Analysis on the migration of first-generation Mythimna separata (Walker) in China in 2013

Mythimna separata (Walker) is an important pest which can cause serious damages to cereal crops. In the past two decades, several heavy outbreaks have taken place in northern China. In order to develop a fine-scale method of forecasting outbreaks, population data were collected in northern China using searchlight traps and ground light traps. A background weather pattern analysis and trajectory analysis were performed via the Weather Research and Forecast (WRF) and FLEXPART models. Our results showed that heavy migration of first-generation M. separata appeared in northern China in 2013. In Yanqing District, Beijing, the cumulative number of captured adults in searchlight traps was around 250 000 and the daily maximum for trapped moths was 86 000. During the peak period, the majority of M. separata moths arrived after 00:00 every night. The sex ratio (female:male) at each monitoring site was greater than 1 and greatly fluctuated with population dynamics. During the migration peak, prevailing downdraft winds benefited M. separata moths to land passively. Trajectory simulation showed that immigrants were from Anhui, Jiangsu and Hubei provinces and most of them could continue to fly into the northeastern regions of China. These results provide technical support for fine-scale forecasting of the outbreak of M. separata at meso- and micro-scale.     

性诱导和黑光灯在甜菜夜蛾和斜纹夜蛾测报上的应用效果比较

在大葱田设置甜菜夜蛾、斜纹夜蛾性诱剂进行成虫诱测,并与黑光灯诱测进行比较。结果表明：性诱剂下的诱测效果明显好于黑光灯,诱蛾总量是黑光灯的5．39～96．71倍,且峰次突出,有蛾天数多,能有效提高两虫监测和预报的准确性。     

Effect of a near-zero magnetic field on development and flight of oriental armyworm(Mythimna separata)

The geomagnetic field affects all living organisms on the Earth. In this study we investigated the developmental and behavioral effects of rearing Mythimna separata in a near-zero magnetic field(500 n T) compared to the local geomagnetic field(approximately 50 μT). The near-zero magnetic field produced by a Helmholtz coil system significantly lengthened larval and pupal development durations, increased male longevity, and reduced pupal weight, female reproduction, and the relative expression level of the vitellogenin(Vg) gene in newly emerged females. Moreover, the near-zero magnetic field had a considerable negative effect on the mating ratio of M. separata adults. In addition, the moths in the near-zero magnetic field displayed less flight activity late in the night than those in the Earth's normal geomagnetic field, indicating that the flight rhythm of M. separata may be affected by the near-zero magnetic field. Reduction in magnetic field intensity may have negative effects on the development and flight of oriental armyworm, with consequent additional effects on its migration.     

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.     

性信息素诱杀防治甜菜夜蛾的技术效应

采用不同密度性诱盆处理与常规化学防治处理的对比试验方法,综合评估性信息素防治甜菜夜蛾的作用和效应.结果显示:性诱盆放置密度直接影响诱获雄蛾的频次与平均日单盆诱蛾量,低密度处理(1 hm2放置3个性诱盆)与高密度处理(1 hm2放置15个性诱盆)诱获雄蛾频次分别为71.22%与48.50%;平均日单盆诱蛾量在3头以上和3头以下的天数,低密度处理分别为29 d和38 d,分别占总诱蛾日的43.30%和56.70%,而高密度处理平均分别为7 d和60 d,分别占总诱蛾日的10.50%与89.50%;按单位面积诱捕雄蛾量计算,高密度处理雄蛾诱杀效果较低密度处理提高93.90%;在甜菜夜蛾主害代以1 hm2放置15个性诱盆的密度进行性诱防治,性诱防治区累计诱捕雄蛾874头,对幼虫的控制效果与常规化学防治相当.表明,应用昆虫性信息素诱杀防治主害代甜菜夜蛾可作为减少化学农药的无公害防治手段列入甜菜夜蛾综合防治体系中.     

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.     

新型甜菜夜蛾诱捕器的设计与田间试验效果分析

根据甜菜夜蛾成虫飞行的生物学行为，设计出了一种结构合理、使用方便的实用新型诱捕器。在田间进行诱蛾试验，结果表明，该种诱捕器诱虫效果（平均总诱蛾量为171．5头）高于常用的水盆诱捕器（平均总诱蛾量为108．5头）和美国的Unitrap诱捕器（平均总诱蛾量为140头）。在使用过程中，操作简单、在能保证诱芯的充分散发的同时，能避免阳光直射和雨水直接冲刷诱芯。该种诱捕器几乎不受田间环境的限制，可常年使用。     

