Telomeres are terminal regions of chromosomes that protect and stabilize chromosome structures. Telomeres are usually composed of specific DNA repeats (motifs) that are maintained by telomerase and a complex of specific proteins. Telomeric DNA sequences are generally highly conserved throughout the evolution of different groups of eukaryotes. The most common motif in insects is TTAGG, but it is not universal, including in the large order Hemiptera. In particular, several derived telomeric motifs were identified in this order by analyzing chromosome-level genome assemblies or by FISH screening the chromosomes of target species. Here, we analyzed chromosome-level genome assemblies of 16 species from three hemipteran suborders, including Sternorrhyncha (Coccoidea: Planococcus citri, Acanthococcus lagerstroemiae, and Trionymus diminutus; Aphidoidea: Tuberolachnus salignus, Metopolophium dirhodum, Rhopalosiphum padi, and Schizaphis graminum), Auhenorrhyncha (Cicadomorpha: Allygus modestus, Arthaldeus pascuellus, Aphrophora alni, Cicadella viridis, Empoasca decipiens, and Ribautiana ulmi), and Heteroptera (Gerromorpha: Gerris lacustris; Pentatomomorpha: Aradus depressus and A. truncatus). In addition, scaffold-level genome assemblies of three more species of Heteroptera (Gerromorpha: Gerris buenoi, Microvelia longipes, and Hermatobates lingyangjiaoensis) were examined. The presumably ancestral insect motif TTAGG was found at the ends of chromosomes of all species studied using chromosome-level genome assembly analysis, with four exceptions. In Aphrophora alni, we detected sequences of 4 bp repeats of TGAC, which were tentatively identified as a telomeric motif. In Gerris lacustris, from the basal true bug infraorder Gerromorpha, we found a 10 bp motif TTAGAGGTGG, previously unknown not only in Heteroptera or Hemiptera but also in Arthropoda in general. Blast screening of the scaffold-level assemblies showed that TTAGAGGTGG is also likely to be a telomeric motif in G. buenoi and Microvelia. longipes, while the results obtained for H. lingyangjiaoensis were inconclusive. In A. depressus and A. truncatus from the basal for Pentatomomorpha family Aradidae, we found a 10 bp motif TTAGGGATGG. While the available data allowed us to present two alternative hypotheses about the evolution of telomeric motifs in Heteroptera, further data are needed to verify them, especially for the yet unstudied basal infraorders Enicocephalomorpha, Dipsocoromorpha, and Leptopodomorpha.

We present a genome assembly from an individual female Tuberolachnus salignus (the giant willow aphid; Arthropoda; Insecta; Hemiptera; Aphididae). The genome sequence is 456.8 megabases in span. Most of the assembly is scaffolded into 10 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 22.43 kilobases in length.

Understanding the factors that promote the success of invasive species is important for managing biological invasions. Interactions between invasives and other species (e.g., competitors, pathogens, or predators), could favor or limit their success. In recent decades, yellowjacket wasps, including Vespula germanica and V. vulgaris, have successfully established in Patagonia. Additionally, the invasive willow Salix fragilis has invaded areas next to watercourses, which in turn are typically colonized by the giant willow aphid (GWA, Tuberolagnus salignus), an additional species characterized as a successful invader in many regions worldwide. Aphid exudate (honeydew) has been reported to be used as a carbohydrate source by social wasps. The aim of our study was to gain a better understanding of the infestation pattern of the GWA in northwestern Patagonia, its effect on exudate availability and its relationship with yellowjacket foraging patterns. The study was conducted under the working hypothesis that the increase in the size of GWA colonies and resulting honeydew production, will fuel an increase in local Vespula spp. We found that the aphid honeydew is produced in relatively high amounts in the region (estimated at 1517 ± 139 Kg/ha/season), with strong indications that it is used by yellowjackets because of the significantly higher abundance levels of yellowjackets foraging on honeydew. The interaction of three invasive species, willows, GWA and yellowjackets, needs to receive special attention to develop future environmentally-sound mitigation tools of these nuisance pest.

