Cotton Bollworm Helicoverpa Armigera Research Articles

Overexpressing a cotton terpene synthase for (E)-β-ocimene biosynthesis in Nicotiana tabacum to recruit the parasitoid wasps

(E)-β-ocimene is a predominant component of volatile terpenes emitted from many plant species in response to herbivore attack, which plays an impotant role in direct and indirect defense of plants. In the current study, (E)-β-ocimene was induced and released in upland cotton Gossypium hirsutum plants infested by chewing caterpillars or sucking bugs. Using genome data mining, a key terpene synthase for (E)-β-ocimene biosynthesis in cotton, GhTPS16, was initially identified. In vitro, recombinant GhTPS16 catalyzed the formation of (E)-β-ocimene using geranyl diphosphate as a substrate. Besides, the GhTPS16 was transferred into Nicotiana tabacum to generate (E)-β-ocimene synthase overexpression lines. Consequently, compared with wild type plants both GhTPS16 expression and (E)-β-ocimene emission of transgenic plants were up-regulated. In behavioral trials, two parasitoid wasps, Peristenus spretus parasitizing green bug Apolygus lucorum and Microplitis mediator parasitizing cotton bollworm Helicoverpa armigera, showed tendency preference for synthetic (E)-β-ocimene and transgenic tobacco plants, respectively. These findings provide new insights into understanding the roles of (E)-β-ocimene in plant-insect interaction. Oversynthesis of (E)-β-ocimene in plants could enhance indirect defense by recruiting parasitoids to facilitate control of the two target pests, green bug and cotton bollworm.

Lipases are differentially regulated by hormones to maintain free fatty acid homeostasis for insect brain development

BackgroundFree fatty acids (FFAs) play vital roles as energy sources and substrates in organisms; however, the molecular mechanism regulating the homeostasis of FFA levels in various circumstances, such as feeding and nonfeeding stages, is not fully clarified. Holometabolous insects digest dietary triglycerides (TAGs) during larval feeding stages and degrade stored TAGs in the fat body during metamorphosis after feeding cessation, which presents a suitable model for this study.ResultsThis study reported that two lipases are differentially regulated by hormones to maintain the homeostasis of FFA levels during the feeding and nonfeeding stages using the lepidopteran insect cotton bollworm Helicoverpa armigera as a model. Lipase member H-A-like (Lha-like), related to human pancreatic lipase (PTL), was abundantly expressed in the midgut during the feeding stage, while the monoacylglycerol lipase ABHD12-like (Abhd12-like), related to human monoacylglycerol lipase (MGL), was abundantly expressed in the fat body during the nonfeeding stage. Lha-like was upregulated by juvenile hormone (JH) via the JH intracellular receptor methoprene-tolerant 1 (MET1), and Abhd12-like was upregulated by 20-hydroxyecdysone (20E) via forkhead box O (FOXO) transcription factor. Knockdown of Lha-like decreased FFA levels in the hemolymph and reduced TAG levels in the fat body. Moreover, lipid droplets (LDs) were small, the brain morphology was abnormal, the size of the brain was small, and the larvae showed the phenotype of delayed pupation, small pupae, and delayed tissue remodeling. Knockdown of Abhd12-like decreased FFA levels in the hemolymph; however, TAG levels increased in the fat body, and LDs remained large. The development of the brain was arrested at the larval stage, and the larvae showed a delayed pupation phenotype and delayed tissue remodeling.ConclusionsThe differential regulation of lipases expression by different hormones determines FFAs homeostasis and different TAG levels in the fat body during the feeding larval growth and nonfeeding stages of metamorphosis in the insect. The homeostasis of FFAs supports insect growth, brain development, and metamorphosis.

BIOLOGICAL EFFICACY OF HELITEC IN COMBATING TOMATO PESTS

The article presents the results of experiments conducted to study the efficacy of the Helitec biopreparation (Helicoverpa armigera NPV – 8%, 5x10^12 polyhedra per liter) against the larvae of the cotton bollworm (Helicoverpa armigera). The findings provide insights into the proper selection of biological preparations to combat the pest and identify effective control methods for use in tomato cultivation.

In vivo functional analysis of the cotton bollworm Helicoverpa armigera 24-dehydrocholesterol reductase (HaDHCR24) in phytosterol metabolism.

