Land-use change drives present and future distributions of Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Migration extent and potential economic impact of the fall armyworm in Europe

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith, 1979), is a major agricultural pest native to the Americas that feeds on several crops, particularly maize. Since 2016, FAW has invaded more than 50 African countries, much of Southeast Asia, and Oceania, severely impacting agriculture and posing a threat to global food security. Following its recent detections in Europe in 2023, this study investigates FAW's migratory capacity and potential direct economic impact on European grain maize production under a "no-control" scenario-areas previously unexplored in the context of Europe. We explored FAW's potential distribution across the European continent by incorporating updated climatic data, refined parameter values, and an expanded occurrence dataset into a revised CLIMEX niche model. Our results reveal sizable potential economic impacts with the southern European Member States facing up to €546 ha- 1 grain maize gross margin annual losses, exceeding €900 million under the worst-case scenario. These member states bear the highest risk since they include areas projected to be climatically suitable for both permanent FAW establishment and transient populations during warmer months. This study provides important insights into the risks posed by FAW to Europe and can inform preparedness and decision-making to mitigate the economic consequences of its invasion.

Spongy moths from Europe and Asia: Who could have higher invasion risk in North American?

North American forest systems are significantly impacted by spongy moths (Lymantria dispar Linnaeus). It is unclear, nevertheless, how are the invasion risks of spongy moths from Asia and Europe in North American relative to each other. In this study, we compared the potential ranges of spongy moths from Asia (ASM) and those from Europe (ESM) in North America, and investigated the range shifts between spongy moths in North America (NASM) and ASM and ESM. ASM and ESM would occupy larger potential ranges in North America than NASM, i.e., 7.16 and 6.98 times, respectively. Thus, one should not undervalue the invasive potential posed by spongy moths from Asia and Europe. Compared to ESM, ASM displayed larger ranges in North America. It is likely due to ASM's tolerance of more variable climates. Consequently, even though ASM was more recently introduced to North America than ESM, it's possible that the former has higher invasion risk in North American.

Potential global distributions of an important aphid pest, Rhopalosiphum padi: insights from ensemble models with multiple variables

Species distribution modeling is extensively used for predicting potential distributions of invasive species. However, an ensemble modeling approach has been less frequently used particularly pest species. The bird cherry-oat aphid Rhopalosiphum padi L. is an important pest of wheat (Triticum aestivum L.) worldwide and causes 30% yield losses. Here, we developed a series of ensemble models with multiple variables to predict the habitat suitability of this pest at a global scale. The current suitable habitat for R. padi is mainly distributed in East Asia, South Asia, Europe, southern North America, southern South America, eastern Australia, and New Zealand. The highly suitable regions are primarily distributed in east of China, Japan, most of North America, southeastern South America, most of Europe, and southeastern edge of Australia. In future scenarios, the suitable habitats will undergo a significant contraction overall northward, and no moderately nor highly suitable habitats are predicted for this pest in other areas. Our findings indicate that a high risk of R. padi outbreaks currently exists for the highly suitable regions mentioned above, especially with wheat cultivation, but the capacity of R. padi to cause such outbreaks will weaken in the future. Climate-associated factors are significantly more important than land use, elevation and host-plant factors, and the BIO11 (mean temperature of the coldest quarter), in particular, predominated in shaping projections of R. padi's distribution. The predicted distribution pattern and key ecological factors affecting this pattern identified herein could provide important guidance for developing management policies targeting this economically important pest.

Effects of Climate Change on the Distribution of Papilio xuthus

The Papilio xuthus is a widely distributed species in the genus Papilio of the family Papilionidae, possessing ecological, ornamental, and socio-economic service values. To determine the ecological role of P. xuthus and assess its population distribution under future climate change scenarios, this study utilized the MaxEnt model to predict the geographic distribution of P. xuthus in the future and evaluate its population dynamics. The results indicated that P. xuthus is currently widely distributed in East Asia, with a high suitability area of 1827.83 × 103 km2, primarily in China, Japan, North Korea, and South Korea. Climate change has a significant impact on the geographic distribution of P. xuthus, with its high suitability areas decreasing in the future, particularly within China, where the change is projected to be as high as 46.46% under the SSP126 scenario by the 2050s. The centroid of its high-suitability area is expected to shift northeastward. Key environmental variable analysis revealed that Temperature Seasonality, Mean Temperature of the Wettest Quarter, Precipitation of the Wettest Month, and Precipitation of the Warmest Quarter are critical factors influencing the selection of suitable habitats by P. xuthus. This study assessed the distribution of P. xuthus and provided conservation recommendations, offering a reference for future population control and conservation efforts.

Oviposition-deterrent activity of p-methyl benzaldehyde and 2-hydroxy-5-methoxybenzaldehyde from the extract of Periplocae cortex for the control of Spodoptera frugiperda

BACKGROUND

The invasion of Spodoptera frugiperda into China has caused serious losses to the food industry and has developed varying degrees of resistance to various chemical pesticides. Developing new plant-based pesticides is of great significance for the sustainable management of S. frugiperda.

RESULTS

p-Methyl benzaldehyde, 2-hydroxy-5-methoxybenzaldehyde and 2-hydroxy-4-methoxybenzaldehyde elicited strong electroantennogram (EAG) reactions from S. frugiperda adults. In particular, 14.4 mg/mL p-methyl benzaldehyde produced the strongest EAG reaction. At this concentration, olfactory selection results showed significant repellent activity against adults, while 0.09 mg/mL had significant attractant activity against males. 2-Hydroxy-5-methoxybenzaldehyde had significant attractive effects at 2.40, 7.20, 14.40 mg/mL. However, 0.80 and 14.4 mg/mL showed significant repellent effects on oviposition selection after treatment with p-methyl benzaldehyde, while 0.09 mg/mL showed significant attractant activity, with an oviposition index of 0.48 ± 0.12. Three treatments of 2-hydroxy-5-methoxybenzaldehyde showed significant repellent activity against the oviposition selection. In addition, exposure to these two substances could significantly inhibit the number of spermatophores and eggs laid by a single female.