Abstract In recent decades, yellowjacket wasps, including Vespula vulgaris, have successfully been established in Patagonia. Additionally, the invasive willow Salix fragilis has also invaded areas next to watercourses, which in turn are typically colonized by the giant willow aphid (GWA, Tuberolagnus salignus), another invasive species. The honeydew exuded by the aphids has been reported to be used as a carbohydrate source by this social wasp. Our aim was to determine whether willows and GWA (invasive complex) on the stream shores promotes yellowjacket population growth. We worked under the hypothesis that GWA provides honeydew (i.e. carbohydrates) to yellowjackets, favouring nest growth and individual fitness. Our results indicate that habitats close (<200 m) to stream margins, where S. fragilis and GWA occur, contain not only a greater abundance of workers but also a higher nest density of V. vulgaris yellowjackets. Even though the nests were similar in size irrespective of the distance to the stream, weight, size and nutritional status of individuals suggest that foraging/nesting in proximity of the invasive complex promotes larger and better nurtured wasps, including reproductive castes, that in the long run could drive population growth and spread of the species in Patagonia. In this context, our study suggests that management of V. vulgaris populations should adopt strategies that encompass a broad approach, especially adopting new strategies designed to contemplate relevant multitrophic interactions between yellowjackets and invasive willows and aphids.

Abstract Invasive insects are a serious problem in New Zealand, and their introduction and successful establishment are predicted to increase with global commerce and climate change. A recent introduction to New Zealand is Tuberolachnus salignus (Gmelin), a large aphid that attacks mainly willows but also other plants such as poplars, apples, and pears. It was first reported in 2013 but has since then spread rapidly throughout the country. We conducted a 2-yr study exploring the direct (on the host plant) and indirect (on other organisms) impacts of the aphid, in a field setting including 15 willow clones selected to represent the variety of species and hybrids present in New Zealand. Our research revealed great variation in the level of resistance/susceptibility of different clones and suggested a trade-off between reproduction, growth, and defense. We investigated the indirect effects of the aphid on honeydew foragers and on the soil ecosystem, through honeydew production and deposition, revealing complex cascading effects involving multiple trophic levels. We also explore and discuss management alternatives including the replacement of willows for native species or resistant varieties, the use of biological control agents, and the feasibility of chemical control. This work is one of few studies on the complex ecological effects of invasive phytophagous insects and could serve as a model for future research and to inform pest management. To conclude, we identify gaps in the knowledge and highlight aspects requiring further research.

The giant willow aphid (GWA), Tuberolachnus salignus (Gmelin) was reported for the first time from the cold arid region of Ladakh, India. The identification of GWA was done based on morphological and molecular characterization. The important morphological characters of GWA are grayish-golden color, covered with numerous fine hairs with a large dark brown tubercle in the center of the back. GWA is a serious pest of willow and poplar trees. There is a need to study the biology and host selection behavior of this pest to develop effective management strategies.

Abstract The giant willow aphid (Tuberolachnus salignus) is an invasive pest that can attain large populations on willows (Salix spp.). This has the potential to have a negative impact on the extensive use of willows for soil conservation, and as a source of pollen and nectar for honey bees in New Zealand. A willow nursery field trial was established to evaluate the aphid populations, and the survival and growth of young plants of several willow species and hybrids, during two growing seasons from planting. The willow species and hybrids varied widely in their susceptibility to the aphid, with large aphid populations and plant mortality in the most susceptible willows, and reductions in plant growth in all but aphid‐resistant willows. The effects on the plants were not seen in the first season, but occurred during the second season. The aphid can be expected to have some negative impacts in New Zealand, with reductions in growth of some willows commonly used for soil conservation, and for pollen and nectar for honey bees.

Abstract The giant willow aphid Tuberolachnus salignus Gmelin is a large phloem‐feeding insect which colonizes the stems of willow trees. This aphid is a new invasive species in New Zealand and there is limited knowledge of its inter‐annual population patterns and the damage it can cause to willow hosts. Our study investigated the T. salignus population dynamics and its effects on the flowering parameters of fifteen willow species and hybrids in a field trial. The aphid population levels were found to vary among the willow species and hybrids. Based on the aphid population levels, the willow species and hybrids were classified as resistant, moderately resistant, susceptible or highly susceptible. T. salignus infestation had no effect on the flowering of resistant and moderately resistant willows, but significantly delayed the flowering time, extended the flowering duration, and decreased the catkin length in susceptible species and hybrids. Interestingly, aphid infestation was found to increase the catkin number and total floral output of some willow species and hybrids. It can be concluded that aphid populations and their effects on flowering are host‐specific, with large differences between resistant and susceptible host plants.

