Bollworm Helicoverpa Armigera Research Articles

The steroid hormone 20-hydroxyecdysone inhibits RAPTOR expression by repressing Hox gene transcription to induce autophagy.

Regulatory-associated protein of TOR (RAPTOR) is a key component of TOR complex 1 (TORC1), which determines the lysosomal location and substrate recruitment of TORC1 to promote cell growth and prevent autophagy. Many studies in recent decades have focused on the posttranslational modification of RAPTOR; however, little is known about the transcriptional regulatory mechanism of Raptor. Using the lepidopteran insect cotton bollworm (Helicoverpa armigera) as model, we reveal the transcriptional regulatory mechanism of Raptor. RAPTOR has different expression profiles in tissues during development from larva to late pupa, with high expression levels at larval feeding stages but low expression levels during metamorphic stages in the epidermis, midgut and fat body. RAPTOR is localized in the larval midgut at the feeding stage but is localized in the imaginal midgut at metamorphic stages. The knockdown of Raptor at the feeding stage results in the production of small pupae, early autophagy of the midgut and fat body, and decreased cell proliferation. However, Raptor knockdown at metamorphic stage represses the development of the epidermis, adult fat body and brain. 20-Hydroxecdysone (20E) represses Raptor transcription. Homeobox (HOX) proteins promote Raptor transcription by binding to its promoter. Overexpression of HOX proteins represses ATG expression and autophagy but increases cell proliferation. 20E represses Hox genes transcription via its nuclear receptor EcR binding to its promoters. Together, these findings suggest that HOX proteins are positive regulators that upregulate Raptor transcription. 20E represses Hox gene transcription, thus repressing Raptor expression, resulting in autophagy and repressing cell proliferation during metamorphosis.

The oviposition of cotton bollworms stimulates the defense against its eggs and larvae in tomato plants.

Herbivorous insects sustain their populations by oviposition. To reduce the damage caused by herbivores, the host plant triggers a defensive response upon detection of egg deposition. However, the specific impact of the egg deposition time of the cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae), on the tomato plant defense remains obscure. This study investigated the effects of tomato plant defenses on cotton bollworm eggs and larvae at different time intervals following egg deposition. The study revealed that tomato plant defense triggered by egg deposition did not directly affect the hatchability of the eggs. Nevertheless, it attracted Trichogramma chilonis 48 h after the egg deposition. Gas chromatography-mass spectrometry analysis of the oviposition-induced plant volatiles (OIPVs) revealed a considerable increase in the amount of α-pinene released by tomato plants 48 h after egg deposition. The olfactory results from Y-tube experiments showed that α-pinene exhibited a substantial attraction towards T. chilonis. In addition, it was found that the defense response induced by egg deposition for 24 and 48 h significantly inhibited the growth and development of the larvae. Metabolomics analysis revealed that the egg deposition of cotton bollworm altered the metabolite composition and caused significant modifications in the metabolic pathways of tomato plants. These findings provide novel insights into pest management by using egg-induced plant defenses to reduce egg hatching, and impede larval growth and development in herbivorous insects. © 2024 Society of Chemical Industry.

Metabolism of Furanocoumarins by Three Recombinant CYP9A Proteins From the Polyphagous Cotton Bollworm Helicoverpa armigera.

Furanocoumarins are a class of chemical compounds with phototoxic properties. For herbivores, efficient detoxification of such defense compounds is the prerequisite to feed successfully on furanocoumarin-containing plants. The cotton bollworm Helicoverpa armigera is a very important polyphagous pest in agriculture, but how it copes with toxic furanocoumarins in some of its host plants is not well understood. Given that cytochrome P450s are well known for their capacity in xenobiotic metabolism, this study attempted to explore the potential roles of cytochrome P450s in furanocoumarin transformation in this pest. Our data showed that two linear structures (psoralen and xanthotoxin) could be metabolized by three recombinant CYP9A enzymes, but no detectable depletion was observed for the linear one with the 8-dimethylallyloxy substituent on the coumarin moiety (imperatorin) and the angular furanocoumarin (angelicin). Initial epoxidation of the double bond connecting C2' and C3' of the furano ring following by cleavage of the epoxidated furan ring, leading to the formation of more soluble, less reactive and nonphotosensitizing metabolites, was identified as a common mechanism of linear furanocoumarin metabolism using a quadrupole/time-of-flight (Q-TOF) mass spectrometry interfaced with a high performance liquid chromatography (HPLC) system. Our data demonstrated that multiple P450s were involved in the detoxification of linear furanocoumarins in the cotton bollworm. These findings contribute to a better understanding of the biochemical basis of adaptation to plant defense chemicals in this economically important pest.