Insects have to obtain sterols from food due to the inability to synthesize this essential nutrient de novo. For lepidopteran insects, they can convert a variety of phytosterols into cholesterol to meet their growth needs. The final step of the cholesterol biosynthesis is the metabolism of desmosterol catalyzed by 24-dehydrocholesterol reductase (DHCR24). In this study, we identified a DHCR24 homolog in the cotton bollworm Helicoverpa armigera, designated as H. armigera 24-dehydrocholesterol reductase (HaDHCR24)-1. The quantitative expression analyses indicated that HaDHCR24-1 was highly enriched in the midgut where dietary sterol uptake occurs. Compared to the control, the DHCR24-1 mutant larvae generated by clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 technology accumulated more desmosterol in the gut, while the content of cholesterol was significantly reduced. A similar phenomenon was observed when the DHCR24 inhibitor, amiodarone, was applied to the insects. Moreover, DHCR24-1 played an important role for the usage of β-sitosterol, a major sterol in plants, in H. armigera, and loss of function of DHCR24-1 resulted in higher mortality on β-sitosterol. However, the DHCR24 homolog does not necessarily exist in the genomes of all insects. The loss of this gene occurred more frequently in the insects feeding on animals, which further support the role of DHCR24-1 in using phytosterols. This gene may have important potential in developing new strategies to control herbivory pests in Lepidoptera and other insect orders.

E93 is involved in regulating larval-pupal metamorphosis and the development of the wing and ovary in Helicoverpa armigera, and it shows great potential for RNAi-based pest control

The ecdysone-induced transcription factor E93 in model insects plays multiple roles in the insect metamorphosis processes, such as remodeling larval tissues and determining adult tissue formation. The knockdown of E93 in insects leads to incomplete metamorphosis, suggesting that E93 is a potential target for pest control. In this study, the HaE93 gene in the cotton bollworm Helicoverpa armigera, a polyphagous pest of various commercial crops worldwide, was identified and found to have high expression in the egg, prepupal, and pupal stages. The injection of dsHaE93 induced about 60% mortality in H. armigera at the larval-pupal stage. About 30% of the H. armigera surviving knockdown of the HaE93 gene showed delayed pupation and developed abnormal wings, and the females developed reduced ovaries. About 90% of the HaE93 knockdown individuals failed to reproduce before they died. The results of qRT-PCR showed that the expression levels of ecdysone primary-response genes, chitin synthesis-related genes, and wing and ovary development-related genes were reduced in HaE93 knockdown H. armigera. These results indicated that HaE93 plays a critical role in larva-pupa-adult metamorphosis and the development of the cuticle, wing, and ovary in female H. armigera by regulating the expression of the associated genes. Bioassays of dsHaE93 administered by either oral delivery or injection showed similar knockdown results, which suggested that HaE93 can be used as a target gene for the RNAi control of the pest H. armigera.

A chromosome-level haplotype-resolved genome assembly of oriental tobacco budworm (Helicoverpa assulta)

Oriental tobacco budworm (Helicoverpa assulta) and cotton bollworm (Helicoverpa armigera) are two closely related species within the genus Helicoverpa. They have similar appearances and consistent damage patterns, often leading to confusion. However, the cotton bollworm is a typical polyphagous insect, while the oriental tobacco budworm belongs to the oligophagous insects. In this study, we used Nanopore, PacBio, and Illumina platforms to sequence the genome of H. assulta and used Hifiasm to create a haplotype-resolved draft genome. The Hi-C technique helped anchor 33 primary contigs to 32 chromosomes, including two sex chromosomes, Z and W. The final primary haploid genome assembly was approximately 415.19 Mb in length. BUSCO analysis revealed a high degree of completeness, with 99.0% gene coverage in this genome assembly. The repeat sequences constituted 38.39% of the genome assembly, and we annotated 17093 protein-coding genes. The high-quality genome assembly of the oriental tobacco budworm serves as a valuable genetic resource that enhances our comprehension of how they select hosts in a complex odour environment. It will also aid in developing an effective control policy.

