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Development of insecticide resistance often changes life history traits of insect pests, because metabolic detoxification of insecticides in insect bodies requires huge energetic reserves. The brown planthopper, Nilaparvata lugens (Stål), an important insect pest of rice crop in East and Southeast Asia, has developed strong resistance to imidacloprid from mid-2000s. The aim of this study was to examine the costs of life history traits and reveal changes in energy reserves with developing imidacloprid resistance. We compared the life history traits (survival time, fecundity, developmental time, and hatchability) and total lipid content between imidacloprid-resistant and imidacloprid-susceptible (control) brown planthopper strains. As compared to the control strains, adults’ survival time of the resistant females was shorter, and their fecundity was lower; the other life history traits did not differ significantly between the resistant and control strains. As the results, net reproductive rates (R0) were lower in the resistant strains than in the susceptible strains. However, the amount of stored lipids was larger in resistant females than control ones. Our findings demonstrated a physiological trade-off between the development of imidacloprid resistance and the reproductive traits of brown planthopper. The imidacloprid-resistant strains are likely to store lipids for metabolic detoxification rather than consume them for reproduction.

BackgroundTo avoid and delay the resistance breakdown of varieties against pathogens and insect pests, broad-spectrum and durable resistance by multiple genes pyramiding are expected to be one of the practical approaches. The indica rice variety PTB33 (Oryza sativa L.) shows high and durable resistance to the brown planthopper (BPH, Nilaparvata lugens Stål). However, this variety gradually lost its resistance against the recent virulence development of BPH. However, breakdown processes are not fully elucidated by individual genetic loci. ResultsEffective QTLs were explored across the whole genomic region against four BPH populations collected in Japan in 1988, 1989, 1999, and 2013 using high-density single-nucleotide polymorphism (SNP) markers obtained by genotyping-by-sequencing. Among seven genomic regions of PTB33 likely conferring BPH resistance, four QTLs, qFSA4a, qFSA6, qFSA11, and qFSA12 on chromosomes 4, 6, 11, and 12, respectively, were validated as BPH resistance QTLs. The PTB33 alleles at the four QTLs positively contributed to BPH resistance. Infestation of monogenic segregating lines showed that the PTB33 alleles at qFSA11, qFSA12, and qFSA4a lost resistance effects at least in 1989, 1999, and 2013, respectively. ConclusionThis study showed breakdown of durable resistance in PTB33 was explained by step-by-step losses of genetic effects at each resistance locus and probably multiple acquisitions of virulence genes in BPH in a gene-by-gene specific manner.

Resistant rice cultivars are an alternative of insecticide control for one of the major rice pests: the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae). However, N. lugens has obtained virulence to resistant rice cultivars as same as insecticide resistance. The monitoring of virulence to differential cultivars is important for detections of the breakdown of resistance genes ‘BPH’ owned by the cultivars. We conducted long-term virulence monitoring (2001–2019) of differential cultivars in N. lugens immigrant populations in Japan. The virulence to the cultivars IR26 (BPH1), Mudgo (BPH1), and ASD7 (BPH2) was higher than that to other differential cultivars. The virulence to Babawee (BPH4) was lower than that to IR26, Mudgo, and ASD7, but it fluctuated over the immigrant years. The virulence to Kanto-PL7 (BPH3), Rathu Heenati (BPH3, BPH17) and Balamawee (BPH27, Three QTLs) was lower than that to other differential cultivars. The immigrant populations have therefore not developed virulence to three differential cultivars. These results suggest that N. lugens continued to develop virulence to differential cultivars that possess BPH1 and BPH2 after the breakdown. However, our results indicate that N. lugens could not break through the efficacy of differential cultivars possessing multiple BPH resistance genes.

Background Long-term monitoring data is helpful to understand the fluctuation of susceptibility and pattern of cross resistance in insecticide resistance management. After the occurrence of imidacloprid resistance, the brown planthopper (BPH) has gradually developed resistance to thiamethoxam and clothianidin since 2010, but not to dinotefuran and nitenpyram. Here, we analyzed susceptibilities data of five neonicotinoids during 2005-2017 in East Asia and Vietnam to conduct cross-resistance patterns among neonicotinoids. To determine the factors of development of cross resistance in laboratory bioassays, we used the imidacloprid resistant and control strains that were selected from filed populations in the Philippines and Vietnam. Results The Linear Mixed Models (LMM) analyses of insecticide susceptibility data showed that the slope values of imidacloprid resistance effects were 0.68 and 1.09 for resistance to thiamethoxam and clothianidin, respectively. Laboratory bioassay results showed that the LD50 values for thiamethoxam and clothianidin in resistant strains (1.4-5.5 μg g-1 ) were 3.2-16.4 times higher than those in the control strains (0.28-1.5 μg g-1 ). However, the increase in the LD50 values for imidacloprid was not related to that for dinotefuran and nitenpyram based on the results of the LMM analysis and laboratory bioassay. Conclusion Our results demonstrate that the development of imidacloprid resistance result in strong-cross resistance to some neonicotinoids, thiamethoxam and clothianidin, but not to others, dinotefuran and nitenpyram. We anticipate that our findings will be a starting point for understanding mechanism of the different trend of cross resistance by analyzing long-term susceptibility data and laboratory bioassays in insect pests. © 2019 Society of Chemical Industry.

