Helicoverpa Species Research Articles

CYP6B6 mediated adaptation to capsaicinoids in the generalist Helicoverpa armigera and specialist H. assulta: Transcriptional response and metabolic detoxification

Capsaicin and dihydrocapsaicin are the principal pungent compounds in hot peppers. The generalist Helicoverpa armigera and the specialist H. assulta are two of the few insects that can feed on hot pepper fruits. To further understand the mechanisms behind physiological adaptation to capsaicinoids in the two agricultural pests, we investigated the transcriptional response and metabolism capacity of CYP6B6 orthologs from the two closely related species to the capsaicinoids. The results showed that the expression of CYP6B6 was either weakly or moderately inducible in a tissue- and dose-specific manner. CYP6B6 induction to greater extent was observed in the larval midguts of the cotton bollworms, indicating that inducible defense is more prominant in the generalist. HassCYP6B6 exhibited a significantly higher activity towards capsaicin than HarmCYP6B6, suggesting that the specialist herbivore has evolved a more efficient enzyme in detoxifying capsaicin compared to the generalist. Multiple known and yet to be elucidated metabolites were detected in the reactions catalyzed by CYP6B6s, with dehydrogenation at the terminal carbon followed by N-macrocyclization and aliphatic hydroxylation being the most dominant pathways. The data make us hypothesize that these two Helicoverpa species have well adapted to capsaicinoids via their high P450-mediated detoxification ability.

Species-specific evolution of lepidopteran TspC5 tetraspanins associated with dominant resistance to Bacillus thuringiensis toxin Cry1Ac

Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have proven to be highly effective in managing some key pests. However, the evolution of resistance by the target pests threatens the sustainability of Bt crops. The L31S mutation in a tetraspanin encoded by HarmTspC5 (previously known as HaTSPAN1) has been shown to confer dominant resistance to the Bt protein Cry1Ac in Helicoverpa armigera, a globally damaging lepidopteran pest. However, the broader implications of the L31S mutation in the tetraspanins of other lepidopteran species remain unclear. The evolutionary analyses in this study indicate that TspC5s have evolved in a species-specific manner among the lepidopteran insects. To investigate the role of TspC5s in conferring dominant resistance to Cry1Ac, we used the piggyBac-based transformation system to generate four transgenic H. armigera strains that express exogenous TspC5 variants from three phylogenetically close species (Helicoverpa zea, Helicoverpa assulta and Heliothis virescens) and one phylogenetically distant species (Plutella xylostella). In comparison with the background SCD strain of H. armigera, the transgenic strains expressing HzeaTspC5-L31S, HassTspC5-L31S, or HvirTspC5-L31S exhibited significant resistance to Cry1Ac (10.0-, 21.4-, and 81.1-fold, respectively), whereas the strain expressing PxylTspC5-L27S remained susceptible. Furthermore, the Cry1Ac resistant phenotypes followed an autosomal dominant inheritance pattern and were closely linked to the introduced mutant TspC5s. These findings reveal the conserved role of TspC5s from Helicoverpa and Heliothis species in mediating the dominant resistance to Cry1Ac, and they provide crucial insights for assessing resistance risks related to mutant tetraspanins and devising adaptive resistance management strategies for these major lepidopteran pests.

Rapid Adaptation and Interspecific Introgression in the North American Crop Pest Helicoverpa zea.

Insect crop pests threaten global food security. This threat is amplified through the spread of nonnative species and through adaptation of native pests to control measures. Adaptations such as pesticide resistance can result from selection on variation within a population, or through gene flow from another population. We investigate these processes in an economically important noctuid crop pest, Helicoverpa zea, which has evolved resistance to a wide range of pesticides. Its sister species Helicoverpa armigera, first detected as an invasive species in Brazil in 2013, introduced the pyrethroid-resistance gene CYP337B3 to South American H. zea via adaptive introgression. To understand whether this could contribute to pesticide resistance in North America, we sequenced 237 H. zea genomes across 10 sample sites. We report H. armigera introgression into the North American H. zea population. Two individuals sampled in Texas in 2019 carry H. armigera haplotypes in a 4 Mbp region containing CYP337B3. Next, we identify signatures of selection in the panmictic population of nonadmixed H. zea, identifying a selective sweep at a second cytochrome P450 gene: CYP333B3. We estimate that its derived allele conferred a ∼5% fitness advantage and show that this estimate explains independently observed rare nonsynonymous CYP333B3 mutations approaching fixation over a ∼20-year period. We also detect putative signatures of selection at a kinesin gene associated with Bt resistance. Overall, we document two mechanisms of rapid adaptation: the introduction of fitness-enhancing alleles through interspecific introgression, and selection on intraspecific variation.

