Pseudaletia Unipuncta Research Articles

Maize Pest and Natural Enemies in the North-West of Türkiye

Maize Pest and Natural Enemies in the North-West of Türkiye ABSTRACT Maize is one of the most significant cereal crops in the world, and insect pests cause the highest economic loss. The objective of this study was to assess the level of insect pests and natural enemies during 2020 and 2022 in the maize fields of Düzce and Sakarya, Türkiye. We performed weekly surveys from the vegetative growth stage of maize to harvest from April through November. A hundred plants were selected with regular and irregular samplings from each field. In the maize fields, a total of 13 pest species from six families in four orders, along with 19 natural enemies from eight families in five orders, were identified. Ostrinia nubilalis Hbn. (Lepidoptera: Crambidae) was found as the primary pest, followed by Helicoverpa armigera Hbn. and Mythimna unipuncta Haw. (Lepidoptera: Noctuidae). Meteorus pendulus Müller (Hymenoptera: Braconidae) was a new record for the East Marmara and Western Black Sea regions, as well as a new host record in Türkiye. Larval parasitoids of M. unipuncta, Nemoraea pellucida Meigen and Pales pavida Meigen (Diptera: Tachinidae) represent new host records for Türkiye. Among the predators, Orius minutus L. (Hemiptera: Anthocoridae) and coccinellids showed an especially notable common in the maize fields of both provinces. Ketwords: Maize, pests, natural enemies, pest status

Rodent Gut Bacteria Coexisting with an Insect Gut Virus in Tapeworm Parasitic Cysts: Metagenomic Evidence of Microbial Selection in Extra-Intestinal Clinical Niches.

In medicine, parasitic cysts (e.g., brain cysticerci) are believed to be sterile, and are primarily treated with antiparasitic medications, not antibiotics, which could prevent abscess formation and localized inflammation. This study quantified the microbial composition of parasitic cysts in a wild rodent, using multi-kingdom metagenomics to comprehensively assess if parasitic cysts are sterile, and further understand gut microbial translocation and adaptation in wildlife confined environments, outside the gut. Analysis was conducted on DNA from two hepatic parasitic cysts from a feline tapeworm, Hydatigera (Taenia) taeniaeformis, affecting a wild vole mouse (Microtus pennsylvanicus), and from feces, liver and peritoneal fluid of this and two other concurrent individual wild voles trapped during pest control in one of our university research vegetable gardens. Bacterial metagenomics revealed the presence of gut commensal/opportunistic species, Parabacteroides distasonis, Bacteroides (Bacteroidota); Klebsiella variicola, E. coli (Enterobacteriaceae); Enterococcus faecium and Lactobacillus acidophilus (Bacillota) inhabiting the cysts, and peritoneal fluid. Remarkably, viral metagenomics revealed various murine viral species, and unexpectedly, a virus from the insect armyworm moth (Pseudaletia/Mythimna unipuncta), known as Mythimna unipuncta granulovirus A (MyunGV-A), in both cysts, and in one fecal and one peritoneal sample from the other non-cyst voles, indicating the survival and adaption potential of the insect virus in voles. Metagenomics also revealed a significantly lower probability of fungal detection in cysts compared to that in peritoneal fluid/feces (p < 0.05), with single taxon detection in each cyst (Malassezia and Pseudophaeomoniella oleicola). The peritoneal fluid had the highest probability for fungi. In conclusion, metagenomics revealed that bacteria/viruses/fungi coexist within parasitic cysts supporting the potential therapeutic benefits of antibiotics in cystic diseases, and in inflammatory microniches of chronic diseases, such as Crohn's disease gut wall cavitating micropathologies, from which we recently isolated similar synergistic pathogenic Bacteroidota and Enterobacteriaceae, and Bacillota.