The recent reemergence of rice black-streaked dwarf virus (RBSDV) has caused severe rice yield losses in several areas of East Asia. To identify the most important infectious sources of RBSDV, we compared the susceptibility of major poaceous plants to RBSDV infection and survival and the RBSDV acquisition efficiency of a vector insect, the small brown planthopper Laodelphax striatellus. RBSDV infection and survival rates of L. striatellus were significantly high in wheat (Triticum aestivum ‘Norin61’) and rice (Oryza sativa ‘Reiho’), indicating that these crops can be important sources of RBSDV. Our results also showed that RBSDV can complete its infection cycle between Italian ryegrass (Lolium multiflorum ‘Hataaoba’) and L. striatellus. These results indicate that control of RBSDV and L. striatellus on winter-spring crops of wheat and Italian ryegrass may avoid an RBSDV epidemic on rice during the following summer. In addition to infections of wheat and Italian ryegrass, RBSDV infections were detected in Avena fatua, Avena sterilis subsp. ludoviciana, Cynosurus echinatus, Festuca arundinacea, Festuca pratensis, Lolium perenne, and Vulpia myuros var. megalura, although the infection efficiency varied.

Background Strong resistance to imidacloprid in Nilaparvata lugens (Stal) has developed in Southeast and East Asia. Although the mode of inheritance for resistance is very useful information for pest control, this information is unknown in N. lugens. Here, we established two resistant strains that were selected from field populations in Vietnam and the Philippines, and conducted crossing experiments to determine the inheritance pattern. Results The resistance ratio of 50% lethal dose (LD50 ) values for the two resistance-selected strains, i.e., resistant strains originating from Vietnam (VT-Res) and the Philippines (PH-Res), to their control strains were ∼ 8- and 157-fold, respectively. Reciprocal cross experiments between VT-Res and the susceptible strain (S-strain), and between PH-Res and the S-strain showed that the degree of dominance was 0.81 and 0.82, and 0.95 and 0.96, respectively. Analysis of the F2 populations and backcrosses to the parental strains indicated that resistance is a major-gene trait following Mendelian inheritance. The strength of the resistance was suppressed by pre-treatment with piperonyl butoxide, an inhibitor of cytochrome P450-monooxygenases. Conclusion Our results suggest that imidacloprid resistance in N. lugens is autosomal and an almost completely dominant major-gene trait that is likely manifested by high expression levels of a detoxification enzyme. © 2019 Society of Chemical Industry.

The tea green leafhopper, Empoasca (Matsumurasca) onukii Matsuda, is one of the dominant pests in major tea production regions of East Asia. Recent morphological studies have revealed variation in the male genitalic structures within and among populations. However, the genetic structure of this pest remains poorly understood. This study explores the genetic diversity and population structure of this pest in nineteen populations from the four main Chinese tea production areas using microsatellite markers, with one Japanese population also examined. The results show low to moderate levels of genetic differentiation with populations grouped into four clusters, i.e. the Jiangbei group, the Southwest group 1, the Southwest group 2 and the South China group. Populations from China have a close phylogenetic relationship but show significant isolation by distance. Lower genetic diversity and genetic differentiation of E. (M.) onukii were found in the Kagoshima population of Japan. Evidence for genetic bottlenecks was detected in the South China and Jiangnan populations. Population expansion was found in the Southwest, Jiangbei and Kagoshima populations. This is the most extensive study of the population genetics of this species and contributes to our understanding of its origin and evolutionary history.