The giant willow aphidTuberolachnus salignusis an invasive pest in New Zealand, attacking over 50 species and hybrids of willow. The aphids produce copious amounts of honeydew, which is used by other insects as a food source.When foraged by honeybees,T. salignushoneydew causes honey to crystallize in the comb and affects bee health; these effects are associated with the elevated melezitose content in the honeydew. The impact of host plant‐related factors onT. salignushoneydew melezitose content remains unknown.This study investigated the effect of willow cultivar and plant age on the melezitose content (and that of other sugars) ofT. salignushoneydew. To do so, we conducted high‐performance liquid chromatography analyses of honeydew samples from 13 willow clones collected in the same season (autumn) from 1‐ and 2‐year old plants under field conditions.Melezitose was the most abundant of the measured sugars in most samples, but its content did not vary significantly with willow cultivar or plant age. By contrast, sucrose was significantly affected by both factors. Fructose and glucose were significantly impacted by willow plant age and cultivar, respectively. A significant cultivar*age interaction was observed for all sugars.We recommend the selection of resistant willow cultivars and further research on potential biocontrol agents to lessen melezitose‐related problems in apiculture industries.

Composition and potential as a prebiotic functional food of a Giant Willow Aphid (Tuberolachnus salignus) honeydew honey produced in New Zealand

The giant willow aphid (Tuberolachnus salignus) is a large stem-feeding insect which forms dense colonies on infested plants. Since T. salignus is a new invasive species in New Zealand, we have a poor understanding of the plant chemical responses to aphid infestation. This study aimed to characterize the volatile organic compounds (VOCs) emissions of fifteen different willow species and hybrids growing in New Zealand, and to evaluate changes in response to T. salignus attack in a field trial. Volatiles were collected using a headspace sampling technique and analysed using gas chromatography-mass spectrometry (GC-MS). We found high variability in the volatile profiles of different species and hybrids, with (Z)-3-hexenyl acetate and (E)-β-ocimene being the only common components to all blends. Taxonomically related plants showed an overlapping pattern of VOC emission, and there seemed to be a clear separation between shrub and tree willows. Responses to aphid infestation were variable, with only four species/hybrids showing changes in their total VOC emission, or that of at least one class of VOCs. A weak positive correlation between aphid population estimates and VOC emissions suggests that responses are species-specific and not infestation-dependent. These results reveal useful information about the interaction between T. salignus and its potential host plants for biological control and pest management purposes.

Infestation of willow plants by the giant willow aphid Tuberolachnus salignus (Hemiptera: Aphididae) is associated with copious deposition of sugar-rich honeydew under the plant canopy. We explored the effect of aphid honeydew on the soil biota and biochemical indicators in a two-year field trial. Soil samples from under aphid-infested and control willow trees, as well as samples from black sooty mould spots under the aphid-infested willows were compared; soil samples before aphid inoculation were used as a baseline. The honeydew deposition had a positive effect on the total soil carbon (C), but not on the total soil nitrogen content or soil pH. Microbial biomass C, basal respiration, number of yeast colony forming units, and the geometric mean of activities for six enzymes were significantly higher in honeydew-affected soils than in the control treatment on both years. The honeydew deposition also increased soil meso-fauna abundance, especially in the black sooty mould spots. The soil biochemical properties, which differed before and after aphid infestation, showed considerable overlap between the first and second year post-infestation. The results highlight the cascading effects of T. salignus on soil biological activity and the importance of using a multitrophic approach to explore similar scenarios.

The giant willow aphid, Tuberolachnus salignus is an invasive insect in New Zealand for which control measures are being sought due to its detrimental effects on willow cultivation and apiculture. We evaluated the biocontrol potential of the harlequin ladybird beetle, Harmoniaaxyridis, by measuring voracity and feeding preference of larvae and adults in laboratory trials. Results show that H. axyridis consumes T. salignus, with females being more voracious than males and larvae. However, H. axyridis fed T. salignus took longer to develop, gained less weight and had lower survival compared with those fed eggs of the Mediterranean flour moth, Ephestiakuehniella. In a choice test, larval and adult H. axyridis preferred the green peach aphid, Myzuspersicae, as prey item, rejecting T. salignus. We suggest that H. axyridis is likely to use T. salignus only as a facultative prey, and therefore cannot be prioritised as a potential biocontrol agent.