Evolutionary shifts in pheromone receptors contribute to speciation in four Helicoverpa species.

Male moths utilize their pheromone communication systems to distinguish potential mates from other sympatric species, which contributes to maintaining reproductive isolation and even drives speciation. The molecular mechanisms underlying the evolution of pheromone communication systems are usually studied between closely-related moth species for their similar but divergent traits associated with pheromone production, detection, and/or processing. In this study, we first identified the functional differentiation in two orthologous pheromone receptors, OR14b, and OR16, in four Helicoverpa species, Helicoverpa armigera, H. assulta, H. zea, and H. gelotopoeon. To understand the substrate response specificity of these two PRs, we performed all-atom molecular dynamics simulations of OR14b and OR16 based on AlphaFold2 structural prediction, andmolecular docking, allowing us to predict a few key amino acids involved in substrate binding. These candidate residues were further tested and validated by site-directed mutagenesis and functional analysis. These results together identified two hydrophobic amino acids at positions 164 and 232 are the determinants of the response specificity of HarmOR14b and HzeaOR14b to Z9-14:Ald and Z9-16:Ald by directly interacting with the substrates. Interestingly, in OR16 orthologs, we found that position 66 alone determines the specific binding of Z11-16:OH, likely via allosteric interactions. Overall, we have developed an effective integrated method to identify the critical residues for substrate selectivity of ORs and elucidated the molecular mechanism of the diversification of pheromone recognition systems.

Interactions between the omnivorous bug Nesidiocoris tenuis (Heteroptera: Miridae) and the tomato pests Helicoverpa armigera (Lepidoptera: Noctuidae) and Phthorimaea absoluta (Lepidoptera: Gelechiidae): predation, phytophagy, and prey preference

Abstract Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a zoophytophagous bug that can derive nutrients from 3 trophic levels: plants, herbivorous arthropods, and other predators. On tomato, besides damaging the plants as they feed, might the mirid also forage on pest species and repel pests. In greenhouse and laboratory experiments, we investigated the functional response of the bug, its prey preference, and its influence on the oviposition potentials of 2 major pest species Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) and Phthorimaea absoluta Meyrick (Lepidoptera: Gelechiidae) on tomato Solanum lycopersicum L. (Solanaceae). Nesidiocoris tenuis showed a Type II functional response to both prey species. The estimated handling time was higher for H. armigera eggs than for P. absoluta yet N. tenuis attack rates did not differ between the 2 prey species. Nesidiocoris tenuis did not show a preference for 1 species when prey eggs were provided in equal proportions. The feeding on tomato plants by N. tenuis did not affect oviposition by the 2 moth species, as neither species showed a preference for clean or N. tenuis-adult-damaged plants and clean or N. tenuis-nymph-damaged plants. This study shows that N. tenuis can prey upon eggs of both moth species as the 3 species co-occur in tomato fields. However, because of the shorter handling time of P. absoluta eggs by the predator and the higher number of eggs laid by H. armigera, the co-occurrence might be less detrimental to the H. armigera populations compared to P. absoluta.

The Genetic Basis of Gene Expression Divergence in Antennae of Two Closely Related Moth Species, Helicoverpa armigera and Helicoverpa assulta.

The closely related species Helicoverpa armigera (H. armigera) and Helicoverpa assulta (H. assulta) have different host plant ranges and share two principal components of sex pheromones but with reversed ratios. The antennae are the main olfactory organ of insects and play a crucial role in host plant selection and mate seeking. However, the genetic basis for gene expression divergence in the antennae of the two species is unclear. We performed an allele-specific expression (ASE) analysis in the antennal transcriptomes of the two species and their F1 hybrids, examining the connection between gene expression divergence and phenotypic differences. The results show that the proportion of genes classified as all cis was higher than that of all trans in males and reversed in females. The contribution of regulatory patterns to gene expression divergence in males was less than that in females, which explained the functional differentiation of male and female antennae. Among the five groups of F1 hybrids, the fertile males from the cross of H. armigera female and H. assulta male had the lowest proportion of misexpressed genes, and the inferred regulatory patterns were more accurate. By using this group of F1 hybrids, we discovered that cis-related regulations play a crucial role in gene expression divergence of sex pheromone perception-related proteins. These results are helpful for understanding how specific changes in the gene expression of olfactory-related genes can contribute to rapid evolutionary changes in important olfactory traits in closely related moths.

