Insecticidal Effects of Transgenic Maize Bt-Cry1Ab, Bt-Vip3Aa, and Bt-Cry1Ab+Vip3Aa against the Oriental Armyworm, Mythimna separata (Walker) in Southwest China.

The oriental armyworm, Mythimna separata (Walker), an important migratory pest of maize and wheat, is posing a severe threat to maize production in Asian countries. As source areas of spring-summer emigratory populations, the control of M. separata in southwestern China is of great significance for East Asian maize production. To assess the toxicity of Bt maize against the pest, bioassays of Bt-(Cry1Ab+Vip3Aa) maize (event DBN3601T), Bt-Cry1Ab maize (event DBN9936), and Bt-Vip3Aa maize (event DBN9501) were conducted in Yunnan province of southwest China. There were significant differences in insecticidal activity between the three Bt maize events, and DBN3601T presented the highest insecticidal role. The results also indicated that the insecticidal effect of various Bt maize tissues took an order in leaf > kernel > silk, which is highly consistent with the expression amounts of Bt insecticidal protein in leaf (69.69 ± 1.18 µg/g), kernel (11.69 ± 0.75 µg/g), and silk (7.32 ± 0.31 µg/g). In field trials, all larval population densities, plant damage rates, and leaf damage levels of DBN3601T maize were significantly lower than the conventional maize. This research indicated that the DBN3601T event had a high control efficiency against M. separata and could be deployed in southwest China for the management of M. separata.

Toxic Effects of Bt-(Cry1Ab+Vip3Aa) Maize on Storage Pest Paralipsa gularis (Zeller).

Paralipsa gularis (Zeller) is a storage pest; however, in recent years it has evolved into a considerable maize pest during the late growth stage in the border region between China and other Southeast Asian countries. Bt transgenic insect-resistant maize is an effective measure in controlling a wide range of lepidopteran pests, but there is a lack of research on the toxic effects of storage pests. We tested the toxicity of Bt-Cry1Ab, Vip3Aa, and their complex proteins against P. gularis via bioassay and investigated the efficiency of Bt-(Cry1Ab+Vip3Aa) maize in controlling P. gularis during the late growth stage of maize in the period 2022-2023. The bioassay results show that the susceptibilities of P. gularis to the two Bt proteins and their complex proteins were significantly different. The LC50 values of DBNCry1Ab ("DBN9936" event), DBNVip3Aa ("DBN9501" event), DBN Cry1Ab+Vip3Aa ("DBN3601T" event), and Syngenta Cry1Ab+Vip3Aa ("Bt11" event × "MIR162" event) were 0.038 µg/g, 0.114 µg/g, 0.110 µg/g, and 0.147 µg/g, and the GIC50 values were 0.014 µg/g, 0.073 µg/g, 0.027 µg/g, and 0.026 µg/g, respectively. Determination of the expression content of the insecticidal protein in different tissues of Bt-(Cry1Ab+Vip3Aa) maize shows that the total Bt protein content in different tissues was in the following order: stalk > bract > cob > kernel. However, the bioassay results show that the mortalities of P. gularis feeding on Bt-(Cry1Ab+Vip3Aa) maize in different tissues at different growth stages were all above 93.00%. The field trial indicates that the occurrence density of larvae and plant damage rate for conventional maize were 422.10 individuals/100 plants and 94.40%, respectively, whereas no larvae were found on Bt-(Cry1Ab+Vip3Aa) maize. In summary, this study implies that Bt-(Cry1Ab+Vip3Aa) maize has a high potential for control of P. gularis, providing a new technical measure for the management of the pest.

Side effects of X-ray irradiation on flight ability of Cydia pomonella moth.

