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- Control of container mosquitoes with triflumuron in key urban land uses
and effects on non-target dipterans-
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Abstract: Abstract Mosquitoes are of major public health importance throughout the world. Recently, there has been an increase in mosquito-borne diseases some of which are newly emerging, and some are remerging. Chemical control remains the main approach to reducing mosquito vector populations, therefore mitigating the transmission and spread of mosquito-borne diseases. Urban land uses have been identified as highly productive for container mosquitoes and thus require vector control interventions. In this study, we compared the effectiveness of the larvicide triflumuron in controlling mosquito vectors in households, cemeteries and tire shops and assessed its potential impact on non-target dipterans in urban temperate Argentina. On average, treatment with triflumuron reduced the occurrence of Aedes aegypti by 81% and Culex pipiens by 45%, with no significant differences among land uses. Two-thirds of the containers with these two mosquito species also harbored at least one non-target dipteran species (other Culicidae, Chironomidae, Psychodidae, Ceratopogonidae, Phoridae, Ephydridae, Syrphidae and Sciomyzidae). Triflumuron application also had unintended effects on non-target dipteran communities, resulting in reduced richness and diversity across all land uses, as well as a reduced density of individuals in tire shops. Triflumuron proved highly effective against Ae. aegypti and moderately effective against Cx. pipiens regardless of land-use patterns. However, unwanted effects against some non-target accompanying Diptera fauna were also recorded, suggesting a severe limitation for the use of this larvicide in areas where biodiversity conservation is of paramount importance. Preserving biodiversity and human welfare must be a primary goal in the search for better vector control measures.
PubDate: 2023-09-15
- Invasion alert for Wasmannia auropunctata: a potential distribution in
southern China and associated invasion risk to urban, rural, agricultural,
and forest lands-
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Abstract: Abstract Wasmannia auropunctata, the little fire ant, is an invasive pest threatening native biodiversity, agricultural and forestry production, and public health. In January 2022, wild populations of W. auropunctata were reported for the first time on the Chinese mainland. However, the stage and degree of W. auropunctata invasion in China are unclear. Therefore, assessing the risk of establishment and the potential impacts associated with this pest is crucial for preventing further spread. This study used the Bayesian additive regression trees (BARTs) model and global occurrence records to assess the potential distribution of W. auropunctata in southern China and the associated risk of invading urban, rural, agricultural, and forest lands. The results from our models indicate that: (1) coastal areas, southwest, and central areas are particularly suitable for W. auropunctata establishment; (2) temperature, clay content, mean normalized differential vegetation index (NDVI), and urban area are important factors in the distribution of W. auropunctata; (3) the agricultural lands in the coastal areas and the Yunnan–Guangxi border, the urban and rural lands in the coastal areas, and grasslands in the southwest should prepare for possible W. auropunctata invasion; and (4) forest lands have the highest area at risk of W. auropunctata invasion in southern China. These results provide valuable information for planning and implementing the monitoring and control strategies against W. auropunctata invasion in China.
PubDate: 2023-09-14
- Effects of elevated CO2 and spinetoram on the population fitness and
detoxification enzymes activities in Frankliniella occidentalis and F.
intonsa-
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Abstract: Abstract Herbivore performance can be impacted by elevated CO2 or insecticides. However, there is insufficient data on how invasive and native species are affected by these dual stresses. Frankliniella occidentalis and F. intonsa are economically important pests. We evaluated the direct effects of elevated CO2 on the sensitivity of thrips to spinetoram, and recorded their population fitness, as well as measured acetylcholinesterase (AChE) and cytochrome P450 (CYP450) activities in adults under short-term (3rd generation) and long-term (30th generation) exposures to these two stresses. Thrips' resistance to spinetoram was accelerated by elevated CO2, and was strongly displayed by F. occidentalis than by F. intonsa. In the 3rd generation, exposure to the two stresses significantly prolonged the longevity of adult F. occidentalis and increased its fecundity, sex ratio, and net reproductive rate (R0), whereas they only increased the fecundity of F. intonsa. Notably, the sex ratio of the former (2.15 ± 0.35) was significantly higher than that of the latter (0.65 ± 0.03). On the other hand, CYP450 activity in F. occidentalis was significantly lower than that of control. At the 30th generation, exposure to the two stresses reduced the population fitness of the two species. Additionally, the fecundity, sex ratio, R0, intrinsic rate of increase (r), and finite rate of increase (λ) of F. occidentalis were significantly higher than that of F. intonsa. Besides, AChE activities in both species were significantly lower than that of the control. We concluded that increased CO2 and spinetoram may hasten the displacement of the native species, F. intonsa by the invasive species, F. occidentalis in the future.
