Radar observations of the seasonal migration of brown planthopper (Nilaparvata lugens Stål) in Southern China

Abundance and Seasonal Migration Patterns of Green Lacewings (Neuroptera: Chrysopidae) across the Bohai Strait in Eastern Asia

Many insects, including green lacewings, migrate seasonally to exploit suitable breeding and winter habitats. Green lacewings are important natural enemies of insect pests worldwide. Here, four dominant green lacewing species, Chrysoperla nipponensis (Okamoto), Chrysopa pallens (Rambur), Chrysoperla furcifera (Okamoto), and Chrysopa formosa Brauer, were investigated for their ability to migrate between northern and northeastern China across the Bohai Strait from late May to late October each year. Furthermore, there were significant interannual and seasonal differences in the number of migratory green lacewings collected. The number of green lacewings in spring was significantly lower than that in summer and autumn, and the highest average number of green lacewings occurred in June. In addition, there were differences in the sex ratio of migrating green lacewings between months, with a greater proportion of females than males. Finally, the seasonal migration trajectories simulated by the HYSPLIT model revealed that the green lacewings captured on Beihuang Island primarily originated from Shandong Province. Accordingly, these findings contribute to our understanding of green lacewing migration in eastern Asia and aid its incorporation within integrated pest management (IPM) packages for several crop pests. Furthermore, long-term tracking of migrant insect populations can reveal ecosystem services and trophic dynamic processes at the macroscale.

Comigration and interactions between two species of rice planthopper (Laodelphax striatellus and Sogatella furcifera) and natural enemies in eastern Asia

BACKGROUND

Natural enemies are important in pest control. However, control by natural enemies is hindered by the migration of rice planthoppers. Therefore, comigration and interactions between Laodelphax striatellus (Fallén) and Sogatella furcifera (Horváth) and five predator species, Chrysoperla sinica Tjeder, Harmonia axyridis (Pallas), Episyrphus balteatus, Syrphus corollae (Fab.) and Chrysopa pallens (Rambur) in eastern Asia were investigated.

RESULTS

From 2012 to 2021, the migration patterns of two rice planthoppers and five natural enemy species were monitored by suction trapping on Beihuang Island, Shandong Province, China. Both planthoppers and the five natural enemies regularly comigrated from late April to late October each year. There were significant interannual and seasonal differences in the numbers of two rice planthoppers migrating across this island. Simulated seasonal migration trajectories indicated different source areas for the two rice planthoppers, which mainly originated in northeast, north and east China. The biomass of planthoppers was significantly positively correlated with that of the ladybug H. axyridis in all migration periods, and significant differences in the ratio of rice planthoppers to natural enemies among months. A time-lag effect between seasons was obtained when natural enemies and pests comigrated.

CONCLUSION

Migration was coordinated between rice planthoppers and natural enemies in East Asia. When natural enemies and rice planthoppers comigrated, time lags between seasons were observed. The unique insights into the migration patterns will help to increase understanding of the occurrence of rice planthoppers in eastern Asia and provide an important theoretical basis for regional monitoring and management of rice planthoppers. © 2023 Society of Chemical Industry.

The influences of green light on locomotion, growth and reproduction in the brown planthopper Nilaparvata lugens

BACKGROUND

Light stimulation at a specific wavelength triggers various responses in insects and can be used for pest control. To develop efficient and ecofriendly photophysical pest control methods, the effects of green light on locomotion, growth (molting and eclosion) and reproduction in Nilaparvata lugens (Stål) (BPH), a major rice pest, were studied. Transcriptomics and transmission electron microscopy (TEM) were used to investigate the mechanisms involved.

RESULTS

BPH adults showed disrupted daily locomotion patterns following green light treatment at night and exhibited abnormal locomotion peaks. Total 6-day locomotion of brachypterous adults was significantly greater than in the control group. The durations of growth stages 1-4 were all shorter under green light treatment than in the control, whereas the time from fourth molting to eclosion (stage 5) was significantly longer. When BPH adults under green light treatment began laying eggs, the egg hatching ratio (36.69%) was significantly lower than in the control (47.49%). Moreover, in contrast to the control, BPH molting and eclosion events tended to happen more at night. Transcriptome analysis proved that green light significantly affected the expression of genes involved in cuticular proteins, chitin deacetylase and chitinase, which are related to cuticular development. TEM observations confirmed abnormal cuticular development in nymph and adult BPHs (endocuticle, exocuticle and pore canals) under green light treatment.

