RFLP analysis of genetic variation in North American populations of the fall armyworm moth Spodoptera frugiperda (Lepidoptera: Noctuidae)

A high level of genetic variability was detected in North American fall armyworm (FA W), Spodoptera frugiperda (J. E. Smith), populations by restriction fragment length polymorphism (RFLP) analysis of genomic DNA. In nearly all cases individual larvae could be differentiated using 22 probe-enzyme combinations. Laboratory colonies formed distinct groups based on RFLP analysis. Individuals from a colony of the previously determined ‘rice strain’ formed a group showing obvious deviation in RFLP patterns from the other five populations, which included a population from a ‘com strain’ colony. The results were consistent with previous studies using allozymes which indicated that there are two genetically differentiated forms of the fall armyworm. Diagnostic markers were also found that distinguish these two groups.     

Chromosome-level genomes of two armyworms,Mythimna separata and Mythimna loreyi,provide insights into the biosynthesis and reception of sex pheromones

Mythimna separata and Mythimna loreyi are global pests of gramineous cereals, heavily controlled with synthetic insecticides. Here, we generated two high-quality chromosome-level genome assemblies for M. separata (688 Mb) and M. loreyi (683 Mb). Our analysis identified Z and W chromosomes, with few genes and abundant transposable elements (TEs) found on the W chromosome. We also observed a recent explosion of long interspersed nuclear elements (LINEs), which contributed to the larger genomes of Mythimna. The two armyworms diverged ~10.5 MYA, with only three chromosomes have intrachromosomal rearrangements. Additionally, we observed a tandem repeat expansion of α-amylase genes in Mythimna, which may promote the digestion of carbohydrates and exacerbate their damage to crops. Furthermore, we inferred the sex pheromone biosynthesis pathway for M. separata, M. loreyi and Spodoptera frugiperda. We discovered that M. loreyi and S. frugiperda synthesized the same major constituents of sex pheromones through different pathways. Specifically, the double bonds in the dominant sex pheromone components of S. frugiperda were generated by Δ9- and Δ11-desaturase, while they were generated by Δ11-desaturase and chain-shortening reactions in M. loreyi. We also identified pheromone receptor (PR) genes and inferred their corresponding components. These findings provide a better understanding of sex pheromone communication and promote the development of a new pest control strategy involving pheromone traps, which are more effective and environmentally friendly than current strategies.     

Treatment of larvae with repeated doses of precocene II induces precocious metamorphic changes in Spodoptera mauritia (Lepidoptera: Noctuidae)

In Spodoptera mauritia repeated daily treatments of larvae with 40 μg of precocene II throughout the fifth and sixth instar larval period had no effect on the larval-larval period but prolonged larval-pupal ecdysis. The resulting pupae showed precocious adult differentiation of mouth parts, wings, eyes, legs, and fat body.     

Effects of plant phenols of performance of southern armyworm larvae

Summary We evaluated the effects of two classes of phenols on performance of penultimate instar southern armyworms, Spodoptera eridania. One class consisted of phenols containing a catechol (ortho-dihydroxybenzene) moiety and included chlorogenic acid, quercetin, rutin, and rhamnetin. A second group consisted of the phenolic glycoside salicin and its derivatives salicortin and tremulacin. The compounds were painted onto lima bean (Phaseolus lunatus) leaves and fed to larvae for the duration of the fifth instar. Chlorogenic acid and rhamnetin had no deleterious effects; rutin and quercetin caused some mortality and rutin reduced growth rates by decreasing consumption and digestion efficiency. Results showed that ortho-dihydroxybenzene groups may be necessary, but are not sufficient for biological activity. Salicin did not affect larvae; salicortin and tremulacin reduced growth rates primarily by decreasing consumption. These two compounds also caused degenerative lesions in midgut tissues. The presence of a benzoyl ester group in tremulacin accentuates its toxicity, relative to that of salicortin.     

斜纹夜蛾inx1,inx4基因的克隆及表达载体构建

无脊椎动物innexin(inx)基因是生物进化上高度保守的基因,区别于脊椎动物的connexin。Inx基因可在细胞膜表面形成功能性的半通道蛋白hemichannel和间隙连接蛋白gap junction,这两种蛋白都与信号传导,胚胎发育,神经系统分化等功能相关。本研究在斜纹夜蛾Spodoptera litura血细胞转录组数据中发现特异的inx1,inx4序列,通过RT-PCR克隆出了Spli-inx1,Spli-inx4,经过比对,确定它们都属于保守的inx基因家族,具有四个保守的跨膜结构域,两个胞外环,一个胞内环,一个位于第二个跨膜结构域前端的YYQWV基序及在胞外环上各有2个半胱氨酸残基。其中,Spli-inx1开放阅读框全长1086 bp,编码361个氨基酸;Spli-inx4开放阅读框全长1116 bp,编码371个氨基酸。构建了包含ORF全长编码区的原核表达载体及真核表达载体,经Western blot证明Spli-inx1和Spli-inx4均可在大肠杆菌及鳞翅目昆虫High Five,Sf9和Spli221细胞系中的表达,初步探索了它们在细胞中的结构和功能。为深入研究Spli Inx1和Spli Inx4的功能奠定基础。     

Starvation‐induced autophagy in Spodoptera frugiperda Sf9 ovarian cells

Autophagy controls insect development and can be targeted for pest control in agriculture. In the present study, starvation‐induced autophagy is investigated in the insect species Spodoptera frugiperda. Bioinformatics analysis and a search of the EST database (http://bioweb.ensam.inra.fr/spodobase) identifies a putative ATG8 gene of S. frugiperda. To generate a biomarker of autophagosome, the DNA sequence encoding the open reading frame of this gene is amplified and cloned into a pIEX‐4‐mCherry‐EGFP‐SfATG8 recombinant vector. Sf9 cells are then transfected with this expression vector and starved in phosphate‐buffered saline solution for 4 h to induce autophagy, which is examined by LysoTracker staining (Life Technologies, Grand Island, New York), western blotting and fluorescence microscopy. The results obtained show that starvation stimulates lipidation of SfATG8‐PE and the formation of autophagosomes, providing a foundation for further research with respect to autophagy in insects.     

