Possible source and migration pathway for early-summer immigrants of the oriental armyworm, Mythimna separata, arriving in northern Japan

The first generation of the oriental armyworm, Mythimna separata(Walker), arrives every year in northern Japan in mainly late May to early June. Analyses of weather maps suggested that this moth’s immigration source could be eastern China, but the accuracy of those analyses was very limited due to the lack of a current standard trajectory analysis. The management of migratory insect pests such as M. separata benefits from the identification of the migration source(s)and pathway(s) of the pests. The present study provides a trajectory analysis for M. separata. Backward trajectories from trap sites in northern Japan were calculated with the HYSPLIT System developed by the U.S. National Oceanic and Atmospheric Administration, taking the flight speed of M. separata and the limitation of low ambient temperature at flight height into account. The ending times of the moth’s short and long trajectories were set at dusk on the day before and two days before the possible arrival date, respectively. The results suggested two types of possible migration pathway: a multi-step pathway from Northeast China, the Korean Peninsula, and eastern Russia, which are destination areas of the first-generation’s migration, and a direct pathway from seasonal main emigration areas in eastern China such as Jiangsu and Shandong provinces. These findings contribute to our understanding of the migration ecology of M. separata and can be used for the development of methods to predict the migration of this insect.

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.

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.

Research on the invasive pest of fall armyworm(Spodoptera frugiperda)in China

The fall armyworm(Spodoptera frugiperda)is a major agricultural pest native to the Americas.It is widely distributed throughout the Western Hemisphere.It damages crops such as maize,wheat,rice,sorghum,cotton,herbage and various weeds,and reportedly feeds on more than 300 species(Montezano et al.2018).Fall army wo rm is a typical lepidoptera pest and goes through four life stages:egg,larva,pupa and adult Adults can lay eggs between 1000 and 2000 and complete a life cycle within about 30 days,reproducing at a fast speed.There are two biotypes of fall armyworm:Corn-biotype(C-strain)and Rice-biotype(R-strain).

Expression profiles of Cry1Ab protein and its insecticidal efficacy against the invasive fall armyworm for Chinese domestic GM maize DBN9936

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 Cry1 Ab 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 Cry1 Ab,via ELISA,indicated a spatio-temporal dynamic,with significant variation of mean Cry1 Ab,ranging from 0.76 to 8.48μg g-1 FW with the Cry1 Ab protein level ranked as:V6-V8 leaf>R1 leaf>R4 leaf>R1 silk>VT tassel>R4 kernel.Among the nine locations,the Cry1 Ab 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-Cry1 Ab 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-Cry1 Ab maize DBN9936 has potential as a promising strategy to manage FAW.

Effects of alternating temperatures on development and reproduction of the armyworm,Mythimna separata (Walker)

Effects of cycling and constant temperature on development and reproduction of the armyworm, Mythimna separata (Walker) were investigated by rearing the insects on the artificial diet under temperatures covering low(16-24℃ vs. 20 ℃ ), medial(20-28℃ vs. 24℃ ) and high(24-32 ℃ vs. 28 ℃) regions. In the low region, all the immature stages of the insect developed significantly faster under alternating temperatures than at corresponding constant temperatures. For the medial region, their development was little affected by variable temperatures. For the high region, developmental durations tended to be longer under cycling temperatures except egg stage.Mean fecundities of the adult moths markedly increased under cycling temperatures as compared with those at respective constant temperature in all regions.Possible reasons for effect of alternating temperatures on insect development are discussed in some details.

Performance and Enzyme Activity of Beet Armyworm Spodoptera exigua (Hübner) (Lepidoptera:Noctuidae) Under Various Nutritional Conditions

We explored the influence of the artificial diets with different protein and glucose contents on larval development,fecundity and enzyme activities of the beet armyworm Spodoptera exigua （Hübner）.Our results suggested that development,fecundity and population growth index of beet armyworm increased with increased nutritional content in the artificial diets;however,when the yeast to cellulose content ratio reached 46.8：53.2,the fecundity and population growth had reached a maximum and additional protein did not yield additional growth.Additionally,3rd instar beet armyworm larvae fed on different artificial diets had increased enzymatic activities of acetylcholinesterase （AChE） with the increased nutritional content,but carboxylesterase （CarE） activities did not significantly change under variation in the nutritional content.

