Fitness of fall armyworm,Spodoptera frugiperda to three solanaceous vegetables

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(R_0) on tomato. Overall, FAW fitness on the three solanaceous vegetables was: tomatopeppereggplant. This study provides the foundation for further assessment of FAW risk to solanaceous vegetables and for establishing corresponding control strategies in China.     

Larval diet affects development and reproduction of East Asian strain of the fall armyworm,Spodoptera frugiperda

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.     

Case study on the first immigration of fall armyworm,Spodoptera frugiperda invading into China

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.     

Windborne migration routes of newly-emerged fall armyworm from Qinling Mountains–Huaihe River region,China

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.     

Flight activity promotes reproductive processes in the fall armyworm,Spodoptera frugiperda

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.     

Population life tables for the invasive fall armyworm,Spodoptera frugiperda fed on major oil crops planted in China

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.     

Adult nutrition affects reproduction and flight performance of the invasive fall armyworm,Spodoptera frugiperda in China

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.     

Migration of invasive Spodoptera frugiperda(Lepidoptera: Noctuidae) across the Bohai Sea in northern China

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.     

Searchlight trapping reveals seasonal cross-ocean migration of fall armyworm over the South China Sea

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.     

蝇蛹金小蜂的交配行为及雄蜂交配次数对雌蜂繁殖的影响

多数昆虫能够进行多次交配,随寄生蜂雄蜂交配次数的增加,雄蜂体内精子减少,雌蜂获得的精子数量减少,产下更多的单倍体卵,发育为雄性后代;一些单寄生性的寄生蜂雌蜂一生仅能够交配1次。描述了蝇蛹金小蜂雌雄蜂的交配行为,探讨了雄蜂交配次数对雌蜂后代产量等的影响以及雌蜂的可交配次数。结果表明,交配过程包括求偶、交尾前期、交尾和交尾后期;雄蜂已交配的次数并不能够显著影响其配偶的寿命、产卵期和后代总数量,但显著影响到其配偶的雌、雄后代数量和性比。随雄蜂交配次数的增加,与之交配的雌蜂的后代雄性百分比显著增大,雌蜂在产卵期内更早地出现较多雄性后代,体内精子不足的现象更加明显。无论已交配的蝇蛹金小蜂雌蜂在产卵期中是否出现精子不足,均不能再次完成交配。     

Biology,invasion and management of the agricultural invader: Fall armyworm,Spodoptera frugiperda(Lepidoptera: Noctuidae)

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.     

Emergence,Mating and Oviposition Behavior of the Chinese Population in Pink Bollworm,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

The pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae) is one of the most serious lepidopteran pests of cotton in the world. This pest invaded China at the onset of the 20th century, possibly through repeated introductions from several different locations worldwide. In this paper, we describe different behavioral parameters of this Hubei P. gossypiella strain under laboratory and field conditions. Using an infra-red video recorder, we observed (nocturnal) emergence, flight and mating activities, and oviposition patterns. Moth emergence started from 13:00 and continued up till 23:00. Under laboratory and field conditions, 2-7-d-old moths initiated flight around sunset, peaked 50 min later and gradually declined until 04:00. Although mating started immediately after darkness (i.e., 20:00), mating behavior was most intense from 23:00 to 03:40. Oviposition also showed distinct time-related patterns, with approx. 70% eggs laid between 20:00 and 22:00. In the studies of the relationship between flight and oviposition, the duration of flight had an effect on oviposition. The 1-d-old moths flown for 6 and 12 h began oviposition earlier than the unflown ones, and the 6-h flight had no effect on the egg production. However, the longevity of the flown moths was shortened after flight. In addition, the peaks of oviposition for the flown moths were advanced 2–3 d. The age when the moths flied affected the oviposition of adult moths. The earlier the moths started to fly after emergence, the greater the fecundity they had. The average egg production of moths flown for 24 h was less than that of non-flown moths which were of the same age. Both flight and delay in mating could advance the oviposition peak. Our study provides detailed insights in nocturnal activities and the reproductive biology of local P. gossypiella populations, which could be employed to fine-tune current pest management programs in China.     