CONCLUSION

p-Methyl benzaldehyde and 2-hydroxy-5-methoxybenzaldehyde in the secondary metabolites of the Chinese medicinal herb Periplocae cortex have obvious regulatory effects on the olfactory behavior and oviposition selection of Spodoptera frugiperda and significantly inhibit fertility. This result is helpful to understand the relationship between non-host plant secondary metabolites and insects, lay the foundation for new active substances as insect behavior regulators. © 2025 Society of Chemical Industry.

Predicting habitat suitability for the soybean pod borer Leguminivora glycinivorella (Matsumura) using optimized MaxEnt models with multiple variables

The soybean pod borer Leguminivora glycinivorella (Matsumura) is one of the most important soybean pests and often causes serious damage to Glycine max (L.) Merr., a leading source of dietary protein and oil in animal feed. However, the potential distribution patterns of this economically important pest and its driving factors require further investigation. Here, we used the optimized MaxEnt model to predict the potential distribution of this pest with multiple variables associated with climate, land use, and host plant, at its recorded range and a globe scale. Based on 4 variable combinations, the results show that the current suitable habitats of L. glycinivorella are primarily distributed in most of China, the Korean Peninsula, and Japan. Whereas no suitable area is present in other continents. In future projections, the suitable region shows a slight northward expansion compared with the result predicted with current climatic conditions, and the suitable areas of almost all future projections were stable in size. Among the 9 bioclimatic factors, BIO03 (isothermality) consistently highly contributes to the predictions, indicating that temperature may be a key factor influencing the habitat distribution of L. glycinivorella. Comparative analyses of projections further show that non-climatic factors are informative in the modeling as routinely used bioclimate variables. The spatio-temporal distribution patterns of suitable habitats and the regulatory factors predicted in this study could provide important guidance for L. glycinivorella management.

Dominant strain shift in the invasive fall armyworm (Lepidoptera: Noctuidae) populations in Thailand as inferred from mitochondrial COI and nuclear Tpi genes

The fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), is a significant global pest, that exhibits 2 discernible strains, corn strain (CS) and rice strain (RS). After initial detection in the eastern hemisphere in 2016, the dominant strain was identified as RS based only on cytochrome C oxidase subunit I (COI) mitochondrial gene from limited samples from various countries, including Thailand. This study aimed to assess strain and haplotype variation in the S. frugiperda populations in Thailand using both mitochondrial COI and nuclear triosephosphate isomerase (Tpi) genes. Analyses of COI sequences (n = 105) revealed 2 predominant haplotypes, COICSh4 (82.86%) and COIRSh1 (17.14%), and the analyses of Tpi sequences (n = 99) revealed 6 haplotypes, with TpiCa1a (53.53%) being the most prevalent. Of the 98 caterpillar samples, the majority exhibited true CS (83.67%) for both genes. Meanwhile, interstrain hybrids, indicated by gene discordance, accounted for the minority (16.33%). Interestingly, despite the initial dominance of RS during the 2018 outbreak, the current study identified CS as the prevalent strain across all localities in Thailand. These findings suggested a shift in S. frugiperda dynamics in Thailand that was possibly influenced by factors, such as competitive exclusion principle, pesticide usage in rice cultivation, and preferences for corn over rice. Our study suggests a need to reexamine the previous reports of rice-strain dominance in various countries in the eastern hemisphere after the initial invasion.

A Host Tree and Its Specialist Insects: Black Locust (Robinia pseudoacacia) Availability Largely Determines the Future Range Dynamics of Its Specialist Insects in Europe

Black locust is the only host of Robinia-specialist insects in Europe. However, no study to date has examined future range shifts of specialist insects, and the relative effects of host plant availability and other factors on their range shifts. Here, we characterized the future range shifts in the host and its four specialist insects and the factors contributing to changes in their ranges. We detected substantial range expansions in all target species. Climate predictors and host plant availability were expected to have the strongest effects on the range shifts in the host and its specialist insects, respectively, suggesting that the specialist insects will track the ranges of their host. Parectopa robiniella showed the largest potential and expanding ranges and should be made a priority species for controlling invasions of Robinia-specialist insects in Europe. The expanding ranges of all specialist species were largely identified in the United Kingdom, Germany, and France, suggesting that these should be priority regions for mitigating their effects on ecosystems. Reducing future climate change is essential for preventing the spreading of specialist insects in Europe since specialist insects track their specialist host plants, and host range expansions are mainly driven by future climate changes.

Forecasting the future of Fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in India using ecological niche model

The Fall armyworm, Spodoptera frugiperda is the most notorious invasive pest species on maize, recently reported in India. The continuous spread of Fall armyworms to new ecological niches raises global concern. The current study is the first in India to forecast the suitability of a habitat for S. frugiperda using a maximum entropy algorithm. Predictions were made based on an analysis of the relationship between 109 occurrence records of S. frugiperda and pertinent historical, current, and predicted climatic data for the study area. The model indicated that S. frugiperda could thrive in different habitats under the current environmental circumstances, particularly in the west and south Indian states like Maharashtra, Tamil Nadu, and Karnataka. The model predicted that areas with higher latitudes, particularly in Uttar Pradesh, Odisha, West Bengal, and some portions of Telangana, Rajasthan, Chhattisgarh, and Madhya Pradesh, as well as some tracts of northeastern states like Assam and Arunachal Pradesh, would have highly climate-suitable conditions for S. frugiperda to occur in the future. The average AUC value was 0.852, which indicates excellent accuracy of the prediction. A Jackknife test of variables indicated that isothermality with the highest gain value was determining the potential geographic distribution of S. frugiperda. Our results will be useful for serving as an early warning tool to guide decision-making and prevent further spread toward new areas in India.

