Inference of adult female dispersal from the distribution of gypsy moth egg masses in a Japanese city

1 The native range of the gypsy moth Lymantria dispar (L.) spans the temperate forests of Eurasia. Across this region, a clinal female flight polymorphism exists; gypsy moth females in eastern Asia are mostly capable of directed flight, those in western and southern Europe are largely incapable of flight and populations distributed across the centre of the distribution exhibit a range of intermediate flight behaviours. 2 Although information exists about the timing and duration of female flight from laboratory and wind tunnel studies, little or no quantitative data are available on average distances flown by Asian gypsy moth females prior to oviposition in the field. This information is critical for estimating risk of contamination at specific ports and transit terminals, as well as for predicting the spread of populations that might someday invade currently uninfested regions of the world. 3 In the present study, an extensive visual survey of gypsy moth egg masses was conducted during a walk through streets and paths in a 3.92 × 5.76 km area in Kanazawa, Japan. This area consisted of a matrix of urban, agricultural and forest land uses. The distribution of egg masses relative to distances from host forests was used to infer the magnitude of pre‐ovipositional female flight. 4 A total of 3172 egg masses was recorded from surveys conducted during the search of a path totalling 384 km. Within urban areas, egg masses were most abundant in the area <1 km from the edge of forest land. 5 These results suggest that most female gypsy moth flight is limited to the area within 1 km of host forests. They also suggest that shipping containers and other parcels located >1 km from forests are at a much lower risk of contamination with Asian gypsy moth egg masses.     

Underestimated mitochondrial diversity in gypsy moth Lymantria dispar from Asia

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中国舞毒蛾六个地理种群的RAPD分析及SCAR标记构建

舞毒蛾Lymantria dispar L.是世界性农林害虫, 包含不同的亚种, 其中亚洲舞毒蛾的雌蛾具有较强的飞行能力, 已成为国际性的重要检疫性有害生物。然而, 不同舞毒蛾亚种及种群间形态难辨, 因此采用传统的手段鉴别舞毒蛾亚种种群是很困难的。本研究首先采用RAPD标记分析了中国舞毒蛾6个地理种群的遗传多态性。结果表明, 所检测的舞毒蛾种群的遗传分化系数G_st为0.7571, 由此推算出的平均有效迁移数（基因流参数）N_em为0.1604, 说明不同舞毒蛾种群间的遗传分化程度较高, 缺乏广泛的基因流动。本研究在RAPD遗传分析基础之上, 筛选出了4个舞毒蛾种群的特异性遗传位点, 然后对这些特异性位点进行了克隆测序、 序列分析和位点特异性引物设计。结果表明, 其中2个舞毒蛾种群的位点特异性引物可产生序列特征性扩增区域（SCAR）标记。经验证, 这些标记可被用来鉴别特定的舞毒蛾地理种群, 因此有助于对这些舞毒蛾地理种群的分布与扩散进行监测。     

The potential for Entomophaga maimaiga to regulate gypsy moth Lymantria dispar (L.) (Lepidoptera: Erebidae) in Europe

Gypsy moth, Lymantria dispar L., is one of the most important pests of deciduous trees in Europe. In regular cycles, it causes large‐scale defoliation mostly of oak, Quercus spp., forests. Government authorities in the most infested countries in Europe conduct large‐scale applications of pesticides against gypsy moth. In 1999, a new natural enemy, the entomopathogenic fungus Entomophaga maimaiga, was successfully introduced into a gypsy moth population in Bulgaria. Recent investigations suggest that now E. maimaiga is quickly spreading in Europe. Herein, past studies are reviewed regarding this fungus with special emphasis on its potential for becoming an important factor regulating gypsy moth populations in Europe, focusing on the host's population dynamics in relation to the fungus, the influence of environmental conditions on fungal activity, the influence of E. maimaiga on the native entomofauna, including other gypsy moth natural enemies, and spread of the fungus. Based on this analysis, the potential of E. maimaiga for providing control in European gypsy moth populations is estimated.     