CONCLUSION

Green light treatment at night notably affected locomotion, growth and reproduction in BPH, thus providing a novel idea for controlling this pest. © 2023 Society of Chemical Industry.

Slowing virulence adaptation in Asian rice planthoppers through migration-based deployment of resistance genes

Advances in molecular biology have accelerated rice breeding for resistance to Asian planthoppers. However, experience shows that planthoppers quickly adapt to resistance in tropical overwintering areas. With only limited sources available, the large-scale deployment of resistance genes can rapidly reduce the utility of these public goods. Planthoppers that migrate from tropical to temperate Asia carry virulence against many resistance genes, but adapt more slowly to resistant rice in temperate regions. Therefore, by restricting deployment of selected genes to temperate regions, virulence-adaptation rates and the volume of migrants returning to overwintering sites could be reduced. The current open exchange of breeding materials throughout Asia urgently requires an international, multidisciplinary, stakeholder coalition to promote a more sustainable deployment of planthopper-resistant rice.

Shifts in Pseudomonas species diversity influence adaptation of brown planthopper to changing climates and geographical locations

The brown planthopper (BPH) is a monophagous sap-sucking pest of rice that causes immense yield loss. The rapid build-up of pesticide resistance combined with the ability of BPH populations to quickly overcome host plant resistance has rendered conventional control strategies ineffective. One of the likely ways in which BPH adapts to novel environments is by undergoing rapid shifts in its microbiome composition. To elucidate the rapid adaptation to novel environments and the contributions of Pseudomonas toward insect survival, we performed Pseudomonas-specific 16S rRNA gut-microbiome profiling of BPH populations. Results revealed the differential occurrence of Pseudomonas species in BPH populations with changing climates and geographical locations. Further, the observed variation in Pseudomonas species composition and abundance correlated with BPH survivability. Collectively, this study, while adding to our current understanding of symbiont-mediated insect adaptation, also demonstrated a complex interplay between insect physiology and microbiome dynamics, which likely confers BPH its rapid adaptive capacity.

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BPH, a major pest of rice, undergoes seasonal shifts in its microbiome composition

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Pseudomonas sp. in BPH microbiome varied with seasons and geographical locations

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Pseudomonas sp. composition and abundance correlated with BPH survivability

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Environment-guided microbial shifts drive rapid stress adaptations in BPH

Genome-Wide Association Study Reveals a New Quantitative Trait Locus in Rice Related to Resistance to Brown Planthopper Nilaparvata lugens (Stål)

Simple Summary

The brown planthopper Nilaparvata lugens (Stål) (BPH) is one of the main rice pests in Asian areas. The development of rice varieties harboring resistance genes is the most economical and effective method of managing BPH. In this study, 123 rice germplasms were identified for resistance and durable resistance by using the rice planthopper resistance identification system. Forty-two of the 123 rice varieties were classified as resistant to brown planthopper, and among them, twelve rice varieties had a long, durable resistance period. One potential durable resistance to brown planthopper locus on chromosome 2 was found by a genome-wide association study (GWAS). There are 13 candidate genes at this locus, and several of them are related to disease and pest resistance. Our study found a potential durable resistance locus to BPH, which has guiding significance for subsequent resistance breeding.