Investigation of the insecticidal potential of curcumin derivatives that target the Helicoverpa armigera sterol carrier protein-2

Cotton bollworm (Helicoverpa armigera) is a highly polyphagous, widely prevalent, and persistent Old World insect pest that affects numerous important crops that are directly consumed by people, including tomato, cotton, pigeon pea, chickpea, rice, sorghum, and cowpea. Insects do not synthesize steroids but obtain them from their diet. Inhibition of dietary uptake of steroids by insects is a potentially effective insecticidal mechanism that should not be toxic to humans and other mammals, who synthesize their steroids. Ten curcumin derivatives were tested against H. armigera sterol carrier protein-2 (HaSCP-2) for their potential as insecticidal agents. Curcumin derivatives were initially docked at the binding site of HaSCP-2 to determine their binding affinities and plausible binding modes. The binding modes predominantly show hydrophobic interactions of derivatives with Phe53, Phe110, and Phe89 as core interacting residues in the active site. Validation of in silico results was carried out by performing a fluorescence binding and displacement assay to determine the binding affinities of curcumin derivatives. Among a collection of curcumin derivatives tested, Cur10 showed the lowest IC50 value of 9.64 μM, while Cur07 was 19.86 μM, and Cur06 was 20.79 μM. There was a significant negative correlation between the ability of the curcumin derivatives tested to displace the fluorescent probe from the sterol binding site of HaSCP-2 and to inhibit Sf9 insect cell growth in culture, which is consistent with the curcumin derivatives acting by the novel mechanism of blocking sterol uptake. Then molecular dynamics simulation studies validated the predicted binding modes and the interactions of curcumin derivatives with HaSCP-2 protein. In conclusion, these studies support the potential use of curcumin derivatives as insecticidal agents.

Life-cycle profiling of cuticular hydrocarbons in the cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae)

Cuticular hydrocarbons (CHCs) are the main components of the wax layer present on insects’ surface, serving as protective agents against environmental stress and/or as communication signals. It has been documented that the chemical composition of CHCs varies with species and even with developmental stage or sex of the same species. However, studies involving in a life-cycle identification of CHCs are rare. In this work, we attempted to profile the components and relative abundance of CHCs in the cotton bollworm Helicoverpa armigera at all the four developmental stages and in both sexes of pupae and adults. A total of 29 CHCs were putatively identified by gas chromatography-mass spectrometer analysis, including 14 n-alkanes, 4 methyl-branched alkenes and 11 methyl-branched alkanes, with 15 of them being detected at all the four developmental stages. Of the 29 CHCs, the straight-chain alkanes with 27, 29 and 31 carbon atoms were the major CHCs. All three classes of CHCs (n-alkanes, methyl-branched alkanes and methyl-branched alkenes) were found in both larvae and pupae, while no unsaturated hydrocarbons were observed in eggs and adults. Methyl-branched alkanes were the main component found in eggs and adults, while the composition of n-alkanes and methyl-branched alkanes in larvae and pupae varied with ages. Principal component analysis (PCA) revealed that the CHC profiles in larvae and adults changed significantly with ages, while the CHC profiles in early pupae (1-day-old) showed distinct difference from those of late pupae. Furthermore, sexual dimorphism in the CHC profile was observed in mature adults (3-day-old and 5-day-old), with male adults possessing more n-C31 and n-C33, but less 3-MeC29 than females.

Monitoring of the content and migration of heavy metals in the soils–melliferous plants–bees–beekeeping products system in biocenoses of the combat areas

Aim. To determine the specificities of perennial dynamics in the number of the main corn insect pests in different natural and climatic zones of Ukraine under climate change. Methods. The field, laboratory, mathematical methods were used. The materials of the phytosanitary entomological monitoring of the State Service of Ukraine on Food Safety and Con- sumer Protection (2005–2021) in the basic 161 enterprises in Ukraine’s regions using methodologically standardized annual registrations of the main harmful organisms of agrocenoses (Borzykh еt al, 2018). Six groups of the main corn insect pests were investigated: corn borers (Ostrinia nubilalis Hübner), wireworms (Elateridae) and false wireworms (Te- nebrionidae), cutworms (Noctuida), southern dusty surface beetle (Tanymecus dilaticollis Gyllenhal), cotton bollworm (Helicoverpa armigera Hübner), and cereal aphids (Schizaphis graminum) Rondani. The database of the Hydrometeoro- logical Center of Ukraine was used to analyze climate parameters (2005–2021). The statistical analysis of the data was conducted using MS Excel and the linear correlation-regression analysis according to Pearson, Student’s criterion was used to evaluate the reliability (probability) of the correlation coefficients. Results. The results of correlational analysis of the state of populations of the main corn insect pests demonstrated that climate change has not considerably affected the number of corn borers as well as wireworms and false wireworms in all the natural and climatic zones of Ukraine yet. A reliable moderate reverse correlation (r = –0.309) was found between the number of cutworms and the sum of effective temperatures (SET) only for the Forest-Steppe conditions – under the increase in the SET, the number of these insects was smaller. The number of the southern dusty surface beetle was in direct, reliable, moderate correlation (r = 0.335) with the SET in the Steppe, for instance, the pest responded to the increase in the SET with the rise in its number. The number of cotton bollworms in Polissia was in reliable moderate correlation (r = –0.489) with the SET. The number of cereal aphids was in a reliable moderate direct correlation (r = 0.529) with the SET in Polissia: at the increase in the SET, the number of these pests was increasing. Conclusions. Conclusions: Climate changes do not considerably affect the state of the populations of the main corn insect pests in all the natural and climatic zones of Ukraine yet: we found the correlations between the number of insect pests and the SET which did not exceed such values as weak, moderate, and conspicuous. Significant changes in the state of insect pest populations should be expected if the sum of effective temperatures during the vegetation period will considerably affect the performance and feeding qualities of the cultivated plants.