Effect of three insect-resistant maizes expressing Cry1le,Cry1Ab/Cry2Aj and Cry1Ab on the growth and development of armyworm Mythimna separata(Walker)

Three transgenic maize events(IE09S034,Shuangkang 12--5 and C0030.3.5)produced Cry1le,Cry1Ab/Cry2Aj and G10-EPSPS,Cry1Ab 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 IE09S034 had insecticidal activity against 1st instar larvae,and the survival rate of armyworm fed with Bt maize for 10 days was 462%,significantly lower than that of the control.The larvae at 3rd--6th instar were more tolerant of the Bt toxin than the early instar larvae.However,Shuangkang 12-5 had good insecticidal activity against 1st-5th instar larvae.The mortality was nearly 100%when the larvae were fed with Shuangkang 12-5 before 3rd instar,and the toxin had quick acting eficacy.This event significantly ihibited the development of armyworm;that is,the larval duration of the 3rd and 4th 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 1st--5th instar larvae effectively.The mortality rates were all over 50%if 1st-3rd larvae were fed with this event.The pupal weight of 4th-6th 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.

Effects of Tebufenozide on the Biological Characteristics of Beet Armyworm (Spodoptera exigua Hübner) and Its Resistance Selection

In this article, the selection of tebufenozide to beet armyworm （Spodoptera exigua Htibner） was studied by the treatments to alternative generations＇ 3rd-instar larvae with LC50 dose and to continuous generations＇ larvae with LC10 dose; the effects of tebufenozide on the biological characteristics of current and subsequent generations were examined by the treatments to 3rd-instar larvae and egg pods in different concentrations. After treatments with LC50 dose till F11, the toxicity of tebufenozide to beet armyworm had no significant change, whereas the pupation rate, pupal weight, and fecundity were reduced markedly. After treatments with LC10 dose till Fl9, the beet armyworm only developed 3.52-fold resistance, and the main biological characteristics were nearly accordant in each generation. The livability was reduced 72 h later after treatments to 3rd-instar larvae, respectively in 2.5-40 μg mL^-1, and larval duration, pupation rate, and pupal weight changed considerably with the increase in concentrations. The fecundity, larval livability, larval weight and pupal weight of subsequent generations were reduced as the dose increased over 10 μg mL^-1. The hatching rate of egg pods did not differ with that of the controls obviously after treatment in 10-300 μg mL^-1. But the larval livability, larval weight and pupal weight were reduced when eggs were exposed to 50 μg mL^-1 dose or more. The results indicated that tebufenozide had low resistance risk to the current and subsequent generations of beet armyworm even if tebufenozide had significant effects on the biological characteristics of this insect.

Regularity of population occurrence and migration in the oriental armyworm, Mythimna separata(Walker)

The oriental armyworm,Mythimna separata（Walker）（Lepidoptera：Noctuidae）,is a major migrant pest of grain in China and other Asian countries,causing huge crop production and economic losses nationwide annually.Much of the uniquely difficult aspects of managing M.separata arises from its long-distance migratory behavior.For example,direction and timing of winds from its overwintering regions in the south largely determine where and when large influxes of migrants arrive in the north to oviposit,making prediction of infestations difficult.

Perception and Level of Knowledge of the Fall Armyworm (Spodoptera frugiperda J.E. Smith) by Maize Farmers in the Southern Agricultural Zone of Niger