大灰象甲非典型气味受体基因SvelOrco的克隆及组织表达谱分析

旨在克隆大灰象甲Sympiezomias velatus的Orco基因，明确其分子特征及其组织表达谱。通过分析成虫触角转录组数据并利用RT-PCR克隆出大灰象甲Orco基因，对大灰象甲Orco蛋白进行结构分析和系统发育分析，并采用qPCR测定Orco基因在大灰象甲成虫不同组织中的表达量。克隆获得大灰象甲Orco基因并命名为SvelOrco(GenBank登录号：OM417062),其开放阅读框长1 449 bp,编码482个氨基酸。预测SvelOrco蛋白的分子质量为53.49 ku,等电点为5.66,主要由α-螺旋和无规则卷曲组成，有7个跨膜结构域。系统发育分析表明大灰象甲与云杉八齿小蠹Ips typographus亲缘关系最近。qPCR结果显示：SvelOrco主要在大灰象甲成虫触角上表达，雄虫触角表达量最高，是雌虫触角表达量的1.22倍，SvelOrco在翅部也有少量表达，在头、胸、腹和足的表达量极低。     

柑橘大实蝇非典型气味受体基因的克隆、序列分析及组织表达模式

旨在探究柑橘大实蝇(Bactrocera minax)非典型气味受体(odorant receptor co-receptor,Orco)基因的分子特征和组织表达模式,通过对前期获得的柑橘大实蝇成虫转录组数据分析,利用RT-PCR技术克隆柑橘大实蝇Orco基因,并对该基因进行生物信息学分析,采用实时荧光定量PCR技术检...     

Role of TRP channels and HSPs in thermal stress response in the aphid parasitoid Aphelinus asychis(Hymenoptera:Aphelinidae)

Aphelinus asychis is an important aphid endoparasitoid. Under field and greenhouse conditions, high temperature is one of the factors limiting the application of A. asychis for biological pest control. To explore the potential role of transient receptor potential(TRP) channels and heat shock proteins(HSPs) in this process, we identified 11 genes encoding TRP channels and nine genes encoding HSPs. Three proteins(AasyTRPA5, AasyPyrexia, AasyPainless) that belong to transient receptor potential ankyrin(TRPA) subfamily and nine HSPs are involved in the response to high temperature. We also investigated the survival of A. asychis and the response of the identified TRP channels and HSPs to high temperature. The results showed that the maximum temperature that allowed A. asychis survival was approximately 41℃; females had higher survival rates than that of the males at 40 and 41℃. Short-term heat-shock resulted in increased expression of Aasyshsp in males, and Aasyhsp40, Aasyhsp68, Aasyhsp70-4, Aasyhsp70-5 and Aasyhsp90 were upregulated and then downregulated, whereas Aasyhsp70-3 was upregulated at 41℃. Moreover, Aasyhsp40 and Aasyhsp90 showed higher expression levels in females, while Aasyshsp and Aasyhsp70-3 presented opposite expression patterns. At temperature above 35℃, expression of AasyPyrexia in females was significant higher than that in males, whereas AasyPainless and AasyTRPA5 presented higher expression in males at 40 and 41℃, respectively. Altogether, these results indicate that protection against thermal stress in A. asychis is coordinated by TRP channels and HSPs. These findings provide a basis for understanding the potential mechanism of A. asychis in response to high temperatures.     

Population occurrence of the fall armyworm,Spodoptera frugiperda(Lepidoptera: Noctuidae), in the winter season of China

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.     

重庆地区草地贪夜蛾肠道细菌的分离鉴定

为了解入侵重庆地区草地贪夜蛾(Spodoptera frugiperda)肠道所携带的细菌组成,以采集自巫溪、巫山地区玉米地里的草地贪夜蛾为材料,运用传统培养方法分离了其肠道优势细菌,并基于16S rDNA测序开展了优势菌的属水平鉴定,共获得了30个细菌分离株,经16S rDNA序列同源性分析,可归于5个属,分别为克雷伯氏菌属(Klebsiella)、不动杆菌属(Acinetobacter)、假单胞菌属(Pseudomonas)、肠杆菌属(Enterobacter)以及气单胞菌属(Aeromonas);其中,克雷伯氏菌属(Klebsiella)的丰度最高,占所有分离菌株的63%;假单胞属(Pseudomonas)和肠杆菌属(Enterobacter)菌株仅在巫山地区分离得到,气单胞菌属(Aeromonas)仅在巫溪地区分离得到.实验确定了入侵重庆地区草地贪夜蛾肠道优势细菌的种类及丰度,为后续研究草地贪夜蛾肠道微生物对宿主的生长发育以及迁飞等重要问题奠定了基础.