Population dynamics of corn insect pests in Ukraine under climate change

Aim. To determine the specificities of perennial dynamics in the number of the main corn insect pests in different natural and climatic zones of Ukraine under climate change. Methods. The field, laboratory, mathematical methods were used. The materials of the phytosanitary entomological monitoring of the State Service of Ukraine on Food Safety and Con- sumer Protection (2005–2021) in the basic 161 enterprises in Ukraine’s regions using methodologically standardized annual registrations of the main harmful organisms of agrocenoses (Borzykh еt al, 2018). Six groups of the main corn insect pests were investigated: corn borers (Ostrinia nubilalis Hübner), wireworms (Elateridae) and false wireworms (Te- nebrionidae), cutworms (Noctuida), southern dusty surface beetle (Tanymecus dilaticollis Gyllenhal), cotton bollworm (Helicoverpa armigera Hübner), and cereal aphids (Schizaphis graminum) Rondani. The database of the Hydrometeoro- logical Center of Ukraine was used to analyze climate parameters (2005–2021). The statistical analysis of the data was conducted using MS Excel and the linear correlation-regression analysis according to Pearson, Student’s criterion was used to evaluate the reliability (probability) of the correlation coefficients. Results. The results of correlational analysis of the state of populations of the main corn insect pests demonstrated that climate change has not considerably affected the number of corn borers as well as wireworms and false wireworms in all the natural and climatic zones of Ukraine yet. A reliable moderate reverse correlation (r = –0.309) was found between the number of cutworms and the sum of effective temperatures (SET) only for the Forest-Steppe conditions – under the increase in the SET, the number of these insects was smaller. The number of the southern dusty surface beetle was in direct, reliable, moderate correlation (r = 0.335) with the SET in the Steppe, for instance, the pest responded to the increase in the SET with the rise in its number. The number of cotton bollworms in Polissia was in reliable moderate correlation (r = –0.489) with the SET. The number of cereal aphids was in a reliable moderate direct correlation (r = 0.529) with the SET in Polissia: at the increase in the SET, the number of these pests was increasing. Conclusions. Conclusions: Climate changes do not considerably affect the state of the populations of the main corn insect pests in all the natural and climatic zones of Ukraine yet: we found the correlations between the number of insect pests and the SET which did not exceed such values as weak, moderate, and conspicuous. Significant changes in the state of insect pest populations should be expected if the sum of effective temperatures during the vegetation period will considerably affect the performance and feeding qualities of the cultivated plants.

Resistance and fitness costs of the Helicoverpa armigera after selection with the tetraniliprole newly developed diamide insecticide

The cotton bollworm (Helicoverpa armigera) (Lepidoptera: Noctuidae) is a highly destructive insect pest that feeds on more than 200 plants including cotton. Diamide insecticides are typically preferred to combat H. armigera. However, many reports of resistance to diamide insecticides such as chlorantraniliprole have been reported. Tetraniliprole is a novel diamide insecticide, but little is known about its resistance risk in H. armigera. After ten generations of treating H. armigera with tetraniliprole, neither the G4946 nor I4775 mutations were detected and no resistance to tetraniliprole was observed. The realized heritability (h2) was 0.094 after ten generations of selection with tetraniliprole, suggesting a low risk of resistance in H. armigera. Additionally, we found that the LD50 of tetraniliprole (4.01 μg/g) was lower than the LD50 of chlorantraniliprole (5.79 μg/g) in the susceptible strain. Molecular docking analysis also found a difference between the ryanodine receptor (RyR) binding sites of tetraniliprole and chlorantraniliprole, the tetraniliprole free binding energy to RyR was −6.9 kcal/mol, which was smaller than for chlorantraniliprole (−6.4 kcal/mol). Our study reveals that there is a low resistance risk to tetraniliprole in H. armigera, thus suggesting that tetraniliprole can be used as a substitute for other insecticides for this pest control.