Abstract

The brown planthopper (BPH) is one of the main pests endangering rice yields. The development of rice varieties harboring resistance genes is the most economical and effective method of managing BPH. To identify new BPH resistance-related genes, a total of 123 rice varieties were assessed for resistance and durable resistance. Three varieties were immune, and nine were highly resistant to BPH. After whole-genome resequencing of all 123 varieties, 1,897,845 single nucleotide polymorphisms (SNPs) were identified. Linkage disequilibrium (LD) decay analysis showed that the average LD of the SNPs at 20 kb was 0.30 (r²) and attenuated to half value (~0.30) at a distance of about 233 kb. A genome-wide association study (GWAS) of durable resistance to BPH was conducted using the Fast-MLM model. One quantitative trait locus, identified on chromosome 2, included 13 candidate genes. Two candidate genes contained a leucine-rich repeat and CC-NBS-LRR or NB-ARC domains, which might confer resistance to pests or diseases. Interestingly, LOC_Os02g27540 was highly expressed and was induced by BPH; GWAS identified potential rice genes coding for durable resistance to BPH. This study helps to elucidate the mechanism of durable resistance to BPH in rice and provides essential genetic information for breeding and functional verification of resistant varieties.

Enhancement of the geomagnetic field reduces the phototaxis of rice brown planthopper Nilaparvata lugens associated with frataxin down-regulation

The geomagnetic field (GMF) is an environmental cue that provides directional information for animals. The intensity of GMF is varied over space and time. Variations in the GMF intensity affect the navigation of animals and their physiology. In this study, the phototaxis of the migratory insect rice planthopper Nilaparvata lugens (N. lugens) and frataxin in N. lugens (Nl-fh), which is a mitochondrial protein required for cellular iron homeostasis and iron-sulfur cluster assembly, were investigated by using different intensities of magnetic field. From the results, individuals of N. lugens showed decreased phototaxis when reared and tested in a behavioral arena under a strong magnetic field. Besides the reduction in performance, an accompanying effect of the strong magnetic field condition was a reduced level of Nl-fh-messenger RNA, and a Nl-fh knockdown indeed impaired the phototactic behavior in a tested sample of insects. This leads to the conclusion that the expression of frataxin is dependent on the strength of the surrounding magnetic field and that functional frataxin facilitates phototactic behavior in N. lugens.

Dispersal of the Common Cutworm, Spodoptera litura, Monitored by Searchlight Trap and Relationship with Occurrence of Soybean Leaf Damage

The common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a major pest of soybean. Pheromone traps are used to monitor male adults, but the catch peaks do not always predict leaf damage in soybean fields. Thus, there is no accurate means of forecasting soybean damage, and insecticide is applied on the basis of farmers’ observations of actual damage in fields. To understand the occurrence of soybean leaf damage, the dispersal of S. litura in a soybean field in southwestern Japan was preliminarily investigated using a searchlight trap in comparison to a pheromone trap at one location, from August to mid-October in 2016–2018. To determine the relationship between pest arrival and crop damage, trap catch numbers and the number of soybean leaves damaged by 1st-instar larvae were examined by separately comparing raw numbers and cumulative numbers. The raw catch numbers of the two trap types in August and September 2016 and 2018 preceded subsequent damage peaks by an average of 5.3 days. This temporal difference coincided with the estimated duration of the egg stage plus an assumed mating period. Furthermore, the cumulative catch numbers of the two traps in August and September were linearly associated with cumulative damaged leaves in the same period in each year and in the three-year period. The coefficient of determination (R²) of linear regression between the cumulative catch numbers of the searchlight trap and the cumulative damaged leaves for the three-year period was much higher than that between the cumulative catch of the pheromone trap and cumulative damage. This suggests that soybean leaf damage is closely linked to the number of S. litura arrivals at the survey site. Thus, the searchlight trap captured S. litura arrivals better than the pheromone trap. As the linear regression function of the cumulative catch of the searchlight trap for the three-year period was tentatively correlated with a prefectural economic injury level for soybean fields, it might be feasible to predict S. litura-induced soybean damage using searchlight traps. The cumulative female catch number of the searchlight trap was also linearly associated with damaged leaves, but the coefficient of determination was generally lower than that with the cumulative total catch. The female ratio of searchlight trap catches in September was <0.5 in contrast to S. litura migrating overseas (>0.5). The advantages and disadvantages of the two trapping methods, as well as necessary further studies are discussed. Our findings provide a foundation for S. litura monitoring with searchlight traps.

