phage and Wolbachia are involved in CI mechanism, the information of this association should be acquired for each specific type of organism for future use of population replacement or gene drive system.     

Cloning and Characterization of Two Novel Crystal Protein Genes, <Emphasis Type="Italic">cry54Aa1</Emphasis> and <Emphasis Type="Italic">cry30Fa1</Emphasis>, from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strain BtMC28

Bacillus thuringiensis strain BtMC28 was isolated from the soil sample in China. Two novel crystal protein genes were found by using the PCR-RFLP method. Moreover, the full-length sequences of two novel genes were obtained by a single oligonucleotide nested (SON)-PCR upstream and downstream strategy. Sequence analysis revealed that one gene encoded a polypeptide of 673 amino acid residues with a molecular mass of 76.3 kDa, 38% identical to Cry10Aa, and the other encoded a polypeptide of 687 amino acid residues with a molecular mass of 77.1 kDa, 74% identical to Cry30Aa. These two novel crystal protein genes were designated as cry54Aa1 and cry30Fa1 by Bt Insecticidal Crystal Proteins Nomenclature Committee, respectively. The Cry54Aa1 and Cry30Fa1 proteins retained five conserved regions commonly found in the existing Cry proteins. Cry54Aa1 protein exhibited insecticidal activities against Laphygma exigua (Lepidoptera), Helicoverpa armigera (Lepidoptera), and Aedes aegypti (Diptera) when its encoding gene was expressed in an Escherichia coli host strain. The authors, Furong Tan and Jun Zhu contributed equally to this work.     

<Emphasis Type="Italic">Oenothera speciosa</Emphasis> versus <Emphasis Type="Italic">Macroglossum stellatarum</Emphasis>: killing beauty

Hovering and dead individuals of the diurnal hawk-moth Macroglossum stellatarum (Linnaeus, 1758) (Lepidoptera: Sphingidae) were found with proboscides got stuck into flowers of the ornamental plant Oenothera speciosa Nutt (Onagraceae). The phenomenon was observed in several locations in Bulgaria where the plant has been introduced. Microscopic examination revealed that the reason for this unusual interaction is pubescence of thick-walled basiscopically oriented trichomes in the basal part of the hypanthium and style of the plant. When a foraging moth inserts its proboscis into this area, the tips of the trichomes are inserted into the transverse grooves of proboscis and hamper its back movement. As a result the moths are suspended for a long time, sometimes until death. Other trapped moth species were also observed but they always effected self-release. This plant–insect interaction is also a conservation issue as an estimation of its impact on wild insect populations is lacking.     

Toxicity of a <Emphasis Type="Italic">Bacillus thuringiensis israelensis</Emphasis>-like strain against <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis>

Bacillus thuringiensis (Bt) Berliner is a promising agent for microbial control of agriculturally and medically important insects. This study aimed at searching for Bt strains encoding Cry proteins that act more efficiently against fall armyworm. Thirty Bt strains were isolated from soil samples in Pernambuco State and evaluated through bioassays. Among these, strain I4A7 was the most efficient against the fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), and thus it was characterized by biochemical sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and molecular (polymerase chain reaction (PCR) and sequencing reaction) methods. The protein pattern of this strain on a SDS–PAGE was similar to that of B. thuringiensis israelensis (Bti). Moreover, I4A7 cry DNA sequence showed high identity (99–100%) to genes cry4Aa, 4Ba, 10Aa, 11Aa, cyt1Aa and cyt2B from Bti. The toxicity of the newly isolated Bti-like strain upon S. frugiperda should be considered as this strain might be used in combination with other Bt strains, such as B. thuringiensis var. kurstaki (Btk). Handling Editor: Helen Roy.     