Single amino acid variations drive functional divergence of cytochrome P450s in Helicoverpa species

Divergence of gene function is a hallmark of evolution, but assessing such divergence in one species or between species requires information on functional alterations of the alleles and homologs. Here, we explore the functional divergence of two paralogs, CYP6AE19 and CYP6AE20, from Helicoverpa armigera, and two close orthologs, CYP6B8 and CYP6B7, from two related species (Helicoverpa zea and H. armigera); although there is high sequence identity within each pair of enzymes, the latter P450 of each pair has lost metabolic competence towards the plant allelochemical xanthotoxin. Multiple chimeric and single/double site mutants were created by exchanging the diverse substrate recognition sites (SRSs) and amino acids within each pair of P450s. Heterologous expression in Sf9 cells and in vitro metabolism studies showed that the exchange of SRS4 swapped the activity of CYP6AE19 and CYP6AE20, and subsequent site-directed mutagenesis demonstrated that the CYP6AE20 V318M substitution causes a gain-of-function towards xanthotoxin. Meanwhile, a single amino acid substitution (L489P) in SRS6 was found to swap activity between the CYP6B orthologs. Sequence alignments of CYP6AE paralogs and all reported insect xanthotoxin-metabolizing P450s suggest M318 and P489 are essential for the catalytic activities of CYP6AE paralogs and CYP6B orthologs, respectively, but P450s in different subfamilies may have different mechanisms towards the same substrate. Our findings demonstrate that a single amino acid substitution can suffice to alter substrate metabolism and this functional divergence resulting from natural mutations will help to further our understanding of the process of natural selection of P450 genes and their role in insect-host plant interactions.

Brain Investigation on Sexual Dimorphism in a Gynandromorph Moth.

Simple SummaryThe noctuid moth, Helicoverpa armigera, is one of the globally most damaging agricultural pest insects. Generally, exploration of the male- and female-specific neural architecture underlying its reproductive behavior is crucial for developing biological and environment-friendly alternatives to the traditional pest control management. In this study, we utilized the opportunity to uncover putative sex differences in H. armigera by comparing details in the brain anatomy between the male and female hemispheres in one gynandromorphic individual. The methods included synapsin immunostaining, confocal microscopy, and the digital reconstruction of several brain areas involved in processing input about odor and vision, respectively. The results demonstrated sex-specific arrangements applying to distinct olfactory neuropils, including not only the primary olfactory center, the antennal lobe, but also higher order levels involved in odor-associated memory formation.The present study was dedicated to investigating the anatomical organization of distinct neuropils within the two brain hemispheres of a gynandromorphic moth of the species Helicoverpa armigera. High quality confocal imaging of a synapsin immuno-stained preparation combined with three-dimensional reconstructions made it possible to identify several brain structures involved in processing odor input and to measure their volumes in the male and female hemispheres. Thus, in addition to reconstructing the antennal lobes, we also made digital models of the mushroom body calyces, the pedunculus, and the vertical and medial lobes. As previously reported, prominent sexual dimorphism was demonstrated in the antennal lobes via the identification of a male-specific macroglomerular complex (MGC) and a female-specific complex (Fc) in each of the two brain hemispheres of the gynandromorph. Additionally, sex-specific differences were found in volume differences for three other neuropil structures—the calyces, pedunculus, and vertical lobe. The putative purpose of larger volumes of three mushroom body neuropils in females as compared to males is discussed.