Evaluation of Commercial Sex Pheromone Lures for Fall Armyworm, Spodoptera frugiperda (J. E. Smith) Monitoring in Bhutan

The fall armyworm has rapidly spread to 11 Dzongkhags in Bhutan by September 2023 since its first detection in 2019. This concerning spread highlights the critical need for comprehensive monitoring strategies. However, there is still a notable gap in understanding the seasonal behavior of fall armyworm in Bhutan, including its response to commercially available sex pheromone lures. Hence, the current study aimed to evaluate the effectiveness of seven commercially available sex pheromone lures (SPFR2111, SPFR2112, SPFR2113, SPFR2114, SPFR2115, PCI and Ecotech) in monitoring fall armyworm in maize fields in Sarpang, Punakha and Chukha Dzongkhags in 2023. The study employed a descriptive observational approach to monitor fall armyworm moth populations in maize fields. Phero T-traps (funnel traps) with specific lures were placed fifty meters apart in maize fields at a density of five traps per acre and positioned approximately 1.5 meters above ground level. The number of fall armyworm moths and non- target species captured by seven lures differed across various locations. Overall, SFPR2114, PCI, and Ecotech lures were more effective in trapping fall armyworm moths based on mean ranks. The lure SPFR2113 and SPFR2112 captured the lowest number of non-target species, while PCI captured the highest number. The peak of fall armyworm moth capture was in April in all the monitoring locations, signifying the need for timely monitoring and scouting during this vulnerable crop growth stages. The study’s findings suggest the use of SPFR2114, SPFR2113, SPFR2112 and Ecotech lures for monitoring fall armyworm populations in Bhutan, particularly during the crucial period of April when there is a notable surge in moth captures for effective fall armyworm monitoring.

Impact of Climate Change on Armyworm Infestation and Horticultural Crop Production in Gilgit-Baltistan

The armyworm is one of the major threats to global food crop security. It is a polyphagous pest that has recently spread to Gilgit Baltistan (GB) from another region of Pakistan. This pest has posed a significant threat to economically important cereal crops like wheat and maize, as well as to vegetable crops such as beans, forage crops like berseem and alfalfa, and fruit trees. While it has been reported in other regions of Pakistan, there has been no confirmed presence of the armyworm in GB, Pakistan. In April 2022, the armyworm invaded crops in districts Gilgit, Nagar, Hunza, Diamer, and Baltistan region. To monitor its movement, the integrated pest and disease management (IPDM) department of GB established mechanical traps in these districts. The armyworm outbreak persisted in these districts until the end of June 2022. The field survey revealed that the pest primarily targeted wheat, beans, maize, berseem, clovers, forage grasses, and vegetables. Suspected armyworm moths were captured and identified as Mythimna unipuncta through morphological analysis. Various pesticides were applied in the aforementioned districts to manage the armyworms. Additionally, the farming community of GB was provided with mechanical traps and spray machines. The invasion of armyworms might be attributed to climate change, which has been observed over the last 4-5 years in GB. This case study confirms the first instance of armyworm immigration into GB, and it will serve as a valuable resource for the monitoring and management of armyworms. Moreover, raising farmer awareness about climate change and its impact on armyworms is essential. To effectively manage insect pests under changing climatic conditions, it is crucial to collaborate with stakeholders and farmers to prepare and enhance armyworm risk assessment maps. Furthermore, a comprehensive study involving molecular identification of the Fall Armyworm (FAW) should be conducted to achieve scientific identification

Calosoma (Coleoptera: Carabidae) biological control introductions to Hawaiʻi: Taxonomic ignorance and confusion lead to an unexpected result

From 1897 until 1957, beetles of the genus Calosoma L. (Coleoptera: Carabidae) were repeatedly introduced to the Hawaiian Islands as predators of nutgrass armyworm, Spodoptera exempta (Walker), armyworm, Mythimna unipuncta (Haworth), and lawn armyworm, Spodoptera mauritia (Boisduval). Through examination of institutional voucher specimens, archival field notes, and the literature, we document failed biological control introductions of eight flight-capable Calosoma species: C. calidum (F.), C. frigidum Kirby, C. marginale Casey, C. peregrinator Guérin-Méneville, C. prominens LeConte, C. protractum LeConte, C. semilaeve LeConte, and C. senegalense Dejean. In contrast, the vestigially-winged C. anthracinum Dejean, a rarely collected Mexican species never intentionally introduced, is the only Calosoma currently resident in Hawaiʻi. Calosoma anthracinum was misidentified initially as C. semilaeve, and thereafter misidentified as Calosoma blaptoides tehuanacum Lapouge. Both C. anthracinum and C. protractum were collected sympatrically at Cuernavaca, Morelos, Mexico during Hawaiʻi-based explorations, and we hypothesize that they were introduced together as a species mixture in a 1923 release made at Waikiʻi, Parker Ranch, Hawaiʻi Island. Calosoma anthracinum was little known to taxonomists at that time due to its limited native distribution, rarity in institutional collections, and absence from taxonomic keys, leading to repeated misidentifications. Calosoma peregrinator and C. prominens, two abundant, sympatric species from the Sonoran and Chihuahuan Deserts, were also taxonomically confused over this period, resulting in mixed-species Hawaiian introductions. Three species that failed to establish upon introduction—C. marginale, C. peregrinator and C. semilaeve—have been intercepted as singletons or pairs of individuals decades later, without apparent establishment. Calosoma beetles’ ecological requirements, dispersal abilities, introduction histories, and native ranges and associated climate are compared among species, the only unique characteristic of the successful colonist being flightlessness. The history of Hawaiian Calosoma introductions illustrates the need for robust and accessible classifications based on accurately determined specimens as well as comprehensive understanding of the biological attributes and habitat requirements of candidate biological control agents.

