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Competitions are common among interacting species for resources or space. In India, recently invaded fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) has to compete with native lepidopterans to become successful in an exotic environment. Invasive FAW and native pink stem borer (PSB), Sesamia inferens belong to the same feeding guild, and hence they are intraguild competitors. FAW is an aggressive pest and is known to have a cannibalism/predation habit and hence a good model system to study the ecological interactions. The present study examined the incidence of different lepidopteran pests in maize fields for three years after the recent invasion. Incidence of FAW increased over the years compared to other lepidopteran pests. Laboratory and field intraguild competition studies were conducted to understand the survival and fitness of FAW and PSB larvae under different competition scenarios. Our study demonstrated that survival of FAW was reduced in intraspecific as compared to interspecific competition. However, survival of PSB was significantly reduced in interspecific competition due to intraguild predation by FAW. Fitness cost analysis of PSB pupae survived in competition with FAW larvae indicated that they were negatively affected with reduced pupal weight. Low field incidence of PSB and its lowest survival in the presence of intraguild competitor, i.e. FAW prove that PSB might get displaced from the maize ecosystem in the near future.

Summary China is the world's second‐largest maize producer and consumer. In recent years, the invasive fall armyworm Spodoptera frugiperda (J.E. Smith) has adversely affected maize productivity and compromised food security. To mitigate pest‐inflicted food shortages, China's Government issued biosafety certificates for two genetically modified (GM) Bt maize hybrids, Bt‐Cry1Ab DBN9936 and Bt‐Cry1Ab/Cry2Aj Ruifeng 125, in 2019. Here, we quantitatively assess the impact of both Bt maize hybrids on pest feeding damage, crop yield and food safety throughout China's maize belt. Without a need to resort to synthetic insecticides, Bt maize could mitigate lepidopteran pest pressure by 61.9–97.3%, avoid yield loss by 16.4–21.3% (range −11.9–99.2%) and lower mycotoxin contamination by 85.5–95.5% as compared to the prevailing non‐Bt hybrids. Yield loss avoidance varied considerably between experimental sites and years, as mediated by on‐site infestation pressure and pest identity. For either seed mixtures or block refuge arrangements, pest pressure was kept below established thresholds at 90% Bt maize coverage in Yunnan (where S. frugiperda was the dominant species) and 70% Bt maize coverage in other sites dominated by Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenée). Drawing on experiences from other crop/pest systems, Bt maize in se can provide area‐wide pest management and thus, contribute to a progressive phase‐down of chemical pesticide use. Hence, when consciously paired with agroecological and biodiversity‐based measures, GM insecticidal crops can ensure food and nutrition security, contribute to the sustainable intensification of China's agriculture and reduce food systems' environmental footprint.

In order to improve both resistance to lepidopteran pests and resistance to the herbicide imazethapyr in mainstay japonica varieties of the Huang-Huai rice region, Sanming dominant genic male sterile (S-DGMS) rice was used as a platform to facilitate the pyramiding of functional genes and the replacement of the genomic background. Twelve novel lines were developed, each carrying a crystal toxin gene conferring resistance to lepidopteran pests and the ALS 627N allele conferring resistance to herbicide imazethapyr in the background of a mainstay japonica variety. The genomic background of the 12 novel lines was examined using 48 specified molecular markers, and each line carried less than two polymorphic markers relative to the corresponding mainstay variety. All 12 lines displayed high resistance to lepidopteran pests and the herbicide imazethapyr. The major agronomic traits of the 12 lines showed no difference relative to the responding mainstay variety when sprayed with pesticide. The popularization of the 12 japonica lines could reduce the use of pesticides and provide highly efficient control of weeds and weedy rice in the future, thus promoting the development of japonica rice production. Therefore, S-DGMS rice could be a powerful tool for the genetic improvement of target traits in rice.

The management of economically important lepidopteran pests has relied heavily on chemical and Bt-bio pesticides since 1940s, which has led to multiple recurring issues in resistance and environment. In this study, to search for a genetic-based control alternative with a distinctively different mode of action, we carried out a toxicological characterization of miR-34-5p , a highly conserved lepidopteran microRNA targeting EcR . Integrating target site prediction, co-localization of miRNA and EcR by fluorescence in situ hybridization, luciferase reporter assays as well as the gain-of-function and loss-of-function experiments, we comprehensively examined the physiological function and insecticidal properties of miR-34-5p among three representative lepidopteran pests, including Helicoverpa armigera , Spodoptera exigua, and Plutella xylostella . The combined results confirm a conserved role of miR-34-5p in the regulation of EcR in multiple lepidopteran pests. Overexpression or knocking down of miR-34-5p through both injection and feeding leads to insecticidal phenotypes, including high mortality, low fecundity, and developmental defects, suggesting that miRNAs can be considered as novel molecular targets in general, miR-34-5p for lepidopteran pests in particular. These results highlight the importance of miR-34-5p in the regulation of EcR expression in lepidopteran insects and provide a solid foundation for development of miRNA-based green pest control technology.

