2021 Vol. 20 No. 3 Previous Issue    Next Issue

    Special Issue: Research on the invasive pest of fall armyworm (Spodoptera frugiperda) in China
    Section 1: Review of current research on fall armyworm
    Section 2: Invasion and migration
    Section 3: Biological and ecological characteristics
    Section 4: Integrated pest management

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    Special Issue: Research on the invasive pest of fall armyworm (Spodoptera frugiperda) in China
    Editorial - Research on the invasive pest of fall armyworm (Spodoptera frugiperda) in China
    XIAO Yu-tao
    2021, 20(3): 633-636.  DOI: 10.1016/S2095-3119(21)63623-7
    Abstract ( )   PDF in ScienceDirect  
    Section 1: Review of current research on fall armyworm
    Spread of invasive migratory pest Spodoptera frugiperda and management practices throughout China
    ZHOU Yan, WU Qiu-lin, ZHANG Hao-wen, WU Kong-ming
    2021, 20(3): 637-645.  DOI: 10.1016/S2095-3119(21)63621-3
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), a notorious migratory pest native to tropical and subtropical America, invaded China in December 2018, then spread through 26 provinces (autonomous regions, municipalities) in 2019 and 27 in 2020, damaging 1.125 and 1.278 million hectares of crops, respectively.  Maize was the most severely affected crop, although wheat and other plants were also ruined.  Considering the biological characteristics, incidence regularity and migration patterns of the FAW populations, Chinese government implemented a regional control strategy and divided the areas infested with FAW into the annual breeding grounds in Southwest and South China, the transitional migration area in Jiangnan and Jianghuai and the key preventive area in the Huang-Huai-Hai region and North China.  The National Agro-Tech Extension and Service Center constructed “the National Information Platform for the Prevention and Control of the Fall Armyworm” at the county level, which would entail people reporting and mapping the spread of fall armyworm.  According to forecasting information, millions of extension workers and small-scale growers in entire country were rallied by local governments to fight the pest through comprehensive control tactics including chemical, physical, biological and ecological measures.  Thanks to the joint prevention and control, the final loss of crops infested was controlled within 5% of the total in 2019 and 2020.  This review also gives a discussion on existing problems and future management scenarios.
    Biology, invasion and management of the agricultural invader: Fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)
    Jing WAN, HUANG Cong, LI Chang-you, ZHOU Hong-xu, REN Yong-lin, LI Zai-yuan, XING Long-sheng, ZHANG Bin, QIAO Xi, LIU Bo, LIU Cong-hui, XI Yu, LIU Wan-xue, WANG Wen-kai, QIAN Wan-qiang, Simon MCKIRDY, WAN Fang-hao
    2021, 20(3): 646-663.  DOI: 10.1016/S2095-3119(20)63367-6
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is native to the Americas.  It has rapidly invaded 47 African countries and 18 Asian countries since the first detection of invasion into Nigeria and Ghana in 2016.  It is regarded as a super pest based on its host range (at least 353 host plants), its inherent ability to survive in a wide range of habitats, its strong migration ability, high fecundity, rapid development of resistance to insecticides/viruses and its gluttonous characteristics.  The inherently superior biological characteristics of FAW contribute to its invasiveness.  Integrated pest management (IPM) of FAW has relied on multiple applications of monitoring and scouting, agricultural control, chemical pesticides, viral insecticides, sex attractants, bio-control agents (parasitoids, predators and entomopathogens) and botanicals.  Knowledge gaps remain to be filled to: (1) understand the invasive mechanisms of S. frugiperda; (2) understand how to prevent its further spread and (3) provide better management strategies.  This review summarizes the biological characters of FAW, their association with its invasiveness and IPM strategies, which may provide further insights for future management.