The exposure of field-grown maize seedlings to weed volatiles affects their growth and seed quality.

Plants exposed to volatiles emitted from artificially damaged conspecific or heterospecific plants exhibit increased resistance to herbivorous insects. Here, we examined whether volatiles from artificially damaged weeds affect maize growth and reproduction. Seven days after germination, maize seedlings were exposed to volatiles emitted by artificially damaged mugwort (Artemisia indica var. maximowiczii) or tall goldenrod (Solidago altissima) plants either separately, or as a mixture of the two, for seven days. Unexposed seedlings were used as controls. Treated and control seedlings were cultivated in an experimental field without any insecticides applied. Plants exposed to either of the three volatile treatments sustained significantly less damage than controls. Additionally, seedlings exposed to either goldenrod or mixed volatiles produced more leaves and tillers than control plants. Furthermore, a significant increase in the number of ears was observed in plants exposed to the volatile mixture. In all treated plants, ear sugar content was significantly higher than that in the controls. Further, we cultivated seedlings that were either exposed to the volatile mixture or unexposed, under the conventional farming method using pesticides. Similar significant differences were observed for sugar content, number of tillers, leaves, damaged leaves, and ears. Laboratory experiments were conducted to further evaluate the mechanisms involved in the improved performance of volatile-treated plants. A significant reduction in the growth of common armyworm (Mythimna separata) larvae was observed when maize plants were exposed to the volatile mixture. This treatment did not affect the amount of jasmonic acid in the seedlings, whereas salicylic acid content increased upon exposure. The characteristic differences in chemical composition of mugwort and goldenrod volatiles were confirmed and, in turn, the volatile mixture differed significantly from the volatiles of either species.

Effect of rearing conditions on fatty acid allocation during flight in nectivorous lepidopteran Mythimna unipuncta

Insect species that are nectivorous as adults acquire essential fatty acids almost exclusively from host plants during larval development. Thus, as essential fatty acids are important for a number of different biological processes, adult allocation of this limited resource may result in important trade-offs. Most lepidopteran species that migrate do so as sexually immature adults, so essential fatty acids used for migratory flight would not be available for subsequent reproduction. Using the true armyworm, Mythimna unipuncta, as a model system we analyzed fat body samples to test the hypothesis that environmental cues would influence the use of essential fatty acids during migratory flight. We used diets manipulated isotopically to trace origins and use of stored lipids and used chromatographic analyses to determine fatty acid composition. In the first experiments, 5-day old moths that had been reared in summer or fall (migratory) conditions and were force flown for different lengths of time (0–6 h) after which samples of the fat body were analyzed. Rearing conditions did not affect fatty acid loading however patterns of use during flight differed with essential fatty acids being conserved under fall but not summer conditions. As migratory flight can take several days, we repeated the experiment when 5-day old moths were flown for 8 h each day for up to 5 days. Some moths were provided access to sugar water after each flight while others were only given water or only given sugar water once. When sugar water was readily or sporadically available, moths reared under fall conditions conserved their essential fatty acids indicating that the environmental cues responsible for the onset of migratory flight result in physiological changes that modify lipid use. However, when moths had only water, the essential fatty acids were not conserved, highlighting the importance of nectar availability at stopovers for the conservation essential fatty acids during migration. Isotopic analysis of the moth fat body indicated a large contribution of adult-derived diet to lipids used as fuel. The implications of using isotopic approaches to other flight studies and future research on differential resource allocation in winged monomorphic migratory insects are discussed. Summary statement: Isotopic tracing methods and gas chromatography were used to demonstrate that environmental cues can impact patterns of fatty acid use in true armyworm moths. In particular, essential fatty acids are conserved during migratory flight. However, availability of adult food sources will determine the degree to which essential fatty acids are conserved.