The microsporidium Nosema pyrausta (Paillot) Weiser, 1961 plays an important role in the mortality of the European corn borer Ostrinia nubilalis (Hübner, 1796), and shows high virulence to the beet webworm Loxostege sticticalis (Linnaeus, 1761). In contrast, the greater wax moth Galleria mellonella (Linnaeus, 1758) and the gypsy moth Lymantria dispar (Linnaeus, 1758) are referred to as resistant hosts, slightly susceptible to this microparasite. The goal of the present study was to test N. pyrausta against a broad range of lepidopteran species with different taxonomy, physiology, and ecology. The susceptibility to N. pyrausta spores fluctuated greatly among members of various families and superfamilies of Lepidoptera. As many as 13 species tested were found to be refractory (not able to support the development of the microsporidium), including three species of Yponomeutoidea, four species of Papilionoidea, one species of Pyraloidea, two species of Bombycoidea, and three species of Noctuoidea. The species found to be susceptible (with a high proportion of specimens displaying developed infection) included: Evergestis forficalis (Linnaeus, 1758) (Crambidae), Aglais urticae (Linnaeus, 1758) (Nymphalidae), and Dendrolimus sibiricus Chetverikov, 1908 (Lasiocampidae). The species newly found to be highly susceptible (high proportion of infected insects accompanied with high levels of early mortality) were: Spodoptera exigua (Hübner, 1808) (Noctuidae) and Aglais io (Linnaeus, 1758). Large quantities of spores can be produced in vivo using substitute laboratory host A. urticae. These results confirm previous observations that physiological host range of microsporidia (observed under experimental conditions) is broader than the ecological one (observed in nature).

Growing a refuge crop is an integral part of transgenic crops with gene(s) from Bacillus thuringiensis (Bt) and a key requirement to delay evolution of Bt resistance in target pests. Poor refuge planting with Bt-cotton in India, for many years, is a major reason for the outbreak of Bt resistance in pink bollworm and consequent erosion in the efficacy of Bt-cotton technology. As a remedial measure, the Ministry of Agriculture, Government of India has directed complete shift to the marketing of Bt-cotton seeds blended with non-Bt refuge cotton seeds (refuge-in-bag; RIB) from this (2020) season onwards. The strengths, weaknesses, opportunities and threats of RIB Bt-cotton combination in the context of known behaviour of cotton lepidopteran pests and prior exposure to the same Bt toxins since 2002, is discussed. Bt-cotton with RIB, if implemented with strong stewardship, will have far-reaching benefits and is expected to delay Bt resistance development in target lepidopteran cotton pests. However, the relevance of RIB for Bt-resistant pink bollworm could be in question.

Certain entomopathogenic fungi, such as Beauveria bassiana, are highly pathogenic to arthropod pests and are able to colonize plant tissues, thereby enhancing both plant growth and disease resistance. This study assessed three B. bassiana strains (CBM1, CBM2, and CBM3) for their pathogenicity toward insect larvae and colonization potential in wheat. The insecticidal activity of the fungi against the larvae of the major lepidopteran pests Helicoverpa armigera, Spodoptera frugiperda, Mythimna separata, and Plutella xylostella was determined. The fungi were then applied to wheat plants using seed immersion and soil drench methods; their colonization rates were compared, and the impacts of fungal colonization on wheat growth and survival were evaluated. The results demonstrated that all three strains were effective in reducing insect damage, with B. bassiana CBM1 exhibiting the highest pathogenicity followed by CBM3 and CBM2. B. bassiana CBM1 was particularly effective, with a significantly higher colonization rate achieved through soil drenching compared to seed immersion. The soil inoculation of B. bassiana resulted in increased plant height at 30 days after sowing (DAS) and root length at 15 DAS compared to the control group. B. bassiana CBM1-colonized wheat increased the mortality of fall armyworm. This research has enriched the biological control microbial resource pool and highlights the potential of B. bassiana in integrated pest management strategies.