Effects of the ant Formica fusca on the transmission of microsporidia infecting gypsy moth larvae

Transmission plays an integral part in the intimate relationship between a host insect and its pathogen that can be altered by abiotic or biotic factors. The latter include other pathogens, parasitoids, or predators. Ants are important species in food webs that act on various levels in a community structure. Their social behavior allows them to prey on and transport larger prey, or they can dismember the prey where it was found. Thereby they can also influence the horizontal transmission of a pathogen in its host's population. We tested the hypothesis that an ant species like Formica fusca L. (Hymenoptera: Formicidae) can affect the horizontal transmission of two microsporidian pathogens, Nosema lymantriae Weiser (Microsporidia: Nosematidae) and Vairimorpha disparis (Timofejeva) (Microsporidia: Burenellidae), infecting the gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae: Lymantriinae). Observational studies showed that uninfected and infected L. dispar larvae are potential prey items for F. fusca. Laboratory choice experiments led to the conclusion that F. fusca did not prefer L. dispar larvae infected with N. lymantriae and avoided L. dispar larvae infected with V. disparis over uninfected larvae when given the choice. Experiments carried out on small potted oak, Quercus petraea (Mattuschka) Liebl. (Fagaceae), saplings showed that predation of F. fusca on infected larvae did not significantly change the transmission of either microsporidian species to L. dispar test larvae. Microscopic examination indicated that F. fusca workers never became infected with N. lymantriae or V. disparis after feeding on infected prey.     

Learning provides mating opportunities for males of a parasitoid wasp

The ability of insects to learn locations of future resources has rarely been studied. Here, we show that males of the solitary parasitoid wasp Pimpla disparis Viereck (Hymenoptera: Ichneumonidae) learn locations of future mates. Male P. disparis reportedly arrest on parasitized pupae of wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae), and gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), when mate emergence is imminent. We tested the hypothesis that male P. disparis identify, memorize, and revisit the location(s) of parasitized host pupae as a strategy to attain mates. We colour‐coded P. disparis males in the field and noticed that they revisit parasitized moth pupae on consecutive days, and arrest on those pupae with a near‐emergence P. disparis parasitoid. In a laboratory experiment with two large corrugated cardboard cylinders (CCCs) as surrogate trees, each CCC bearing two parasitized moth pupae with a near‐emergence P. disparis parasitoid or two pupae not parasitized, males on day 1 of the experiment visited parasitized pupae more often than pupae not parasitized. On day 2, when each CCC had been replaced and now carried pupae that were not parasitized, males returned to the same CCC, or the same micro‐location on that CCC, which on day 1 had carried parasitized pupae. Field and laboratory data combined indicate that male P. disparis learn the location of future mates. With female P. disparis being haplodiploid and capable of reproducing without mating experience, the onus to find a mate is on males. They accomplish this by detecting parasitized pupae, learning their location, revisiting them frequently, and then arresting on them when the prospective mate nears emergence, taking a 50% chance that it is indeed a female.     

Behavioural and physiological plasticity of gypsy moth larvae to host plant switching

Larvae of the gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), a generalist species, frequently encounter spatial and temporal variations in diet quality. Such variation favoured the evolution of high behavioural and physiological plasticity which, depending on forest stand composition, enables more or less successful exploitation of the environment. Even in mixed oak stands, a suitable habitat, interspecific and intraspecific host quality variation may provoke significant variation in gypsy moth performance and, consequently, defoliation severity. To elucidate the insufficiently explored relationship between gypsy moth and oaks (Fagaceae), we carried out reciprocal switches between Turkey oaks (Quercus cerris L.) and less nutritious Hungarian oaks (Quercus frainetto Ten.) (TH and HT groups), under controlled laboratory conditions, and compared larval performance between the switched larvae and larvae continuously fed on either Turkey oak (TT) or Hungarian oak (HH). We found that larval traits were most strongly affected by among‐tree variation in oak quality and identity of the host consumed during the fourth instar. Switching from Turkey to Hungarian oak (TH) led to a longer period of feeding, decrease of mass gain, growth, and consumption rate, lower efficiency of food use and nutrient conversion, and increase of protease and amylase activities. Larvae exposed to the reverse switch (HT) attained values of these traits characteristic for TT larvae. It appeared that the lower growth in the TH group than in the TT group was caused by both behavioural (consumption, pre‐ingestive) and metabolic (post‐digestive) effects from consuming oaks. Multivariate analyses of growth, consumption, and efficiency of food use revealed that early diet experience influenced the sensitivity of the most examined traits to less suitable Hungarian oaks, suggesting the development of behavioural and physiological adjustments. Our results indicate that lower risks of defoliation by gypsy moth might be expected in mixed stands with a higher proportion of Hungarian oak.     