Monitoring ten insect pests in selected orchards in three Azorean Islands: The project CUARENTAGRI.

The data we present are part of the CUARENTAGRI project, which involves all archipelagos of the Macaronesia (Azores, Madeira, Canary Islands and Cabo Verde). The project aims to: i) identify and evaluate the risks associated with the introduction of new arthropod pests; ii) study the population dynamics of selected arthropod pest species currently responsible for the damage of key target crops and iii) develop monitoring systems, based on prediction and/or population dynamics of the crop pests, creating warnings and a phytosanitary prevention system. In this contribution, we compile data for three Azorean Islands (Terceira, São Jorge and São Miguel Islands), where pheromone-baited traps were placed in pastures, potato fields and several orchards' types (apples, banana, chestnuts, olives, orange and strawberry), during three consecutive years (2020, 2021 and 2022). A total of 114,827 specimens of insects (Arthropoda, Insecta) were collected, belonging to four orders, six families and ten recorded pest species. A total of eight species are considered introduced (Cosmopolitessordidus (Germar, 1824), Drosophilasuzukii (Matsumura, 1931), Bactroceraoleae (Rossi, 1790), Ceratitiscapitata (Wiedemann, 1824), Phthorimaeaoperculella (Zeller, 1873), Cydiapomonella (Linnaeus, 1758), Cydiasplendana (Hübner, 1799) and Grapholitamolesta (Busck, 1916); n = 84,986 specimens) and two native non-endemic (Mythimnaunipuncta (Haworth, 1809) and Spodopteralittoralis (Boisduval, 1833); n = 17,465 specimens). This study intended to contribute to a better knowledge of the arthropods pests that can affect the Azorean crops and will serve as a baseline for future monitoring actions, pest risk assessments and prevention systems.

Fermented or Floral? Developing a Generalized Food Bait Lure to Monitor Cutworm and Armyworm Moths (Lepidoptera: Noctuidae) in Field Crops

Cutworms and armyworms (Lepidoptera: Noctuidae) are a pest complex in North America that cause sporadic damage in field crops on the Canadian Prairies; however, no methods have been developed to reliably monitor population densities. Food-based semiochemicals attract both sexes of adult moths and could be used to monitor multiple species with a single lure in a single trap. Here, we focus on enhancing the attractiveness of acetic acid and 3-methyl-1-butanol (AAMB) lures to redbacked cutworm (Euxoa ochrogaster) (RBC) and other noctuid pests. Experiments conducted in canola and wheat fields tested AAMB lures at different release rates, from different devices and in combination with other semiochemicals. High-release lures captured more females in canola, while low-release lures captured more males in wheat. Thus, crop volatiles may influence response to lures. Semiochemicals embedded in an inert matrix caught more RBC moths than semiochemicals released from Nalgene or polyethylene dispensers did. More RBC females were attracted to AAMB lures with 2-methyl-1-propanol than phenylacetaldehyde. Fermented volatiles appear to be a more reliable attractant than floral volatiles for these species. RBC moth antennae produced significant responses to all doses of phenylacetaldehyde tested in electroantennogram assays, but only to higher doses of acetic acid and 3-methyl-1-butanol. Physiological state of the RBC moths also influenced responsiveness to the tested semiochemical. Feeding status did not influence the antennal response to acetic acid and phenylacetaldehyde in either sex, but it increased the response to 3-methyl-1-butanol in females when fed. AAMB lures should be further developed to monitor RBC moths and other noctuid pests in field crops.

A cold high-pressure system over North China hinders the southward migration of Mythimna separata in autumn