    Section 2: Invasion and migration
    Case study on the first immigration of fall armyworm, Spodoptera frugiperda invading into China
    SUN Xiao-xu, HU Chao-xing, JIA Hui-ru, WU Qiu-lin, SHEN Xiu-jing, ZHAO Sheng-yuan, JIANG Yu-ying, WU Kong-ming
    2021, 20(3): 664-672.  DOI: 10.1016/S2095-3119(19)62839-X
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda is one of the most damaging crop pests, and it has become major threat to the food security of many countries.  In order to monitor possible invasion of this pest into China, a searchlight trap was established in March 2018 in western Yunnan Province, China, where it has served as the “first station” for many pests that have migrated from Myanmar to China.  A number of suspected FAW moths were captured and identified by DNA sequencing.  The results showed that the FAW moth was first captured on December 11 and formed its first immigration peak in mid-December 2018.  DNA detection revealed that the early invading FAW population was the “corn-strain”.  The field survey indicated that the pest mainly colonized corn in Pu’er, Dehong and Baoshan areas.  Migration trajectory simulation implied that the moths might have mainly come from the eastern area in the mid-latitude region of Myanmar (20–25°N, 94–100°E).  This case study confirmed the first immigration of FAW into China, and will be helpful for guiding monitoring and management work to control this pest.
    Searchlight trapping reveals seasonal cross-ocean migration of fall armyworm over the South China Sea
    ZHOU Xian-yong, WU Qiu-lin, JIA Hui-ru, WU Kong-ming
    2021, 20(3): 673-684.  DOI: 10.1016/S2095-3119(20)63588-2
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda, is a migratory noctuid pest that has recently invaded eastern Asia.  From 2017 up till 2020, searchlight trapping was used to assess the extent of FAW migration across the South China Sea.  Molecular and morphology-based identification confirmed that FAW made its first appearance on Yongxing Island on 11 April 2019, with most trapped individuals belonging to the S. frugiperda “corn-strain”.  Carbon isotope analysis further showed that FAW moths originated from C4 host plants, while trajectory analyses revealed that migratory S. frugiperda adults are able to cross the South China Sea and enter mainland China.  This long-distance migration process plausibly results in frequent genetic mixing between domestic FAW populations and those of neighboring Southeast Asian countries.  Overall, this work provides unique insights into FAW migration across eastern Asia and ultimately can help advance pest forecasting, risk assessment and area-wide pest management.
    Migration of invasive Spodoptera frugiperda (Lepidoptera: Noctuidae) across the Bohai Sea in northern China
    JIA Hui-ru, GUO Jiang-long, WU Qiu-lin, HU Chao-xing, LI Xiao-kang, ZHOU Xian-yong, WU Kong-ming
    2021, 20(3): 685-693.  DOI: 10.1016/S2095-3119(20)63281-6
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is an important agricultural pest with a strong migratory ability.  While the species is native to the Americas, it has recently invaded China, ravaging crops in many provinces (autonomous regions, municipalities).  Its long-distance migration, which is critical to understand for pest management programs, has been well studied in its native region.  In other regions however, the moth’s migration patterns have not yet been characterized.  Here, the migratory behavior of FAW populations in China was studied on an isolated island located in the center of the Bohai Strait from spring to autumn 2019, the year in which FAW first reached this region, by using searchlight trapping, stable carbon isotopes and trajectory simulation.  The main results were summarized as follows: (i) The number of FAW moths caught by searchlight trapping provided direct evidence that the species migrated across the Bohai Sea.  (ii) Species identification was confirmed by both morphology and molecular methods, and only the “corn-strain” that preferentially infests maize and sorghum was found in the collections.  (iii) Stable carbon isotope measurements showed that up to 95.07% of captured moths displayed the C4 isotope signature, thus providing additional evidence that this species is a migrant as there are no major C4 plants at the trapping site.  (iv) Backward trajectory analysis indicated that the pest now threatens to expand its range into the agriculturally important region of Northeast China, and thus authorities in this region should be vigilant to the threat posed by this species.  Together, these findings add to our knowledge concerning the occurrence of FAW in northern China, and will help us to develop sustainable and effective monitoring, forecasting, and pest management strategies.