BACKGROUND: The sterile insect technique (SIT) has proven to be an effective approach in managing the population of major invasive pests. Our previous studies showed that irradiation of Cydia pomonella males at a dosage of 366 Gy X-rays resulted in complete sterility. However, the mating competitiveness of sterilized males is significantly compromised, which can be attributed to a decline in their ability to fly. RESULTS: In this study, we examined the flight patterns of both male and female adults of C. pomonella. The results revealed significant variations in the average flight speed of both genders at different stages of maturity, with females displaying longer flight duration and covering greater distances. Effect of irradiation on the flight performance of 3-day-old male moths was further evaluated, as they demonstrated the longest flight distance. The findings indicated a significant decrease in flight distance, duration, and average speed, due to wing deformities caused by irradiation, which also limited the dispersal distance of moths in orchards, as indicated by the mark-and-recapture assay. Reverse-transcription quantitative polymerase chain reaction analysis revealed a down-regulation of flight-related genes such as Flightin, myosin heavy chain, and Distal-less following radiation exposure. CONCLUSION: These findings demonstrate that X-ray irradiation at a radiation dose of 366 Gy has a detrimental effect on the flight ability of male C. pomonella adults. These insights not only contribute to a better understanding of how radiation sterilization diminishes the mating competitiveness of male moths, but also aid in the development and improvement of SIT practices for the effective control of C. pomonella. © 2023 Society of Chemical Industry.

Evaluation of green waste, green waste compost and cow dung as amendments for white wine distillers' grains vermicomposting.

The application of organic additives is an efficient strategy to promote the vermicomposting of organic wastes. This study investigated the changes in earthworm growth, nutrients, enzyme activities, microbial composition, and seedling growth during 60 days of vermicomposting of white wine distillers' grains (WWDG) mixed (50:50, w/w) with green waste (GW), green waste compost (GWC), or cow dung (CD). Our data showed that GW, GWC, and CD addition significantly enhanced the survival rate (73.33%-89.17%), growth, and reproduction of earthworms compared to the control treatment. The degradation rate of TOC, the increasing rate of nutriments (total N, total P, total K, available P, available K, humic acid, NH4+, NO3-), and the germination index were significantly higher in the additive treatments than in the control treatment. Dehydrogenase, phosphatases, and urease activities were significantly elevated in the vermicompost amended with additives. The additives remarkably stimulated bacteria, such as Streptomyces, Steroidobacter, Bacillus, Luteibacter, and Rhodanobacter, etc., which were closely related to the biocontrol of phytopathogens and the decomposing recalcitrant substances. Moreover, additives significantly promoted the generation and growth parameters of tomato and lettuce seedlings when compared with the control. In summary, these results indicated that all three additives facilitated the vermicomposting of WWDG and improved the compost quality by enhancing earthworm and enzyme activities as well as altering compost bacterial community, especially when the GWC addition yields the best compost quality and shows strong potential for future application. This study developed a new method for improving WWDG utilization rate and it will promote organic waste recycling in China.

The Effect of X-ray Irradiation on the Fitness and Field Adaptability of the Codling Moth: An Orchard Study in Northeast China.

The codling moth, Cydia pomonella (L.), is an invasive agricultural pest of pome fruits and walnuts in China that threatens the apple industry in the Loess Plateau and Bohai Bay; it has developed resistance to many insecticides. Sterile insect technique (SIT) combined with area-wide integrated pest management (AW-IPM) can reduce the risk of resistance to insecticides and effectively control some insect pest species. Our previous laboratory experiment found that irradiation with 366 Gy of X-ray caused the males of the codling moth to become sterile. However, the sterility and adaptability of males after being irradiated with 366 Gy X-ray in the field are still unclear. In this study, we investigated the effect of X-ray irradiation on the fitness of male adults that emerged from pupae irradiated with 366 Gy to explore their adaptability and mating competitiveness, and to examine the effect of releasing sterile male insects in orchards in northeast China on the fruit infestation rate of the Nanguo pear. The results showed that 366 Gy of X-ray irradiation significantly reduced the mating competitiveness of males and the hatching rate of the eggs laid by females pairing with sterile males. Meanwhile, the lifespan of the sterile male moths was significantly shorter than that of the normal ones in the field. A pilot test showed that the release twice of sterile male moths in the orchards had no significant effect on the fruit infestation rate. Our field experiments provide a scientific basis for the further optimization of the SIT technology program for controlling C. pomonella.