BackgroundIn warm regions or seasons of the year, the planetary boundary layer is occupied by a huge variety and quantity of insects, but the southward migration of insects (in East Asia) in autumn is still poorly understood.MethodsWe collated daily catches of the oriental armyworm (Mythimna separata) moth from 20 searchlight traps from 2014 to 2017 in China. In order to explore the autumn migratory connectivity of M. separata in East China, we analyzed the autumn climate and simulated the autumn migration process of moths.ResultsThe results confirmed that northward moth migration in spring and summer under the East Asian monsoon system can bring rapid population growth. However, slow southerly wind (blowing towards the north) prevailed over the major summer breeding area in North China (33°–40° N) due to a cold high-pressure system located there, and this severely disrupts the autumn ‘return’ migration of this pest. Less than 8% of moths from the summer breeding area successfully migrated back to their winter-breeding region, resulting in a sharp decline of the population abundance in autumn. As northerly winds (blowing towards the south) predominate at the eastern periphery of a high-pressure system, the westward movement of the high-pressure system leads to more northerlies over North China, increasing the numbers of moths migrating southward successfully. Therefore, an outbreak year of M. separata larvae was associated with a more westward position of the high-pressure system during the previous autumn.ConclusionThese results indicate that the southward migration in autumn is crucial for sustaining pest populations of M. separata, and the position of the cold high-pressure system in September is a key environmental driver of the population size in the next year. This study indicates that the autumn migration of insects in East China is more complex than previously recognized, and that the meteorological conditions in autumn are an important driver of migratory insects’ seasonal and interannual population dynamics.

Design, Synthesis, and SAR Studies of Some Novel Chalcone Derivatives for Potential Insecticidal Bioefficacy Screening on Spodoptera frugiperda (Lepidoptera: Noctuidae).

Spodoptera frugiperda is a species of the order Lepidoptera. It is one of the species of fall armyworm moths distinguished by its larval life stage, is found in different regions of Africa, and can cause incredible damage. This is the first report produced by the preparation of an indexed combinatorial library of novel chalcone derivatives 3a-k via treatment of 4-formylphenyl4-methylbenzenesulfonate (1) with some acetyl compounds 2a-k in the presence of NaOH. The structures of the synthesized compounds were proven by different spectroscopic techniques such as infrared, 1H NMR, 13C NMR, and elemental analyses. In this work, we studied their toxicity effect against S. frugiperda, followed by a structure-reaction relationship. Moreover, newly prepared chalcone derivatives were tested as insecticides using S. frugiperda. It has been found that most compounds have good to excellent potential effectiveness. Among all of the compounds, 3b, 3g, and 3j exhibited excellent effectiveness. Furthermore, compound 3c showed the most activity, with LC50 = 9.453 ppm of the second instar larva and LC50 = 66.930 of the fourth instar larva .

An experimental investigation on the aerodynamics of the Pseudaletia Unipuncta moth subjected to varying upstream flow conditions

The effects of varying flow conditions on the flight and wake of the Pseudaletia Unipuncta moth were investigated, for the first time, using Particle Image Velocimetry (PIV) measurements on a live tethered moth, subjected to three upstream flow conditions: no flow (hover), smooth flow and perturbed flow. High-Speed Imaging (HSI) was used to study the basic kinematics of the moth, from which the wingbeat frequency (F) of the moth was found to be approximately 45 Hz. In configurations with no upstream flow, a possible Leading Edge Vortex (LEV) was observed as well as counter-rotating vortices in the moth’s wake. Varying the upstream flow conditions significantly changed the mean turbulent statistics in the moth’s wake, with larger levels of mean turbulent kinetic energy being observed in configurations with upstream flow compared to configurations with no upstream flow. It was observed that the mean flow perturbation modified the wake generated by the moth.

Population dynamics of eight pests on different potato cultivars in southwest China

Yunnan province is most important area of potato planting in China. Meanwhile, there are many factors constraint to its developments, especially pest damage. So, eleven potato cultivars (such as Hezuo 88, Lishu 6, Qingshu 9 and Yunshu 304) of vital commercial variety in Yunnan were selected for pests investigation. The field survey of eleven potato cultivars in two cropping seasons (spring and autumn) was conducted from 2020 to 2021 in Yunnan province, China. During autumn planting season of 2020 and 2021, populations of eight insect pests including aphid, thrips, whitefly, leafhopper, potato tuber moth, tomato leaf miner, beet armyworm and cabbage moth were surveyed. All pest’s population peaked in October. Meanwhile, Qingshu 9 and Yunshu 304 has the largest population of aphid. The largest population of whitefly were reported on Hezuo 88 and Yunshu 304, respectively. The largest population of thrips were found on Hezuo 88, whereas Qingshu 9 has the lowest population of whitefly. The lowest population of aphid were observed on Lishu 6. The lowest population of thrips were found on Yunshu 304. During spring planting season of 2021, population of thrips, leafhopper and adult potato tuber moth were surveyed. The highest population was appeared in June. But there was no significant difference for the pests populations among different cultivars. These results of pests population dynamics during the cropping period would be helpful for making appropriate and sustainable pest management strategies.