ABSTRACTThe first records of Tuberolachnus salignus (Gmelin), the giant willow aphid, were reported from New Zealand and Australia in December 2013 and March 2014 respectively. The host plants are various members of Salix and Populus. The pathway used by the aphid to enter Australasia remains unknown, but natural aerial dispersal across the Tasman Sea is proposed to explain its first appearance within 3 months in Australia and New Zealand. Previous examples of aphids crossing the Tasman Sea are summarised. Windborne transmission due to the predominantly westerly winds from Australia to New Zealand is more likely based on past experience. However, we demonstrate using the HYSPLIT air trajectory model that it is possible that the aphid was carried on a reverse trajectory from New Zealand to southern Tasmania. Without more regular and systematic surveillance of New Zealand and Australian insect biota, it will continue to be difficult to ascertain the timing, origin and dispersal pathways of introduced insects.


 
 
 The giant willow aphid, was first found in New Zealand in 2013 and is now established throughout the country. An orchardist in the Tasman district reported infestation of his commercial block of young ‘Envy’ apple trees after harvest in May 2016, adjacent to two large willow trees heavily infested with giant willow aphid. Regular observations commenced soon after to determine seasonal activity, apple tree infestation, timing and impact and any alternative host plants or possible natural enemies. Key observations since are that the giant willow aphids appear in late September on willow shoots near the base of the tree reaching low numbers before disappearing again in late November. At this time, a ladybird species (Adalia bipunctata), where observed in the willows and on other plants nearby. In late December the aphids reappeared on the willows and numbers built to a peak in late February and remained on the willows until leaf fall. The aphids were not seen on the apple trees in any signi cant numbers until February when infestation and feeding continued until late autumn. After two seasons of infestation, the apple trees closest to the infested willows are now visibly ‘sick’ with yellowing leaves, stunted growth, reduced fruit production and branches blackened with sooty mould.
 
 

Abstract AimAnimals' phylogeographical patterns are frequently explained by Pleistocene glacial fluctuations and topographical environments. However, species‐specific biological traits are thought to have profound impacts on distribution patterns, particularly in aphids. We hypothesize that the phylogeographical patterns and/or population dynamics of two sympatric aphids may be different due to their different reproductive modes and feeding sites, even though they share the same hosts and environmental conditions.LocationChina.MethodsWe explored our hypothesis in Chaitophorus saliniger and Tuberolachnus salignus, two aphids that share the same host plants (genus Salix) but differ biologically. Chaitophorus saliniger is characterized by alternating sexual and asexual reproduction and only feeds on willow leaves, whereas T. salignus has obligate asexual reproduction and feeds on trunks and branches. The genetic diversity, population structure and demographic history of the aphids were analysed based on both mitochondrial DNA (cytochrome c oxidase subunit I and cytochrome b) and nuclear DNA (translation elongation factor 1 alpha). Ecological niche models (ENMs) were used to explore historical changes in distribution. The chief environmental variables that discriminate the different haplogroups were identified through multivariate statistical analysis.ResultsThere were striking differences in the phylogeographical patterns between the species. The sexual C. saliniger exhibited higher genetic diversity and population variations than the asexual T. salignus. According to genetic analyses and ENMs, both species experienced glacial contraction and post‐glacial expansion. Multivariate statistical analysis revealed that the climatic differences between the divergent haplogroups were explained by principal components mainly loaded with temperature and elevation.Main conclusionsOur results suggest that species‐specific biological traits and historical climate fluctuations have both shaped the current phylogeographical patterns of both aphid species. Their distinct genetic diversity and population structures highlight the importance of intrinsic biological features in driving phylogeographical patterns.