    Windborne migration routes of newly-emerged fall armyworm from Qinling Mountains–Huaihe River region, China
    WU Qiu-lin, SHEN Xiu-jing, HE Li-mei, JIANG Yu-ying, LIU Jie, HU Gao, WU Kong-ming
    2021, 20(3): 694-706.  DOI: 10.1016/S2095-3119(20)63207-5
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW, Lepidoptera: Noctuidae), Spodoptera frugiperda (J. E. Smith), invaded China in mid-December 2018; since then, it has become a great threat to Chinese agricultural production.  Qinling Mountains–Huaihe River region (QM–HRR) is the transitional zone between northern and southern China, an important region for both corn and wheat production.  Based on the actual occurrence of QM–HRR invaded by FAW in 2019, daily mean surface air temperature and nocturnal wind conditions at 925 hPa were examined, and migratory routes of FAW moths originated in QM–HRR were modeled by a forward-trajectory-analysis approach.  The results indicated that migratory activities of FAW adults emerged in QM–HRR were initiated from late June.  The moths from western QM–HRR, where has complex topographic terrain, mainly flied to Ningxia and Inner Mongolia before mid September.  However, FAW moths from the eastern QM–HRR primarily engaged in high-altitude northward transport assisted by the prevailing southerly winds before mid August, and the North China Plain was identified as the main destination of FAW.  Meanwhile, the migration trajectories of FAW moths had a possibility to reach the Northeast China Plain.  From mid August, FAW moths in eastern QM–HRR largely migrated southward and returned to the Yangtze River Valley.  This study provides detailed information on the occurrence and migration routes of FAW moths from QM–HRR and will be helpful for early warning and development of integrated pest management strategies for the control of this exotic insect pest.
    Laboratory-based flight performance of the fall armyworm, Spodoptera frugiperda
    GE Shi-shuai, HE Li-mei, HE Wei, YAN Ran, Kris A. G. WYCKHUYS, WU Kong-ming
    2021, 20(3): 707-714.  DOI: 10.1016/S2095-3119(20)63166-5
    Abstract ( )   PDF in ScienceDirect  
    In late 2018, the fall armyworm (FAW) Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) made its arrival in China and its populations have since proliferated across most of eastern Asia.  While S. frugiperda exhibits a considerable dispersal capacity and engages in long-distance migration, there’s only scant information on the species’ flight capability.  Here, we empirically assessed S. frugiperda flight activity under varying climatic conditions using a flight mill.  More specifically, under laboratory conditions, FAW exhibited superior flight performance at 20–25°C and 60–90% relative humidity (RH).  When quantifying flight performance over five consecutive nights (i.e., 10 h/night), all flight parameters initially increased and then gradually dropped and FAW adults attained a total flight distance, duration and velocity equal to 63.73 km (48.42–94.12 km) (median, quartile range), 24.12 h (20.87–27.73 h) and 2.73 km h–1 (2.13–3.33 km h–1), respectively.  Our work constitutes a first comprehensive assessment of S. frugiperda flight performance and provides baseline information for future efforts to forecast spatiotemporal changes in its geographical distribution, movement patterns and invasion trajectories.  Such can ultimately permit a timely and targeted deployment of area-wide pest management measures against this newly-invasive pest in China and across eastern Asia. 
    Adult nutrition affects reproduction and flight performance of the invasive fall armyworm, Spodoptera frugiperda in China
    HE Li-mei, JIANG Shan, CHEN Yu-chao, Kris A. G. WYCKHUYS, GE Shi-shuai, HE Wei, GAO Xi-wu, WU Kong-ming
    2021, 20(3): 715-726.  DOI: 10.1016/S2095-3119(20)63198-7
    Abstract ( )   PDF in ScienceDirect  
    Floral resources, such as carbohydrate-rich nectar or pollen, can bolster fitness and raise reproductive output of adult lepidopterans.  Here, we used laboratory experiments to assess how those plant-derived foods impact adult fecundity, reproductive physiology and flight performance of an invasive strain of the fall armyworm, Spodoptera frugiperda (FAW; Lepidoptera: Noctuidae) in China.  More specifically, supplementary feeding on bee pollen and honey enhanced FAW flight duration, testis size, ovarian development, longevity and adult fecundity.  FAW adults attained the longest pre-oviposition (10.8 days) and oviposition period (6.8 days) and longevity (19.2 days) on 5% acacia honey.  Upon access to 2.5% acacia honey and 2.5‰ pine pollen, S. frugiperda attained the highest mating rate (79.7%), fecundity (644.9 eggs/female) and egg hatching rate (82.3%).  Feeding on honey further delayed decay of male testes, while ovarian development was enhanced when female moths were allowed access to 2.5% honey and 2.5‰ pine pollen.  Upon feeding on 5% honey solution, S. frugiperda engaged in flight over the longest duration (9.5 h), distance (29.9 km) and speed (3.1 km h–1).  Honey had a comparatively greater effect on the above parameters than pollen.  Our findings help decipher FAW invasion patterns and population dynamics, facilitate the development of nutritional attractants, and contribute to integrated pest management of this newly-invasive pest in eastern Asia.