Revision of the species of Mythimna Ochsenheimer, 1816 (Pseudaletia) (Lepidoptera: Noctuidae: Noctuinae: Leucaniini) occurring in Brazil

The genus Mythimna Ochsenheimer, 1816 groups aproximatelly 270 species worldwide. This genus is subdivided into many subgenera and species-groups, with those species occurring in the Neotropical region included in the subgenus Mythimna (Pseudaletia) Franclemont, 1951. Species of this subgenus frequently reach high population levels, causing economic damage to Poaceae cultivars. Hence, it is crucial a well-defined taxonomy allowing rapid and precise identifications. However, the species of this subgenus are cryptic, their recognition requires molecular analyses and in-depth morphological studies, which has often resulted in misidentifications. In Brazil, the occurrence of the following species had been mentioned: Mythimna (P.) adultera (Schaus, 1894), Mythimna (P.) roraimae Franclemont, 1951, Mythimna (P.) sequax Franclemont, 1951, and Mythimna (P.) unipuncta (Haworth, 1809). Yet, until now, we lack a broader knowledge about the geographic distribution and taxonomy of these species. Thus, this study aims to revise the taxonomy of those species based on morphological and molecular (COI) data to provide an updated comprehension of this group in the country. The analysis of 1,664 specimens allowed us to confirm the presence of three species in the country: Mythimna (P.) adultera, Mythimna (P.) sequax, and Mythimna (P.) unipuncta. A lectotype for Mythimna (P.) adultera is designated; a new synonym is proposed: Pseudaletia roraimae syn. nov. of Mythimna (P.) unipuncta; and a new species, Mythimna (P.) celiae sp. nov. is described from Bagé, Rio Grande do Sul, Brazil.

The Inhibitory Effect of Powdery Mildew-Induced Volatiles from Rose on Host Selection Behavior of Beet Armyworm Moths (Lepidoptera: Noctuidae)

Abstract Plant-mediated indirect interactions (PMIIs) between phytopathogenic fungi and herbivorous insects on shared host plants occur in nature. Knowledge of PMIIs is critical in plant molecular breeding and integrated pest management. We studied the response and chemical mechanism of beet armyworm, Spodoptera exigua (Hübner), adults to rose plants, Rosa chinensis Jacquin, infected with rose powdery mildew, Podosphaera pannosa (Wallr.: Fr.) de Bary. Using gas chromatography-electroantennographic detection (GC-EAD) coupled with electroantennogram (EAG), we found that beet armyworm antennae responded to 8, 11, and 3 volatile organic compounds (VOCs) from noninfected roses, mildew-infected roses, and mildew alone, respectively. The EAG analyses showed 11 chemicals (e.g., limonene [1], 2-ethyl-1-hexanol [2], linalool [3], nonanal [4], (E)-β-caryophyllene [5], 1-dodecanol [7], nhexadecane [9], 1-hexadecanol [11], methyl palmitate [12], 1-octadecanol [14], and n-butyl hexadecanoate [15]) elicited electrophysiological responses of beet armyworm antennae with significant dose-response relationships (P &amp;lt; 0.05). The EAG responses to the three chemicals (3, 11, and 15) were greater than that to the reference chemical [i.e., (E)-2-hexenal] at 0.5, 5.0, and 50.0 mg/ml. Olfactory and ovipositional behavior assays indicated that three chemicals (2, 3, and 5) significantly attracted beet armyworm females and four chemicals (7, 11, 14, and 15) strongly repelled females. Chemicals 2, 3, and 5 from healthy roses appear to be responsible for the attraction of beet armyworm moths to healthy roses, whereas chemicals 7, 11, 14, and 15 from mildew-infected roses play key roles in inhibiting attraction of moths. VOCs from mildew alone did not attract or repel beet armyworm moths.

Source Regions of the First Immigration of Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) Invading Australia.