Maize is one of the cereals most consumed by households in Niger. Its production remains marginal despite the efforts made in hydro-agricultural development both around the Niger River and in the interior of the country. The detection of the fall armyworm (Spodoptera frugiperda J.E. Smith) in 2016 in Niger, followed by its rapid spread where in less than a year it has spread over almost the entire national territory is not without consequence on the yields of the but already very low in the main production areas. As a result, maize production is increasingly being abandoned in the southern agricultural zone of Niger. In fact, this caterpillar has become a major pest of maize because of the significant damage observed on this crop during its growth and development cycle. This situation calls for research to be conducted to help maize producers better manage this pest. The objective of this study is to assess the level of knowledge and management of FAW by maize farmers in the southern agricultural zone of Niger. A survey was conducted in July and August 2020 on a sample of 408 farmers in this zone using an individual questionnaire designed and integrated into the ODK data collection software. The results obtained showed that 93% of the producers recognize FAW through its morphology and the aspects of its damage;53.25% estimate that the attack rate is very high and 60.75% of the producers use pesticides in the management of this pest against only 1.5% who use biopesticides. These results clearly indicate the severity of FAW attacks on corn and the massive use of pesticides by producers.

云南昭通市2021年草地贪夜蛾成虫种群动态及物理防控效益分析

草地贪夜蛾(Spodoptera frugiperda)自入侵以来就对中国粮食生产安全造成巨大的威胁,明晰昭通市草地贪夜蛾种群动态、采取有效防控措施是粮食生产安全的重要保障。2021年对云南省昭通市草地贪夜蛾成虫动态进行全年定点监测,并建立防控示范区对防控方案进行对比研究。结果表明:(1)昭通市的草地贪夜蛾成虫于3月1日起开始陆续出现;出现时序由西南向东北发展;(2)草地贪夜蛾成虫发生主要集中在巧家县、鲁甸县、永善县、彝良县、昭阳区和大关县;(3)昭通市西南部巧家县和永善县4—6月为草地贪夜蛾种群数量最多时期,鲁甸县、彝良县、昭阳区8月出现大量草地贪夜蛾迁入;(4)性诱、灯诱、性诱+灯诱混合防控的物理诱控方式能够显著降低草地贪夜蛾的危害,减少玉米产量损失,其中性诱+灯诱混合防控方式效果最为显著。

Resistance of the fall armyworm,Spodoptera frugiperda,to transgenic Bacillus thuringiensis Cry1 F corn in the Americas:lessons and implications for Bt corn IRM in China

The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a major target pest of Bt crops(e.g.,corn,cotton,and soybean)in North and South America.This pest has recently invaded Africa and Asia including China and the invasion has placed a great threat to the food security in many countries of these two continents.Due to the extensive use of Bt crops,practical resistance of S.frugiperda to Cry IF corn(TC 1507)with field control problems has widely occurred in Puerto Rico,Brazil,Argentina,and the mainland United States.Analyzing data generated from decade-long studies showed that several factors might have contributed to the wide development of the resistance.These factors include(1)limited modes of action of Bt proteins used in Bt crops;(2)cross-resistance among Cryl proteins;(3)use of nonhigh dose Bt crop traits;(4)that the resistance is complete on Bt corn plants;(5)abundant in initial Cry IF resistance alleles;and(6)lack of fitness costs/recessive fitness costs of the resistance.The long-term use of Bt crop technology in the Americas suggests that Bt corn can be an effective tool for controlling S.frugiperda in China.IRM programs for Bt corn in China should be as simple as possible to be easily adopted by small-scale growers.The following aspects may be considered in its Bt corn IRM programs:(1)use of only"high dose^traits for both S.frugiperda and stalk borers;(2)developing and implementing a combined resistance monitoring program;(3)use“gene pyramiding”as a primary IRM strategy;and(4)if possible,Bt corn may not be planted in the areas where S.frugiperda overwinters.Lessons and experience gained from the global long-term use of Bt crops should have values in improving IRM programs in the Americas,as well as for a sustainable use of Bt corn technology in China.