Molecular recognition between volatile molecules and odorant binding proteins 7 by homology modeling, molecular docking and molecular dynamics simulation

BACKGROUND

Odorant-binding proteins (OBPs) in insects are key to detection and recognition of external chemical signals associated with survival. OBP7 in Spodoptera frugiperda's larval stage (SfruOBP7) may search for host plants by sensing plant volatiles, which are important sources of pest attractants and repellents. However, the atomic-level basis of binding modes remains elusive.

RESULTS

SfruOBP7 structure was constructed through homology modeling, and complex models of six plant volatiles ((E)-2-hexenol, α-pinene, (Z)-3-hexenyl acetate, lauric acid, O-cymene and 1-octanol) and SfruOBP7 were obtained through molecular docking. To study the detailed interactions between the six plant volatile molecules and SfruOBP7, we conducted three 300 ns molecular dynamics simulations for each study object. The correlation coefficients between binding free energy obtained by molecular mechanics/generalized Born surface area together with solvated interaction energy methods and experimental values are 0.90 and 0.88, respectively, showing a good correlation. By comparing binding free energy along with interaction patterns between SfruOBP7 and the six volatile molecules, hotspot residues of SfruOBP7 when binding with different volatile molecules were determined. Hydrophobic interactions stemming from van der Waals interactions play a significant role in SfruOBP7 and these plant volatile systems.

CONCLUSION

The optimized three-dimensional structure of SfruOBP7 and its binding modes with six plant volatiles revealed their interactions, thus providing a means for estimating the binding energies of other plant volatiles. Our study will help to guide the rational design of effective and selective insect attractants. © 2024 Society of Chemical Industry.

Predicting the Potential Global Distribution of the Plum Fruit Moth Grapholita funebrana Treitscheke Using Ensemble Models

The plum fruit moth, Grapholita funebrana Treitschke, is one of the most significant borer pests, often causing huge economic losses in fruit production. However, the potential distribution range of this economically important pest is still poorly understood. For this study, we simulated an ensemble species distribution model to predict the spatiotemporal distribution pattern of G. funebrana at a global scale. The results show that the suitable habitats for this moth, under current environmental conditions, are mainly distributed in Europe; East Asia, including China and Japan; Central Asia; and some parts of America. In future projections, the suitable habitats are predicted to generally expand northward, while the suitable area will remain unchanged overall. However, the area of highly suitable habitat will decrease to only 17.49% of that found under current conditions. None of the nine factors used were revealed to be predominant predictors in terms of contributing to the model, suggesting that the integrated effects of these variables shape G. funebrana's distribution. In this study, the distribution range that has been predicted, especially for the regions with a highly suitable habitat, poses a high risk of G. funebrana outbreaks, highlighting the urgency of pest management. Moreover, in the United States of America (USA) and Japan (for which G. funebrana distributions were not previously recorded), especially in areas highly suitable for this moth, monitoring and quarantine measures should be strengthened to prevent the colonization and further dispersal of this pest, as seen with its close relative G. molesta, which has become a cosmopolitan pest species, migrating from its native region (East Asia) to other continents, including the Americas.

Range dynamics of Anopheles mosquitoes in Africa suggest a significant increase in the malaria transmission risk

Despite a more than 100-year effort to combat malaria, it remains one of the most malignant infectious diseases globally, especially in Africa. Malaria is transmitted by several Anopheles mosquitoes. However, until now few studies have investigated future range dynamics of major An. mosquitoes in Africa through a unified scheme. Through a unified scheme, we developed 21 species distribution models to predict the range dynamics of 21 major An. species in Africa under future scenarios and also examined their overall range dynamic patterns mainly through suitability overlap index and range overlap index. Although future range dynamics varied substantially among the 21 An. species, we predicted large future range expansions for all 21 An. species, and increases in suitability overlap index were detected in more than 90% of the African continent for all future scenarios. Additionally, we predicted high range overlap index in West Africa, East Africa, South Sudan, Angola, and the Democratic Republic of the Congo under future scenarios. Although the relative impacts of land use, topography and climate variables on the range dynamics depended on species and spatial scale, climate played the strongest roles in the range dynamics of most species. Africa might face an increasing risk of malaria transmissions in the future, and better strategies are required to address this problem. Mitigating climate change and human disturbance of natural ecosystems might be essential to reduce the proliferation of An. species and the risk of malaria transmissions in Africa in the future. Our strategies against their impacts should be species-specific.

Future Climate Change and Anthropogenic Disturbance Promote the Invasions of the World's Worst Invasive Insect Pests

Invasive insect pests adversely impact human welfare and global ecosystems. However, no studies have used a unified scheme to compare the range dynamics of the world's worst invasive insect pests. We investigated the future range shifts of 15 of the world's worst invasive insect pests. Although future range dynamics varied substantially among the 15 worst invasive insect pests, most exhibited large range expansions. Increases in the total habitat suitability occurred in more than ca. 85% of global terrestrial regions. The relative impacts of anthropogenic disturbance and climate variables on the range dynamics depended on the species and spatial scale. Aedes albopictus, Cinara cupressi, and Trogoderma granarium occurred four times in the top five largest potential ranges under four future climate scenarios. Anoplophora glabripennis, Aedes albopictus, and Co. formosanus were predicted to have the largest range expansions. An. glabripennis, Pl. manokwari, Co. formosanus, and So. invicta showed the largest range centroid shifts. More effective strategies will be required to prevent their range expansions. Although the strategies should be species-specific, mitigating anthropogenic disturbances and climate change will be essential to preventing future invasions. This study provides critical and novel insights for developing global strategies to combat the invasions of invasive insect pests in the future.