Simple SummaryThe fall armyworm, Spodoptera frugiperda, is a serious invasive, crop-destroying pest, which is the subject of a global warning from the United Nations Food and Agriculture Organization (FAO). The surprisingly rapid spread of fall armyworm and its significant capacity to generate high-yield losses has attracted increased attention worldwide. In January 2020, fall armyworm was first confirmed in Torres Strait (Saibai and Erub Islands) and mainland Australia (Bamaga). However, the possible source region of the first immigration of fall armyworm was still obscure. A better understanding of the migration paths and the source regions of fall armyworm immigrants, will be useful for the monitoring and early warning of this pest in Australia. The migratory paths and wind systems for the first case of the immigration of fall armyworm invading Australia were simulated using a three-dimensional trajectory analysis program. This study has confirmed that the immigration of fall armyworm to Australia was most likely from Sulawesi and Moluccas Islands of Indonesia.Fall armyworm is recognized as one of most highly destructive global agricultural pests. In January 2020, it had first invaded Australia, posing a significant risk to its biosecurity, food security, and agricultural productivity. In this study, the migration paths and wind systems for the case of fall armyworm invading Australia were analyzed using a three-dimensional trajectory simulation approach, combined with its flight behavior and NCEP meteorological reanalysis data. The analysis showed that fall armyworm in Torres Strait most likely came from surrounding islands of central Indonesia on two occasions via wind migration. Specifically, fall armyworm moths detected on Saibai and Erub Islands might have arrived from southern Sulawesi Island, Indonesia, between January 15 and 16. The fall armyworm in Bamaga most likely arrived from the islands around Arafura Sea and Sulawesi Island of Indonesia, between January 26 and 27. The high risk period for the invasion of fall armyworm is only likely to have occurred in January–February due to monsoon winds, which were conducive to flight across the Timor Sea towards Australia. This case study is the first to confirm the immigration paths and timing of fall armyworm from Indonesia to Australia via its surrounding islands.

Topical and dietary toxicity of emamectin benzoate, chlorantraniliprole, cyantraniliprole and indoxacarb to larvae of the common armyworm Mythimna convecta (Lepidoptera: Noctuidae).

The common armyworm Mythimna convecta is an important pest of pastures and graminaceous crops in Australia, but materials currently registered for its control are limited to broad-spectrum compounds incompatible with integrated pest management (IPM) systems. In this study we assessed the response of M.convecta larvae to four alternative compounds using topical and dietary bioassays. Emamectin benzoate [LC50 (lethal concentration for 50% of insects tested) values 2.69 μg mL-1 topical, 0.017 μg active ingredient (AI)g-1 dietary] and chlorantraniliprole (LC50 values 4.87 μg mL-1 topical, 0.080 μg AI g-1 dietary) were significantly more active than either indoxacarb or cyantraniliprole. Our results showed strong parallels with data on the more extensively studied Australian strains of Helicoverpa armigera, with the most notable differences being the higher contact toxicity of emamectin benzoate to M.convecta and the lower acute dietary activity of formulated cyantraniliprole to this species, which was linked to feeding deterrence. Cyantraniliprole at dietary concentrations of ≥0.02 μg AI g-1 significantly reduced the weight of surviving larvae and frass production (an indirect measure of food consumption) over the seven-day exposure period. There was also some evidence of chlorantraniliprole deterring larval feeding, although to a much more limited extent. Both emamectin benzoate and chlorantraniliprole are suitable for use against M.convecta. The decision as to which of these compounds should be prioritized for further development should be based on their potential effects on beneficial species once their optimal field rates have been determined.

Fitness Costs of Two Maize Lepidopteran Pests Fed on Bacillus thuringiensis (Bt) Diets Enriched with Vitamins A and C