Molecular characterization, spatial-temporal expression and magnetic response patterns of iron-sulfur cluster assembly1 (IscA1) in the rice planthopper, Nilaparvata lugens

The mechanisms of magnetoreception have been proposed as the magnetite-based, the chemical radical-pair and biocompass model, in which magnetite particles, the cryptochrome (Cry) or iron-sulfur cluster assembly 1 (IscA1) may be involved. However, little is known about the association among the molecules. Here we investigated the molecular characterization and the mRNA expression of IscA1 in different developmental stages, tissues and magnetic fields in the migratory brown planthopper (BPH), Nilaparvata lugens. NlIscA1 contains an open reading frame of 390 bp, encoding amino acids of 129, with the predicted molecular weight of 14.0 kDa and the isoelectric point of 9.10. Well-conserved Fe-S cluster binding sites were observed in the predicted protein. Phylogenetic analysis demonstrated NlIscA1 to be clustered into the insect's IscA1. NlIscA1 showed up-regulated mRNA expression during the period of migration. The mRNA expression of NlIscA1 could be detected in all the three tissues of head, thorax and abdomen, with the highest expression level in the abdomen. For the macropterous migratory Nilaparvata lugens, mRNA expression of NlIscA1 and N. lugens cryptochrome1 (Nlcry1) were up-regulated under the magnetic fields of 5 Gauss and 10 Gauss in strength (vs. local geomagnetic field), while N. lugens cryptochrome2 (Nlcry2) remained stable. For the brachyterous non-migratory Nilaparvata lugens, no significant changes were found in mRNA expression of NlIscA1, Nlcry1 and Nlcry2 among different magnetic fields. These findings preliminarily reveal that the expression of NlIscA1 and Nlcry1 exhibited coordinated responses to the magnetic field. It suggests some potential associations among the putative magneto-sensitive molecules of cryptochrome and iron-sulfur cluster assembly.

Seasonal Migration Pattern of Nilaparvata lugens (Hemiptera: Delphacidae) Over the Bohai Sea in Northern China

The brown planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) is a major, regionally migratory pest of rice crops in Asia. Despite intensive studies, the seasonal pattern of migration in this species remains largely unknown, especially in northern China. Analysis of monitoring data of light trapping at Beihuang island in northern China showed that brown planthopper migrants could be found at the island in any month from July to October. However, the daily number of brown planthopper migrants varied considerably from day to day, month to month, and year to year. Most of migrants were caught from July to September, with fewer in October. Simulation of backward trajectories showed that there was temporal variation in the source areas of brown planthopper migrants trapped at Beihuang. A majority of migrants trapped at Beihuang in July came from south of Beihuang. In contrast, migrants caught in August and September could be from any direction around the island. Results suggested that the brown planthopper migrants likely traveled northward in July, and Multidirectionally in August and September in northern China. Some of brown planthopper in northeastern China could escape the 'Pied Piper effect' and migrate southward in September.

Seasonal Migration of Pantala flavescens Across the Bohai Strait in Northern China

Pantala flavescens (Fabricius 1798) (Odonata: Libellulidae) is one of the most common species of migratory dragonflies. P. flavescens adults were captured by a searchlight trap on Beihuang Island (BH Island; 38°24'N, 120°55'E) from 2003 to 2016, where there is no freshwater. This inspired our research to analyze the pattern of seasonal migration and population dynamics. Stable hydrogen isotope measurement and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) were used to simulate the migration pathway of P. flavescens between different breeding habitats. The results showed that there was no significant difference among population numbers of this overseas migration across years (F13, 2161 = 0.85, P = 0.604); however, the numbers were significantly different across months (F5, 2161 = 3.91, P = 0.003). Our geospatial natal assignment model suggested that P. flavescens trapped on BH were originated in different geographical regions and might have three movement strategies: wandering around northern China and north-bound (positive) and south-bound (negative) movements. Among them, the majority were engaged in wandering around northern China. Model simulations suggested that P. flavescens toured around BH. The results contribute to the knowledge of P. flavescens population ecology in a large-scale geographic region and will aid in the prediction and interpretation of insect migration patterns in response to climate change.