Trajectory modeling revealed a southwest-northeast migration corridor for fall armyworm Spodoptera frugiperda(Lepidoptera:Noctuidae)emerging from the North China Plain

The fall armyworm Spodoptera frugiperda,an invasive insect pest native to the Americas,has established populations throughout eastern China.The North China Plain一a key corn-producing area in East China with a unique topography一was invaded by fall armyworm in 2019 and is seriously threatened by this migratory pest.However,the spatiotemporal extent of the migratory movements of fall armyworm from the North China Plain remains poorly understood.Using an air transport-based trajectory modeling approach that incorporates flight behavior,we simulated the potential nocturnal migration trajectories of fall armyworm from the North China Plain based on historical meteorological data from June to October of 2015-2019,and examined the night-time atmospheric conditions associated with their possible flights.The emigration patterns showed monthly variation in the main landing area and common migration direction.The displacement of newly emerged moths from the North China Plain was concentrated in the Northeast China Plain(including Liaoning,Jilin and Heilongjiang provinces)before late summer,after which they were most likely to undertake return flights to the south(especially into Hubei,Anhui and Hunan provinces).This southwest-northeast aerial migration corridor follows the topography of East China and is affected by the East Asian monsoon.These topographic-atmospheric conditions have resulted in the North China Plain becoming a key stopover for fall armyworm populations engaging in multigenerational long-distance migration across East China.These findings contribute to our knowledge of fall army-worm migration and will aid in the implementation of management and control strategies against this highly migratory agricultural pest.

Effects of DIMBOA on impulse discharges of maxillary lateral sensillum styloconicum of armyworm larvae

THE DIMBOA (2, 4-dihydroxy-7-methoxy-1, 4-benzoxazin-3-one), a secondary product present in corn plants, plays an important role in protecting the plant against the pest attack. DIMBOA is rich in seedlings of cereal crops, especially in maize. Many investigators demonstrated a linear relationship between the DIMBOA content in plant and the resistance of the plant to pest. Feng et al. (1992) summarized that the toxicity of DIMBOA is associated

Effects of neem-based insecticides on beet armyworm （Lepidoptera： Noctuidae）

Three commercial neem [Azadirachta indica A. Juss (Meliaceae)]-based insecticides, Agroneem, Ecozin, and Neemix, and a non-commercial neem leaf powder,were evaluated for oviposition deterrence, antifeedant effect on larvae, and toxicity to eggs and larvae of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae),on cotton leaves in the laboratory. Oviposition deterrence in no-choice, and two- and fivechoice assays, was observed for the neem-based insecticide treatments when compared with a non-treated control. Neem-based insecticides also deterred feeding by beet armyworm larvae. Direct contact with neem-based insecticides decreased the survival of beet armyworm eggs. Survival of beet armyworm larvae fed for 7 days on leaves treated with neembased insecticides was reduced to 27, 33, 60, and 61% for neem leaf powder, Ecozin,Agroneem, and Neemix, respectively. Possibilities for adoption of neem-based insecticides in commercial cotton for beet armyworm control are discussed.

Effect of Artificial and Corn Leaves Diets on Development, Survival and Reproduction of Spodoptera frugiperda (Lepidoptera: Noctuidae) in Sierra Leone

The use of artificial diets to mass reared insect stock under laboratory conditions, promotes knowledge about the biology, behavior, and nutritional requirements of insects;with such information being fundamental for the formulation of efficient integrated pest management programs (IPM) strategies. However, the artificial diets used for rearing Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in the laboratory in this study, do not contain wheat germ, used for routine laboratory rearing. The aim of this study was to compare food preference and consumption by S. frugiperda larvae, as well as evaluate insect developmental parameters in the standard diet and the bean-based diets under laboratory conditions. Four artificial diets were used: a standard diet based on broad beans (Phaseolus vulgaris L.) used to rear S. frugiperda (D1), a diet with the substitution of two types of beans, cowpea (Vigna unguiculata L.) (D2) and pigeon pea (Cajanus cajan L) (D3);and a diet of fresh corn leaves (D4), the host plant of the pest species. Using a multiple-choice test, we observed that the larvae preferred diets D4 followed by D1. The relative consumption rate (RCR), relative growth rate (RGR), relative metabolic rate (RMR), approximate digestibility (AD), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and the metabolic cost (CM) for S. frugiperda fifth instar larvae varied among diets. The diet D4 resulted in better ingestion, digestion, assimilation, and conversion of food, but with a metabolic cost to assimilate the food. The different bean varieties present in the diet influenced larval length, larval periods, larval survival, pupal periods, sex ratio, pupal weight, and pupal survival;but fecundity and longevity of adults were not affected. The different bean-based diets did positively influence population growth, with the most outstanding being D4. From the results of this study, the most adequate diet for rearing S. frugiperda in the laboratory is D4.