The invasive Spodoptera frugiperda (J.E. Smith) has displaced Ostrinia furnacalis (Guenée) as the dominant maize pest in the border area of southwestern China.

BACKGROUND: The invasive fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera: Noctuidae) has widely colonized the tropics and subtropics of Asia. However, the impact on the succession of the Asiatic corn borer (ACB) Ostrinia furnacalis (Lepidoptera: Pyralidae), a perennial dominant stemborer of maize in these areas, remains elusive. Here we analyzed the predation relationship, mimicked population competition, and surveyed the pest populations in the border area of Yunnan (southwestern China). RESULTS: Laboratory assays revealed that the 2nd to 6th instar larvae of FAW preyed on ACB, and only the 4th and 5th instar larvae of ACB preyed on FAW (1st instar larvae only, 50% predation rate). The 6th instar FAW preyed on the 1st to 5th instar ACB with a theoretical maximum of 14.5-58.8 ACB individuals (per maize leaf) and 4.8-25.6 individuals (per tassel). When maize plants were infested with eggs of either FAW or ACB in field cage trials, maize damage was 77.6% and 50.6%, respectively, compared with 77.9% and 2.8% upon co-infestation. In field surveys conducted in 2019-2021, FAW density was significantly greater than that of ACB, which took a great impact on maize growth. CONCLUSION: Our findings indicate that FAW can outcompete ACB at both the individual and population levels, which may result in FAW becoming the dominant pest. These results provide a scientific basis for further analysis of the mechanism by which FAW invades new agricultural areas and offers early-warning strategies for pest management. © 2023 Society of Chemical Industry.

Gut Microbiota of Freshwater Gastropod (Bellamya aeruginosa) Assist the Adaptation of Host to Toxic Cyanobacterial Stress.

Gut microbes play a critical role in helping hosts adapt to external environmental changes and are becoming an important phenotype for evaluating the response of aquatic animals to environmental stresses. However, few studies have reported the role that gut microbes play after the exposure of gastropods to bloom-forming cyanobacteria and toxins. In this study, we investigated the response pattern and potential role of intestinal flora in freshwater gastropod Bellamya aeruginosa when exposed to toxic and non-toxic strains of Microcystis aeruginosa, respectively. Results showed that the composition of the intestinal flora of the toxin-producing cyanobacteria group (T group) changed significantly over time. The concentration of microcystins (MCs) in hepatopancreas tissue decreased from 2.41 ± 0.12 on day 7 to 1.43 ± 0.10 µg·g-1 dry weight on day 14 in the T group. The abundance of cellulase-producing bacteria (Acinetobacter) was significantly higher in the non-toxic cyanobacteria group (NT group) than that in the T group on day 14, whereas the relative abundance of MC-degrading bacteria (Pseudomonas and Ralstonia) was significantly higher in the T group than that in the NT group on day 14. In addition, the co-occurrence networks in the T group were more complex than that in the NT group at day 7 and day 14. Some genera identified as key nodes, such as Acinetobacter, Pseudomonas, and Ralstonia, showed different patterns of variation in the co-occurrence network. Network nodes clustered to Acinetobacter increased in the NT group from day 7 to day 14, whereas the interactions between Pseudomonas and Ralstonia and other bacteria almost changed from positive correlations in the D7T group to negative correlations in the D14T group. These results suggested that these bacteria not only have the ability to improve host resistance to toxic cyanobacterial stress by themselves, but they can also further assist host adaptation to environmental stress by regulating the interaction patterns within the community. This study provides useful information for understanding the role of freshwater gastropod gut flora in response to toxic cyanobacteria and reveals the underlying tolerance mechanisms of B. aeruginosa to toxic cyanobacteria.