PubDate: 2023-09-13
- The larvae of Phyllotreta striolata share the same olfactory cues for
locating Brassicaceae plant with conspecific adults-
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Abstract: Abstract The sophisticated olfactory system of insects plays crucial roles in host plant location. In comparison with comprehensive studies on the molecular mechanisms of olfactory cues detection in lepidopteran moths, little is known about how coleopteran beetles detect host plant cues. Phyllotreta striolata is a devastating coleopteran pest of Brassicaceae crops, and its larvae feed on roots underground, while its adults destroy leaves aboveground. In this study, we focus on the molecular basis of olfactory cues detection in P. striolata and attempt to determine whether P. striolata larvae share the same specific olfactory cues for host plant location with conspecific adults and whether the detection mechanism is conserved. A two-choice behavioral bioassay was conducted to examine the behavioral responses of P. striolata to different types of isothiocyanates (ITCs), which are the characteristic volatiles of Brassicaceae crops. The results showed that both P. striolata adults and larvae were attracted by allyl ITC, although adults showed a broader behavioral response range. The transcriptome sequencing of P. striolata adults and larvae was performed, and 157 chemosensory genes were identified, among which 6 OBPs, 2 CSPs, 1 OR, 1 IR and 1 GR were found to be preferentially expressed in both P. striolata adults and larvae. Functional studies of PstrOBP9, PstrOBP13 and PstrOBP17, three of the six OBPs that were highly expressed in both adults and larvae, revealed that PstrOBP9 strongly bound allyl ITC and eight other ITCs. Taken together, these findings demonstrated that P. striolata larvae and adults could employ the same olfactory proteins to detect specific plant volatiles for host location, which provides a new perspective on the development of environmentally friendly pest management targeting both P. striolata adults and larvae.
PubDate: 2023-09-11
- Flight phenology and landscape predictors of invasive Coleophora
deauratella populations in Oregon and New Zealand red clover-
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Abstract: Abstract Red clover casebearer moth (Coleophora deauratella) (Leinig and Zeller) (Lepidoptera: Coleophoridae) is an invasive insect pest in red clover (Trifolium pratense L.) seed production systems in North America and New Zealand. Recent discoveries of C. deauratella in Oregon and New Zealand prompted research investigating the seasonal phenology and population dynamics of C. deauratella to inform management strategies and develop a risk prediction framework to mitigate outbreak severity. We sampled 76 site-years across three geographic regions, including western (Willamette Valley) and eastern Oregon and New Zealand. An attractant-based trap network was deployed across sampled regions using a female sex pheromone to lure male moths in commercial red clover seed production fields. Remotely sensed temperature and landscape composition data were extracted for phenological and geospatial modeling. Nonlinear logistic regression was used to develop regionally explicit phenology models that predict the unimodal timing of C. deauratella flights. Molecular gut-content analyses revealed the dietary history of early-season captures and informed landscape analysis covariate selection. A spatial Bayesian generalized linear mixed model (GLMM) was developed to test landscape-level effects of landscape composition and configuration predictors on C. deauratella abundance. The spatiotemporal dominance of clover and grassland land area was positively associated with Oregon C. deauratella populations. These results can be used to forecast C. deauratella risk across space and time and advise integrated pest management practices.
PubDate: 2023-09-07
- Correction: Variation in egg mass scale thickness of three Spodoptera
species and its effects on egg parasitoid performance-
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PubDate: 2023-09-01
- Genetic architecture and insecticide resistance in Chinese populations of
Spodoptera frugiperda-
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Abstract: Abstract The fall armyworm (FAW), Spodoptera frugiperda invaded China in December 2018 and has since spread quickly countrywide. Two sympatric biotype strains of FAW, rice-strain and corn-strain, have been classified and showed to have different susceptibilities to chemical insecticides. Present FAW control has primarily relied on insecticides, which resulted in a rapid evolution of the resistance to insecticides in FAW. Herein, sixteen geographical populations of FAW were collected annually from maize fields in China between 2019 and 2021, both Tpi genotyping (n = 3079) and feeding preference bioassay (n = 2892) showed Chinese FAW were predominantly the corn-strain. Resistance monitoring revealed that FAW had not evolved resistance to chlorantraniliprole since it invaded China with RRs of 0.32–2.32 and a very low mutation frequency RyR of 0.14%. Most FAW populations were susceptible to emamectin benzoate, spinetoram, indoxacarb, lambda-cyhalothrin and acephate. However, low resistance levels (5 < RR < 10) were detected in some populations, suggesting rotational or mixed applications of insecticides and further resistance monitoring must be strengthened to prevent or delay the development of insecticide resistance. The mutation frequency of ace-1 at the locus A201S and F290V was 21.27% and 84.51%, respectively. The mutation frequency of VGSC at the locus T929I and L1014F was 0.11% and 0.15%, respectively. The detoxification enzyme activities of P450s, ESTs and GSTs were relatively consistent among different populations. Our study provides a systematical understanding of the current genetic architecture and resistance status of FAW in China and will contribute to the region-wide chemical control and the development of resistance management strategies for FAW in China.