Impact of Climate Change on the Distribution of Three Rare Salamanders (Liua shihi, Pseudohynobius jinfo, and Tylototriton wenxianensis) in Chongqing, China, and Their Conservation Implications

The Wushan Salamander (Liua shihi), Jinfo Salamander (Pseudohynobius jinfo), and Wenxian Knobby Salamander (Tylototriton wenxianensis) are rare national Class II protected wild animals in China. We performed MaxEnt modeling to predict and analyze the potential distribution and trends of these species in Chongqing under current and future climate conditions. Species distribution data were primarily obtained from field surveys, supplemented by museum collections and the existing literature. These efforts yielded 636 records, including 43 for P. jinfo, 23 for T. wenxianensis, and 570 for L. shihi. Duplicate records within the same 100 m × 100 m grid cell were removed using ENMTools, resulting in 10, 12, and 58 valid distribution points for P. jinfo, T. wenxianensis, and L. shihi, respectively. The optimization of feature class parameters (FC) and the regularization multiplier (RM) were applied using R package "ENMeval 2.0" to establish the optimal model with MaxEnt. The refined models were applied to simulate the suitable distribution areas for the three species. The results indicate that the current suitable habitat area for L. shihi accounted for 9.72% of the whole region of the Chongqing municipality. It is projected that, by 2050, the proportion of suitable habitat will increase to 12.54% but will decrease to 11.98% by 2070 and further decline to 8.80% by 2090. The current suitable habitat area for P. jinfo accounted for 1.08% of the whole region of the Chongqing municipality, which is expected to decrease to 0.31%% by 2050, 0.20% by 2070, and 0.07% by 2090. The current suitable habitat area for T. wenxianensis accounted for 0.81% of the whole region of the Chongqing municipality, which is anticipated to decrease to 0.37% by 2050, 0.21% by 2070, and 0.06% by 2090. Human disturbance, climate variables, and habitat characteristics are the primary factors influencing the distribution of three salamander species in Chongqing. The proximity to roads significantly impacts L. shihi, while climate conditions mainly affect P. jinfo, and the distance to water sources is crucial for T. wenxianensis. The following suggestions were made based on key variables identified for each species: (1) For L. shihi, it is imperative to minimize human disturbances and preserve areas without roads and the existing vegetation within nature reserves to ensure their continued existence. (2) For P. jinfo, the conservation of high-altitude habitats is of utmost importance, along with the reduction in disturbances caused by roads to maintain the species' ecological niche. (3) For T. wenxianensis, the protection of aquatic habitats is crucial. Additionally, efforts to mitigate the impacts of road construction and enhance public awareness are essential for the preservation of this species and the connectivity of its habitats.

Entomopathogenic fungi based microbial insecticides and their physiological and biochemical effects on Spodoptera frugiperda (J.E. Smith)

Background

'The fall armyworm, Spodoptera frugiperda', represents a significant threat to maize production, a major staple crop in Asian countries.

Methods

In pursuit of more effective control of this insect pest, our study assessed the physiological and biochemical effects of the entomopathogenic fungus Metarhizium anisopliae against the larvae of S. frugiperda.

Results

Results revealed that, following nine days of treatment, a high concentration of conidia (1.5x107 conidia/mL-1) was toxic to all stages of larvae (second to fifth instar), resulting in 97% mortality of the second instar, 89% mortality of the third instar, 77% mortality of the fourth instar, and 72% mortality of fifth instar. All larval instars were found to have dose-dependent mortality effects. Treated S. frugiperda larvae further displayed significant physiological, morphological, and behavioral changes. Here, treated larvae displayed significantly lower levels of acetylcholinesterase, α-carboxylesterase, and β-carboxylesterase enzyme activity when compared to control groups. Treated larvae underwent an outward morphological change as the result of a decrease in the exterior cuticle of the anal papillae and a demelanization of the interior cuticle. Treated larvae also exhibited abnormal feeding behaviors as a consequence of the negative impact of conidia treatment on the neuromuscular system. Investigation into the effect of M. anisopliae on the non-target organism, the earthworm Eudrilus eugeniae, revealed that M. anisopliae conidia did not produce significant pathogenicity following three days of treatment. Furthermore, histological analysis revealed no significant effect of the entomopathogenic fungi on the gut tissue of the non-target organism.

Conclusion

This study highlights the potential of M. anisopliae in the control of S. frugiperda.

Transcriptomics and interactomics during the primary infection of an SfNPV baculovirus on Spodoptera frugiperda larvae

The fall armyworm (FAW), Spodoptera frugiperda, has been the most devastating pest of corn as well as of other crops in America, and more recently in Africa and Asia. The development of resistance to chemical insecticides led the search for environmentally friendly biological alternatives such as baculoviruses. This study focuses on the primary infection of the baculovirus SfNPV-Ar in the FAW's midgut epithelium, by analyzing the differential expression of transcripts in excised midguts at 6, 12, and 24 h post-infection (hpi), and predicted their interactions. Interaction of viral factors with the infected midgut tissue could alters various cellular processes, such as the apoptotic system due to the up-regulation observed of FABP at 6 hpi and of HSP90 at 24 hpi, along with the down-regulated PRX at 6 hpi and FABP transcripts between 12 and 24 hpi. Changes in transcript regulation could affect the cellular architecture of infected cells due to up-regulation of ARP 2/3 at 6 and 12 hpi, followed by down-regulation at 24 hpi. In relation to protein folding proteins, HSP90 was up-regulated at 24 hpi and PDI was down-regulated between 6 and 12 hpi. With respect to metabolism and cellular transport, AcilBP and ATPS0 were up regulated at 6 hpi and 12 hpi, respectively. In reference to transcription and translation up-regulation of RPL11 at 6 hpi and of FPN32 and RPL19 at 24 hpi was detected, as well as the down-regulation of RPL19 at 6 hpi, of PDI and RPL7 at 12 hpi, and of FABP at 24 hpi. In conclusion, gene regulation induced by viral infection could be related to the cytoskeleton and cellular metabolism as well as to oxidative stress, apoptosis, protein folding, translation, and ribosomal structure. The results presented in this work are an approach to understanding how the virus takes control of the general metabolism of the insect host during the primary infection period.

Climatic niche and range shifts of grey squirrels (Sciurus carolinensis Gmelin) in Europe: An invasive pest displacing native squirrels

BACKGROUND

As an invasive pest from North America, grey squirrels (GSs; Sciurus carolinensis Gmelin) are displacing native squirrels in Europe. However, the climatic niche and range dynamics of GSs in Europe remain largely unknown. Through niche and range dynamic models, we investigated climatic niche and range shifts between introduced GSs in Europe and native GSs in North America.