Although Japan has maintained the state of eradication of the oriental fruit fly, Bactrocera dorsalis Hendel complex (Diptera: Tephritidae) since 1986, B. dorsalis complex are occasionally trapped within a limited area and short time period on Japan's small south‐western islands. Trapping events occurred on Amamioshima Island, Kagoshima Prefecture, in 2015, and male adults were also caught in surveillance traps on neighbouring Tokunoshima (south of Amamioshima) and Yakushima (north of Amamioshima) islands as well as on several islands in Okinawa Prefecture (south of Amamioshima). To investigate possible domestic dispersal of the pest from Amamioshima Island, a trajectory analysis was performed to reveal the timing and flight distance of possible dispersal. Surveillance data indicated that the first trappings on Tokunoshima and Yakushima islands occurred in November, which was after the number of trapped male adults on Amamioshima Island peaked in late October. Backward trajectories from Tokunoshima Island beginning 14 days prior to the first trapping passed over Amamioshima Island, which suggested possible dispersal between the islands. Several backward trajectories from the islands in Okinawa Prefecture also passed Amamioshima Island. Moreover, forward trajectories from Amamioshima Island beginning during peak occurrence, from mid‐October to early November, arrived over Tokunoshima, Iheya and Okinawa islands where the flies were caught. Such circumstantial evidence suggests that domestic dispersal of B. dorsalis complex occurred on Amamioshima Island. A situation similar to that on Tokunoshima Island also occurred on Yakushima Island. However, since the number of traps has been limited until the first capture, it was not clear when and from where the immigrants arrived on the island.

Background The brown planthopper, Nilaparvata lugens (Stal), is one of the most notorious pests of rice throughout Asia. The brown planthopper have developed high resistance to imidacloprid, a member of neonicotinoid insecticides. Several genes and mutations conferring imidacloprid resistance in N. lugens, especially in eastern and southeastern Asia populations, have been reported. Thus, the key mechanisms of imidacloprid resistance need to be examined. Results RNA-seq analyses revealed that only one cytochrome P450 monooxygenase gene, CYP6ER1, was commonly upregulated in the five resistant strains tested. Sequences of CYP6ER1, which were highly expressed in the imidacloprid-resistant strains, contained a three-nucleotide deletion in the coding region, and amino acid substitutions and deletion, compared to that in an imidacloprid-susceptible strain. RNAi-mediated gene knockdown of CYP6ER1 increased imidacloprid susceptibility in a resistant strain. Further, we established two simple and convenient PCR-based molecular diagnostic methods to detected the CYP6ER1 locus with the three-nucleotide deletion. Using these methods, the resistance of F2 progenies derived from the crosses of F1 siblings from susceptible and resistant parents was analyzed, showing that the imidacloprid resistance had a relationship to the CYP6ER1 locus with the three-nucleotide deletion. Conclusion The overexpression of a variant CYP6ER1 with amino acid substitutions and deletion was involved in imidacloprid resistance in N. lugens. Based on these findings, molecular diagnostic methods have been developed and are promising tools for monitoring imidacloprid resistance in paddy fields. This article is protected by copyright. All rights reserved.

In electrospray, excess charges are supplied to a sample solution by the occurrence of electrochemical reactions. Recently, different versions of electrospray, e.g., dielectric barrier electrospray ionization, inductive desorption electrospray ionization, and electrostatic-ionization driven by dielectric polarization, have been reported in which the sample solution was not in direct contact with the metal electrode but separated by dielectric materials. The objective of the current work is to elucidate the mechanism of dielectric barrier electrospray. A sealed borosilicate glass capillary inserted with a fine acupuncture needle was used as a probe. A sample solution (~ 400 nL) was captured on the glass capillary tip and a positive high voltage (HV) pulse (+ 4.5 kV) was applied to the internal metal electrode. Mass spectra were measured as a function of the HV pulse width from μs to 10 s. Ions started to be detected with the pulse width of ~ 5 ms. The ion intensities increased slowly with time and reached a plateau in a few seconds. The charge distribution of cytochrome c [M + nH]n+ shifted to higher n values from a few ms to seconds. In addition to cone-jet mode normal electrospray that lasted until all the liquid sample was depleted from the glass tip, the polarization-induced electrospray ionization was observed at the early stage of the HV application.

For quick, noninvasive, and high-sensitivity surface analysis of foods and agricultural products, a touch sensor was developed and applied to sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS). Upon making contact with the sample, the probe stopped by detecting the current flowing through the circuit and analytes on the sample surface were extracted in the solvent preloaded in the plastic capillary. By lifting up the probe to the default position, an electrospray ionization mass spectrum of the sample was obtained. By scanning the sample stage using a programming tool, a point analysis of targeted positions of biological samples with a spot diameter of ≤0.3 mm was achieved. It took less than 10 s for one sample spot. This method was applied to various plants and animal tissues.