PubDate: 2023-09-01
- Comparative effects of biopesticides on fall armyworm management and
larval parasitism rates in northern Ghana-
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Abstract: Abstract The outbreak of the fall armyworm, Spodoptera frugiperda, in Africa has led to several recommendations of insecticides, including biopesticides. However, the effects of these products on the environment, especially on parasitoids have not been assessed under field conditions. Here, we investigated the effect of commonly used biopesticides on S. frugiperda management and larval parasitoids of S. frugiperda in northern Ghana. The experiments were conducted both on-station in Wa and Nyankpala and on-farm in Wa during the 2020 rainy season. Active ingredients tested included neem oil (3% Azadirachtin), maltodextrin (282 g/l), 55% Bacillus thuringiensis (Bt) combined with 45% Monosultap, and a Pieris rapae granulosis virus combined with 5% Bt. A chemical insecticide based on emamectin benzoate and acetamiprid was used as positive control while non-treated maize plots were considered as untreated control. The two most abundant parasitoids in Wa were Coccygidium luteum and Chelonus bifoveolatus, while in Nyankpala they were C. luteum and Meteorus sp. Total larval parasitism rates on-station were 18.7% and 17.6% in Wa and Nyankpala, respectively, and 8.8% in Wa on-farm. Parasitoid species diversity and evenness indexes did not vary among treatments, but parasitism rates were significantly lower with the chemical on-station in Wa and with the virus and Bt product in Nyankpala. Untreated maize plots showed the highest larval density and plant damage, the highest cob damage, and generated the lowest yields. The other treatments showed hardly any difference in cob damage and yields, suggesting that biopesticides should be preferred over chemical pesticides for S. frugiperda control.
PubDate: 2023-09-01
- What’s shaking for caterpillars' Leaf-borne vibratory stimuli and
behavioral responses in the fall armyworm, Spodoptera frugiperda-
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Abstract: Abstract Leaf-borne vibrations are predicted to be significant for caterpillar communication and risk assessment, but the caterpillar’s vibratory landscape remains largely unknown. To address this, we used the fall armyworm Spodoptera frugiperda, as a model in our study with two main goals: (1) to characterize the vibratory landscape on a leaf in the presence of abiotic (wind and rain) and biotic (conspecifics and invertebrate predator) stimuli; and (2) to assess whether different larval instars detect and respond to those vibrations. Our findings show that abiotic and biotic vibrations were distinct from background noise, except for those produced by 1st instar larvae. Wind-induced leaf movement produced vibrations with a low-frequency and high-amplitude (< 100 Hz and 2.97 mm s−1), in contrast with raindrops (> 174 Hz; 3.25 mm s−1). The 2nd to 5th instar larvae and predatory stinkbugs moving on leaves produced vibrations with dominant frequencies ranging from 140 to 326 Hz and amplitudes from 1.42 to 2.95 mm s−1. Furthermore, the spatial distribution of vibrations across bean leaves revealed that abiotic vibrations were more widely spread across leaves, unlike the more concentrated biotic vibrations. Regarding the caterpillar response to vibratory stimuli, caterpillars exposed to abiotic stimuli behaved differently from undisturbed caterpillars, regardless of instar. By contrast, caterpillars exposed to biotic stimuli do not respond consistently. Our findings contribute insights into a caterpillar’s vibroscape and support the hypothesis that armyworms can perceive and respond to both abiotic and biotic vibrations, filling a knowledge gap about this economically important pest species' sensory ecology.