    Flight activity promotes reproductive processes in the fall armyworm, Spodoptera frugiperda
    GE Shi-shuai, HE Wei, HE Li-mei, YAN Ran, ZHANG Hao-wen, WU Kong-ming
    2021, 20(3): 727-735.  DOI: 10.1016/S2095-3119(20)63204-X
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), has invaded many countries in Africa and Asia since 2016, posing a major threat to world food security.  Long-distance migration and strong reproductive ability form the biological basis of its rapid population expansion, but the relationship between the flight and reproduction of FAW has not been studied in depth.  Here, an empirical assessment of this relationship in an invasive FAW population in China found that 1–3-day-old adults which had undergone 10-h tethered flights had a significantly shorter pre-oviposition period and greater oviposition synchronization, but did not show any differences in fecundity, oviposition period, mating percentage or other reproductive variables.  Further studies on moths after 1.25–15-h tethered flights indicated that the reproductive process of adults could be fully triggered by flight activity longer than 2.5 h.  Dissection of the reproductive organs also showed that tethered flight promoted ovarian and testicular development of FAW.  These results show that appropriate moth flight activity significantly speeds up the reproductive process of FAW, which increases our knowledge on its migratory biology in relation to regional outbreaks.
    Section 3: Biological and ecological characteristics
    Larval diet affects development and reproduction of East Asian strain of the fall armyworm, Spodoptera frugiperda
    HE Li-mei, WANG Teng-li, CHEN Yu-chao, GE Shi-shuai, Kris A. G. WYCKHUYS, WU Kong-ming
    2021, 20(3): 736-744.  DOI: 10.1016/S2095-3119(19)62879-0
    Abstract ( )   PDF in ScienceDirect  
    In December 11, 2018, the fall armyworm (FAW), Spodoptera frugiperda invaded China and has since impacted local maize, sorghum and other crops.  Here, we draw on laboratory experiments to show how different host crops (i.e., maize, sorghum, wheat and rice) and artificial diet affect larval growth and adult reproduction of one local FAW strain.  Larval diet affected development duration, pupation rate, survival and emergence rate of pupae, and S. frugiperda adult fecundity.  FAW attained the slowest larval development (19.4 days) on sorghum and the fastest (14.1 days) on artificial diet, with larvae attaining 99.6% survival on the latter food item.  On rice, FAW larvae attained survival rate of 0.4% and were unable to pupate successfully.  Pupation rate and pupal survival varied substantially between artificial diet and live plantlets at different phenological stages.  Pupal weight was the highest (0.26 g) on artificial diet and the lowest (0.14 g) on sorghum, while FAW females reached the highest fecundity (699.7 eggs/female) on 2-leaf stage maize.  Egg hatching rate equaled 93.6% on 4- or 5-leaf stage maize and 36.6% on artificial diet.  FAW intrinsic rate of natural increase and the finite rate of increase varied between larval diets, reflecting how young maize leaves are the most suitable diet.  Our findings can help to refine laboratory rearing protocols, devise population forecasting models or guide the deployment of ‘area-wide’ integrated pest management (IPM) modules in FAW-invaded areas of China and other Asian countries. 
    Population life tables for the invasive fall armyworm, Spodoptera frugiperda fed on major oil crops planted in China
    HE Li-mei, WU Qiu-lin, GAO Xi-wu, WU Kong-ming
    2021, 20(3): 745-754.  DOI: 10.1016/S2095-3119(20)63274-9
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda, is a newly invasive, widespread agricultural pest in China.  Understanding the suitability of the main field crops in Chinese agricultural system as host for this polyphagous herbivore is especially important for making control strategy.  Here, after FAWs were fed three important oil-bearing crops (oilseed rape, soybean and sunflower) planted in China and resultant population parameters were compared using the age-stage, two-sex life table method, survival of larvae on soybean was significantly lower than that on oilseed rape and sunflower.  Developmental duration of larvae on soybean was also the longest (23.3 days).  The highest pupation rate was recorded on sunflower.  The highest pupal mass (0.19 g) was attained on oilseed rape, significantly higher than on the other host plants; the lowest mass was on soybean (0.15 g).  On soybean, oilseed rape and sunflower, respectively, the average generation period was 42.21, 39.10 and 40.44 d; the intrinsic rate of increase (r) was 0.0844, 0.1041 and 0.1134; the finite rate of increase (λ) was 1.0881, 1.1098 and 1.1202.  While the most suitable host plant overall was sunflower, S. frugiperda completed development and increased its population on all three host plants.  Thus, soybean, oilseed rape and sunflower were all suitable for FAW, and population monitoring and management of FAW in these crops should be increased.