RESULTS

GSs in North America can survive in more variable climatic conditions and have much wider climatic niche breadth than do GSs in Europe. Based on climate, the potential range of GSs in Europe included primarily Britain, Ireland, and Italy, whereas the potential range of GSs in North America included vast regions of western and southern Europe. If GSs in Europe could occupy the same climatic niche space and potential range as GSs in North America, they would occupy an area ca. 2.45 times the size of their current range. The unfilling ranges of GSs in Europe relative to those of GSs in North America were primarily in France, Italy, Spain, Croatia, and Portugal.

CONCLUSION

Our observations implied that GSs in Europe have significant invasion potential, and that range projections based on their occurrence records in Europe may underestimate their invasion risk. Given that small niche shifts between GSs in Europe and in North America could lead to large range shifts, niche shifts could be a sensitive indicator in invasion risk assessment. The identified unfilling ranges of the GS in Europe should be prioritized in combating GS invasions in the future. © 2023 Society of Chemical Industry.

Life table study of Spodoptera frugiperda at different wheat stages and the effect of larval population density on wheat yield

BACKGROUND

Spodoptera frugiperda is an invasive, widespread agricultural pest in China. However, there have been no reports assessing feeding damage on wheat caused by S. frugiperda. To clarify the fitness and potential damage of S. frugiperda to wheat, this study analyzed the population parameters of S. frugiperda fed on wheat in a laboratory and simulated the potential damage in field conditions.

RESULTS

The population parameters of S. frugiperda were compared using life tables on wheat at the seedling and adult plant stages. The adult female longevity of S. frugiperda varied from 12.29 days on seedling plants to 16.60 days on adult plants. Egg production was significantly higher when fed on wheat at the seedling stage (646.34 eggs) than when fed on adult plants (495.86 eggs). On wheat at the seedling and adult plant stages, the mean generation times were 35.42 and 38.34 days, respectively, and the intrinsic rates of increase were 0.15 and 0.14, respectively. Spodoptera frugiperda completed development and increased its population in wheat at both plant growth stages. In the field, the effect of different larval densities on the 1000-kernel weight of wheat was significantly different. An action threshold of 40 larvae per m2 was estimated, and the higher population densities caused a yield loss of 17.7%.

CONCLUSION

Spodoptera frugiperda can complete its life cycle on wheat at different stages. Wheat can serve as an alternative host for S. frugiperda. If S. frugiperda reaches 320 larvae per m2 density during wheat growth, it will cause yield loss exceeding 17%. © 2023 Society of Chemical Industry.

Association of growth-regulating insecticides and limonoid-based formulations: physicochemical compatibility and toxicity against Spodoptera frugiperda (Lepidoptera: Noctuidae)

The objective of this study was to evaluate the physicochemical compatibility of mixtures of synthetic and botanical limonoid-based insecticides, as well as the toxicity of these associations, in the management of Spodoptera frugiperda (J.E. Smith) under laboratory and field conditions. For this, the associations of 4 commercial botanical insecticides based on neem registered in Brazil (Azamax, Agroneem, Azact CE, and Fitoneem) were tested with synthetic insecticides from the group of growth regulators (IGRs [triflumuron, lufenuron, methoxyfenozide and tebufenozide]). When mixed, all combinations caused a significant reduction in the pH of the mixture and a significant increase in electrical conductivity. However, all tested combinations showed similar stability behavior to the negative control (distilled water), which demonstrated their physicochemical compatibility. Furthermore, in laboratory and field bioassays, mixtures of IRGs with limonoid-based formulations provided satisfactory effects in the management of S. frugiperda. However, binary mixtures of insecticide Intrepid 240 SC with Azamax or Azact CE (at LC25 previously estimated) showed the highest toxicities on S. frugiperda larvae in laboratory bioassays and damage reduction caused by S. frugiperda in a 2-yr field experiments. Therefore, mixtures of IGRs with limonoid-based botanical insecticides are promising alternatives for the management of S. frugiperda and important component of integrated pest management and insect resistance management programs.

Migration risk of fall armyworm (Spodoptera frugiperda) from North Africa to Southern Europe

With the development of globalization and agriculture trade, as well as its own strong migratory capacity, fall armyworm (FAW) (Spodoptera frugiperda) (J.E. Smith) has invaded more than 70 countries, posing a serious threat to the production of major crops in these areas. FAW has now also been detected in Egypt in North Africa, putting Europe, which is separated from it only by the Mediterranean Sea, at high risk of invasion. Therefore, this study integrated multiple factors of insect source, host plant, and environment to provide a risk analysis of the potential trajectories and time periods of migration of FAW into Europe in 2016~2022. First, the CLIMEX model was used to predict the annual and seasonal suitable distribution of FAW. The HYSPLIT numerical trajectory model was then used to simulate the possibility of the FAW invasion of Europe through wind-driven dispersal. The results showed that the risk of FAW invasion between years was highly consistent (P<0.001). Coastal areas were most suitable for the expansion of the FAW, and Spain and Italy had the highest risk of invasion, with 39.08% and 32.20% of effective landing points respectively. Dynamic migration prediction based on spatio-temporal data can enable early warning of FAW, which is important for joint multinational pest management and crop protection.