PubDate: 2023-09-01
- Development of a recombinant baculovirus with dual effects to mediate
V-ATPase interference by RNA in the fall armyworm Spodoptera frugiperda-
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Abstract: Abstract The fall armyworm (FAW) Spodoptera frugiperda has rapidly spread from the American continent to many other areas and caused serious damage to local agriculture. To explore a more environmentally friendly and effective strategy to control this pest, we developed a dual-effect RNAi system based on baculovirus infection and gene silencing. V-ATPase subunits A and B of FAW (SfvATPaseA and SfvATPaseB) were cloned to construct a recombinant baculoviruses (rBviruses) of Bacmid-dsSfvATPaseA and Bacmid-dsSfvATPaseB with the capacity to produce small interfering RNA. The efficacy of baculovirus-mediated RNAi was evaluated by injection delivery. The results showed that the relative expression levels of SfvATPaseA and SfvATPaseB were significantly suppressed by the constructed rBviruses, with reduction rates of 73.85% and 69.82%, respectively. The inhibition rates of larval body weight and length resulting from RNAi were more than 82% and 40%, respectively. More importantly, these two rBviruses greatly accelerated the larval death of FAW; compared to a bacmid control, the total mortality was two days less. After ten serial passages, both rBviruses exhibited excellent genetic stabilities. These results suggest that the creation of dual-effect biopesticides with both viral infection and gene silencing activities is feasible and prospective.
PubDate: 2023-09-01
- Modeling fall armyworm resistance in Bt-maize areas during crop and
off-seasons-
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Abstract: Abstract Entomologists have often used computational modeling to study the dynamics of insects in agricultural landscapes. Recently, important issues such as the movement of adults and immatures associated with insect resistance to GMO (genetically modified organism) crops have been addressed using computational models. We developed an individual-based model using the cellular automata approach (CA) to investigate how an intercropping system composed of maize engineered with Bacillus thuringiensis (Bt) gene, refuge areas (non-Bt maize), and grasses combined with off-season periods might influence the evolution of resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae), one of the leading agricultural pests targeted by GMOs. We designed the Bt and non-Bt plants in two different arrangements: (a) a seed mixture and (b) strips rows, adding grasses in areas adjacent to the field. We added the seasonal planting dynamics (crop season and off-season), to evaluate a total of six agricultural scenarios. We followed a crop calendar from the United States to create simulations close to agricultural practice. The results showed that the frequency of the resistance allele was strongly related to the landscape arrangements and their dynamics. Since the adult insects are mobile, the seed-mixture scenario increased the frequency of the resistance the most (95.86%), followed by strips (82.10%), without grass fields. The maize harvest made it possible to reduce the frequency of resistance allele below 1%. Based on our results, we can expect that the maintenance of pasture areas, for instance next to the corn crops, will act as a reservoir of susceptible insects during off-season periods.
PubDate: 2023-09-01
- Fitness costs associated with spinetoram resistance in Spodoptera
frugiperda is driven by host plants-
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Abstract: Abstract Insecticide resistance is usually associated with fitness costs. The magnitude of the fitness costs is affected by environmental and ecological factors. Here, we explored how host plants could affect fitness costs associated with insecticide resistance. Initially, spinetoram-resistant and susceptible strains of Spodoptera frugiperda were selected using a F2 screen from a population collected in São Desidério, Bahia State, Brazil. In addition to the RR and SS strains, fitness costs were also assessed for a heterozygous strain (RS). Life-history traits were evaluated to estimate population growth parameters of each strain feeding on corn, soybean, and cotton plants. The relative fitness of the RR strain was 1.06 higher compared to the SS strain on corn plants, while in soybean and cotton plants these values were 0.84 and 0.67 lower, respectively. The relative fitness of the RS strain was similar to the SS strain regardless of the host plant, suggesting a recessive fitness cost. No differences were found between the strains fed on corn plants. The larval development time was greater for the RR strain fed on soybean and cotton plants compared to the RS and SS strains. Low survival rate and fecundity of the RR strain were found when larvae fed on soybean and cotton plants. The results of this study showed that fitness costs of spinetoram resistance in S. frugiperda depend on the host plants that S. frugiperda larvae fed on. Such information can be used to design resistance management strategies considering the host plants of the agricultural landscape.