    Fitness of fall armyworm, Spodoptera frugiperda to three solanaceous vegetables
    WU Li-hong, ZHOU Cao, LONG Gui-yun, YANG Xi-bin, WEI Zhi-yan, LIAO Ying-jiang, YANG Hong, HU Chao-xing
    2021, 20(3): 755-763.  DOI: 10.1016/S2095-3119(20)63476-1
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW), Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) is an important agricultural pest that invaded China in the middle of December 2018.  As a polyphagous pest, FAW is identified as a serious threat to agricultural production and food security in China.  Pepper (Capsicum annuum L.), tomato (Solanum lycopersicum Mill.) and eggplant (Solanum melongena L.) are three of dominant solanaceous vegetables of this country.  To our knowledge, the effects of these plants on the performances of FAW have not been well studied.  In this study we assessed the fitness of this pest to these three plants.  Results showed that FAW can complete its life cycle when fed with tomato and pepper, but not on eggplant.  The population parameters of FAW fed with maize (Zea mays L.) and the three solanaceous vegetables were compared using the age-stage, two-sex life table method.  Developmental duration was significantly different in the larval stage, but not in the pupae stage.  FAW fed with pepper had the longest pre-adult period (41.73 d) and the lightest pupal weight (0.1134 g); the survival rate was lower than FAW fed with tomato.  Significant differences were observed in the mean fecundity of female, with the highest (943.95 eggs) laid by FAW fed with tomato.  FAW had the shortest mean generation time (T), the highest intrinsic rate of increase (r) and finite rate of increase (λ) on maize, and the highest net reproductive rate (R0) on tomato.  Overall, FAW fitness on the three solanaceous vegetables was: tomato>pepper>eggplant.  This study provides the foundation for further assessment of FAW risk to solanaceous vegetables and for establishing
    Cold hardiness of the invasive fall armyworm, Spodoptera frugiperda in China
    ZHANG Dan-dan, ZHAO Sheng-yuan, WU Qiu-lin, LI Yu-yan, WU Kong-ming
    2021, 20(3): 764-771.  DOI: 10.1016/S2095-3119(20)63288-9
    Abstract ( )   PDF in ScienceDirect  
    Fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797), a crop pest native to tropical and subtropical regions of America, has invaded and spread into most regions in China, posing a severe threat to China’s agriculture.  The cold hardiness directly determines its geographic distribution through adapting to winter temperatures of different regions.  Here, we measured supercooling points and lethal time (LT) at low temperatures of S. frugiperda.  The supercooling points for developmental stages in increasing order were: adults (–15.05°C)<pupae (–13.25°C)<prepupae (–10.50°C)<larvae (–9.03°C).  Among eggs and 1st to 4th instar larvae, the 99% lethal time (LT99) was the highest for 4th instar larvae, with 99% of larvae dying after 18.59 d at 2°C, 58.72 d at 7°C, and 66.28 d at 13°C.  LT99 was the lowest for eggs with LT99 of 5.33 d at 2°C, 9.28 d at 7°C, and 12.97 d at 13°C.  This study provides an understanding of overwintering regions of S. frugiperda in China, which will be helpful for population forecasting and management.
    Population occurrence of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), in the winter season of China
    YANG Xian-ming, SONG Yi-fei, SUN Xiao-xu, SHEN Xiu-jing, WU Qiu-lin, ZHANG Hao-wen, ZHANG Dan-dan, ZHAO Sheng-yuan, LIANG Ge-mei, WU Kong-ming
    2021, 20(3): 772-782.  DOI: 10.1016/S2095-3119(20)63292-0
    Abstract ( )   PDF in ScienceDirect  
    Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), has become an important pest in Chinese agricultural systems since its invasion on 11 December 2018.  After its establishment, FAW months in the year-round breeding region have become the main source population migrating to other areas in China.  Field investigations were conducted in tropical and subtropical regions to improve understanding of its year-round breeding area in China.  The results showed that FAW larval density was significantly correlated with the seasonal temperature of the location surveyed.  The FAW larvae maintained a high density in the tropical area and were frequently found in sites of the south subtropical region, but were absent from the north subtropical region and the northern part of the central subtropical region.  These results indicated that FAW can reproduce annually in the tropical and south subtropical regions of China, including Hainan, Taiwan and the southern area of Fujian, Guangdong, Guangxi, Guizhou, and Yunnan.  Hence, great effort should be made to monitor and control FAW in the year-round breeding region to suppress the population density of this area and to reduce migration of moths into northern parts of China.  This study clarifies the occurrence area of the pest in winter in China and provides much valuable information for its population forecasting and management.