Integration of Transcriptomics and Microbiomics Reveals the Responses of Bellamya aeruginosa to Toxic Cyanobacteria.

Frequent outbreaks of harmful cyanobacterial blooms and the cyanotoxins they produce not only seriously jeopardize the health of freshwater ecosystems but also directly affect the survival of aquatic organisms. In this study, the dynamic characteristics and response patterns of transcriptomes and gut microbiomes in gastropod Bellamya aeruginosa were investigated to explore the underlying response mechanisms to toxic cyanobacterial exposure. The results showed that toxic cyanobacteria exposure induced overall hepatopancreatic transcriptome changes. A total of 2128 differentially expressed genes were identified at different exposure stages, which were mainly related to antioxidation, immunity, and metabolism of energy substances. In the early phase (the first 7 days of exposure), the immune system may notably be the primary means of resistance to toxin stress, and it performs apoptosis to kill damaged cells. In the later phase (the last 7 days of exposure), oxidative stress and the degradation activities of exogenous substances play a dominant role, and nutrient substance metabolism provides energy to the body throughout the process. Microbiomic analysis showed that toxic cyanobacteria increased the diversity of gut microbiota, enhanced interactions between gut microbiota, and altered microbiota function. In addition, the changes in gut microbiota were correlated with the expression levels of antioxidant-, immune-, metabolic-related differentially expressed genes. These results provide a comprehensive understanding of gastropods and intestinal microbiota response to toxic cyanobacterial stress.

Mating Competitiveness of Male Spodoptera frugiperda (Smith) Irradiated by X-rays.

Spodoptera frugiperda, an invasive pest, has a huge impact on food production in Asia and Africa. The potential and advantages of sterile insect techniques for the permanent control of S. frugiperda have been demonstrated, but the methods for their field application are still unavailable. For the purposes of this study, male pupae of S. frugiperda were irradiated with an X-ray dose of 250 Gy to examine the effects of both the release ratio and the age of the irradiated males on the sterility of their offspring. The control effect of the irradiated male release ratio on S. frugiperda was evaluated using field-cage experiments in a cornfield. The results showed that when the ratio of irradiated males to non-irradiated males reached 12:1, the egg-hatching rate of the offspring of S. frugiperda decreased to less than 26%, and there was also no significant difference in mating competitiveness among the different ages. Field-cage testing showed that when irradiated males were released at ratios of 12:1-20:1 to normal males, the leaf protection effect for the corn reached 48-69% and the reduction in the insect population reached 58-83%. In this study, an appropriate release ratio is suggested, and the mating competitiveness of irradiated and non-irradiated males of S. frugiperda is investigated, thus providing a theoretical basis for the use of sterile insect techniques to control S. frugiperda.

Stable Isotopes Indicate Seasonal Changes in Natal Geographic Origins and Host Plants of Ostrinia furnacalis (Guenée) Migrants Across the Bohai Strait in China.

The Asian corn borer, Ostrinia furnacalis (Guenée), is a notorious pest of maize that migrates seasonally in Asia. Two migration peaks were found on Beihuang island in the Bohai Strait of China by observing the number of migrants. However, the origins and host plants of the migrants in the two migration periods remain unclear. Here, stable hydrogen (δ2H) and carbon (δ13C) isotope levels were measured to infer the origin and host plants of the O. furnacalis captured on Beihuang island in 2017-2019. δ2H in wings of spring-summer O. furnacalis captured from May to June ranged from -99 to -56‰, while that of autumn migrants from August to September ranged from -127 to -81‰. Based on the linear relationship between δ2H in the wing of migrants (δ2Hw) and δ2H in precipitation (δ2Hp), the spring-summer O. furnacalis likely originated from the summer maize area in the Huang-Huai-Hai Plain in China. In contrast, the autumn migrants came from the northern spring maize area in Liaoning, Jilin and Inner Mongolia. Based on δ13C, the spring-summer migrants fed on both C3 plants such as wheat (47.76%) and C4 weeds or belonged to the over winter individuals in maize field (52.24%), while the autumn migrants mainly fed on maize (C4, 91.21%). The results point to a northward migration in spring-summer and southward migration in autumn of O. furnacalis. Our study gives an important knowledge for improving the forecasting and management level of this pest.