Method for disrupting the reproductive pheromone bond of the cotton bollworm on sunflower crops

Background: Synthetic analogs of sexual pheromones provide an effective method of biorational control of the number of phytophagous insects based on the directed disruption of reproductive functions in populations of the target pest on the protected crop without affecting the integrity of the agrocenosis. The work aims to determine the biological effectiveness of methods of mass trapping and disorientation of the cotton bollworm (Helicoverpa armigera) to protect sunflower (Helianthus annuus) crops.Methods: The experiments were carried out in 2022-2023 in the Central Zone of the Krasnodar Territory, Russia in the stationary scientific crop rotation at the Federal Research Center for Biological Plant Protection, Krasnodar (2.5 ha) and the Kononenko farm, Novovelichkovskaya village, Dinsky district (10 ha). The biological effectiveness of elimination and disorientation methods was judged by the degree of damage to plants and buds. The disorientation effect was calculated by the number of males captured at the disorientation sites compared to the control sites.Result: The decrease in males’ search activity (disorientation effect) reached 85.3%. The damage to buds by the pest in this variant was 2.0% compared to 10.8% in the control group. In the mass trapping variant, it equaled 1.5-3.0 and 7.5%, respectively, indicating the prospects of including these techniques in the H. armigera biorational control system.Conclusion: Our findings could aid future research on insect chemical communication to develop effective biological control methods.Keywords: Biological plant protection; Sunflower; Cotton bollworm; Synthetic sex pheromones; Elimination; Disorientation; Biological effectiveness

Progresses in lowland pulse insect pest management in Ethiopia

Grain legumes are one of the important cash crops for Ethiopian smallholder farmers and a significant agricultural commodity contributing to export earnings. Lowland pulses are comparatively inexpensive sources of protein in Ethiopia. However, these economically important crops are affected by various pests. Among the most damaging in storage are bruchids (Acanthoscelides obtectus, Zabrotes subfasciatus, and Callosobruchus spp.), while in production fields, the primary pests include the bean stem maggot (Ophiomyia spp.), African bollworm (Helicoverpa armigera), and aphids (Aphis craccivora Koch). Estimated yield losses due to bean stem maggot and African bollworm range from 11-100% and 12-16%, respectively. Various pest control strategies have been employed, including the use of resistant varieties, biological control, botanical treatments, and chemical control. This review summarizes relevant scientific studies on these economically important crops, the associated insect pests, the aggravating factors in Ethiopia, and available management options.

INFESTATION OF DIFFERENT INSECT PESTS ON NOVEL COTTON CULTIVARS AND THEIR IMPACTS ON COTTON FIBER QUALITY PARAMETERS

Pakistan is the 5th largest producer of cotton in the world. Exports of cotton and textile products have a share of around 60 percent in overall exports of the country. A field experiment was conducted to evaluate the different fiber quality parameters in relation to different insect pest populations. The introduction of this new types of cultivars may satisfy the needs of farmers for better quality and quantity, laborers who harvest crops, and other investors, including those in the cotton sector. A field research was carried out at the Cotton Research Station, Faisalabad, Pakistan, during the year 2023 cotton cultivars (VH-447, FH-1133, BH-228, SLH-94, MNH-S GOLD, BH-227, FH-1214, MNH-1095, VH-442, MNH-1090, RH-BAGHO BAHAR, MNH-1050, and MNH-TP) were evaluated for resistance to sucking pests such as whitefly (Bemisia tabaci); jassid (Amrasca biguttula biguttula); and thrips (Thrips tabaci) as well as bollworms such as pink bollworm (Pectinophora gossypiella); spotted bollworm (Earias insulana; E. vitelli); and American bollworm (Helicoverpa armigera). There were notable variations across the genotypes in terms of the population of sucking and bollworm insect pest infestation, which lowers cotton production and negatively affects fiber quality. FH-1133 showed the lowest average populations of thrips (1.00/leaf), jassid (0.27/leaf), and whiteflies (2.00/leaf), indicating the highest resistance. The average population (9.84%) of pink bollworm larvae in residual boll. The virus percentage on different cotton genotypes recorded after 30, 60, 90, and 120 days was 0.00, 9.00, 14.00, and 19.00%, respectively. The cultivar FH-1133 was observed to be good for all other genotypes of cotton due to its yield (2372.50 kg/acre), and it had the following lint quality attributes: GOT (46.50%), staple length (28.50 mm), fiber fineness (4.70 µg/inch), and fiber strength (33.20 g/tex).

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.

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.

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.

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.