    Section 4: Integrated pest management
    Insecticide resistance monitoring for the invasive populations of fall armyworm, Spodoptera frugiperda in China
    ZHANG Dan-dan, XIAO Yu-tao, XU Peng-jun, YANG Xian-ming, WU Qiu-lin, WU Kong-ming
    2021, 20(3): 783-791.  DOI: 10.1016/S2095-3119(20)63392-5
    Abstract ( )   PDF in ScienceDirect  
    Fall armyworm has invaded China and colonized its populations in tropical and sub-tropical regions of South China since December 2018.  Chemical spray has been widely used to control the pest, which shall lead to resistance evolution.  In this research, we collected five populations of the pest from Yunnan, Hainan, Tibet, and Fujian of China, and tested their susceptibilities to pyrethroid, organophosphorus, oxadiazine, diamide, antibiotics and other types of insecticides (14 insecticides totally) in the laboratory.  Based on the susceptible baseline published from the previous studies, the resistance ratio was 615–1 068-fold to chlorpyrifos, 60–388-fold to spinosad, 26–317-fold to lambda-cyhalothrin, 13–29-fold to malathion, 9–33-fold to fenvalerate, 8–20-fold to deltamethrin, 3–8-fold to emamectin benzoate and 1–2-fold to chlorantraniliprole, respectively.  The median lethal concentration (LC50) of other six insecticides without the susceptible baselines was 148.27–220.96 µg mL–1 for beta-cypermethrin, 87.03–128.43 µg mL–1 for chlorfenapyr, 16.35–99.67 µg mL–1 for indoxacarb, 10.55–51.01 µg mL–1 for phoxim, 7.08–8.78 µg mL–1 for M-EBI (the mixed insecticide of emamectin benzoate and indoxcarb) and 1.49–4.64 µg mL–1 for cyantraniliprole.  This study can be helpful for chemical control as well as for resistance monitoring and management of the pest in China.
    Expression profiles of Cry1Ab protein and its insecticidal efficacy against the invasive fall armyworm for Chinese domestic GM maize DBN9936
    LIANG Jin-gang, ZHANG Dan-dan, LI Dong-yang, ZHAO Sheng-yuan, WANG Chen-yao, XIAO Yu-tao, XU Dong, YANG Yi-zhong, LI Guo-ping, WANG Li-li, GAO Yu, YANG Xue-qing, YUAN Hai-bin, LIU Jian, ZHANG Xiu-jie, WU Kong-ming
    2021, 20(3): 792-803.  DOI: 10.1016/S2095-3119(20)63475-X
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm (FAW) Spodoptera frugiperda, which originated in the Americas, is advancing across China and threatening the nation’s maize crops.  Currently, one widely used tool for its control is genetically modified (GM) Bacillus thuringiensis (Bt) maize.  Sufficient content of Bt protein in appropriate plant parts is crucial for enhancing resistance against insect pests.  In this study, we conducted a systematic investigation of Cry1Ab levels in Chinese domestic GM maize DBN9936, which has recently obtained a biosafety certificate, and evaluated its efficacy against FAW.  Quantification of expression levels of Cry1Ab, via ELISA, indicated a spatio-temporal dynamic, with significant variation of mean Cry1Ab, ranging from 0.76 to 8.48 μg g–1 FW with the Cry1Ab protein level ranked as: V6–V8 leaf>R1 leaf>R4 leaf>R1 silk>VT tassel>R4 kernel.  Among the nine locations, the Cry1Ab levels in DBN9936 of the Xinxiang, Langfang, and Harbin fields were significantly lower than those from Wuhan and Shenyang, and were slightly, but not significantly lower than those from the other four fields.  Furthermore, the artificial diet–Cry1Ab mixture and plant tissue feeding bioassays revealed that DBN9936 has high efficacy against FAW.  The insecticidal efficacy of different tissues against FAW larvae reached 34–100% with a descending order of lethality as follows: VT leaf>R4 leaf>R1 husk>R1 silk>VT tassel>R4 kernel.  Taken together, our results showed that Bt-Cry1Ab maize DBN9936 has potential as a promising strategy to manage FAW.