Bacillus thuringiensis-Based Bioproduct: Characterization and Performance Against Spodoptera frugiperda Strains in Maize Under Different Environmental Temperatures

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an important pest in several regions being the use of Bacillus thuringiensis-based bioproducts an alternative for its control. Firstly, 3 L of an aqueous bioproduct suspension was produced and characterized. Its 50% lethal concentration against molecularly identified corn and rice S. frugiperda strains using an artificial diet were 77.01% (95% CL, 68.16-90.47) and 2.22% (95% CL, 0.01-6.68), respectively. The next objective of this work was to evaluate the performance of this bioproduct in maize against S. frugiperda strains under different simulated agrological regions mimicking their corresponding periodic day/night temperatures. Thus, the impact of environmental temperature on the bioproduct efficacy (E) was studied. It was observed that a warmer scenario (35 °C day/30 °C night) could favor the tolerance of corn S. frugiperda strain to the bioproduct (E = 56.36 ± 0.61%) maintaining a high efficacy (92.44 ± 6.55%) when it was tested against rice S. frugiperda strain. Conversely, under temperate conditions, efficacy values ranged from 84 to 95% for both S. frugiperda strains. On the other hand, based on a foliar feeding damage analysis, our bioproduct displayed a significant foliar protection in maize plants infested with either corn or rice S. frugiperda strains.

Fall armyworm from a maize multi-peril pest risk perspective

We assembled 3,175 geo-tagged occurrences of fall armyworm worldwide and used that data in conjunction with information about the physiological requirements of the pest to spatially assess its global climate suitability. Our analysis indicates that almost the entire African maize crop is grown in areas with climates that support seasonal infestations of the insect, while almost 92% of the maize area supports year-round growth of the pest. In contrast, rich-country maize production largely occurs in temperate areas where only 2.3% of the area may allow the pest to survive year-round, although still subject to worrisome seasonal risks. This means the African maize crop is especially susceptible to damaging infestation from fall armyworm, on par with the risk exposure to this pest faced by maize producers throughout Latin America. We show that the maize grown in Africa is also especially vulnerable to infestations from a host of other crop pests. Our multi-peril pest risk study reveals that over 95% of the African maize area deemed climate suitable for fall armyworm, can also support year-round survival of at least three or more pests. The spatial concurrence of climatically suitable locations for these pests raises the production risk for farmers well above the risks posed from fall armyworm alone. Starkly, over half (52.5%) of the African maize area deemed suitable for fall armyworm is also at risk from a further nine pests, while over a third (38.1%) of the area is susceptible to an additional 10 pests. This constitutes an exceptionally risky production environment for African maize producers, with substantive and complex implications for developing and implementing crop breeding, biological, chemical and other crop management strategies to help mitigate these multi-peril risks.

Modelling the current and future potential distribution of the bean bug Riptortus pedestris with increasingly serious damage to soybean

BACKGROUND

The bean bug, Riptortus pedestris, has received intense attention in recent years because of its involvement in increasing outbreaks of staygreen syndrome in soybean (Glycine max (L.)), often causing almost 100% loss of soybean yield in China. However, for this pest of great economic importance, potential current and future distribution patterns and their underlying driving factors remain unclear.

RESULTS

Maxent modelling under climate, elevation and land-use (including the distribution information of G. max) variables showed that the current potential distribution covered a vast geographic range, primarily including most parts of south, South East and east Asia. Under future environmental scenarios, suitable habitat expanded markedly. Areas that would become highly suitable for R. pedestris were primarily located in north-east China and west India. Five bioclimatic (BIO13, BIO08, BIO18, BIO02 and BIO07) and one land-use (C3 annual crops) predictors contributed approximately 95% to the modelling, and analyses of curve responses showed that to a certain extent, R. pedestris preferred relatively high temperature and precipitation. Our results indicate that a high risk of R. pedestris outbreaks is present in parts of Asia, especially in the soybean-growing regions of China, and this risk will continue in the future.

CONCLUSION

The predicted distribution pattern and key regulating factors identified herein could provide a vital reference for developing pest management policies and further alleviate the incidence of staygreen syndrome in soybean. © 2022 Society of Chemical Industry.

Pest population dynamics are related to a continental overwintering gradient

Overwintering success is an important determinant of arthropod populations that must be considered as climate change continues to influence the spatiotemporal population dynamics of agricultural pests. Using a long-term monitoring database and biologically relevant overwintering zones, we modeled the annual and seasonal population dynamics of a common pest, Helicoverpa zea (Boddie), based on three overwintering suitability zones throughout North America using four decades of soil temperatures: the southern range (able to persist through winter), transitional zone (uncertain overwintering survivorship), and northern limits (unable to survive winter). Our model indicates H. zea population dynamics are hierarchically structured with continental-level effects that are partitioned into three geographic zones. Seasonal populations were initially detected in the southern range, where they experienced multiple large population peaks. All three zones experienced a final peak between late July (southern range) and mid-August to mid-September (transitional zone and northern limits). The southern range expanded by 3% since 1981 and is projected to increase by twofold by 2099 but the areas of other zones are expected to decrease in the future. These changes suggest larger populations may persist at higher latitudes in the future due to reduced low-temperature lethal events during winter. Because H. zea is a highly migratory pest, predicting when populations accumulate in one region can inform synchronous or lagged population development in other regions. We show the value of combining long-term datasets, remotely sensed data, and laboratory findings to inform forecasting of insect pests.

Niche and range dynamics of Tasmanian blue gum (Eucalyptus globulus Labill.), a globally cultivated invasive tree

The ecological niche concept has provided insights into various areas in ecology and biogeography. Although there remains much controversy regarding whether species niches are conserved across space and time, many recent studies have suggested that invasive species conserve their climatic niche between native and introduced ranges; however, whether the climatic niche of cultivated invasive species, whose niches are strongly affected by human activities, are conserved between native and introduced ranges remains unclear. Additionally, the range dynamics of invasive species in their native and introduced regions have not been extensively studied. Here, we investigated the niche and range dynamics of Tasmanian blue gum (Eucalyptus globulus Labill.), a globally cultivated invasive tree, using ecological niche models and niche dynamic analyses. The most important factors affecting the niche changes between native and introduced Tasmanian blue gum were max temperature of the warmest month and precipitation of the wettest month. The climate niche was not conserved between introduced and native range Tasmanian blue gum; moreover, the niche area of the former was ca. 7.4 times larger than that of the latter, as introduced Tasmanian blue gum could survive in hotter, colder, wetter, and drier climates. In addition, the potential range of introduced Tasmanian blue gum was ca. 32 times larger than that of its native counterpart. Human introduction and cultivation may play a key role in the niche and range expansion of introduced Tasmanian blue gum. Given that small increases in niche area can result in large range expansions, the niche expansion of an invasive species could be used to evaluate invasion risk, which might even be more sensitive than range expansions.