粘虫不同迁飞世代雄蛾对性诱反应的田间观察

本试验对田间两个不同迁飞世代粘虫成虫的性诱反应作了观察,并且同其对糖醋液的趋性进行了比较。结果表明:迁入代雄蛾对性诱剂反应强烈,迁出代雄蛾对性诱剂基本上不反应。这种现象与迁入迁出世代中雌蛾在生殖滞育上存在显著差别相对应。因此,本文提出粘虫雄蛾存在类似于雌蛾的“生殖滞育”的可能性,并指出雄性“生殖滞育”对了解迁飞机理的意义。     

利用RNAi技术沉默东方粘虫V-ATP酶H亚基研究

昆虫V-ATP酶(vacular-type ATPase)是以ATP为能量跨膜转运H+的质子泵,对其亚基进行干扰都会影响ATPase的活性,进而影响昆虫的生理生化指标。本研究利用特异性引物通过RT-PCR法扩增东方粘虫(Mythimna separata)V-ATPase H亚基的2个片段,合成相应dsRNA,通过显微注射导入3龄粘虫体内,观察试虫表型及存活情况,RT-PCR检测试虫体内H亚基的表达。结果表明,注射粘虫V-ATPase H亚基的dsRNA能够显著降低粘虫中肠V-ATPase H亚基的表达水平,直至导致目的基因沉默和粘虫死亡。本项研究成功实现东方粘虫体内V-ATPase H亚基基因沉默。     

Effect of three insect-resistant maizes expressing Cry1Ie,Cry1Ab/Cry2Aj and Cry1Ab on the growth and development of armyworm Mythimna separata(Walker)

Three transgenic maize events(IE09 S034, Shuangkang 12–5 and C0030.3.5) produced Cry1 Ie, Cry1 Ab/Cry2 Aj and G10-EPSPS, Cry1 Ab and EPSPS, respectively, all of which target the Asian corn borer. The oriental armyworm Mythimna separata(Walker) is the secondary target. In this study, the effects of the three Bt maizes on the development and survival of armyworm were studied. The results showed that IE09 S034 had insecticidal activity against 1 st instar larvae, and the survival rate of armyworm fed with Bt maize for 10 days was 46.2%, significantly lower than that of the control. The larvae at 3 rd–6 th instar were more tolerant of the Bt toxin than the early instar larvae. However, Shuangkang 12-5 had good insecticidal activity against 1 st–5 th instar larvae. The mortality was nearly 100% when the larvae were fed with Shuangkang 12-5 before 3 rd instar, and the toxin had quick-acting efficacy. This event significantly inhibited the development of armyworm; that is, the larval duration of the 3 rd and 4 th instar larvae fed with Shuangkang 12-5 was prolonged by 4.5 and 3.0 days, respectively. The pupal weight and egg number were also significantly lower than those of the control. For C0030.3.5, it could control 1 st–5 th instar larvae effectively. The mortality rates were all over 50% if 1 st–3 rd larvae were fed with this event. The pupal weight of 4 th–6 th instar larvae fed with Bt maize were only 53.9, 56.8 and 54.6%, respectively, compared to that of the control. The number of eggs laid was significantly less than the control. The results indicate that all three transgenic maize events exhibit the potential to provide effective control of early instar larvae of armyworm, which can be commercialized in future to control lepidoptera pests such as Asian corn borer and armyworm.     

黏虫蜜源植物花蜜中游离氨基酸的测定与分析

为探讨黏虫成虫与迁飞中转地蜜源植物的营养关系,利用氨基酸分析仪测定了其蜜源植物油菜和紫云英花蜜中游离氨基酸的种类和含量。结果显示,油菜和紫云英花蜜中都含17种氨基酸,油菜花蜜中游离氨基酸的总含量是紫云英花蜜的2.47倍。紫云英花蜜与油菜花蜜中各游离氨基酸的含量不同。油菜花蜜中除胱氨酸、蛋氨酸、苯丙氨酸、赖氨酸、精氨酸外,其他游离氨基酸的含量均比紫云英花蜜中相应的氨基酸高,其中丙氨酸、酪氨酸、丝氨酸、甘氨酸、天冬氨酸的含量分别是紫云英花蜜的14.36倍、11.35倍、5.70倍、4.69倍、4.11倍。研究还发现,紫云英蜂蜜中氨基酸总量是紫云英花蜜中氨基酸总量的4.29倍,油菜花蜜比油菜蜂蜜多含了胱氨酸和亮氨酸。因此,不能用油菜蜂蜜、紫云英蜂蜜代替油菜花蜜、紫云英花蜜来研究紫云英和油菜花蜜对黏虫的营养效应。     