BACKGROUND The two rice planthoppers Nilaparvata lugens and Sogatella furcifera, have different life cycles in the regions of East Asia, the Red River Delta, and the Mekong Delta. The susceptibilities of these species to a range of insecticides have not previously been compared among the three regions over multiple years. Here we describe the differences and similarities in insecticide susceptibilities of the two species among the three regions from 2006–2011. RESULTS In all three regions during 2006 to 2011, N. lugens developed high and moderate levels of resistance to imidacloprid and thiamethoxam, respectively, but this species did not develop resistance to fipronil. In contrast, S. furcifera developed a high level of resistance to fipronil. The ranges in LD50 values for N. lugens treated with both imidacloprid and thiamethoxam were similar over time between East Asia and the Red River Delta, and were different in the Mekong Delta. CONCLUSION The results support the idea that resistant populations migrate from the Red River Delta region to East Asia. Therefore, continuous monitoring of the susceptibility of N. lugens to insecticides in the Red River Delta is very important for insecticide resistance management in East Asia.

The recent spread of Oryza sativa L. (rice) ssp. indica-derived cultivars in East and Southeast Asia increases the risk of white-backed planthopper, Sogatella furcifera, and Southern rice black-streaked dwarf virus (SRBSDV) outbreaks. We compared the degree of ovicidal response to S. furcifera and susceptibility to SRBSDV among two Oryza sativa ssp. japonica, two Oryza sativa ssp. indica and one Oryza sativa ssp. indica-derived rice cultivars. The ovicidal response of the O. sativa ssp. indica-derived cultivar was significantly higher than that of the tested O. sativa ssp. indica cultivars and was equivalent to that of the O. sativa ssp. japonica cultivars that we used, supporting previous findings that the ovicidal response is higher in O. sativa ssp. japonica cultivars than in O. sativa ssp. indica cultivars and is a quantitative trait controlled by a few relevant genes. Contrary to the varied ovicidal response, the SRBSDV infection rate among the cultivars and the height of SRBSDV-infected plants between most pairs of cultivars did not differ significantly, although twisting of the leaf tips, a typical symptom of SRBSDV, was not observed in the O. sativa ssp. japonica cultivars. These results indicate that damage by S. furcifera and SRBSDV can occur in O. sativa ssp. japonica as well as in O. sativa ssp. indica and O. sativa ssp. indica-derived cultivars; therefore, in the cultivation of O. sativa ssp. japonica, measures should also be taken against white-backed planthopper during high levels of emergence.

Fluorene and 9,9-dialkyl fluorenes were examined by electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS). From the major peaks: M+ , [M+H]+, [M−R]+, and [M−R−(R−H)]+detected by EDI/SIMS, information on the molecular masses (M) and the side chains (R) could be obtainedfor dioctyl-, dihexyltri-, dioctyltri- and dihexylheptafluorenes. Despite the different alkyl substituents, dihexyltrifluorene (C75H98) and dioctyltrifluorene (C87H122) gave similar fragment-ion distribution patterns with the common peak values at m/z 339 and 517 in the two envelopes. This suggests that the fragmentation paths are similar for these two compounds. The ions with m/z 339 and 517 were tentatively assigned asC27H15+ and C41H25+in which all the alkyl substituents (R) were eliminated. Fragmentation paths of protonated fluorenes were examined by DFT calculations.The reaction paths of the elimination of side two alkyl chains to give fluorenyl cations as the final products were postulated for 9,9-dimethylfluorene and 9,9-dioctylfluorene.

The temporal profiles of ion signals were measured for probe electrospray ionization (PESI) and nano-electrospray ionization (nESI) by changing the pulse width of the high voltage applied to the emitters (PESI: 0.12 mm o.d. and 700 nm tip diameter metal needle; nESI: metal-coated 15 μm i.d. silica capillary). The ion signals started to be detected at ∼400 μs and 5 ms, respectively, for PESI and nESI (solution: 10−5 M cytochrome c and 0.1–1% acetic acid in H2O/MeOH (1/1)). With the addition of 10 mM ammonium acetate in 10−5 M cytochrome c solution, the threshold for the signal appearance became about one order of magnitude longer with weaker signal intensities than those for acidic solutions. PESI was applied to real samples such as mayonnaise, natto (fermented soybeans), tomato ketchup and salmon eggs. Marked sequential electrospray was observed for these samples.