Performance of the domestic Bt corn event expressing pyramided Cry1Ab and Vip3Aa19 against the invasive Spodoptera frugiperda (J. E. Smith) in China.

BACKGROUND: The invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), has caused serious corn yield losses and increased the frequency of insecticide spraying on corn in Africa and Asia. Drawing lessons from the use of Bt corn to manage fall armyworm in the Americas, China released a certificate for the genetically modified corn event DBN3601T pyramidally expressing Cry1Ab and Vip3Aa19 for industrialization in 2021. Performance of the DBN3601T event against invasive fall armyworm in China was evaluated by plant tissue-based bioassays and field trials during 2019-2021. RESULTS: In the bioassays, tissues and organs of DBN3601T corn differed significantly in lethality to fall armyworm neonates in the order: leaf > husk > tassel and kernel > silk. In field trials, compared with non-Bt corn, DBN3601T corn greatly suppressed fall armyworm populations and damage; larval density, damage incidence, and leaf damage scores for DBN3601T corn were significantly lower than for non-Bt corn at different vegetative stages, and efficacy against larval populations during the 3 years ranged from 95.24% to 98.30%. CONCLUSION: A laboratory bioassay and 3-year field trials confirmed that DBN3601T corn greatly suppressed fall armyworm populations and has high potential as a control of this invasive pest, making it a key tactic for integrated management of fall armyworm in China. © 2022 Society of Chemical Industry.

Bt maize can provide non-chemical pest control and enhance food safety in China.

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.

Wheat-Bran-Based Artificial Diet for Mass Culturing of the Fall Armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae).

Spodoptera frugiperda Smith (fall armyworm (FAW)) has invaded many countries in Africa and Asia in recent years, considerably restricting global agricultural production. In this study, we assessed the rearing performance of four artificial diets (D1: an artificial FAW diet based on wheat bran and soybean, maize, and yeast powders; D2: an artificial diet developed for Helicoverpa armigera (Hübner), based on wheat bran and soybean and yeast powders; D3: an artificial diet based on soybean powder; D4: an artificial diet based on wheat bran) for FAWs. We designed D4 based on a traditional diet (D2) but substituted the wheat bran for soybean and yeast powders. At 25 ± 1 °C, 75% ± 5% RH, and a 16:8 h L:D photoperiod, the larval stage of FAWs fed on D4 lasted 15.88 d, the pupal stage lasted 9.48 d, the pupal mass was 270.45 mg, the number of eggs deposited was 1364.78, and the mating rate was 89.53%. Most biological indicators of the larvae that were fed D4 were basically consistent with those of the larvae fed on the traditional diet (D2), but the intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) of the D4 FAWs were lower than those of the D2 FAWs. The flight capacity (flight distance, duration, and velocity were 19.73 km, 6.91 h, and 2.90 km/h, respectively) of the D4 FAWs was comparable to that of the FAWs fed a traditional diet and maize leaves. Compared with the three other formulas, the cost of using D4 was lower by 26.42% on average. These results show that using cheap wheat bran instead of soybean flour and yeast powder as the basic material for an artificial diet for FAWs is feasible, which will substantially reduce rearing costs and promote the development of new controlling measures for FAWs. In addition, this study also has a reference value for reducing the cost of artificial diets for other insects.

Seasonal migratory activity of SPODOPTERA FRUGIPERDA (J.E. Smith) (Lepidoptera: Noctuidae) across China and Myanmar.