First record of Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) in Slovakia

The entomopathogenic fungus Entomophaga maimaiga was found for the first time in Slovakia in 2013. Late instar larvae of gypsy moth, Lymantria dispar, from two sites with different population densities were dissected to evaluate the presence of pathogens. The presence of conidia and resting spores of E. maimaiga in gypsy moth cadavers was confirmed from both sites.     

Survey ofLymantria obfuscata and its natural enemies in India

The status ofLymantria obfuscata Walker in India is discussed. Notes on its taxonomy, distribution, life-history and economic importance are given for comparison with those of the gypsy moth,Lymantria dispar (L.). Parasites ofL. obfuscata in India are reviewed. A survey in 1961–66 revealed an additional 50 species of natural enemies ofL. obfuscata in India. The incidence and biology of some of the important ones are presented. A comparison is made between these parasites and those ofL. dispar. Some of the natural enemies ofL. obfuscata already attackL. dispar in America. Others are closely related to the parasites of the gypsy moth. The scope for utilisation of parasites ofL. obfuscata in other countries is discussed. Possible use of parasites ofL. dispar from the U.S.A. or elsewhere againstL. obfuscata in India is suggested. Research financed in part by the U.S.D.A. under grant PL-480.     

Distribution of the entomopathogenic fungus Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) at the northern edge of its range in Europe

The gypsy moth Lymantria dispar is a serious economic pest in European broadleaf forests. However, the entomopathogenic fungus Entomophaga maimaiga, which has a great potential to regulate gypsy moth numbers, has recently spread in the Central and Eastern European area of the moth's range. In the current study, 39 plots in oak forests in the Slovak Republic and the Czech Republic were monitored for E. maimaiga from 2014 to 2016. These plots were located along the northern edge of the E. maimaiga range where gypsy moth outbreaks have occurred in the past. The fungus was detected in 16 of the 39 plots. The results thus confirm that E. maimaiga is quite widespread along the northern edge of its range in Europe and can be considered to be established in that area.     

Effects of SPLAT® GM sprayable pheromone formulation on gypsy moth mating success

Several integrated pest management programs rely on the use of mating disruption tactics to control insect pests. Some programs specifically target non‐native species, such as the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae). We evaluated SPLAT^® GM, a new sprayable formulation of the gypsy moth sex pheromone disparlure, for its ability to disrupt gypsy moth mating. The study was conducted in 2006, 2007, and 2008 in forested areas in Virginia, USA. Mating success of gypsy moth females was reduced by >99% and male moth catches in pheromone‐baited traps by >90%, in plots treated with SPLAT^® GM at dosages ranging from 15 to 75 g of active ingredient (a.i.) ha^?1. Dosage‐response tests conducted in 2008 indicated that SPLAT^® GM applied at a dosage of 7.5 g a.i. ha^?1 was as effective as a 15 g a.i. ha^?1 dosage.     

Potential risk of accidental introduction of Asian gypsy moth (Lymantria dispar) to Australasia: effects of climatic conditions and suitability of native plants

1 The potential risk of the establishment of the Asian strain of the gypsy moth (AGM) (Lymantria dispar) in New Zealand and Australia (Australasia) was assessed from a study of the insect's host range and potential distribution. In New Zealand, viable eggs of AGM have been continuously intercepted on cargo from Asia, and therefore there is a high probability of accidental introductions of AGM to Australasia. 2 We predicted potential distribution ranges of AGM based on climatic conditions. Asian gypsy moth is predicted to be able to persist in N and SE New Zealand and SE and SW Australia. 3 Using three populations of AGM and 59 species (seven families) of plant (55 from Australasia and four from elsewhere), we also conducted laboratory trials to examine the ability of AGM larvae to complete development on native plants from Australasia. Asian gypsy moth was able to complete development on 26 out of the 55 native species tested. Furthermore, larval performance on at least five species of Australian native plant was as good as on AGM's preferred host species (Quercus pubescens and Q. robur). 4 Larval performance of AGM was poor on all but one species of New Zealand native tree species (Nothofagus solandri), and therefore the risk of establishment in the indigenous forests of New Zealand is considered to be low. 5 Given the suitability of some Australian plants and the climatic suitability for the establishment of AGM, this insect should be treated as a serious quarantine threat and managed accordingly, particularly in Australia.     