Comparative Characterization of Chitinases from Silkworm (<Emphasis Type="Italic">Bombyx mori</Emphasis>) and Bollworm (<Emphasis Type="Italic">Helicoverpa armigera</Emphasis>)

Chitinases play an important role in the degradation of the cuticular chitin during the process of ecdysis. In this study, we compared the chitinases of two insect species, Bombyx mori (silkworm) and Helicoverpa armigera (bollworm), to assess the relation between characteristics and chitinase patterns. Differences between two chitinases were observed after purification using ammonium sulfate precipitation, affinity chromatography, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) assay. Although the specific activities of the purified enzymes were different, the purification yields were similar. One band of 88 kDa was observed for B. mori, and the other band of 75 kDa was detected for H. armigera. When a range of properties was tested, it was found that the optimum temperatures of B. mori and H. armigera chitinases were 45 and 50°C, respectively; the optimum pH value was 6.0 for both chitinases. Mn²⁺ played catalytic role while Cu²⁺ and SDS strongly inhibited activities of both enzymes. Between two chitinases, differences in K _M were also observed. K _M of chitinase from silkworm and bollworm was found to be 22.3 and 41.0 μmol/l, respectively. Both the chitinases significantly inhibited the spore germination of two fungal species, Saccharomyces cerevisiae and Penicillium.     

Herbivore- and MeJA-induced volatile emissions from the redroot pigweed <Emphasis Type="Italic">Amaranthus retroflexus</Emphasis> Linnaeus: their roles in attracting <Emphasis Type="Italic">Microplitis mediator</Emphasis> (Haliday) parasitoids

The redroot pigweed Amaranthus retroflexus Linnaeus (Caryophyllales: Amaranthaceae), an annual weed, is a host plant of the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Microplitis mediator (Haliday) (Hymenoptera: Braconidae) is a parasitoid of H. armigera. Here, the electrophysiological and behavioral responses of M. mediator to induced redroot pigweed volatiles were investigated. Female parasitoids were significantly attracted to odors from plants induced by H. armigera damage, H. armigera continuous feeding, and 10 mM methyl jasmonate (MeJA) spray. The gas chromatography–mass spectrometry (GC–MS) results demonstrated that there were significant changes in volatiles from these three treatments in comparison with the control. When the constitutive compound 6-methyl-5-hepten-2-one was emitted in significant amounts from treated plants, it could elicit a medium electrophysiological response (0.2?≤?value?<?0.8) , a significant behavioral response of M. mediator females. β-Elemene, emitted from two treatments (plants damaged by H. armigera, plants with H. armigera continuous feeding), showed a very weak electrophysiological response (value?<?0.2), but was significantly attractive to M. mediator. The results showed that 6-methyl-5-hepten-2-one and β-elemene might play important roles in mediating the foraging behavior of M. mediator. Further work will be conducted to evaluate the function of these two compounds under semi-field and field conditions and exploit them as attractants for M. mediator to control H. armigera.     

Effects of Bt maize on the herbivore <Emphasis Type="Italic">Spodoptera littoralis</Emphasis> (Lepidoptera: Noctuidae) and the parasitoid <Emphasis Type="Italic">Cotesia marginiventris</Emphasis> (Hymenoptera: Braconidae).

Recent studies have shown that transgenic insect resistant plants can have negative effects on non-target herbivores as well as on beneficial insects. The study of tritrophic interactions gives insight into the complex mechanisms of food webs in the field and can easily be incorporated into a tiered risk assessment framework. We investigated the effects of transgenic maize (Zea mays) expressing insecticidal proteins derived from Bacillus thuringiensis (Bt maize) on Spodoptera littoralis, a non-target herbivore, and on the hymenopteran parasitoid Cotesia marginiventris. In a laboratory study, S. littoralis larvae were reared for their whole lifespan on a mixture of leaves and stems from 2–4-week old Bt maize plants. S. littoralis survival, developmental times and larval weights were significantly affected by Bt maize diet. However, adult moths, which survived development on Bt maize, were the same size as the adults from the control group.C. marginiventris survival, developmental times and cocoon weights were significantly negatively affected if their S. littoralis host larva had been fed Bt maize. ELISA tests confirmed that S. littoralis larvae ingest high amounts of Cry1A(b) toxin while feeding on Bt maize. In S. littoralis pupae and in C. marginiventris cocoon silk, only traces of the toxin could be detected. No toxin was found in S. littoralis and C. marginiventris adults. Thus the toxin is not accumulating in the trophic levels and in fact appears to be excreted. Our results suggest that the effects on C. marginiventris when developing in susceptible S. littoralis larvae are indirect (host mediated). The biological relevance of those results and the significance of this study in risk assessment are discussed.