The high invasion success of fall armyworm is related to life-history strategies across a range of stressful temperatures

BACKGROUND

Insects living in unfavorably high or low temperatures are predicted to display a fast or slow life-history strategy. Here, we examined life histories of fall armyworm (FAW), a globally important invasive species with a broad ecological niche, at five constant temperatures of 13, 19, 25, 31 and 37°C, to study life-history responses to different temperatures.

RESULTS

In our experiment, FAW had lower lifetime fecundity at unfavorable temperatures, a finding that is consistent with the idea that FAW can shift resources from reproduction to other functions under stressful conditions-such as heat or cold tolerance. Given the adverse effects of stressful temperatures, life-history strategies arise from individuals having limited remaining resources to allocate towards vital functions like survival or reproduction. Here we show plasticity in life-history strategies adopted at different temperatures. Rather than simply varying along a fast-slow continuum, FAW at unfavorably high temperatures exhibited lower daily fecundity and longer reproductive lifespans, and at unfavorably low temperatures showed a shorter peak in reproduction later in life, compared with FAW at 25°C. Such patterns, if adaptive, could suggest a strategy mitigating reproductive and mortality risk in unfavorable environments, however, this remains to be tested.

CONCLUSION

Our analysis suggests that the high invasion success of FAW may result from their ability to adjust life-history strategies, across a range of stressful temperatures, in a way that reduces not only mortality, but also fecundity loss. The adoption of such strategies may be instrumental for the global invasion success of FAW. © 2022 Society of Chemical Industry.

Designing a Pest and Disease Outbreak Warning System for Farmers, Agronomists and Agricultural Input Distributors in East Africa

Simple Summary

Designing early warning systems for threats to food crops in Africa must respond to the needs of potential users of the system. This paper provides evidence from professional distributors, retailers, researchers, and agronomists in East Africa who may be able to use and communicate the results of the predictive modeling of pest outbreaks. Understanding the timing and spatial extent of required warnings will help guide research and engagement in these rapidly commercializing countries.

Abstract

Early warnings of the risks of pest and disease outbreaks are becoming more urgent, with substantial increases in threats to agriculture from invasive pests. With geospatial data improvements in quality and timeliness, models and analytical systems can be used to estimate potential areas at high risk of yield impacts. The development of decision support systems requires an understanding of what information is needed, when it is needed, and at what resolution and accuracy. Here, we report on a professional review conducted with 53 professional agronomists, retailers, distributors, and growers in East Africa working with the Syngenta Foundation for Sustainable Agriculture. The results showed that respondents reported fall armyworm, stemborers and aphids as being among the most common pests, and that crop diversification was a key strategy to reduce their impact. Chemical and cultural controls were the most common strategies for fall armyworm (FAW) control, and biological control was the least known and least used method. Of the cultural control methods, monitoring and scouting, early planting, and crop rotation with non-host crops were most used. Although pests reduced production, only 55% of respondents were familiar with early warning tools, showing the need for predictive systems that can improve farmer response.

Including Host Availability and Climate Change Impacts on the Global Risk Area of Carpomya pardalina (Diptera: Tephritidae)

Fruit flies are a well-known invasive species, and climate-based risk modeling is used to inform risk analysis of these pests. However, such research tends to focus on already well-known invasive species. This paper illustrates that appropriate risk modeling can also provide valuable insights for flies which are not yet “on the radar.” Carpomya pardalina is a locally important cucurbit-infesting fruit fly of western and central Asia, but it may present a risk to other temperate countries where melons are grown. MaxEnt models were used to map the risk area for this species under historical and future climate conditions averaged from three global climate models under two shared socio-economic pathways in 2030 and 2070 from higher climate sensitivity models based on the upcoming 2021 IPCC sixth assessment report. The results showed that a total of 47.64% of the world’s land mass is climatically suitable for the fly; it could establish widely around the globe both under current and future climates with host availability. Our MaxEnt modeling highlights particularly that Western China, Russia, and other European countries should pay attention to this currently lesser-known melon fly and the melons exported from the present countries. The current and expanding melon trade could offer direct invasion pathways to those regions. While this study offers specific risk information on C. pardalina, it also illustrates the value of applying climate-based distribution modeling to species with limited geographic distributions.

Gene Expression Differences Between Developmental Stages of the Fall Armyworm (Spodoptera frugiperda)

The fall armyworm (Spodoptera frugiperda) is one of the most significant agricultural pests in the world and invaded China in early 2019. We sampled and sequenced RNA-seq data from 15 individuals across different developmental stages. Developmental stages were the larval stage (5th instar larvae and 6th instar larvae), chrysalis stage, and adult stage (female adult and male adult). Individual samples were mainly clustered by developmental stages and we then identified variation between developmental stages of differentially expressed transcripts (DETs). There were 2136 upregulated DETs and 1391 downregulated DETs in the larval stage when comparing larval and chrysalis stages. In the comparison between the chrysalis and adult stages, there were 2033 upregulated DETs and 1391 downregulated DETs in the chrysalis stage. In total, 19,195 abundantly expressed transcripts were obtained and 10% of them were DETs. We then obtained stage-specific DETs to investigate the potential function of the fall armyworm during different developmental stages. We also constructed our annotation background set for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. This indicated that the fall armyworm may undergo active metabolism during its lifespan, even in the chrysalis stage. And it also may experience detoxifying and xenobiotic metabolism throughout its life, especially in the larval stage, which partially explains the difficulty to eradicate using chemical control. Our study is the first insight into the developmental patterns of the fall armyworm and we also provide the fundamental information about enhanced drug resistance at the level of transcriptome. These results are beneficial for a future investigation related to the eradication and/or control stage.

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.