Migration Analysis of Sogatella furcifera (Hemiptera: Delphacidae) in the Northeastern Hunan Province in June

The Sogatella furcifera (Horváth) is a notorious and destructive insect pest, targeting >4 million hectares of rice cultivated in the Hunan Province. To understand the immigration dynamics, we collected S. furcifera light trap catches from 2006 to 2012 at Niangxiang, Linxiang, and Hanshou. We conducted a migration analysis to estimate the immigration source for the northeastern Hunan Province in June. Moreover, we dissected the ovaries of S. furcifera to classify population characteristics. We found that the first appearance of S. furcifera occurred from late April to early May, with June as the primary time for migrations into the northeastern Hunan Province. The majority of June ovaries caught in light traps were Grade I and Grade II, whereas those collected in paddy fields were Grade III and Grade IV, suggesting that the majority of S. furcifera immigrated into the northeastern Hunan Province. Our analysis points toward the northern and central Indo China Peninsula, the southern Hunan Province, the Guangxi Zhuang Autonomous Region Province, the Guangdong Province, and the Hainan Province as possible immigration sources of S. furcifera in June for the northeastern Hunan Province. We propose terrain, loss of forward flow, and wind shear as causes for the difference observed in light trap catches between Ningxiang, Linxiang, and Hanshou monitoring stations in the June of 2009. Thus, our results suggest that monitoring and forecasting of S. furcifera should be done with particular emphasis in June.

Evidence for the presence of biogenic magnetic particles in the nocturnal migratory brown planthopper, Nilaparvata lugens

Biogenic magnetic particles have been detected in some migratory insects, which implies the basis of magnetoreception mechanism for orientation and navigation. Here, the biogenic magnetic particles in the migratory brown planthopper (BPH), Nilaparvata lugens were qualitatively measured by SQUID magnetometry, and their characteristics were further determined by Prussian Blue staining, electron microscopy and energy dispersive x-ray spectroscopy. The results indicate that there were remarkable magnetic materials in the abdomens and not in the head or thorax of the 3^rd–5^th instar nymphs, and in macropterous and brachypterous female and male adults of BPH. The size of magnetic particles was shown to be between 50–450 nm with a shape factor estimate of between 0.8–1.0 for all the tested BPHs. Moreover, the amount of magnetic particles was associated with the developmental stage (the 3^rd–5^th instar), wing form (macropterous vs. brachypterous) and sex. The macropterous female adults had the largest amount of magnetic particles. Although the existence of magnetic particles in the abdomens of BPH provides sound basis for the assumption of magnetic orientation, further behavioral studies and complementary physical characterization experiments should be conducted to determine whether the orientation behavior of BPH is associated with the magnetic particles detected in this study.

Source Areas for the Early Immigration of Sogatella furcifera (Homoptera: Delphacidae) at Xiushan in the Middle Reach of Yangtze River of China

The spatiotemporal distribution of source areas for the early immigration of the white-backed planthopper, Sogatella furcifera (Horvάth), at Xiushan in the middle reach of Yangtze River of China, was analyzed with HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and ArcGIS 10.0. The analysis was based on light trap data collected during April-July in 2000-2012. The synoptic meteorology backgrounds during the immigration periods were analyzed by GrADS (Grid Analysis and Display System). The light trap catches of S. furcifera varied monthly and annually. S. furcifera started immigration in Xiushan in early April to early May, whereas the main immigration period was in July. The distribution of the source areas varied monthly, and the core was moved from the south to the north gradually. The main source areas of S. furcifera in May were in southwestern Guangxi and northern Vietnam. The source areas of S. furcifera in June were located in southwestern Guangxi and western Hunan. Additionally, some of the pests were from southeastern Yunnan. The source areas in July were in northwestern Guangxi, southwestern Guizhou, eastern Yunnan, and the transitional parts of Guangxi, Guizhou, and Yunnan. The sum frequencies of southwest and south winds on the 850 hPa isobaric surface of Xiushan of May-July in heavy occurrence years were more than the light occurrence years. The key meteorological factors were suggested to be vertical perturbation, precipitation, and wind shear during S. furcifera immigration periods.