Willow Aphid Research Articles

The genome sequence of the giant willow aphid, Tuberolachnus salignus (Gmelin, 1790).

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.

Honeydew production by the Giant Willow Aphid (Tuberolachnus salignus, Hemiptera: Aphididae) and its effect on foraging yellowjackets (Hymenoptera: Vespidae).

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.

Are invasive species promoting yellowjacket invasion in Patagonia?

AbstractIn 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.

First Record of an Invasive Pest, Giant Willow Aphid, Tuberolachnus salignus (Gmelin) (Hemiptera: Aphididae) on Salix alba in the Cold Arid Region of Ladakh, India

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.

The giant willow aphid (Tuberolachnus salignus) and its effects on the survival and growth of willows

AbstractThe 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.

Phytophagous energy plantings of willow

Purpose. Investigation of the species composition and the number of plant feeders in energy willow plantations.
 Method. Field, accounting, statistical, analytical.
 Results. Today, growing plants for the production of biofuels is a promising source of energy that have a high potential for energy recovery. Biomass of energy crops such as willow is a renewable energy source with zero balance of carbon dioxide and methane. Fast-growing trees such as willow are perennials that are able to produce biomass over a long period. However, like any plant, willow is a host tree for many living organisms, including insects. According to the results of our observations and records, among the latter, this crop is damaged by both soil and land plant feeders. Of the soil pests, the most dangerous for willow are the larvae of several species of May beetles, which feed on the roots causing significant inhibition of growth and development of plants or even their death. The number of these insects per square meter in different zones ranges from 0.6–0.8 to 1.6–1.9. In the focuses, the population density of the larvae per square meter reaches 8.8. In addition to beetle larvae, the root system of willow is damaged by the larvae of click beetles, Elatericlae, Blaps and Anisoplia austriaca larvae. The number of these larvae per square meter ranges between 0.8 and 2.3 and between 0.5 and 2.7, respectively. Of land pests, willow is damaged by Chrysomela saliceti (0.7–7.2, in focuses 3.2–22.0 pests/plant), willow aphid (population score 1.1–1.8, in focuses 1.7–2.3), Hyponomeuta malinellus (population ratio 1.1–1.2, in focuses 1.8–2.1), Leucoma salicis (0.2–0.3, in focuses 1.9–6.1 larvae/plant), Chionaspis salicis (0.7–1.0, in focuses 2.3–10.0 individuals), Tetranychus urticae (population score 1.0–1.3, in focuses 1.4–2.3) and Philaenus spumarius, (0.1–0.8 in focuses 1.0–3.4 pests/plant). The control of the number of these plant feeders is carried out by soaking of cuttings before planting in insecticide solutions, as well as spraying the plants with chemicals against land pests.
 Conclusions. Energy willow plants are damaged by many species of soil and land plant feeders, the number of which depends on the area of growing. Controlling of their number is carried out by soaking cuttings before planting in insecticide solutions and spraying plants.

Seasonal abundance of Tuberolachnus salignus and its effect on flowering of host willows of varying susceptibility

AbstractThe 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.

Effect of willow cultivar and plant age on the melezitose content of giant willow aphid (Tuberolachnus salignus) honeydew

The giant willow aphid Tuberolachnus salignus is 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. salignus honeydew 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 on T. salignus honeydew melezitose content remains unknown. This study investigated the effect of willow cultivar and plant age on the melezitose content (and that of other sugars) of T. salignus honeydew. 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, GWA) is an invasive pest insect in New Zealand, which excretes honeydew. European honeybees collect this honeydew and make it into a type of honey that crystallizes in the comb, representing a significant loss to apiarists. This crystallization has been ascribed to high concentrations of oligosaccharides, particularly melezitose. In this research, the first carbohydrate profile of GWA honeydew honey, a sample of GWA honeydew honey was found to contain 37.8% total oligosaccharides of which 27.4% was melezitose, and 2.5% gluconic acid (higher than typical honeydew honeys); 41.2% monosaccharides (lower than typical honeydew honeys); and 0.054% salicylic acid (higher than previous estimates). Melezitose extracted from GWA honeydew honey was not significantly hydrolyzed in crude human-stomach and human-small-intestine simulations and may therefore meet the prebiotic criterion of human indigestibility.

Volatile Profiling of Fifteen Willow Species and Hybrids and Their Responses to Giant Willow Aphid Infestation

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.

Honeydew Deposition by the Giant Willow Aphid (Tuberolachnus salignus) Affects Soil Biota and Soil Biochemical Properties.

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 potential of harlequin ladybird beetle Harmonia axyridis as a predator of the giant willow aphid Tuberolachnus salignus: voracity, life history and prey preference

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.

Possible windborne transmission of giant willow aphid Tuberolachnus salignus (Gmelin) (Hemiptera: Aphididae: Lachninae) westward from New Zealand to Australia

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.