    Ovipositional responses of Spodoptera frugiperda on host plants provide a basis for using Bt-transgenic maize as trap crop in China
    HE Li-mei, ZHAO Sheng-yuan, GAO Xi-wu, WU Kong-ming
    2021, 20(3): 804-814.  DOI: 10.1016/S2095-3119(20)63334-2
    Abstract ( )   PDF in ScienceDirect  
    Spodoptera frugiperda, the pest fall armyworm (FAW), is widespread in more than 100 countries.  To date, planting insect-resistant transgenic crops is one of the main control methods in its native countries.  In this study we evaluated Bt-transgenic maize (Bt maize) and non-transgenic (conventional) maize and six other host plants in greenhouse pot experiments and field trials for oviposition preference by the Chinese populations of FAW.  In laboratory trials, female moths preferred to oviposit on maize with no significant preference between conventional and Bt maize.  However, after conventional and transgenic maize were exposed to FAW larvae and damaged, oviposition was significantly higher on transgenic maize than on the conventional one.  Field trials showed that for plants less damaged at an early stage (seedling stage), oviposition of FAW on transgenic and conventional maize was significantly higher than that on wheat, sorghum, foxtail millet, peanut and soybean while showing no significant difference between transgenic or conventional maize.  FAW adults mainly laid eggs on Bt maize, while the larval density and leaf damage rating or percentage of damaged plants were significantly lower than on conventional maize.  Larval density and its damage on conventional maize were significantly higher than that on Bt maize and the other five hosts.  Thus, maize is a highly preferred and suitable host for S. frugiperda feeding and ovipositing, and Bt maize can be used as trap crop to protect other crops.
    Genome editing of the SfABCC2 gene confers resistance to Cry1F toxin from Bacillus thuringiensis in Spodoptera frugiperda
    JIN Ming-hui, TAO Jia-hui, LI Qi, CHENG Ying, SUN Xiao-xu, WU Kong-ming, XIAO Yu-tao
    2021, 20(3): 815-820.  DOI: 10.1016/S2095-3119(19)62772-3
    Abstract ( )   PDF in ScienceDirect  
    ATP-binding cassette transporter C2 (ABCC2) is known to be a receptor for Bacillus thuringiensis (Bt) toxins in several lepidopteran insects.  Mutations in the ABCC2 gene have been genetically linked to field-evolved resistance to the Cry1F toxin from Bt in Spodoptera frugiperda.  Here we generated a SfABCC2 knockout strain of S. frugiperda using the CRISPR/Cas9 system to provide further functional evidence of the role of this gene in susceptibility and resistance to Cry1F.  Results from bioassays showed that the SfABCC2 knockout S. frugiperda strain displayed 118-fold resistance to Cry1F compared with the parental DH19 strain, but no resistance to Vip3A toxin from Bt.  These results provide the first reverse genetic evidence for SfABCC2 as a functional receptor for Cry1F.
    Analysis of phototactic responses in Spodoptera frugiperda using Helicoverpa armigera as control
    LIU Ying-jie, ZHANG Dan-dan, YANG Li-yu, DONG Yong-hao, LIANG Ge-mei, Philip DONKERSLEY, REN Guang-wei, XU Peng-jun, WU Kong-ming
    2021, 20(3): 821-828.  DOI: 10.1016/S2095-3119(19)62863-7
    Abstract ( )   PDF in ScienceDirect  
    Light traps are widely utilized to monitor and manage insect pest populations.  In late 2018, the fall armyworm (FAW), Spodoptera frugiperda, invaded China through Yunnan Province representing a huge threat to grain production.  To estimate the efficiency of light traps on FAW moths, we first identified the opsin genes from FAW by using the transcriptome.  Phylogenetic analysis indicated that the four opsins of FAW were clustered with those of other Noctuidae species.  The expressed levels of opsins in S. frugiperda were lower than in Helicoverpa armigera, suggesting a different phototactic response between the two species.  Then, we determined the phototactic behavior of FAW using H. armigera as a control, which is widely monitored and managed using light traps in China.  Our results indicated that the two moths species showed significantly different phototactic behavior and both female and male FAW displayed faster flight-to-light speed than H. armigera.  This may be due to a faster flight capacity in FAW compared to H. armigera.  However, the capture rate of both female and male of S. frugiperda was significantly lower than that of H. armigera, which was consistent with the expression levels of opsins.  These results support the positive phototaxis of S. frugiperda moths and suggest light traps could be used for monitoring and managing the pests, but with a lower efficiency than H. armigera.