Updated assessment of potential biopesticide options for managing fall armyworm (Spodoptera frugiperda) in Africa

The fall armyworm (FAW, Spodoptera frugiperda) has recently spread to many countries in Africa, the Near East, Asia and the Pacific. In sub-Saharan Africa (SSA), more than 300 million people depend on FAW’s preferred host plant, maize, as a staple crop. Hence, the spread of FAW in SSA has the potential to negatively affect livelihoods and food security. Many farmers have responded to FAW by increasing their use of synthetic pesticides, but these are not always used safely or effectively. More information on sustainable alternatives to high-risk synthetic pesticides is needed to inform decisions by farmers and policy makers. In a previous paper, the authors responded to this information need by identifying fifty biopesticides which had been registered for FAW management in one or more of 30 countries in FAWs native region and Africa. For each biopesticide identified, detailed profiles with information on their efficacy against FAW; associated human health and environmental hazards; their agronomic sustainability; and whether or not they are practical for use by smallholder farmers were developed Research for development (R4D) efforts is ongoing in Africa and Asia for development and use of biopesticides for FAW management. Hence, in this study the authors assessed the current state of knowledge and documented how information gaps have been filled (or not) since the previous paper was published. The authors found that for many biopesticides there is a growing body of information on their efficacy in the field in Africa and increased availability of commercialized products. They also note remaining information gaps, particularly the compatibility of the biopesticides with other recommended management practices, and cost-benefit analyses, important for developing and implementing sustainable IPM. An updated list of priority biopesticides for research, development and promotion is provided.     

Influence of post-treatment temperature, solvents and emulsifiers on the toxicity of cypermethrin to larvae of Spodoptera litura (Fab.)

Larvae of the tobacco caterpillar, Spodoptera litura (Fab.) were topically bioassayed with cypermethrin emulsion formulation and proprietary EC in combination with different solvents and emulsifiers for their toxicity at 16 ± 2°C and 27 ± 1°C. Among different solvents, the descending order of efficacy (with relative toxicity in parenthesis) against 9 ± 1 day old larvae of S. litura (Fab.) at 16 ± 2°C than 27 ± 1°C was: xylene (7.41), aromex (5.54), cyclohexane (4.93), C-IX (3.93), benzene (2.40) and toluene (2.26). With emulsifier, the order was: Triton X-100 (7.41), SN₄S (4.60), Teepol (2.90), Tween-80 (1.49), Swascofix DP-50 (1.28), SN₄R (1.10) and S₅₂B (1.07). However, the proprietary cypermethrin EC was 2.31 times more toxic at 16 ± 2°C than at 27 ± 1°C.     

Electrophysiological response to herbivore-induced host plant volatiles in the moth Spodoptera littoralis

In cotton, Gossypium hirsutum (Malvacae), the volatiles emitted from the plant change in response to herbivory. Ovipositing females of the Egyptian cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) can discriminate between cotton plants subjected to larval feeding and undamaged plants during oviposition. In this study we investigate whether females of this moth can detect the herbivore-induced cotton volatiles. The response of female S. littoralis antennae to volatiles collected from cotton plants subjected to larval feeding was studied using GC-EAD (coupled gas chromatography electroantennographic-detection). By GC-EAD, responses to over 10 different cotton volatiles were observed. Using single sensillum technique the responses of short sensilla trichodea on the antennae of S. littoralis females to 19 cotton volatiles and 12 general plant volatiles were investigated. Responses to these volatiles were recorded from 108 receptor neurones. Several neurones activated by herbivore-induced cotton volatiles were recorded. For example, a neurone type responding to two homoterpenes [(E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene and (E)-4,8-dimethyl-1,3,7-nonatriene] and (E,E)-α-farnesene was frequently found. We also observed sensitive neurones responding specifically to the herbivore-induced volatiles (+/–)-linalool and indole. In general, a stimulus load of less than 1 ng was needed to activate these neurones. In addition, specific neurones were found for constitutive cotton volatiles released in connection with damage to the plant. An abundant neurone type responded to β-caryophyllene and α-humulene. Another neurone type responded specifically to the non-induced cotton volatile (Z)-jasmone. These results show that females of S. littoralis have receptor neurones that would make it possible to discriminate between damaged and undamaged plants using volatile signals.     

Quantification of Invasion of Two Strains of Steinernema carpocapsae (Weiser) into Three Lepidopteran Larvae

Studies with last instar larvae of the fall armyworm, Spodoptera frugiperda (J. E. Smith), the black cutworm, Agrotis ipsilon (Hufnagel), and the greater wax moth, Galleria mellonella (L.) were used to quantify the invasive ability of two strains (All and Mexican) of Steinernema carpocapsae and to determine how factors in the bioassay procedure affect both nematode invasion and host mortality. Nematode invasive ability was variable, with 10-50% of nematodes successfully infecting the host. The percentage of infectives invading the host (invasion efficiency) was positively related to increases in length of host exposure time and number of hosts per arena, negatively related to increases in substrate surface area per host, and not affected by nematode concentration. There was a direct relationship between concentration applied and the number of nematodes invading the host. Mortality was less affected than invasion efficiency by bioassay conditions and appears to be a much less sensitive index of nematode activity than invasive ability.