Pests of energy willow and practices to control their number

Purpose. To determine the pest species composition in bioenergy willow plantations and develop practices to control their number.Methods. Field, accounting, statistical and analytical.Results. The main pests species composition of bioenergy willow plantation in different zones have been determined, namely in the zone of sufficient moisture at the Uladivka-Liulyntsi Research Breeding Station (ULRBS), in the zone of insufficient moisture at Veselyi Podil Research Breeding Station (VPRBS) and in the zone of unstable moisture at the Bila Tserkva Research Breeding Station (BTsRBS). Of the soil pests, the most harmful for sugar beet species were found May bug, June bug and marble bug, the number of which in different areas ranged from 0.1 to 0.4 (VPRBS) to 2.0 to 4.0 (ULRBS) per 1 m2. In addition to these harmful species, there were larvae of grasshoppers and Tenebrionidae, the number of which was 0.9 to 4.0 per 1 m2, as well as larvae of cereal chafer and caterpillars of winter owl moth. The density of the soil pests population somewhat exceeded the economic thresholds of harmfulness, which should be taken into account when establishing willow plantations and during the growing season. With regard to terrestrial species, the most dangerous for willow is brown willow beetle, willow aphid and apple black miner, the number of which was also not the same everywhere. Thus, the highest population density of the brown willow beetle (beetle/10 plants) was recorded in BTsRBS (3.0 to 36.0), in ULRBS (0.5 to 3.0) and VPRBS (0.2 to 3.6). The willow aphid was found in all zones at the settlement score of 1.0 to 1.5, while apple black miner was recorded only in spring in ULRBS and BTsRBS at the settlement score of 1.0. The control of the number of phytophages in willow plantation was carried out with the aid of insecticides through pre-planting soaking cuttings and spraying planted cuttings. Soaking of cuttings in solutions of systemic action insecticides contributes to a 12.9 ̶ 22.9% increase in the plant survival compared to soaking them in water. The use of insecticides for spraying cuttings during vegetation season provides a high efficiency (76.7–100.0%) of pest control.Conclusions. Energy willow is damaged by a number of soil and terrestrial pests, namely larvae of May bug, grasshopper, Tenebrionidas, cereal chafer, Carabidae (soil pests), and brown willow beetle, willow aphid and apple bark miner (terrestrial pests). The control of the number of these phytophages is carried out mainly with the aid of insecticides through pre-planting soaking cuttings or spraying planted cuttings.

Monitoring giant willow aphid (<i>Tuberolachnus salignus</i>) on apple trees in close proximity to infested willows


 
 
 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.
 
 

Potential impacts ofTuberolachnus salignus(giant willow aphid) in New Zealand and options for control

The giant willow aphid Tuberolachnus salignus was discovered in New Zealand in late 2013. Despite being a recent addition to the New Zealand fauna, the aphid is already widespread and abundant throughout the country. The giant willow aphid is expected to have negative impacts on host trees, primarily willows (Salix spp.), as has been observed elsewhere. All willows are exotic to New Zealand and a few have formal weed status, however many species are valued for multiple purposes, including flood protection, land stabilization, shelterbelts, and as early season pollen and nectar resources for honey bees. Tuberolachnus salignus presents a unique problem for New Zealand's thriving honey and honey products industries. Bees readily forage on the vast quantities of honeydew secreted by the aphid, however the honeydew contains melezitose sugar. The low solubility of this sugar results in honey crystallizing in the comb, making it difficult to extract and thereby reducing yield. It is also considered to be poor food for bees, and has been linked to bee dysentery and low overwintering survival. We elaborate on the potential complications for New Zealand as a result of the arrival of this new species and present options for its control and management.

Spontaneous electrical activity recorded from the aphid central nervous system

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.

Ant‐mediated dispersal of the black willow aphid Pterocomma salicis L.; does the ant Lasius niger L. judge aphid‐host quality?

Ant‐mediated dispersal of the black willow aphid <i>Pterocomma salicis</i> L.; does the ant <i>Lasius niger</i> L. judge aphid‐host quality?

Host selection and performance of the giant willow aphid, Tuberolachnus salignus Gmelin – implications for pest management

Abstract1 The recent increase in planting of selected willow clones as energy crops for biomass production has resulted in a need to understand the relationship between commonly grown, clonally propagated genotypes and their pests.2 For the first time, we present a study of the interactions of six willow clones and a previously unconsidered pest, the giant willow aphid Tuberolachnus salignus.3 Tuberolachnus salignus alatae displayed no preference between the clones, but there was genetic variation in resistance between the clones; Q83 was the most resistant and led to the lowest reproductive performance in the aphid4 Maternal effects buffered changes in aphid performance. On four tested willow clones fecundity of first generation aphids on the new host clone was intermediate to that of the second generation and that of the clone used to maintain the aphids in culture.5 In the field, patterns of aphid infestation were highly variable between years, with the duration of attack being up to four times longer in 1999. In both years there was a significant effect of willow clone on the intensity of infestation. However, whereas Orm had the lowest intensity of infestation in the first year, Dasyclados supported a lower population level than other monitored clones in the second year.

Effect of temperature on fecundity and development of the Giant Willow Aphid, Tuberolachnus salignus (Sternorrhyncha: Aphididae)

This study investigates the thermal requirements, nymphal development rates and the fecundity of both alate and apterous adults of the giant willow aphid, Tuberolachnus salignus (Gmelin) at several temperatures. Nymphal development rate increased linearly with temperature. It was estimated that 196 ± 4 degree-days above a threshold temperature of 5.5 ± 0.3°C were required for apterae to complete development from birth to final ecdysis. The alate morph was significantly less fecund than the apterous morph and its fecundity did not vary with temperature. The apterous morph displayed highest fecundity at 20°C. Survival to reproduction was lower in the alate morph, but temperature had no effect on the proportion reproducing in either morph.