PubDate: 2023-09-01
- Providing aged parasitoids can enhance the mass-rearing efficiency of
Telenomus remus, a dominant egg parasitoid of Spodoptera frugiperda, on
Spodoptera litura eggs-
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Abstract: Abstract Telenomus remus (Nixon) is an egg parasitoid of several Spodoptera spp. insects, especially the destructive agricultural pest Spodoptera frugiperda (J. E. Smith). Studies showed that this parasitoid can be efficiently reared on Spodoptera litura (Fabricius) eggs. Understanding the relationship among parasitoid age, host egg age, and parasitism efficiency is an important part of mass-rearing biological control agents. To this end, we measured the impacts of female T. remus age (1-, 2-, 3-, and 4-day-old), S. litura egg age (1-, 2-, and 3-day-old), and their interactions on parasitism capacity, developmental time, offspring fitness, and oviposition behavior. The results indicated that the 3-day-old and 4-day-old parasitoids had higher parasitism performance on all age eggs than 1-day-old and 2-day-old parasitoids, especially on 3-day-old eggs. The number of parasitized eggs decreased as egg age increased, and the developmental time of the progeny increased. The emergence rate and percentage of females were hardly affected. For oviposition behavior, 4-day-old parasitoids showed the same drumming and oviposition time on different age eggs, while for others the drumming, drilling, oviposition, and total time increased with increasing S. litura egg age. In summary, the optimal combinations were 3-day-old or 4-day-old female parasitoids and 1-day-old or 2-day-old S. litura eggs. The findings presented in this study can be employed to enhance T. remus mass-rearing efficiency and availability.
PubDate: 2023-09-01
- Cold storage effects on biological parameters of Telenomus remus, a
promising egg parasitoid of Spodoptera frugiperda, reared on Spodoptera
litura eggs-
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Abstract: Abstract Telenomus remus (Nixon) is a promising egg parasitoid for the management of Spodoptera frugiperda (J. E. Smith). This species has been successfully reared on alternative hosts under laboratory conditions. However, the production of biocontrol agents is often out of sync with the demands in the field. Appropriate cold storage techniques can drastically prolong their shelf-life to synchronize the release schedule with field needs and reduce production costs. Past studies on the cold storage of T. remus only focused on certain developmental stages, but not all stages. Here, we comprehensively evaluated the impacts of storage temperature (8, 11, and 14 °C) and duration (7, 14, 21, 28, and 35 days) on the maternal emergence and offspring fitness of T. remus stored at different developmental stages (first instar larvae, second instar larvae, prepupae, and pupae) using Spodoptera litura (Fabricius) eggs as alternative hosts. For each developmental stage, emergence percentage and parasitism capacity of parents all decreased with increased storage duration and decreased storage temperature. Maternal female longevity, offspring emergence percentage and percentage of females were barely affected by cold storage. We concluded that storage of the first instar larvae at 14 °C for 21 days was the optimum storage scheme for T. remus. Our findings can be directly used as guidance in mass production and storage of this parasitoid.
PubDate: 2023-09-01
- Potential utilization of the brewery’s hop wastes as an insecticidal
synergist and repellent against Spodoptera frugiperda-
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Abstract: Abstract The fall armyworm, Spodoptera frugiperda, is becoming a serious invasive insect pest in Asia, Africa, and Oceania due to its broad spectrum of host plants and long flight distances. In response to the increasing risk of insecticide resistance, there is a growing need to develop more effective pest management options. One such option involves the use of synergists, which are substances that, while inert on their own, can enhance the toxicity of other insecticides when combined. In the present study, spent hop from a beer-brewing process was tested to evaluate the synergistic effect on conventional chemical insecticides. Among the five insecticidal compounds frequently used for controlling the fall army worm, spent hop oil and its major constituent, β-myrcene, enhanced the toxicity of deltamethrin, emamectin benzoate, and spinetoram, displaying synergistic interactions in the topical application and injection assays. Electrophysiological studies showed that the neurological responses in the larval CNS were significantly boosted in all three synergistic combinations compared to the individual applications of the insecticides. The remaining ones which did not show any synergistic toxicity in the bioassays also failed to display any neuronal change. β-Myrcene did not show any inhibitory activity on the major detoxifying enzymes of the larval extract. These two observations imply a new and novel neurological synergistic mechanism compared to the traditional synergists. Moreover, β-myrcene also displayed spatial repellency in the larvae of the fall armyworm, which may potentiate multiple usefulness of the spent hop oil for controlling this pest. The synergistic effects on deltamethrin and spinetoram were further confirmed in the simulated spray test using emulsified samples.