Gaseous ions generated by the ultrasonic atomization of liquids were measured by mass spectrometry for the first time. The aqueous solutions of 10−5 M drugs, peptides, proteins, surface-active agents, rhodamine B, explosives saccharides, and polyethylene glycol were supplied to the edge of the ultrasonically vibrating blade (22 kHz) through the 20 μm i.d. silica capillary with the flow rate of 1 μL/min. The analytes were detected mainly as sodiated, protonated, or deprotonated forms. The ion signal intensities were highly dependent on the surface-activity values of the analyte ions, i.e., the higher the surface-activity values, the stronger the ion signal intensities. The addition of 0.5% acetic acid in the solutions led to the drastic decrease in ion signal intensities.

The brown planthopper (BPH: Nilaparvata lugens St&aring, l.) is a major pest of rice, Oryza sativa, in Asia. Host plant resistance has tremendous potential to reduce the damage caused to rice by the planthopper. However, the effectiveness of resistance genes varies spatially and temporally according to BPH virulence. Understanding patterns in BPH virulence against resistance genes is necessary to efficiently and sustainably deploy resistant rice varieties. To survey BPH virulence patterns, seven near-isogenic lines (NILs), each with a single BPH resistance gene (BPH2-NIL, BPH3-NIL, BPH17-NIL, BPH20-NIL, BPH21-NIL, BPH32-NIL and BPH17-ptb-NIL) and fifteen pyramided lines (PYLs) carrying multiple resistance genes were developed with the genetic background of the japonica rice variety, Taichung 65 (T65), and assessed for resistance levels against two BPH populations (Hadano-66 and Koshi-2013 collected in Japan in 1966 and 2013, respectively). Many of the NILs and PYLs were resistant against the Hadano-66 population but were less effective against the Koshi-2013 population. Among PYLs, BPH20+BPH32-PYL and BPH2+BPH3+BPH17-PYL granted relatively high BPH resistance against Koshi-2013. The NILs and PYLs developed in this research will be useful to monitor BPH virulence prior to deploying resistant rice varieties and improve rice&rsquo, s resistance to BPH in the context of regionally increasing levels of virulence.

The brown planthopper (BPH: Nilaparvata lugens Stål.) is a major pest of rice, Oryza sativa, in Asia. Host plant resistance has tremendous potential to reduce the damage caused to rice by the planthopper. However, the effectiveness of resistance genes varies spatially and temporally according to BPH virulence. Understanding patterns in BPH virulence against resistance genes is necessary to efficiently and sustainably deploy resistant rice varieties. To survey BPH virulence patterns, seven near-isogenic lines (NILs), each with a single BPH resistance gene (BPH2-NIL, BPH3-NIL, BPH17-NIL, BPH20-NIL, BPH21-NIL, BPH32-NIL and BPH17-ptb-NIL) and fifteen pyramided lines (PYLs) carrying multiple resistance genes were developed with the genetic background of the japonica rice variety, Taichung 65 (T65), and assessed for resistance levels against two BPH populations (Hadano-66 and Koshi-2013 collected in Japan in 1966 and 2013, respectively). Many of the NILs and PYLs were resistant against the Hadano-66 population but were less effective against the Koshi-2013 population. Among PYLs, BPH20+BPH32-PYL and BPH2+BPH3+BPH17-PYL granted relatively high BPH resistance against Koshi-2013. The NILs and PYLs developed in this research will be useful to monitor BPH virulence prior to deploying resistant rice varieties and improve rice’s resistance to BPH in the context of regionally increasing levels of virulence.

The recent reemergence of rice black-streaked dwarf virus (RBSDV) has caused severe rice yield losses in several areas of East Asia. To identify the most important infectious sources of RBSDV, we compared the susceptibility of major poaceous plants to RBSDV infection and survival and the RBSDV acquisition efficiency of a vector insect, the small brown planthopper

In previous work, probe electrospray ionization/mass spectrometry (PESI/MS) and sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS) were reported for the rapid and minimally invasive analysis of food. In this work, a modified version of sfPESI will be reported. The sample surface was pricked with an acupuncture needle inserted in the sfPESI probe that protruded from the terminus of the tip by 5 mm. The invasion depth of the needle into the sample was ∼1 mm. After sampling, the needle was retracted into the solvent-preloaded capillary with a protrusion length of 0.1–0.2 mm from the tip. A mass spectrum of the sample captured on the needle was obtained by applying a high voltage to the needle. This method could be applicable to profiling analyses of plants with the epicuticular wax covering on the surfaces that are difficult to analyze by sf-PESI. The on-site mass spectrometric analysis for a growing apricot in the field was performed to monitor the developing stage of the fruit.