湖北省草地贪夜蛾种群分布的区域差异及其受温度条件的影响

草地贪夜蛾是近几年迁入我国的重大农作物害虫,而湖北省是该害虫每年从南向北迁飞的重要通道.为了解湖北省草地贪夜蛾的种群分布特征,选取湖北省22个县市具有代表性的点位,通过玉米田间设置的诱捕装置对草地贪夜蛾成虫发生情况进行抽样调查,获得了各样点5—10月成虫日捕获数的抽样调查数据并结合各样点的日平均温度数据进行了统计分析.结果显示:湖北省草地贪夜蛾的发生时间主要在7—10月,全年峰值出现在8月中旬至9月上旬.从空间上看,鄂东和鄂中地区草地贪夜蛾虫量较高,两区域的全年峰值时间分别是9月中旬和8月下旬,样点的日捕获虫量最高可达74头和32头以上,鄂西虫量极少,样点的日捕获虫量最高不到1头.回归分析显示:各样点的对数虫量(诱捕数量的对数)与日平均气温之间存在显著的线性关系,表明日均温对诱捕数量具有显著影响.综上,湖北省草地贪夜蛾的种群分布存在明显的区域差异,而温度条件可能是导致这种差异的一个重要的影响因素.

鲜食玉米品种心叶期对草地贪夜蛾抗性评价及不同品种受害后的产量损失

为初步探究鲜食玉米对草地贪夜蛾Spodoptera frugiperda的抗性水平,在田间草地贪夜蛾自然发生条件下对28个不同类型(甜玉米10个、甜糯玉米8个、糯玉米10个)的鲜食玉米品种进行了心叶期抗虫性鉴定,研究了不同抗性水平及不同类型鲜食玉米的产量损失;在室内研究了取食不同品种玉米苗对草地贪夜蛾幼虫发育历期的影响。经鉴定,28个品种中无高抗及抗虫品种,中抗品种12个,感虫品种15个,高感品种1个,分别占鉴定资源总数的42.86%、53.57%和3.57%。28个品种的产量损失为8.30%~40.93%,室内喂饲后幼虫的发育历期为11.29~15.31 d。不同类型鲜食玉米的叶部受害级别、产量损失和草地贪夜蛾幼虫发育历期无显著差异。甜玉米、糯玉米的叶部受害级别与产量损失呈正相关,相关系数分别为0.61和0.79,甜糯玉米的叶部受害级别与产量损失不相关。

滇西保山地区草地贪夜蛾的种群动态及其对气候因子的响应

草地贪夜蛾(Spodoptera frugiperda)是联合国粮农组织全球预警的重大农业害虫,成虫具有较强的迁飞能力.滇西保山地区是草地贪夜蛾进入我国最早的地区之一,为监测其种群动态,本研究在云南省保山隆阳区芒宽乡和施甸县旧城乡,采用主要成分为顺-9-十四碳烯乙酸酯和顺-7-十二碳烯乙酸酯的草地贪夜蛾性信息素,通过带气候仪的自动监测设备对草地贪夜蛾成虫开展为期2 a的种群监测,并分析种群动态与气候因子的相关性.结果表明,草地贪夜蛾在云南保山玉米种植区全年有发生,种群波动在芒宽乡比旧城乡大,种群活动高峰出现在3—5月.与2020年相比,2021年草地贪夜蛾种群数量明显减少,这可能与开展的防治措施有关.在草地贪夜蛾种群发生的高峰月份,种群日动态变化分析显示,旧城乡和芒宽乡诱集到虫口数量最多的时间分别为晚上21:00和凌晨3:00;草地贪夜蛾种群存在一定的时空变化规律,但2个监测地的种群发生规律存在差异.此外,草地贪夜蛾种群动态受温湿度影响,与温度和湿度分别呈三次曲线和二次曲线关系,其成虫活动的最适温度为26.21℃,最适湿度为53.0%.研究结果为草地贪夜蛾的防控提供了科学依据.