Simple SummaryBiotechnologists are designing new transgenic plants enriched with micronutrients and vitamins that are resistant to insects. These new plants could favor the development of some pest insects. This work aims to discover the effect of adding two vitamins, A and C, to insect diets prepared with Bt and no-Bt maize in two maize insect pests. M. unipuncta was less sensitive to the toxin, although ingestion of the Bt diet resulted in longer larval development and lower pupal weight, which were not mitigated by any of the vitamins. However, the two vitamins reduced the mortality of H. armigera larvae fed on the Bt diet. In addition, we found evidence of the antioxidant function of vitamin A. The results obtained here indicate that crops enriched with these vitamins will hardly favor the development of H. armigera and suggest that they do not affect M. unipuncta’s development at all.Serious malnutrition problems occur in developing countries where people’s diets are mainly based on staple crops. To alleviate this, high-production crops are being developed that are better adapted to climate change, enriched in micronutrients and vitamins, or resistant to pests. In some cases, new varieties have been developed with several of the characteristics mentioned above, such as biofortified and pest-resistant crops. The development of biofortified Bacillus thuringiensis (Bt) crops raises the question of whether vitamin enrichment of Bt crops can in any way favor those pests that are not very susceptible to the Bt toxin that feed on these crops, such as Helicoverpa armigera (Hübner) or Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae). In this study, the response to a Bt diet enriched with vitamins A (β-carotene) and C (ascorbic acid) was somewhat different between the two species. M. unipuncta was less sensitive to the toxin than H. armigera, although the ingestion of the Bt diet resulted in oxidative stress (longer larval development and lower pupal weight) which was not mitigated by the vitamins. However, the two vitamins reduced the mortality of H. armigera larvae fed on a Bt-enriched diet; in addition, ß-carotene reduced the activity of the antioxidant glutathione S-transferase (GST) of both species, suggesting it has an antioxidant role. The results obtained here indicate that biofortified Bt crops will not favor the development of H. armigera very much and will not affect M. unipuncta’s development at all, although the effect of the increase in vitamins may be very variable and should be studied for each specific phytophagous.

Genetic Screening to Identify Candidate Resistance Alleles to Cry1F Corn in Fall Armyworm Using Targeted Sequencing.

Simple SummaryMonitoring of resistance alleles is critical to the sustainability of transgenic crops producing insecticidal Cry proteins. Highly sensitive and cost-effective DNA-based methods are needed to improve current bioassay-based resistance screening. Our goal was to evaluate the use of targeted sequencing in detecting known and novel candidate resistance alleles to Cry proteins. As a model, we used field-collected fall armyworm (Spodoptera frugiperda) from Puerto Rico, the first location reporting continued practical field-evolved S. frugiperda resistance to corn producing the Cry1F insecticidal protein, and sequenced the SfABCC2 gene previously identified as critical to Cry1F toxicity. Targeted sequencing of SfABCC2 detected a previously reported Cry1F resistance allele and mutations originally identified in populations from Brazil. Importantly, targeted sequencing also identified nonsynonymous and frameshift mutations as novel candidate resistance alleles. These results advocate for the use of targeted sequencing in screening for resistance alleles to Cry proteins and support potential gene flow, including resistance alleles, between S. frugiperda from Brazil and the Caribbean. Evolution of practical resistance is the main threat to the sustainability of transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt crops). Monitoring of resistance to Cry and Vip3A proteins produced by Bt crops is critical to mitigate the development of resistance. Currently, Cry/Vip3A resistance allele monitoring is based on bioassays with larvae from inbreeding field-collected moths. As an alternative, DNA-based monitoring tools should increase sensitivity and reduce overall costs compared to bioassay-based screening methods. Here, we evaluated targeted sequencing as a method allowing detection of known and novel candidate resistance alleles to Cry proteins. As a model, we sequenced a Cry1F receptor gene (SfABCC2) in fall armyworm (Spodoptera frugiperda) moths from Puerto Rico, a location reporting continued practical field resistance to Cry1F-producing corn. Targeted sequencing detected a previously reported Cry1F resistance allele (SfABCC2mut), in addition to a resistance allele originally described in S. frugiperda populations from Brazil. Moreover, targeted sequencing detected mutations in SfABCC2 as novel candidate resistance alleles. These results support further development of targeted sequencing for monitoring resistance to Bt crops and provide unexpected evidence for common resistance alleles in S. frugiperda from Brazil and Puerto Rico.

A nonlinear model for stage-structured population dynamics with nonlocal density-dependent regulation: An application to the fall armyworm moth

The assessment and the management of the risks linked to insect pests can be supported by the use of physiologically-based demographic models. These models are useful in population ecology to simulate the dynamics of stage-structured populations, by means of functions (e.g., development, mortality and fecundity rate functions) realistically representing the nonlinear individuals physiological responses to environmental forcing variables. Since density-dependent responses are important regulating factors in population dynamics, we propose a nonlinear physiologically-based Kolmogorov model describing the dynamics of a stage-structured population in which a time-dependent mortality rate is coupled with a nonlocal density-dependent term. We prove existence and uniqueness of the solution for this resulting highly nonlinear partial differential equation. Then, the equation is discretized by finite volumes in space and semi-implicit backward Euler scheme in time. The model is applied for simulating the population dynamics of the fall armyworm moth (Spodoptera frugiperda), a highly invasive pest threatening agriculture worldwide.