Identification of Helicoverpa armigera promoters for biotechnological applications

Helicoverpa armigera and Helicoverpa zea are highly polyphagous major agricultural pests with a global distribution. Their control is based on insecticides, however, new, effective, and environmentally friendly control tools are required to be developed and validated. In an effort to facilitate the development of advanced biotechnological tools in these species that will take advantage of new powerful molecular biology techniques like CRISPR/Cas9, we used available transcriptomic data and literature resources, in order to identify RNA polymerase II and III promoters active in RP-HzGUT-AW1(MG), a midgut derived cell line from Helicoverpa zea. Following functional analysis in insect cell lines, four RNA polymerase II promoters from the genes HaLabial, HaTsp-2A, HaPtx-I and HaCaudal were found to exhibit high transcriptional activity in vitro. The HaTsp-2A promoter did not exhibit any activity in the non-midgut derived cell lines Sf-9 and Hi-5 despite high sequence conservation among Lepidoptera, suggesting that it may function in a gut specific manner. Furthermore, considering the utility of RNA polymerase III U6 promoters in methodologies such as RNAi and CRISPR/Cas9, we identified and evaluated four different U6 promoters of H. armigera. In vitro experiments based on luciferase and GFP reporter assays, as well as in vivo experiments targeting an essential gene of Helicoverpa, indicate that these U6 promoters are functional and can be used to experimentally silence or knockout target genes through the expression of shRNAs and sgRNAs respectively. Taking our findings together, we provide a set of promoters useful for the genetic manipulation of Helicoverpa species, that can be used in various applications in the context of agricultural biotechnology.

Comparison of functions of pheromone receptor repertoires in Helicoverpa armigera and Helicoverpa assulta using a Drosophila expression system

Helicoverpa armigera and H. assulta are sympatric closely related species sharing two sex pheromone components, (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) but in opposite ratios, 97:3 and 3:97 respectively. This feature makes them a feasible model for studying the evolution of pheromone coding mechanisms of lepidopteran insects. Despite a decade-long study to deorphanize the pheromone receptor (PR) repertoires of the two species, the comparison of the function of all PR orthologs between the two species is incomplete. Moreover, the ligands of OR14 and OR15 have so far not been found, likely due to the missing of the active ligand(s) in the compound panel and/or incompatibility of heterologous expression systems used. In the present study, we expressed the PR repertoires of both Helicoverpa species in Drosophila T1 neurons to comparatively study the function of PRs. Among those PRs, OR13, OR6, and OR14 of both species are functionally conserved and narrowly tuned, and the T1 neurons expressing each of them respond to Z11-16:Ald, (Z)-9-hexadecenol (Z9-16:OH), and (Z)-11-hexadecenyl acetate (Z11-16:Ac), respectively. While HarmOR16-expressing neurons respond strongly to (Z)-9-tetradecenal (Z9-14:Ald) and (Z)-11-hexadecenol (Z11-16:OH), the neurons expressing HassOR16 mainly respond to Z9-14:Ald and also weakly respond to (Z)-9-tetradecenol (Z9-14:OH). Moreover, HarmOR14b-expressing neurons are activated by Z9-14:Ald, whereas HassOR14b-expressing neurons are sensitive to Z9-16:Ald, Z9-14:Ald, and (Z)-9-hexadecenol (Z9-16:OH). In addition, HarmOR15-expressing neurons are selectively responsive to Z9-14:Ald. However, the Drosophila T1 neurons expressing either HarmOR11 or HassOR11 are silent to all of the compounds tested. In summary, except for OR11, we have deorphanized all the PRs of these two Helicoverpa species using a Drosophila expression system and a large panel of pheromone compounds, thereby providing a valuable reference for parsing the code of peripheral coding of pheromones.

Helicoverpa armigera and Helicoverpa zea hybridization: constraints, heterosis, and implications for pest management.

The invasion of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) into the New World has made it possible for this pest to hybridize with a native American species, H. zea (Boddie), under natural conditions. We investigated the viability and development of hybrids of these two Helicoverpa species. We reared the parental species and evaluated crosses between H. armigera males and H. zea females and vice versa, two intercrosses between hybrids, and eight backcrosses between hybrids and parental species. We estimated the length of immature stages, fecundity, survival, sex ratio, and heterosis. Although hybridization occcurred, with heterosis during the development of immatures, reproductive incompatibilities also were observed between the parental species and between hybrids from subsequent crosses. The interspecific crosses between hybrids and backcrosses confirmed the possibility of introgression events and their perpetuation in field populations. The results indicate that hybridization events are favored at high population levels, while at low population levels the 'species identities' will be maintained. The possibility of interspecific gene flow and its perpetuation through successive crosses and backcrosses suggests several recommenations for management. Populations of both species should be maintained at an equilibrium level to reduce the chance of interspecific crosses, which are presumably more likely to occur during pest outbreaks. The existence of hybridization and resistance to different active pesticide ingredients should be monitored. All practices related to managing the resistance of these pests to chemical and biological insecticides should be systematized to reduce the chance of selecting for resistant individuals.