BACKGROUND: The fall armyworm (FAW) Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) invaded Myanmar and China in 2018 and greatly impacted agricultural production and ecosystem balance in these areas. FAW is a migratory insect, but its seasonal migration pattern between the two countries has been largely unknown. From 2019 to 2021, we monitored the seasonal migration of FAW in the China-Myanmar border area using a searchlight trap, assessed the reproductive development status of female migrants and traced the migratory routes by trajectory simulation. RESULTS: FAW moths were trapped by the searchlight trap in Lancang County (Yunnan, China) all year, with obvious seasonal differences in the number caught. There were small-scale persistent trapping peaks in spring and summer, and obvious peaks in autumn; only a small number of moths were trapped in winter. Examination of the ovaries of female moths collected in different seasons showed that most females had matured, indicating that the moths were migrating and did not take off from the local area. In the migration trajectory simulation, FAW mainly migrated from Myanmar to Southwest China in spring and summer and back to Myanmar in autumn. CONCLUSION: Our findings indicate that FAW migrates between China and Myanmar according to the monsoon circulation, which will help guide cross-border regional monitoring and management strategies against this pest. © 2022 Society of Chemical Industry.

Effect of X-ray irradiation on development, flight, and reproduction of Spodoptera litura.

Spodoptera litura is an omnivorous pest that has spread globally. Because irradiation sterilization technology has a great potential for control of S. litura, the effect of 25-150 Gy doses of X-rays on pupal survival, flight and reproductive variables of adult moths were analyzed in this research. The X-ray irradiation with the dose of 25-150 Gy significantly affected the reproductive ability of females. Irradiating male pupae with 25-150 Gy doses of X-rays had no effect on mating, life span, or flight ability of adult moths, but significantly reduced survival and fecundity of their offspring, and the sterility rate of the F1 generation was 52.65%-99.9%. The results of logistic curve fitting showed that the sterility impact was 84% at the most appropriate irradiation dose (71.26 Gy). The sterility control was 91% in an indoor mating competition experiment when the release ratio of irradiated males (75 Gy) to nonirradiated males reached 12.6:1. The effects of X-ray irradiation doses on biological variables of S. litura and the most effective release ratio determined here provide a theoretical foundation for using radiation sterilization technology to control S. litura.

Responses of Gut Microbial Community Composition and Function of the Freshwater Gastropod Bellamya aeruginosa to Cyanobacterial Bloom.

Freshwater gastropods are widely distributed and play an important role in aquatic ecosystems. Symbiotic microorganisms represented by gut microbes can affect the physiological and biochemical activities of their hosts. However, few studies have investigated the response of the gut microbial community of snails to environmental stress. In this study, the dynamics of the gut microbiota of the gastropod Bellamya aeruginosa were tracked to explore their responses in terms of their composition and function to cyanobacterial bloom. Differences in gut microbial community structures during periods of non-cyanobacterial bloom and cyanobacterial bloom were determined. Results showed that the alpha diversity of the gut microbiota exposed to cyanobacterial bloom was lower than that of the gut microbiota exposed to non-cyanobacterial bloom. The main genera differentiating the two periods were Faecalibacterium, Subdoligranulum, Ralstonia, and Pelomonas. Microcystins (MCs) and water temperature (WT) were the primary factors influencing the gut microbial community of B. aeruginosa; between them, the influence of MCs was greater than that of WT. Fourteen pathways (level 2) were notably different between the two periods. The pathways of carbohydrate metabolism, immune system, environmental adaptation, and xenobiotics biodegradation and metabolism in these differential pathways exhibited a strong linear regression relationship with MCs and WT. Changes in the functions of the gut microbiota may help B. aeruginosa meet its immunity and energy needs during cyanobacterial bloom stress. These results provide key information for understanding the response pattern of freshwater snail intestinal flora to cyanobacterial blooms and reveal the underlying environmental adaptation mechanism of gastropods from the perspective of intestinal flora.

Effects of X-ray irradiation on the fitness of the established invasive pest fall armyworm Spodoptera frugiperda.