Recent outbreaks of viral diseases of rice in east Asia are caused by migratory planthoppers. Epidemic models of these viral diseases are required to predict the annual emergence of the viruses based on established forecasting systems of outbreaks of the planthoppers. Here, we develop an epidemic model for southern rice black-streaked dwarf virus (SRBSDV), which is transmitted by the white-backed planthopper, Sogatella furcifera, as the first epidemic model of viruses borne by migratory planthoppers. The epidemic model, consisting of a Leslie model for the population dynamics of S. furcifera and a transmission model for SRBSDV, predicted a high contribution of the density of viruliferous immigrant S. furcifera to SRBSDV emergence. Early immigration of S. furcifera into paddy fields after transplanting of rice also promoted the virus epidemic primarily because of the emergence of viruliferous old nymphs during the period during which rice plants are susceptible to the virus. The epidemic model developed could be expanded to other planthopper-borne viruses and is effective for understanding the ecological aspects of virus epidemics in the field and for assessing the risk of viral diseases transmitted by migratory vectors.

Oviposition preferences of herbivorous insects affect offspring performance. Both positive and negative links between oviposition preference and offspring performance have been reported for many species. A gall-inducing leafhopper, Cicadulina bipunctata Melichar (Hemiptera: Cicadellidae), feeds on various Poaceae plants and induces galls of enhanced nutritional value for their offspring. Although gall induction by C. bipunctata improves nymphal performance, the oviposition preference of females between galled and non-galled host plants is still unclear. In this paper, the nymphal performance and oviposition and feeding-site preference of C. bipunctata were investigated using galled wheat, Triticum aestivum L., and non-galled barley, Hordeum vulgare L., as host plants. The survival rate of C. bipunctata on wheat was significantly higher than on barley. In the choice test, significantly more eggs were laid into barley, whereas the number of eggs deposited on both hosts was not significantly different in the no-choice test. The number of settling individuals per leaf area was not significantly different between wheat and barley, suggesting no clear preference for oviposition between these plants. Experience as a nymph with a growing host did not affect oviposition preference as adult female. The inconsistent correspondence between offspring performance and oviposition preference of C. bipunctata may reflect the high mobility of nymphs and/or differences in leaf area between host plants. The results indicate that the previous finding that oviposition preference and offspring performance are not always positively correlated in herbivorous insects is applicable to gall-inducing insects.

In southern Japan, sweet potato weevils Euscepes postfasciatus (Fairmaire) are being eradicated using the sterile insect technique because of their damaging effects on sweet potato crops. However, the effect of irradiation on the dispersal and survival of this species needs to be evaluated. We observed the dispersal of normal and irradiated weevils for 21 days after their release in a sweet potato field during all four seasons, and estimated their survival using the Weibull function. Normal weevils generally moved further than irradiated weevils, and all weevils had greater dispersal distances in the summer than in the winter, with spring and autumn intermediate between these two extremes (summer: 0.23 m/day versus 0.29 m/day; winter: 0.15 m/day versus 0.07 m/day; spring: 0.20 m/day versus 0.17 m/day; autumn: 0.20 m/day versus 0.15 m/day, respectively). Normal weevils had low variation in mean life expectancy (approximately 8 days throughout the year), whereas the life expectancy of irradiated weevils was drastically reduced in the summer (2.20 days). The implications of these results for the efficiency of this eradication technique are discussed.

Since the 1980s, the maize orange leafhopper, Cicadulina bipunctata, has been gradually expanding its range in east Asia associated with global warming. This leafhopper induces maize wallaby ear symptom (MWES) on young maize plants and has become a threat to forage maize production in southern parts of temperate Japan since around 2000. In this study, using predictions of future temperature and precipitation calculated from Atmosphere–Ocean Coupled General Circulation Models, the future risk of C. bipunctata expansion and MWES occurrence in Japan (spatial resolution: 1 km2) was predicted. A nominal logistic regression analysis showed a significant contribution of cumulative low temperature during winter to the current distribution of C. bipunctata. The range of C. bipunctata was predicted to expand northward, particularly in Kyushu, Shikoku and the southern part of Honshu after the 2060s. Predicted intensification of MWES would reduce the efficacy of maize cultivars that are currently tolerant to MWES, in southern Kyushu in the 2020s, and in most parts of Kyushu, Shikoku and southwestern Honshu in the 2060s. These results suggest the need for measures to counter further expansion of C. bipunctata and improvement of current tolerant maize cultivars.

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&rsquo, 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&ndash, 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 &lt, 0.5 in contrast to S. litura migrating overseas (&gt, 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.