A Real‐time PCR assay for rapid identification of Helicoverpa armigera (Lepidoptera: Noctuidae) from closely related species

AbstractThe bollworm, Helicoverpa armigera, is one of the most important agricultural pests in the world. Diagnosis of this species morphologically is difficult from the similar species H. assulta, H. punctigera and H. zea as the adults are identified based on genitalia morphology and larval identification is limited due to shared morphological characters. To provide an accurate diagnosis of New Zealand border interceptions, we have developed a real‐time PCR assay to identify H. armigera from commonly occurring exotic Helicoverpa species, H. assulta and H. zea. Preliminary studies, using the already available real‐time ITS2 primer–probe detecting H. armigera and H. zea tested on samples obtained from NZ border interceptions and from overseas showed cross reactions with low intensities among H. armigera, H. assulta and H. zea. This prompted PHEL to develop a new real‐time PCR assay to accurately identify H. armigera. The newly designed primer and probe were optimized, and the assay demonstrated its specificity to H. armigera with no false positives observed in the non‐target species tested in this study. The specificity of the assay was tested against 64 samples of Lepidoptera from 14 countries including 48 Helicoverpa samples. The sensitivity of the assay showed it can detect up to 1 copy/µl of the DNA fragment. Therefore, this assay can be used for rapid detection of H. armigera, which is imperative in quarantine application to determine the presence of exotic species regardless of its life stage.

Identifying two moth species (Lepidoptera: Ditrysia) from Saudi Arabia using mitochondrial 16S rRNA sequences.

The mitochondrial genetic markers are considered useful tools for discrimination between more closely related lepidopteran taxa. Therefore, the present study aimed to investigate the role of mitochondrial (mt) 16 s rRNA gene in the determination of the taxonomic position for two moth species within Ditrysia clade. Maximum likelihood analysis has indicated a well-supported dendrogram based on the Tamura-Nei model for the recovered lepidopterans. The mt 16 s rRNA query sequences from 24 species within seven families were analyzed. This analysis and bootstrap confidence revealed two major clades representing Glossata suborder within Lepidoptera, with a close relationship of Noctuoidea + (Pyraloidea (Hesperioidea + Papilionoidea)). The subfamily Heliothinae forming a sister group with Risobinae (Noctinae + Hadeninae). In addition, there is a clear observation about the close relation between Phycitinae + Galleriinae within Pyraloidea and Cyrestinae + Limenitidinae within Papilionoidea. The present study supported that the Helicoverpa and Meroptera species are the first accounts of these genera inhabiting Saudi Arabia.

Successful development and implementation of a practical proactive resistance management plan for Bt cotton in Australia.

This article describes the design and > 20 years of effective implementation of a proactive resistance-management plan for transgenic Bacillus thuringiensis (Bt) cotton that targets Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) in Australia, considering pest biology and ecology, insights from resistance-evolution modelling, and the importance of the human component to effective implementation. This is placed in the context of processes associated with adaptive resource management. Bt cotton has provided Australian cotton growers with technology to manage Helicoverpa species that previously challenged the industry's viability, while at the same time resulting in no detectable changes in the resistance allele frequency in field populations of either Helicoverpa species in eastern Australia. This is the most long-lived and successful global example of a proactive resistance management plan for an insect pest. Six key learnings important to the successful development and implementation of a proactive transgenic-crop resistance management plan are: the programme has to have a strong science base; there has to be broad stakeholder support at all levels; there has to be a strong implementation programme; the plan needs to be supported by auditing and enforced remediation of deviations from the mandated resistance management plan; A programme of rigorous and on-going resistance allele monitoring; an attitude of continuous improvement for all aspects of the resistance management plan. The lessons learnt from the deployment of Bt cotton in Australia are relevant globally and provide important guidelines for the deployment of transgenic crops for insect control wherever they are grown. © 2021 Society of Chemical Industry.