Iridopsis panopla Prout (Lepidoptera: Geometridae) is an important lepidopteran defoliator of eucalyptus. I. panopla eggs were collected naturally in a commercial plantation of Eucalyptus urograndis W. Hill (Myrtaceae) in Três Lagoas, Mato Grosso do Sul, Brazil. After nine days, the natural emergence of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) occurred from I. panopla eggs. Parasitism was evaluated under laboratory and field conditions, this being the first record for eucalyptus in Brazil. Based on the biological characteristics evaluated in the laboratory, I. panopla eggs are suitable for T. pretiosum reproduction. The obtained percentage parasitism, particularly when 72,000 adult females of T. pretiosum per hectare were employed, provide valuable insights regarding the potential of T. pretiosum as an effective biological control agent against I. panopla in eucalyptus plantations. Iridopsis panopla Prout (Lepidoptera: Geometridae) é um importante desfolhador de eucalipto. Ovos de I. panopla foram coletados naturalmente em uma plantação comercial de Eucalyptus urograndis, em Três Lagoas, Mato Grosso do Sul, Brasil. Após nove dias, ocorreu a emergência natural de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) nos ovos de I. panopla. O parasitismo foi avaliado em condições de laboratório e campo, sendo este o primeiro registro para eucalipto no Brasil. Com base nas características biológicas avaliadas em laboratório, os ovos de I. panopla são adequados para a reprodução de T. pretiosum. As taxas de parasitismo obtidas, especialmente quando foram empregadas 72.000 fêmeas adultas de T. pretiosum por hectare, fornecem informações valiosas sobre o potencial de T. pretiosum como um agente de controle biológico eficaz contra I. panopla em plantações de eucalipto.

Genetically modified crops that produce insecticidal proteins from Bacillus thuringiensis (Bt) are currently the most efficient and safest method of pest control worldwide. However, the prolonged planting period has led to a reduction in the efficacy of Bt crops due to the evolution of pest resistance in the field. This review paper examines the resistance status of lepidopteran pests to Bt crops under field conditions, elucidates the molecular mechanism underlying their resistance to Bt Cry toxins, and discusses resistance management strategies based on these mechanisms. Extensive research has demonstrated that mutations and alterations in expression patterns of midgut receptor genes are closely associated with Bt resistance. As our understanding of molecular mechanisms progresses, several innovative approaches such as DNA molecular detection techniques, engineering modified Cry toxins, and combining Bt toxin with RNAi technology have been developed for effective pest control measures. Future research will further unravel the intricate molecular mechanisms underlying this phenomenon to develop scientifically sound integrated pest management strategies.

Bacillus thuringiensis (Bt) is a biological alternative to the indiscriminate use of chemical insecticides in agriculture. Due to resistance development on insect pests to Bt crops, isolating novel Bt strains is a strategy for screening new pesticidal proteins or strains containing toxin profile variety that can delay resistance. Besides, the combined genomic and proteomic approaches allow identifying pesticidal proteins and virulence factors accurately. Here, the genome of a novel Bt strain (Bt TOL651) was sequenced, and the proteins from the spore–crystal mixture were identified by proteomic analysis. Toxicity bioassays with the spore–crystal mixture against larvae of Diatraea saccharalis and Anticarsia gemmatalis, key pests of sugarcane and soybean, respectively, were performed. The toxicity of Bt TOL651 varies with the insect; A. gemmatalis (LC50 = 1.45 ng cm−2) is more susceptible than D. saccharalis (LC50 = 73.77 ng cm−2). Phylogenetic analysis of the gyrB gene indicates that TOL651 is related to Bt kenyae strains. The genomic analysis revealed the presence of cry1Aa18, cry1Ac5, cry1Ia44, and cry2Aa9 pesticidal genes. Virulence factor genes such as phospholipases (plcA, piplc), metalloproteases (inhA), hemolysins (cytK, hlyIII, hblA, hblC, hblD), and enterotoxins (nheA, nheB, nheC) were also identified. The combined use of the genomic and proteomic data indicated the expression of Cry1Aa18, Cry1Ac5, and Cry2Aa9 proteins, with Cry1Ac5 being the most abundant. InhA1 also was expressed and may contribute to Bt TOL651 pathogenicity. These results provide Bt TOL651 as a new tool for the biocontrol of lepidopteran pests.