Susceptibility of Bombyx mori larvae to the microsporidium Nosema bombycis from the silkworm and Nosema sp. from the cotton bollworm

Microsporidia are widespread parasites and cause diseases in economically important insects. A microsporidian isolate NspHA22 was discovered in the cotton bollworm Helicoverpa armigera in South-Western Russia. It showed 100 % sequence identity of small subunit rRNA gene to Nosema bombycis, a natural parasite of the silkworm Bombyx mori. However, after feeding second or third instar B. mori larvae with spores of the new isolate, insect mortality didn’t differ from that of the control, and no sporulation was revealed in alive and perished insects. In contrast, feeding N. bombycis spores isolated from B. mori resulted in high levels of host mortality and intense parasite sporulation at all the infection dose and larval instars used. This likely indicates that the isolate NspHA22 belongs to a species different from N. bombycis, in spite of identity of rDNA sequences.

Development of a soybean leaf disc assay for determining oral insecticidal activity in the lepidopteran agricultural pest Helicoverpa armigera

Pest insects pose a heavy burden on global agricultural industries with small molecule insecticides being predominantly used for their control. Unwanted side effects and resistance development plagues most small molecule insecticides such as the neonicotinoids, which have been reported to be harmful to honeybees. Bioinsecticides like Bacillus thuringiensis (Bt) toxins can be used as environmentally-friendly alternatives. Arachnid venoms comprise another promising source of bioinsecticides, containing a multitude of selective and potent insecticidal toxins. Unfortunately, no standardised insect models are currently available to assess the suitability of insecticidal agents under laboratory conditions. Thus, we aimed to develop a laboratory model that closely mimics field conditions by employing a leaf disk assay (LDA) for oral application of insecticidal agents in a bioassay tray format. Neonate larvae of the cotton bollworm (Helicoverpa armigera) were fed with soybean (Glycine max) leaves that were treated with different insecticidal agents. We observed dose-dependent insecticidal effects for Bt toxin and the neonicotinoid insecticide imidacloprid, with imidacloprid exhibiting a faster response. Furthermore, we identified several insecticidal arachnid venoms that were active when co-applied with sub-lethal doses of Bt toxin. We propose the H. armigera LDA as a suitable tool for assessing the insecticidal effects of insecticidal agents against lepidopterans.

Potential Biopesticides from Seed Extracts: A Sustainable Way to Protect Cotton Crops from Bollworm Damage

In the current study, the inhibitory effect of extracts from Gramineae (wheat, barley, and corn) and Leguminosae (sophora, bean, and pea) seeds was studied on the digestive alpha-amylase activity in cotton bollworm (Helicoverpa armigera Hubner). The insect was bred on artificial food based on Vigna unguiculata in the greenhouse condition (26 ± 2 °C, 60 ± 10% (Relative Humidity), R.H., 16:8 (Light: Darkness), L: D). The extracts of wheat (95.2%), barley (84.6%), corn (73.8%), sophora (77%), Vigna unguiculata (52%), and pea (56.7%) significantly inhibited the alpha-amylase activity in H. armigera. Studying the impact of different fractions (obtained via deposition at various concentrations of ammonium sulfate salt) on the alpha-amylase enzyme activity demonstrated that in 0–30% fractions, wheat, barley, and sophora have the highest effect (95.26%, 94.65%, and 94.73%, respectively) compared to the other fractions. The inhibitory activities of 0–30% fractions of corn, bean, and pea were 83.3, 56.94, and 50.92%, respectively. In 30–50% fractions, the most effective ones were those of wheat and barley with the inhibitory activity of 79.7% and 82.9%, respectively. In addition, bean and pea fractions inhibited 25.2% and 27.5%, in that order. No significant inhibitory impact was detected in 50–70% or higher fractions. The investigation of the impact of pH values (i.e., 2, 4, 8, and 10) on the inhibition of the alpha-amylase enzyme activity introduced 8–10 as the optimum pH in H. armigera. Nanotechnology offers several ways to enhance plant-based pesticides, which are a solution for making plant extract usage more efficient. The exploration of plant-based pesticides, in conjunction with the incorporation of nanotechnology and other scientific fields, offers a wide range of prospects for further investigation.