Rearing of Helicoverpa armigera Hubner and Characterization of its Gut Proteinases

Background: The genus Helicoverpa includes the Old-World species Helicoverpa armigera, Hubner (Lepidoptera: Noctuidae) generally considered to be the most important species within group. It has been recorded on more than 200 host species in India and is most damaging to cotton, pigeon pea, cow pea, chick pea, ground nut, sorghum, pearl millet, tomato and many other crops of economic importance. H. armigera is being polyphagous pest with high reproductive and damaging potential, its suppression became difficult over past decade due to development of resistance to several chemicals. The current study was aimed to isolate and characterize the gut proteinases of Helicoverpa armigera.Methods: During the period 2016-2018, H. armigera larvae were collected from the field and reared on an artificial diet and maintained under controlled conditions in the laboratory at Dr. Panjabrao Deshmukh Krishi Vidyapith, Akola, India. The laboratory conditions were maintained at temperature 28±2oC, humidity 75±5% and 14:10 hours light: dark period. The gut proteinases were isolated and were estimated by Bradford method. The total Helicoverpa gut proteinase activity, trypsin like activity, chymotrypsin like activity and electrophoretic visualisation of proteinases were done.Result: Total Proteinases activity was found to be 2.10 U/gut. Trypsin like activity was found to be 1.89 U/gut and chymotryptic activity was observed as 1.81 U/gut. The trypsin like activity was slightly more than chymotryptic activity.

Plant Metabolites Drive Different Responses in Caterpillars of Two Closely Related Helicoverpa Species.

The host acceptances of insects can be determined largely by detecting plant metabolites using insect taste. In the present study, we investigated the gustatory sensitivity and feeding behaviors of two closely related caterpillars, the generalist Helicoverpa armigera (Hübner) and the specialist H. assulta (Guenée), to different plant metabolites by using the single sensillum recording technique and the dual-choice assay, aiming to explore the contribution of plant metabolites to the difference of diet breadth between the two species. The results depicted that the feeding patterns of caterpillars for both plant primary and secondary metabolites were significantly different between the two Helicoverpa species. Fructose, glucose, and proline stimulated feedings of the specialist H. assulta, while glucose and proline had no significant effect on the generalist H. armigera. Gossypol and tomatine, the secondary metabolites of host plants of the generalist H. armigera, elicited appetitive feedings of this insect species but drove aversive feedings of H. assulta. Nicotine and capsaicin elicited appetitive feedings of H. assulta, but drove aversive feedings of H. armigera. For the response of gustatory receptor neurons (GRNs) in the maxillary styloconic sensilla of caterpillars, each of the investigated primary metabolites induced similar responding patterns between the two Helicoverpa species. However, four secondary metabolites elicited different responding patterns of GRNs in the two species, which is consistent with the difference of feeding preferences to these compounds. In summary, our results of caterpillars’ performance to the plant metabolites could reflect the difference of diet breadth between the two Helicoverpa species. To our knowledge, this is the first report showing that plant secondary metabolites could drive appetitive feedings in a generalist insect species, which gives new insights of underscoring the adaptation mechanism of herbivores to host plants.

Helicoverpa armigera Harm 1 Haplotype Predominates in the Heliothinae (Lepidoptera: Noctuidae) Complex Infesting Tomato Crops in Brazil.

Tomato (Solanum lycopersicum L.) is a natural host for the Helicoverpa-Chloridea (Lepidoptera: Noctuidae: Heliothinae) pest complex. The species Helicoverpa armigera (Hübner) was responsible for significant yield losses in several crops after its detection in Brazil. The morphology of its larval stage resembles common Heliothinae species, making pest control decisions difficult. The overall lack of studies on the Heliothinae associated with tomatoes in Brazil and the establishment of H. armigera in the country plus their recent outbreaks supported our investigation about the relative importance of the insects from the Helicoverpa-Chloridea complex in this vegetable crop. A nationwide survey was carried out across fresh-market and processing tomato fields. Molecular analyses targeting a segment of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene and their sequence analyses indicated the presence of a pest complex, comprising the introduced species H. armigera and the indigenous species, Helicoverpa zea (Boddie), and Chloridea virescens (Fabricius). The Harm 1 haplotype of H. armigera was identified as the predominant Heliothinae pest infesting fresh-market tomatoes. The New World species Chloridea subflexa (Guenée) as well as the exotic Solanaceae-specific species Helicoverpa assulta (Guenée) were not found in our survey. Additional larvae surveys in processing tomato fields during 2013/2014 in Central Brazil also indicated H. armigera as the most abundant Heliothinae species (95%) together with H. zea (4.75%) and C. virescens (0.25%). The occurrence of distinct Helicoverpa species (which are potentially capable of interbreeding) indicates that novel crop management strategies will be necessary in order to minimize damages caused by this pest complex in tomatoes.