Species‐Specific PCR‐Based Assay for Identification and Detection of Phomopsis (Diaporthe) azadirachtae Causing Die‐Back Disease in Azadirachta indica

Die‐back disease caused by Phomopsis (Diaporthe) azadirachtae is the devastating disease of Azadirachta indica. Accurate identification of P. azadirachtae is always problematic due to morphological plasticity and delayed appearance of conidia. A species‐specific PCR‐based assay was developed for rapid and reliable identification of P. azadirachtae by designing a species‐specific primer‐targeting ITS region of P. azadirachtae isolates. The assay was validated with DNA isolated from different Phomopsis species and other fungal isolates. The PCR assay amplified 313‐bp product from all the isolates of P. azadirachtae and not from any other Phomopsis species or any genera indicating its specificity. The assay successfully detected the pathogen DNA in naturally and artificially infected neem seeds and twigs indicating its applicability in seed quarantine and seed health testing. The sensitivity of the assay was 100 fg when genomic DNA of all isolates was analysed. The PCR‐based assay was 92% effective in comparison with seed plating technique in detecting the pathogen. This is the first report on the development of species‐specific PCR assay for identification and detection of P. azadirachtae. Thus, PCR‐based assay developed is very specific, rapid, confirmatory and sensitive tool for detection of pathogen P. azadirachtae at early stages.     

Spatial analysis of gypsy moth populations in Sardinia using geostatistical and climate models

• 1 Spatial fluctuations of the Sardinian population of the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae) were characterized using geostatistical and climate models. Data on gypsy moth egg mass abundance recorded at 282 permanent monitoring sites from 1980 to 2004 were incorporated in a geographic information system with the vegetational, geomorphological and pedological features of the sites.
• 2 Statistical analyses revealed that the relative outbreak frequency was related to the predominant host tree, slope and elevation of the monitoring sites, whereas there was no correlation between outbreak frequency and exposure and soil type.
• 3 By using bioclimatic modelling, probability maps of gypsy moth outbreaks were generated. The model identified a probability surface with climatic conditions favourable to gypsy moth outbreaks and thus potentially subject to defoliation. The maps included 92 sites where outbreaks never occurred, suggesting that the Sardinian climate may not be a determinant factor for gypsy moth outbreaks.
• 4 The geostatistical method cokriging with outbreak frequency as a covariate was found to be the most suitable technique to estimate gypsy moth egg mass abundance. Semivariograms showed spatial correlation of egg mass abundance within the range 18.5–53 km. The results obtained were used to create regional gypsy moth distribution maps by cokriging, which demonstrated the outbreak foci and different infestation levels at each monitoring area. These results can help to delimit the treatment areas and develop rational gypsy moth management programmes.

     

Facilitation between invasive herbivores: hemlock woolly adelgid increases gypsy moth preference for and performance on eastern hemlock

1. Interactions between invertebrate herbivores with different feeding modes are common on long-lived woody plants. In cases where one herbivore facilitates the success of another, the consequences for their shared host plant may be severe. Eastern hemlock (Tsuga canadensis), a canopy-dominant conifer native to the eastern U.S., is currently threatened with extirpation by the invasive stylet-feeding hemlock woolly adelgid (Adelges tsugae). The effect of adelgid on invasive hemlock-feeding folivores remains unknown. 2. This study evaluated the impact of feeding by hemlock woolly adelgid on gypsy moth (Lymantria dispar) larval preference for, and performance on, eastern hemlock. To assess preference, 245 field-grown hemlocks were surveyed for gypsy moth herbivory damage and laboratory paired-choice bioassays were conducted. To assess performance, gypsy moth larvae were reared to pupation on adelgid-infested or uninfested hemlock foliage, and pupal weight, proportional weight gain, and larval period were analysed. 3. Adelgid-infested hemlocks experienced more gypsy moth herbivory than did uninfested control trees, and laboratory tests confirmed that gypsy moth larvae preferentially feed on adelgid-infested hemlock foliage. Gypsy moth larvae reared to pupation on adelgid-infested foliage gained more weight than larvae reared on uninfested control foliage. 4. These results suggest that the synergistic effect of adelgid and gypsy moth poses an additional threat to eastern hemlock that may increase extirpation risk and ecological impact throughout most of its range.     