Virtually all aphids (Aphididae) harbor Buchnera aphidicola as an obligate endosymbiont to compensate nutritional deficiencies arising from their phloem diet. Many species within the Lachninae subfamily seem to be consistently associated also with Serratia symbiotica. We have previously shown that both Cinara (Cinara) cedri and Cinara (Cupressobium) tujafilina (Lachninae: Eulachnini tribe) have indeed established co-obligate associations with both Buchnera and S. symbiotica. However, while Buchnera genomes of both Cinara species are similar, genome degradation differs greatly between the two S. symbiotica strains. To gain insight into the essentiality and degree of integration of S. symbiotica within the Lachninae, we sequenced the genome of both Buchnera and S. symbiotica endosymbionts from the distantly related aphid Tuberolachnus salignus (Lachninae: Tuberolachnini tribe). We found a striking level of similarity between the endosymbiotic system of this aphid and that of C. cedri. In both aphid hosts, S. symbiotica possesses a highly reduced genome and is found exclusively intracellularly inside bacteriocytes. Interestingly, T. salignus’ endosymbionts present the same tryptophan biosynthetic metabolic complementation as C. cedri’s, which is not present in C. tujafilina’s. Moreover, we corroborate the riboflavin-biosynthetic-role take-over/rescue by S. symbiotica in T. salignus, and therefore, provide further evidence for the previously proposed establishment of a secondary co-obligate endosymbiont in the common ancestor of the Lachninae aphids. Finally, we propose that the putative convergent split of the tryptophan biosynthetic role between Buchnera and S. symbiotica could be behind the establishment of S. symbiotica as an obligate intracellular symbiont and the triggering of further genome degradation.

Whilst many classes of insecticides target the insect central nervous system (CNS), their effects in the CNS of pest aphids have not been demonstrated. In this report, we describe an electrophysiological method for recording spontaneous neuronal activity from the giant willow aphid (Tuberolachnus salignus). Using extracellular recording electrodes and two analysis methods (threshold and template search), spontaneous spike activity was shown to exhibit sensitivity to the neuroexcitatory insecticide imidacloprid. This method allows changes in the frequency of action-potentials to be monitored during direct bath exposure to chemical agents, enabling a means of assessing and comparing neurotoxic effects of insecticides in a previously inaccessible superfamily of pest insects.

This study reports the results obtained in an investigation of the putatively parthenogenetic aphid species Tuberolachnus salignus Gmelin. Tuberolachnus salignus is one of the largest aphid species in the world but where and how it overwinters is not known. It has recently become noteworthy because it is increasingly found on commercially grown willows used in bioenergy production. Seven newly‐developed polymorphic microsatellite markers were used to investigate the genetic diversity of the species, and also to confirm its reproduction strategy. Tuberolachnus salignus shows very low clonal diversity; only 16 genotypes were found in 660 specimens from 27 populations in five countries. There was limited geographical structuring in the samples, although the two most common genotypes, which comprised more than half of the specimens collected, had a very wide distribution. Furthermore, we determined that these aphids, which live in very dense colonies, can consist of more than one genotype, suggesting aggregation of colonizing T. salignus. These results confirm the parthenogenetic nature of T. salignus and demonstrate the presence of common genotypes that are widespread in time and space.

Cytogenetic study was carried out on willow aphids viz. Cavariella aegopodii and Tuberolachnus salignus in order to ascertain the karyotype and sex determination in these aphids from different localities of Himachal Pradesh, India. In Cavariella aegopodii, collected from Shimla, Mashobra and Shoghi localities, 2n is 10. There is 1 pair of long, 2 pairs of medium sized and 2 pairs of short chromosomes. However, karyotypic variation was observed in aphid populations collected from the Solan locality, where the variable diploid chromosome numbers such as 2n=8, 9 and 10 were also recorded. The male sexuals of Cavariella aegopodii are diploid having 2n=9 with 4 pairs of autosomes and a single X chromosome. The various stages of meiosis in the testes of the male mainly occur during the early developmental stages and can also be found in the first and second instar nymphs. The Cavariella aegopodii has XX-XO type of sex determination system.In Tuberolachnus salignus collected from the Shimla, Mashobra and Shoghi localities, 2n is 20. The idiogram of Tuberolachnus salignus reveals the gradual decrease in chromosome length. However, karyotypic variation was observed in aphids collected from the Solan locality where the diploid chromosome number (2n) ranged from 18 to 20.