IS HELICOVERPA ARMIGERA (LEPIDOPTERA: NOCTUIDAE) A KEY PEST IN WESTERN ROMANIAN PAPRIKA PEPPER CROPS?

Recent changes in intensive vegetable production systems in Romania, but also throughout Europe, with the frequent and sometimes exclusive use of monoculture for certain groups of vegetables, including the Solanaceae group, have resulted in major changes in entomofauna in these areas. In addition, we are witnessing global climate change that also affects the composition and density of entomofauna in these agro-ecological areas. Under the influence of these two decisive factors, the dynamics of a pest population is oscillating and, therefore, some less known or newly entered species in the research area (invasive species) begin to cause significant damage to crops and especially to their control. 20 years after the first mentions of the attack, this pest causes considerable damage to the pepper crop, in the case of the present study, paprika. From the pepper crop for paprika, in 2020 in Chișlaca locality, Arad County, a number of 11 pest species were collected. The species Helicoverpa armigera was the predominant species, registering the highest number of specimens.The dynamics of larval populations showed an oscillating evolution, depending on climatic conditions, the maximum threshold being reached on the third decade of August.

Hybridization and introgression between Helicoverpa armigera and H. zea: an adaptational bridge

BackgroundInvasion of organisms into new ecosystems is increasingly common, due to the global trade in commodities. One of the most complex post-invasion scenarios occurs when an invasive species is related to a native pest, and even more so when they can hybridize and produce fertile progeny. The global pest Helicoverpa armigera was first detected in Brazil in 2013 and generated a wave of speculations about the possibility of hybridization with the native sister taxon Helicoverpa zea. In the present study, we used genome-wide single nucleotide polymorphisms from field-collected individuals to estimate hybridization between H. armigera and H. zea in different Brazilian agricultural landscapes.ResultsThe frequency of hybridization varied from 15 to 30% depending on the statistical analyses. These methods showed more congruence in estimating that hybrids contained approximately 10% mixed ancestry (i.e. introgression) from either species. Hybridization also varied considerably depending on the geographic locations where the sample was collected, forming a ‘mosaic’ hybrid zone where introgression may be facilitated by environmental and landscape variables. Both landscape composition and bioclimatic variables indicated that maize and soybean cropland are the main factors responsible for high levels of introgression in agricultural landscapes. The impact of multiple H. armigera incursions is reflected in the structured and inbred pattern of genetic diversity.ConclusionsOur data showed that the landscape composition and bioclimatic variables influence the introgression rate between H. armigera and H. zea in agricultural areas. Continuous monitoring of the hybridization process in the field is necessary, since agricultural expansion, climatic fluctuations, changing composition of crop species and varieties, and dynamic planting seasons are some factors in South America that could cause a sudden alteration in the introgression rate between Helicoverpa species. Introgression between invasive and native pests can dramatically impact the evolution of host ranges and resistance management.

Management of Euxesta spp. in Sweet Corn with McPhail Traps.

Pests attacking the ear of sweet corn, such as Helicoverpa and Euxesta species, cause economic losses for the producer and the processing industry. Feeding on the style-stigmata preventing fertilization and on the developing grain and the association with pathogens are the main causes of product depreciation. The traditional control such as spraying with chemicals is not effective, even with several applications directed to the corn ear. Bacillus thuringiensis (Bt) corn also does not reach the fly. McPhail traps that have been used to monitor the pest can be a control strategy. This work evaluated the efficiency of food attractants placed inside McPhail traps to remove adult insects, in order to reduce ear damage. Twelve McPhail-type traps were installed in a randomized complete block design containing Bio Anastrepha® alone or combined with different doses of insecticide. Every 10 days, all the captured insects were counted and separated by species and sex. Only Euxesta eluta and Euxesta mazorca were found. The occurrence of insects was greater in the period between silk emergence and grain filling. The number of females was higher, probably due to the need to feed before oviposition. The number of E. mazorca females caught in the treatment containing only Bio Anastrepha® was higher compared with that of others. The mean ear damage was very low, and there was no interaction between the production parameters and the distance between the trap and the harvested plant. In short, the use of McPhail trap containing food attractants may be a viable alternative to control corn silk flies.