    Two-way predation between immature stages of the hoverfly Eupeodes corollae and the invasive fall armyworm (Spodoptera frugiperda J. E. Smith)
    LI Hui, JIANG Shan-shan, ZHANG Hao-wen, GENG Ting, Kris A. G. WYCKHUYS, WU Kong-ming
    2021, 20(3): 829-839.  DOI: 10.1016/S2095-3119(20)63291-9
    Abstract ( )   PDF in ScienceDirect  
    Since its 2018 invasion of eastern Asia, the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) has become a key pest in local maize production.  Though pesticides have been widely used to mitigate the initial S. frugiperda attack, biological control is receiving ample attention as a desirable, environmentally-sound alternative to chemical control.  Hoverflies (Diptera: Syrphidae) are abundant natural enemies in Chinese maize fields and have been observed to consume S. frugiperda larvae.  In this study, we use laboratory assays to study the two-way interaction between immature stages of S. frugiperda and the endemic syrphid Eupeodes corollae.  To mimic natural conditions, assays were performed in the presence of fresh maize leaves.  Those 2nd or 3rd instar larvae of E. corollae preyed on 1st and 2nd instar S. frugiperda larvae with a Holling type III response, consuming a respective theoretical maximum of 43.48 and 83.33 larvae over a 24-h period.  Conversely, once S. frugiperda larvae reached 3rd instar, they exhibited aggressive behavior and equally preyed on syrphid larvae with a Holling type III response.  Those 5th and 6th instar larvae of S. frugiperda consumed a respective 16.39–19.23, 6.02–19.61 and 6.76–8.26 of 1st, 2nd and 3rd instar E. corollae larvae per day.  Though our results await field-level validation, S. frugiperda agonistic (i.e., defensive) and consumptive behavior towards resident natural enemies such as E. corollae possibly degrades biotic resistance and raises its invasion potential.  Our findings shine new light on the interaction between lepidopteran herbivores and their natural enemies, and can help advance the development of conservation biological control and other integrated pest management (IPM) strategies against S. frugiperda in China and abroad.  
    Susceptibility and tissue specificity of Spodoptera frugiperda to Junonia coenia densovirus
    CHEN Zu-wen, YANG Yan-chao, ZHANG Jian-feng, JIN Ming-hui, XIAO Yu-tao, XIA Zhi-chao, LIU Yuan-yuan, YU Sai-zhen, YANG Yong-bo, WANG Yuan, LI Yi, LIU Kai-yu
    2021, 20(3): 840-849.  DOI: 10.1016/S2095-3119(20)63163-X
    Abstract ( )   PDF in ScienceDirect  
    The fall armyworm, Spodoptera frugiperda, which destroys many economic crops such as rice and maize, has recently invaded China.  Insect viruses as biological control agents play important roles in killing pests.  One potential viral insecticide is the environmentally highly infective and virulent densovirus.  We successfully rescued Junonia coenia densovirus (JcDV) using its infectious clone in different insect cell lines and larvae of three insect species.  Results showed that the lysate of cultured insect cells transfected by the JcDV infectious clone killed the 2nd instar S. frugiperda.  The LD50 of homogenate from JcDV-infected Spodoptera litura to the 2nd instar S. frugiperda (1.76×108 viral genome copies per larva during 10 d post infection) was higher than that of the 2nd instar S. litura (7.39×107 JcDV genome copies) or Helicoverpa armigera larvae (9.71×107 JcDV genome copies).  The LT50 of the S. litura homogenate (2.60×109 viral genome copies each larva) to the 2nd instar S. frugiperda was 6.96 d, longer than that of the S. litura (6.18 d) or the 2nd instar H. armigera (5.94 d).  JcDV could infect the fat body of H. armigera, but not S. frugiperda or S. litura.  Although JcDV can infect all three lepidopteran species, their susceptibility to the virus differs.  JcDV has great potential as a biological control agent against pests such as S. frugiperda.