黏虫蜜源植物花蜜比较特征时空稳定性的初步研究

紫云英和油菜是黏虫春季迁飞路径上的常见蜜源植物,已发现河南省罗山县中午和下午紫云英花蜜糖含量和单花泌蜜量均低于油菜,确定2种蜜源植物花蜜这些比较特征的稳定性是揭示紫云英更适合黏虫的基础。为此,采集并测定了江西婺源紫云英和油菜花蜜糖含量、单花泌蜜量。结果表明:在江西婺源,盛花期油菜中午及下午的花蜜糖含量(分别为53.77%、40.93%)显著高于同时间的紫云英(分别为35.17%、31.50%)(P<0.05),而在早上两者的花蜜糖含量相近;盛花期油菜单花泌蜜量在早上、中午及下午均为同时间紫云英单花泌蜜量的10倍以上。这些结果与河南省罗山县的花蜜特征具有部分相似性,即盛花期紫云英中午及下午的花蜜糖含量、单花泌蜜量均显著低于同时间油菜的花蜜糖含量、单花泌蜜量(P<0.05),初步说明紫云英和油菜花蜜单花泌蜜量和糖含量的比较特征具有一定的时空稳定性。     

Optimization of the sex pheromone-based method for trapping field populations of Phthorimaea operculella(Zeller) in South China

Despite the identification of the potato tuber moth Phthorimaea operculella(Zeller) sex pheromone, no effective application based on this pheromone has yet been developed and evaluated. This study investigated the effect of pheromone lures, trap densities, heights of trap deployment, and pheromone doses in Yunnan, China, for the purpose of increasing the control efficiency of P. operculella and improving the application of pheromone technology in the field. The results showed that lures made of corn oil and red PVC pipes attracted the highest number of moths(11.73±1.90 per trap per day). Sex pheromone loading of 100 μg was optimal for trapping moths, but higher doses of pheromone inhibited attraction. The density of traps did not affect capture rates; therefore, the optimum trap density was 30–40 traps ha~(–1). The optimum height of trap deployment was not above the height of the plant canopy. This study provides technical details necessary for the monitoring and control of potato tuber moth using sex pheromones.     

Mutagenesis of odorant coreceptor Orco reveals the distinct role of olfaction between sexes in Spodoptera frugiperda

Odorant receptor (OR) is crucial for insects to detect and recognize external chemical cues closely related to their survival. The insect OR forms a heteromeric complex composed of a ligand-specific receptor and a ubiquitously odorant receptor coreceptor (Orco). This study used the CRISPR/Cas9 technique to knock out (KO) Orco and reveal its essential role in acting on OR-meditated olfactory behavior in a critical invasive agricultural pest, the fall armyworm (FAW), Spodoptera frugiperda. Electroantennogram (EAG) results suggested that the Orco mutants of both male and female moths severely reduced their electrophysiological responses to the eight tested plant volatiles and two sex pheromones. However, the Orco gene played distinct roles in mating behavior between sexes: the mating behavior was fully disrupted in mutated males but not in mutated females. The oviposition result indicated that the Orco KO females displayed reduced egg laying by 24.1% compared with the mated wild type (WT) females. Overall, these results strongly suggest that Orco is an excellent target for disrupting FAW’s normal behavior and provides a feasible pest control approach.     

Insecticide resistance of the field populations of oriental armyworm,Mythimna separata (Walker) in Shaanxi and Shanxi provinces of China

Resistance of five field populations of Mythimna separata(Walker) collected from Shaanxi and Shanxi provinces of China to six different insecticides was evaluated by leaf dip method in the laboratory. The results showed that all populations were relatively sensitive to emamectin benzoate with a resistance ratio(RR) of 0.583–1.583 folds. All populations showed susceptible or low level resistance to chlorantraniliprole and beta-cypermethrin. Compared with a relatively susceptible strain of M. separata, the resistance level of the whole populations ranged from susceptible to moderate to chlorpyrifos and lambda-cyhalothrin, moderate to high to phoxim(RR=19.367–70.100) except for population from Sanyuan County(RR=2.567). Pair-wise correlation analysis among different insecticides indicated that chlorpyrifos has a significantly positive and significant correlation with emamectin benzoate. Chlorantraniliprole didn't have significant correlation with emamectin benzoate, chlorpyrifos and phoxim. Therefore, emamectin benzoate, chlorantraniliprole and beta-cypermethrin are recommended to control oriental armyworm. Meanwhile, to postpone the occurrence and development of insecticide resistance in Shaanxi and Shanxi provinces, alternative and rotational application of insecticides between chlorantraniliprole and emamectin benzoate or chlorpyrifos is necessary.     

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.     

湘西野生蜜粉源植物资源的研究

经调查研究:湘西地区野生蜜粉源植物共有64科、162属、273种。其中主要野生蜜粉源植物24科、34属、36种;辅助蜜粉源植物47科、132属、217种;有毒蜜粉源植物12科、17属、20种。介绍了湘西地区36种主要野生蜜粉源植物、55种辅助蜜粉源植物、8种有毒蜜粉源植物的分布,最后提出了开发利用和保护的具体措施。     

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.