Insectivorous bats provide more pest suppression services than disservices - a case study in China

Many studies have investigated the role of insectivorous bats as natural enemies of agricultural pests. However, insectivorous bats have a broad diet, and whether their prey species are beneficial or harmful is unknown; thus, accurately assessing the services provided by bats is challenging. In China, most people, including farmers and plant protection workers, have an insufficient understanding of the ecological value of bats in biological control. Therefore, we collected the fecal samples of 10 bat species from three different sampling sites located in Guizhou Province, China, and conducted DNA metabarcoding to determine the diet composition of bats. We also categorized the prey species from the diet of bats as harmful or beneficial, based on previous studies, and recorded the industries they affect. Our results showed that the 10 bat species consumed prey from 19 orders and 96 families; most of them being lepidopterans. Among 564 total prey species recorded, 390 (69.15%) were pests and 28 (4.96%) were beneficial insects. Among them, 326 (57.80%) were agriculture or forestry pests, such as globally present Cotton bollworm (Helicoverpa armigera) and Beet armyworm (Spodoptera exigua). These results indicated that insectivorous bats have more beneficial effects than harmful effects, especially in the context of agriculture and forestry, as they suppressed very few beneficial arthropod mesopredators. By comparing the differences in the diet of I. io in different regions, we found that bats present in different regions can provide different predation services. Our study showed that insectivorous bats provide excellent pest suppression services in various industries and regions. It might be helpful for increasing awareness among people and bat conservation in China and other regions.

Suitability of Satellite Imagery for Surveillance of Maize Ear Damage by Cotton Bollworm (Helicoverpa armigera) Larvae

The cotton bollworm (Helicoverpa armigera, Lepidoptera: Noctuidae) poses significant risks to maize. Changes in the maize plant, such as its phenology, influence the short-distance movement and oviposition of cotton bollworm adults and, thus, the distribution of the subsequent larval damage. We aim to provide an overview of future approaches to the surveillance of maize ear damage by cotton bollworm larvae based on remote sensing. We focus on finding a near-optimal combination of Landsat 8 or Sentinel-2 spectral bands, vegetation indices, and maize phenology to achieve the best predictions. The study areas were 21 sweet and grain maze fields in Hungary in 2017, 2020, and 2021. Correlations among the percentage of damage and the time series of satellite images were explored. Based on our results, Sentinel-2 satellite imagery is suggested for damage surveillance, as 82% of all the extremes of the correlation coefficients were stronger, and this satellite provided 20–64% more cloud-free images. We identified that the maturity groups of maize are an essential factor in cotton bollworm surveillance. No correlations were found before canopy closure (BBCH 18). Visible bands were the most suitable for damage surveillance in mid–late grain maize (|rmedian| = 0.49–0.51), while the SWIR bands, NDWI, NDVI, and PSRI were suitable in mid–late grain maize fields (|rmedian| = 0.25–0.49) and sweet maize fields (|rmedian| = 0.24–0.41). Our findings aim to support prediction tools for cotton bollworm damage, providing information for the pest management decisions of advisors and farmers.

Endocytosis-mediated entry of a caterpillar effector into plants is countered by Jasmonate

Insects and pathogens release effectors into plant cells to weaken the host defense or immune response. While the imports of some bacterial and fungal effectors into plants have been previously characterized, the mechanisms of how caterpillar effectors enter plant cells remain a mystery. Using live cell imaging and real-time protein tracking, we show that HARP1, an effector from the oral secretions of cotton bollworm (Helicoverpa armigera), enters plant cells via protein-mediated endocytosis. The entry of HARP1 into a plant cell depends on its interaction with vesicle trafficking components including CTL1, PATL2, and TET8. The plant defense hormone jasmonate (JA) restricts HARP1 import by inhibiting endocytosis and HARP1 loading into endosomes. Combined with the previous report that HARP1 inhibits JA signaling output in host plants, it unveils that the effector and JA establish a defense and counter-defense loop reflecting the robust arms race between plants and insects.