Strong resistance to imidacloprid in Nilaparvata lugens (Stål) has developed in Southeast and East Asia. Although the mode of inheritance for resistance is very useful information for pest control, this information is unknown in N. lugens. Here, we established two resistant strains that were selected from field populations in Vietnam and the Philippines, and conducted crossing experiments to determine the inheritance pattern.The resistance ratio of 50% lethal dose (LDOur results suggest that imidacloprid resistance in N. lugens is autosomal and an almost completely dominant major-gene trait that is likely manifested by high expression levels of a detoxification enzyme. © 2019 Society of Chemical Industry.

Pymetrozine is a promising chemical agent for controlling the brown planthopper, Nilaparvata lugens (Stal), after resistance to some neonicotinoid insecticides developed nearly a decade ago. Susceptibility tests by assessing mortality resulting from insecticidal activity are not available for pymetrozine because its key biological action suppresses the reproductive performance of treated N. lugens females. In this study, a new simple method for monitoring the susceptibility of N. lugens to pymetrozine was developed by combining topical application and assessment of the number of offspring using young rice seedlings in a test tube. The ED50 values of the Osaka strain (collected in 1971) and Kumamoto strain (collected in 2011) of N. lugens against pymetrozine were 0.036 and 0.091 μg/g, respectively. In the future, this method will be used to monitor the susceptibility of N. lugens to pymetrozine.

The oriental fruit fly and its relatives, Bactrocera dorsalis complex Hendel (Diptera: Tephritidae) were eradicated from the islands of Okinawa Prefecture, southwestern Japan, in 1986. Since just after the eradication, however, re-invasion of B. dorsalis complex has been continuing to date, and the cause of the re-invasion has not been fully analyzed yet. It is believed that there are two possible routes of the re-invasion: wind-borne immigration and importation of infested fruits. This study analyzed the former natural factor by calculating backward trajectories for B. dorsalis complex males caught in monitoring traps from 1986 to 2012. In 65.8 % of the total re-invasion events, trajectories could be traced to at least one of the insect’s native regions: Taiwan (71.8 %), the Philippines (24.3 %) and southern China (3.9 %). In these possible immigration events, the influencing meteorological factors were found to be fronts (44.6 %), typhoons (36.0 %), high-pressure system ridges (12.0 %) and tropical depressions (7.5 %). The number of insects caught per trap was found to greater on the islands near the estimated sources than those further from the sources, supporting the hypothesis of wind-borne immigration of B. dorsalis complex into Okinawa.

The maize orange leafhopper (Cicadulina bipunctata) induces maize wallaby ear symptom (MWES) in forage maize in temperate southwest Japan. Using 10 years of field data (2004–2013), we developed a forecasting model for C. bipunctata based on climate and density factors that can guide the minimum level of control required to prevent MWES. The multiple regression analysis selected both temperature and precipitation from the previous winter to summer and maximum C. bipunctata density in the previous August as determinant factors in the model for forecasting occurrence of C. bipunctata in summer. This forecasting model could predict C. bipunctata occurrence with an accuracy of

The rice cultivar ASD7 (Oryza sativa L. ssp. indica) is resistant to the brown planthopper (BPH; Nilaparvata lugens Stal) and the green leafhopper (Nephotettix virescens Distant). Here, we analyzed multiple genetic resistance to BPH and the green rice leafhopper (GRH; Nephotettix cincticeps Uhler). Using two independent F2 populations derived from a cross between ASD7 and Taichung 65 (Oryza sativa ssp. japonica), we detected two QTLs (qBPH6 and qBPH12) for resistance to BPH and one QTL (qGRH5) for resistance to GRH. Linkage analysis in BC2F3 populations revealed that qBPH12 controlled resistance to BPH and co-segregated with SSR markers RM28466 and RM7376 in plants homozygous for the ASD7 allele at qBPH6. Plants homozygous for the ASD7 alleles at both QTLs showed a much faster antibiosis response to BPH than plants homozygous at only one of these QTLs. It revealed that epistatic interaction between qBPH6 and qBPH12 is the basis of resistance to BPH in ASD7. In addition, qGRH5 controlled resistance to GRH and co-segregated with SSR markers RM6082 and RM3381. qGRH5 is identical to GRH1. Thus, we clarified the genetic basis of multiple resistance of ASD7 to BPH and GRH.