Evolutionary genomics of gypsy moth populations sampled along a latitudinal gradient

The European gypsy moth (Lymantria dispar L.) was first introduced to Massachusetts in 1869 and within 150 years has spread throughout eastern North America. This large‐scale invasion across a heterogeneous landscape allows examination of the genetic signatures of adaptation potentially associated with rapid geographical spread. We tested the hypothesis that spatially divergent natural selection has driven observed changes in three developmental traits that were measured in a common garden for 165 adult moths sampled from six populations across a latitudinal gradient covering the entirety of the range. We generated genotype data for 91,468 single nucleotide polymorphisms based on double digest restriction‐site associated DNA sequencing and used these data to discover genome‐wide associations for each trait, as well as to test for signatures of selection on the discovered architectures. Genetic structure across the introduced range of gypsy moth was low in magnitude (F_ST = 0.069), with signatures of bottlenecks and spatial expansion apparent in the rare portion of the allele frequency spectrum. Results from applications of Bayesian sparse linear mixed models were consistent with the presumed polygenic architectures of each trait. Further analyses indicated spatially divergent natural selection acting on larval development time and pupal mass, with the linkage disequilibrium component of this test acting as the main driver of observed patterns. The populations most important for these signals were two range‐edge populations established less than 30 generations ago. We discuss the importance of rapid polygenic adaptation to the ability of non‐native species to invade novel environments.     

Parasitoid complex of the Asian gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) in Primorye Territory,Russian Far East

A study of the moth parasitoid complex attacking gypsy moth, Lymantria dispar (L.) was carried out in Primorye territory, Russia Far East. Season-long collections at three sites in the Vladivostok area and collections at seven sites of central region of Primorye revealed the 18 primary parasites: one egg parasitoid, 11 larval parasitoids, one larval-pupal parasitoid, one parasitic nematode, one ectoparasitoid, and three diseases including NPV (nuclear polyhedrosis virus) and Entomophaga maimaiga. Phobocampe species (Ichneumonidae) dominated the parasitoid complex, parasitizing 5.5% of the larvae in the Vladivostok area and 9.3% in central Primorye, rates which are much higher than those detected from other Asiatic regions of Russia and Northeastern Asia. The insect parasitoid complex was found to be somewhat depauperate. The 11.8% average total parasitism in eastern Russian is similar to the 12% recorded in the US. Both regions have large gypsy moth outbreaks, but other factors including diseases have compensated for the rather low mortality exerted by the parasitoid complex in the Russian Far East.     

Key sites residues involved in interacting with chemicals of pheromone‐binding proteins from Lymantria dispar

Pheromone‐binding proteins (PBPs) are distributed widely on the antennae of insects, and they are believed to be involved in the process of chemical signal transduction, but their interaction with chemicals is largely unknown. Here, we present our findings on the key amino acid residues of PBPs in the gypsy moth, Lymantria dispar. Potential key residues were screened with the Calculate Mutation Energy program and molecular docking methods. Mutated proteins were obtained by mutating residues to alanine via site‐directed mutagenesis. Circular dichroism (CD) spectroscopy showed that the mutated proteins formed α‐helix, and the stability of protein structure was influenced due to mutations. Fluorescence binding assays were further conducted with the mutated proteins, sex pheromones and analogues. Results showed that to PBP 1, tyrosine at position 41 and phenylalanine at position 76 could be the key amino acid residues influencing the stability of structure; in addition, phenylalanine at 36 and lysine at position 94 could be key amino acid residues interacting with chemicals. To PBP 2, glycine at position 49, phenylalanine at position 76 and lysine at position 121 could be the key amino acid residues in the structural stability. These results shed light on the relationship between the specific amino acids and functions of PBPs in transmitting the chemical signals.     

Patterns of Gene Duplication in Lepidopteran Pheromone Binding Proteins

We have isolated and characterized cDNAs representing two distinct pheromone binding proteins (PBPs) from the gypsy moth, Lymantria dispar. We use the L. dispar protein sequences, along with other published lepidopteran PBPs, to investigate the evolutionary relationships among genes within the PBP multigene family. Our analyses suggest that the presence of two distinct PBPs in genera representing separate moth superfamilies is the result of relatively recent, independent, gene duplication events rather than a single, ancient, duplication. We discuss this result with respect to the biochemical diversification of moth PBPs. Received: 19 March 1997 / Accepted: 11 July 1997     

Mechanical thinning to restore oak savanna promoted predator assemblages of gypsy moth pupae in Michigan

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