PubDate: 2023-09-01
- The natural control agents of the fall armyworm, Spodoptera frugiperda in
Togo: moderating insecticide applications for natural control of the pest'
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Abstract: Abstract Although there has been intensive use of insecticides for the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) management, their effects on population reduction and natural enemies’ performance have not been adequately studied. Therefore, this study investigated the diversity and activity of natural enemies under insecticide and insecticide-free applications. Natural enemies were collected annually from 2016 to 2022 from 348 maize farms throughout the West African nation of Togo. The collections included an entomopathogenic nematode, unidentified bacteria from Enterobacteriaceae and Enterococcus, unidentified viruses from Ascoviruses and Baculoviruses, and several fungal species. Parasitoids collected included hymenopteran and dipteran species that attacked eggs and larvae. The collected predators included species in the following families: Anthocoridae, Carabidae, Chrysopidae, Coccinellidae, Forficulidae, Formicidae, Mantidae, and Reduviidae. The parasitism rates were from 14.72% in 2018 to 45.38% in 2022 for egg masses and from 1.32% in 2016 to 41.85% in 2021 for larvae. The parasitism rates were three to four times higher in unsprayed farms than sprayed farms.
PubDate: 2023-09-01
- Variation in egg mass scale thickness of three Spodoptera species and its
effects on egg parasitoid performance-
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Abstract: Abstract Egg batches of Spodoptera moths are protected by scales deposited by females around and/or over eggs as a physical defense. These scales may affect the parasitism of some parasitoids, rendering biocontrol of Spodoptera eggs ineffective. In this study, we investigated the daily oviposition pattern of moths and the dynamics of egg mass scales of three Spodoptera species and examined the fitnesses of three potential egg parasitoid species to different egg mass scale thicknesses. The observations revealed that the three Spodoptera species share similar scale dynamics. From initial oviposition, S. exigua egg batches maintained a relatively high level of scale thickness (> 134.7 μm) for 2 days and S. frugiperda and S. litura for 3 days (> 105.9 μm, > 161.2 μm, respectively). During this period, the scales effectively hindered parasitism by Trichogramma species (parasitized 0.4%–14.9% eggs). Thereafter, the thickness of the scales decreased daily. The scales of the three Spodoptera species were all relatively thin (< 20.0 μm) after oviposition for 8 days, and subsequently, Trichogramma parasitized eggs more actively (parasitized up to 33.4%–36.5% eggs). Relatively, Trichogramma dendrolimi on S. frugiperda eggs, and Trichogramma chilonis on S. exigua eggs had higher parasitism. Meanwhile, Telenomus remus maintained a very stable and better performance than Trichogramma on Spodoptera species eggs with different scale thicknesses (parasitized 100% egg masses and 46.2%–60.0% eggs), which demonstrated its excellent potential as a Spodoptera species biocontrol agent. The findings elucidate the effect of egg mass scale thickness on effective parasitism by these egg parasitoid species and provide baseline information for the mixed use of Te. remus and Trichogramma against Spodoptera species.
PubDate: 2023-09-01
- Development of multiple transgenic CRISPR/Cas9 methods for genome editing
in the fall armyworm, Spodoptera frugiperda-
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Abstract: Abstract The use of CRISPR/Cas9 system in model insects has facilitated functional genomics studies. However, this system has not been applied to many pest insects. Here, we report on the establishment of multiple transgenic CRISPR/Cas9-based genome editing methods in a global agricultural pest, the fall armyworm (FAW), Spodoptera frugiperda. To identify fluorescent proteins suitable for screening for transgenic FAW, nine transgenic lines expressing genes coding for fluorescent proteins under the control of different promoters were produced and evaluated. The enhanced green fluorescent protein and a red fluorescent protein, tdTomato genes driven by the hr5ie1 promoter were found to be suitable for the identification of transgenic FAW. Multiple lines of transgenic FAW expressing Cas9 were generated and microinjection of sgRNAs into the embryos of these lines failed to induce target gene knockout. To overcome this problem, sgRNAs were expressed in FAW using U6-sgRNA and U6-tRNA-sgRNA systems, U6-tRNA-sgRNA system was found to be more efficient than U6-sgRNA system. Expression of Cas9 and sgRNAs in the same transgenic animal or in two separate strains followed by crossing them to bring Cas9 and sgRNA together resulted in an efficient knockout of target genes. The multiple transgenic CRISPR/Cas9-based genome editing methods developed provide invaluable tools for gene editing and functional genomics studies in this global pest and other lepidopteran pests.
PubDate: 2023-09-01
- Cannibalism and intraguild predation involved in the intra- and
inter-specific interactions of the invasive fall armyworm, Spodoptera
frugiperda, and lepidopteran maize stemborers-
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Abstract: Abstract Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies.
PubDate: 2023-09-01
- The fall armyworm: recent advances in biology and management
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PubDate: 2023-08-19
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