RATIONALE Probe electrospray ionization (PESI) is only applicable to liquid or wet samples. In this study, a sheath-flow PESI method for remote sampling mass spectrometry that can be applied to dry samples was developed. METHODS An acupuncture needle (0.12 mm outer diameter, 700 nm tip diameter) was inserted into a gel-loading tip with a 0.1 mm protrusion out of the tip. Analytes were extracted by filling the latter tip with solvent and softly touching the sample surface for a short time (

The two rice planthoppers, Nilaparvata lugens and Sogatella furcifera, have different life cycles in the regions of East Asia, the Red River Delta, and the Mekong Delta. The susceptibilities of these species to a range of insecticides have not previously been compared among the three regions over multiple years. Here, we describe the differences and similarities in insecticide susceptibilities of the two species among the three regions in 2006-2011.In all three regions in 2006 - 2011, N. lugens developed high and moderate levels of resistance to imidacloprid and thiamethoxam, respectively, but this species did not develop resistance to fipronil. In contrast, S. furcifera developed a high level of resistance to fipronil. The ranges in 50% lethal dose (LDThe results support the idea that resistant populations migrate from the Red River Delta region to East Asia. Therefore, continuous monitoring of the susceptibility of N. lugens to insecticides in the Red River Delta is very important for insecticide resistance management in East Asia. © 2017 Society of Chemical Industry.

This study examined the acetylcholinesterase 1 gene (AChE1) in Plutella xylostella strains with different sensitivities to acephate. Multiple haplotypes of the gene were found in the field-collected strains including distinct haplotypes carrying one or both previously reported mutations (A298S and G324A). Moreover, sequencing results indicated the presence of duplicated copies of the gene in the field-collected strains. No correlation was found between copy numbers of AChE1 and levels of resistance to acephate suggesting that extensive AChE1 duplication is not a major resistance factor at least in some P. xylostella strains. Proportions of the A298S and G324A mutations showed no correlation with levels of resistance to acephate. This suggests that acephate resistance of P. xylostella is complex and cannot be evaluated based on the AChE1 copy number or proportions of the resistance mutations alone.

Rapid, direct, on-site and noninvasive food analysis is strongly needed for quality control of food. To satisfy this demand, the technique of dipping probe electrospray ionization/mass spectrometry (dPESI/MS) was developed. The sample surface was pricked with a fine acupuncture needle and a sample of ∼200 pL was captured at the needle tip. After drying the sample, the needle tip was dipped into the solvent for ∼50 ms and was moved upward. A high-voltage was applied to the needle to generate electrospray when the needle reached the highest position, and mass spectra were measured with a time-of-flight mass spectrometer. For evaluation of the method, the technique was used to analyze foods such as vegetables, salmon flesh, cow’s milk, yogurt, and soy-bean milk. The detected major ions for cow’s milk and yogurt were [(Lac)n + Ca]2+ with n = 1–6 (where (Lac) is lactose), indicating that Ca2+ is tightly bound by Lac molecules.

In migration analysis of the brown planthopper, Nilaparvata lugens (Stal), in a tropical region, it is difficult to know the arrival timing of the immigrants because rice plants in different growth stages are simultaneously cultivated, and local insects may already occur in destination areas. Due to this analytical difficulty, additional information is necessary to discriminate between immigrants and locally originated individuals in the light trap catch. This study applied rice phenology maps retrieved from satellite images to analysis of N. lugens’s migration in the Vietnamese Mekong Delta. The analysis also employed occurrence data by dense light traps and trajectory analysis. The result showed that the occurrence of N. lugens peaked periodically at an interval of 27.2–30 days, changing in association with the rice cropping area in the harvesting stage. For an N. lugens occurrence in late July 2009 in the delta, the rice phenology suggested catch increases in light traps in a destination area could likely be attributed to immigrants from outside the area. Therefore, the migration analysis suggested that N. lugens that emigrated from paddy fields in An Giang and Kien Giang provinces possibly moved to east-neighboring provinces. The migration distance was estimated to be about 100 km at a maximum.

Spiroplasma-mediated late male killing was found in the small brown planthopper, Laodelphax striatellus. Female-biased colonies (maternal lines, N = 4) were established from planthoppers collected in Taiwan and Japan. This sex ratio distortion was maternally inherited (sex ratio of total number of progenies [female:male]: 488:0 in F1, 198:7 in F2, 407:0 in F3; likelihood ratio test of all generations, P < 0.0001) and caused by male death during nymphal stages. The female-biased colonies were doubly infected with Spiroplasma and Wolbachia, and the non-biased colonies were infected solely with Wolbachia. Antibiotic treatment resulted in a normal sex ratio, strongly suggesting that bacteria are manipulating host reproduction. Spiroplasma-singly-infected planthopper colonies created by the antibiotic treatment produced progeny with strongly female-biased sex ratios (181:2; likelihood ratio test, χ(2) = 231.6, P < 0.0001). This is the first report of Spiroplasma-mediated male killing in hemimetabolous insects.