BACKGROUND: Spodoptera frugiperda has spread to Africa, Asia, and Oceania, posing a serious threat to global agriculture. We estimated the appropriate dose of X-ray sterilization for S. frugiperda using an X-ray irradiation instrument to investigate environmentally acceptable control techniques, laying the framework for future applications of sterile insect technology (SIT) to manage the pest environmentally-friendly. RESULTS: This study is the first to investigate the effects of X-ray irradiation on the growth, development, survival, reproduction, and flight of S. frugiperda. The results showed that irradiation with 50-400 Gy had no significant effect on pupal eclosion, but females were more sensitive than males in terms of reproductive parameters, especially when doses of radiation were > 350 Gy. After irradiation with a sub-sterilizing dose of 250 Gy, the parental sterility rate was > 85%, and the sterility traits could be passed on to their offspring, resulting in a continuous decrease in the population of F1 and F2 generations. CONCLUSION: Our laboratory experiments theoretically confirmed the feasibility of SIT for controlling S. frugiperda in the field using X-ray radiation. This study provides a theoretical basis for future regional pest management strategies. © 2022 Society of Chemical Industry.

Partiti-like viruses from African armyworm increase larval and pupal mortality of a novel host: the Egyptian cotton leafworm.

BACKGROUND: The general principle of using microbes from one species to manage a different pest species has a clear precedent in the large-scale release of mosquitoes carrying a Wolbachia bacterium derived from Drosophila flies. New technologies will facilitate the discovery of microbes that can be used in a similar way. Previously, we found three novel partiti-like viruses in the African armyworm (Spodoptera exempta). To investigate further the utility and consistency of host shift of insect viruses as a potential pest management tool, we tested the interaction between the partiti-like viruses and another novel host, the Egyptian cotton leafworm (Spodoptera littoralis). RESULT: We found that all three partiti-like viruses appeared to be harmful to the novel host S. littoralis, by causing increased larval and pupal mortality. No effect was observed on host fecundity, and partiti-like virus infection did not impact host susceptibility when challenged with another pathogen, the baculovirus SpliNPV. Transcriptome analysis of partiti-like virus-infected and noninfected S. littoralis indicated that the viruses could impact host gene-expression profiles of S. littoralis, but they impact different pathways to the two other Spodoptera species through effects on pathways related to immunity (Jak-STAT/Toll and Imd) and reproduction (insulin signaling/insect hormones). CONCLUSION: Taken together with the previous findings in the novel host S. frugiperda, these results indicate a parasitic relationship between the partiti-like viruses and novel insect hosts, suggesting a possible use and novel pest management strategy through the artificial host shift of novel viruses. © 2021 Society of Chemical Industry.

Population genetics unveils large-scale migration dynamics and population turnover of Spodoptera exigua.

BACKGROUND: Migration is a widespread phenomenon among many insect species, including herbivorous crop pests. At present, scant information exists on the long-range migration of the polyphagous armyworm, Spodoptera exigua and its underlying climatic determinants (i.e. East Asian or South Asian monsoon circulation). In this study, we employed a population genetics approach to delineate S. exigua migration patterns across multiple Asian countries. RESULTS: Using mitochondrial cytochrome I (COI) and microsatellite markers, low-to-moderate levels of genetic diversity were detected among 101 S. exigua populations collected across China, Pakistan and Vietnam. Haplotype diversity and nucleotide diversity did not differ between years. Two spatially explicit genetic clusters were detected, an eastern and a western clade, with the former comprising populations in the East Asia monsoon area. No genetic differentiation was recorded among armyworm populations in the year-round breeding area, nor among those of the overwintering and nonoverwintering areas. Five of the most widespread mitochondrial haplotypes reflected the extensive gene flow across at a large spatial scale. CONCLUSION: Low-to-moderate levels of genetic diversity were observed, and evidence was found for genetic clustering in certain geographical areas. Accordingly, our unique insights into S. exigua population genetics and spatiotemporal migration dynamics help to guide applied ecological studies, ecological intensification schemes or (area-wide) pest management campaigns in China and abroad. © 2021 Society of Chemical Industry.