Revision of Helicoverpa armigera insecticide resistance status in Greece

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a major pest of numerous crops specially cotton and its control is mainly based on the application of insecticides. Studies on the efficacy levels of insecticides are limited in Greece and such information is essential of the implementation of rational IPM schemes. The aim of this study was to investigate the status of resistance against insecticides registered for the control of cotton bollworm, namely spinetoram, emamectin benzoate, lambda-cyhalothrin, cyantraniliprole and chlorantraniliprole on different populations. The insecticide resistance to the tested compounds was evaluated using laboratory dose-response bioassays in three field populations of H. armigera collected from cotton fields located in Larissa, Thessaloniki and Serres/Drama, Greece, during 2020 using artificial diets with chemical overlay. All tested populations of H. armigera remained susceptible to spinetoram (RR = 0.9–1), emamectin benzoate (RR = 1.2–2.4), cyantraniliprole (RR = 2.4–3.1) and chlorantraniliprole (RR = 1–1.9). While, lambda-cyhalothrin exhibited RR values between 4 and 46 folds in the tested populations, suggesting potential cases of resistance development. This study sets the foundation for evidence-based pest management in Greece and facilitates early detection of incipient resistance cases in the future.

Variation of Helicoverpa armigera symbionts across developmental stages and geographic locations.

Cotton bollworm (Helicoverpa armigera) poses a global problem, causing substantial economic and ecological losses. Endosymbionts in insects play crucial roles in multiple insect biological processes. However, the interactions between H. armigera and its symbionts have not been well characterized to date. We investigated the symbionts of H. armigera in the whole life cycle from different geographical locations. In the whole life cycle of H. armigera, Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were the dominant bacteria at the phylum level, while Enterococcus, Enterobacter, Glutamicibacter, and Bacillus were the four dominant bacteria at the genus level. Furthermore, high similarity in symbiotic bacterial community was observed in different stages of H. armigera, which were dominated by Enterococcus and Enterobacter. In fields, the dominant bacteria were Proteobacteria and Bacteroidetes, whereas, in the laboratory, the dominant bacteria were Proteobacteria. At the genus level, the dominant bacteria in cotton bollworm eggs of wild populations were Enterobacter, Morganella, Lactococcus, Asaia, Apibacter, and Enterococcus, and the subdominant bacteria were Bartonella, Pseudomonas, and Orbus. Moreover, the symbionts varied with geographical locations, and the closer the geographical distance, the more similar the microbial composition. Taken together, our study identifies and compares the symbiont variation along with geographical gradients and host development dynamic and reveals the high flexibility of microbiome communities in H. armigera, which probably benefits for the successful survival in a complicated changing environment.

Mechanisms of feeding cessation in Helicoverpa armigera larvae exposed to Bacillus thuringiensis Cry1Ac toxin

Insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have been applied in sprayable formulations and expressed in transgenic crops for the control of pests in the field. When exposed to Bt proteins insect larvae display feeding cessation, yet the mechanism for this phenomenon remains unknown. In this study, we investigated the feeding behavior and underlying mechanisms of cotton bollworm (Helicoverpa armigera) larvae after exposure to the Cry1Ac protein from Bt. Three H. armigera strains were studied: the susceptible SCD strain, the C2/3-KO strain with HaABCC2 and HaABCC3 knocked out and high-level resistance to Cry1Ac (>15,000-fold), and the SCD-KI strain with a T92C point mutation in tetraspanin (HaTSPAN1) and medium-level resistance to Cry1Ac (125-fold). When determining the percentage of insects that continued feeding after various exposure times to Cry1Ac, we observed quick cessation of feeding in larvae from the susceptible SCD strain, whereas larvae from the C2/3-KO strain did not display feeding cessation. In contrast, larvae from the SCD-KI strain rapidly recovered from the initial feeding cessation. Histopathological analyses and qRT-PCR in midguts of SCD larvae after Cry1Ac exposure detected serious epithelial damage and significantly reduced expression of the neuropeptide F gene (NPF) and its potential receptor gene NPFR, which are reported to promote insect feeding. Neither epithelial damage nor altered NPF and NPFR expression appeared in midguts of C2/3-KO larvae after Cry1Ac treatment. The same treatment in SCD-KI larvae resulted in milder epithelial damage and subsequent repair, and a decrease followed by an initial increase in NPF and NPFR expression. These results demonstrate that the feeding cessation response to Cry1Ac in cotton bollworm larvae is closely associated with midgut epithelial damage and downregulation of NPF and NPFR expression. This information provides clues to the mechanism of feeding cessation in response to Bt intoxication and contributes to the mode of action of the Cry1Ac toxin in target pests.