Bioclimatic zonation and potential distribution of Spodoptera frugiperda (Lepidoptera: Noctuidae) in South Kivu Province, DR Congo

BACKGROUND

The fall Armyworm (FAW) Spodoptera frugiperda (JE Smith), is currently a devastating pest throughout the world due to its dispersal capacity and voracious feeding behaviour on several crops. A MaxEnt species distributions model (SDM) was developed based on collected FAW occurrence and environmental data's. Bioclimatic zones were identified and the potential distribution of FAW in South Kivu, eastern DR Congo, was predicted.

RESULTS

Mean annual temperature (bio1), annual rainfall (bio12), temperature seasonality (bio4) and longest dry season duration (llds) mainly affected the FAW potential distribution. The average area under the curve value of the model was 0.827 demonstrating the model efficient accuracy. According to Jackknife test of variable importance, the annual rainfall was found to correspond to the highest gain when used in isolation. FAWs' suitable areas where this pest is likely to be present in South Kivu province are divided into two corridors. The Eastern corridor covering the Eastern areas of Kalehe, Kabare, Walungu, Uvira and Fizi territories and the Western corridor covering the Western areas of Kalehe, Kabare, Walungu and Mwenga.

CONCLUSIONS

This research provides important information on the distribution of FAW and bioclimatic zones in South Kivu. Given the rapid spread of the insect and the climatic variability observed in the region that favor its development and dispersal, it would be planned in the future to develop a monitoring system and effective management strategies to limit it spread and crop damage.

Overwintering Distribution of Fall Armyworm (Spodoptera frugiperda) in Yunnan, China, and Influencing Environmental Factors

Simple Summary

The fall armyworm (Spodoptera frugiperda) is a nondiapausing insect pest capable of causing large reductions in the yield of crops, especially maize. Every year, the new generation of fall armyworms from Southeast Asia flies to East Asia via Yunnan, and some of them will grow, develop and reproduce in Yunnan since the geographical location and environmental conditions of Yunnan are very beneficial for the colonization of fall armyworms. This study explored the potential overwintering distribution of fall armyworms in Yunnan and the influence of environmental factors on its distribution. These results provide a basis for the precise prevention and control of fall armyworms by guiding management and decision-making and may facilitate meaningful reductions in pesticide application.

Abstract

The first fall armyworm (FAW; Spodoptera frugiperda) attack in Yunnan, China, occurred in January 2019. Because FAW lacks diapause ability, its population outbreaks largely depend on environmental conditions experienced during the overwinter months. Thus, there is an urgent need to make short-term predictions regarding the potential overwintering distribution of FAW to prevent outbreaks. In this study, we selected the MaxEnt model with the optimal parameter combination to predict the potential overwintering distribution of FAW in Yunnan. Remote sensing data were used in the prediction to provide real-time surface conditions. The results predict variation in the severity and geographic distribution of suitability. The high potential distribution shows a concentration in southwestern Yunnan that suitability continues to increase from January to March, gradually extending to eastern Yunnan and a small part of the northern areas. The monthly independent contributions of meteorological, vegetation, and soil factors were 30.6%, 16.5%, and 3.4%, respectively, indicating that the suitability of conditions for FAW was not solely dominated by the weather and that ground surface conditions also played a decisive role. These results provide a basis for the precise prevention and control of fall armyworms by guiding management and decision-making and may facilitate meaningful reductions in pesticide application.

Understanding smallholders' responses to fall armyworm (Spodoptera frugiperda) invasion: Evidence from five African countries

Fall armyworm (FAW) is a new invasive pest that is causing devastating effects on maize production and threatening the livelihoods of millions of poor smallholders across sub-Saharan Africa and Asia. Using unique survey data from 2356 maize-growing households in Ghana, Rwanda, Uganda, Zambia and Zimbabwe, we examined how smallholder farmers are fighting this voracious pest. In particular, we assessed the FAW management strategies used by smallholders, socio-economic factors driving the choice of the management options, the complementarities or tradeoffs among the management options, and the (un)safe pesticide use practices of farmers. Results showed that smallholder farm households have adopted a variety of cultural, physical, chemical and local options to mitigate the effects of FAW, but the use of synthetic pesticides remains the most popular option. Results from multivariate probit regressions indicated that the extensive use of synthetic pesticides is driven by household asset wealth, and access to subsidised farm inputs and extension information. We observed that farm households are using a wide range of pesticides, including highly hazardous and banned products. Unfortunately, a majority of the households do not use personal protective equipment while handling the pesticides, resulting in reports of acute pesticide-related illness. Our findings have important implications for policies and interventions aimed at promoting environmentally friendly and sustainable ways of managing invasive pests in smallholder farming systems.

Double-edged effects of climate change on plant invasions: Ecological niche modeling global distributions of two invasive alien plants

The prediction of the potential distribution of invasive alien species is key for the control of their proliferation. This study developed ensemble niche models to explore the distribution patterns of Cecropia peltata and Ulex europaeus under baseline and future conditions, as well as the factors that regulate them. The models were based on occurrence records as well as climate, land-use and topography datasets. Climatic factors played a stronger role than land-use and topographical factors in their distribution patterns. Additionally, temperature seasonality and temperature annual range were the optimal predictor for the global distributions of C. peltata and U. europaeus, respectively. Under the baseline-RCP 8.5 scenario in 2070, significant increases in habitat suitability for C. peltata were generally detected in tropical regions, while for U. europaeus under the same condition, significant increases in habitat suitability were generally observed in west coast of South America and Europe, suggesting the impacts of climate changes on species distribution may be species specific. The contrast changes of suitable habitat areas for U. europaeus under the baseline-2.6 and 8.5 scenarios may suggest that the scenarios of climate changes may modify its distribution patterns and variations in suitable habitats. The double-edged effects of global warming on plant invasions may be a result of the scenario specific climate change and the species-specific responses to changes in climate. Our findings highlight the importance of climate change scenario specific and species-specific research on the impact of climate change on plant invasions.