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Giant willow aphid - Tuberolachnus salignus

By N A Martin (2017)

Classification

Phylum:
Arthropoda
Class:
Insecta
Order:
Hemiptera
Family:
Aphididae
Scientific Name:
Tuberolachnus (Tuberolachnus) salignus (Gmelin, 1790)
  • Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and one of the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
    Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and one of the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
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Common Names

Giant willow aphid, Large Willow Aphid
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Synonyms

Aphis salignus Gmelin, 1790
Aphis salicina Zetterstedt, 1840
Aphis salicis Sulzer, 1776 (ambiguous synonym)
Aphis viminalis Boyer de Fonscolombe, 1841 (ambiguous synonym)
Aphis vitellinae Hartig, 1841 (ambiguous synonym)
Cinara salicis (Sulzer, 1776)
Cinara saligna (Gmelin, 1790)
Lachnus punctatus Burmeister, 1835
Lachnus viminalis Burmeister, 1835
Pterochlorus longipes Zetterstedt, 1840 (ambiguous synonym)
Pterochlorus viminalis (Boyer de Fonscolombe, 1841)
Tuberolachnus punctatus (Burmeister, 1835)
Tuberolachnus salignus (Burmeister, 1835) (ambiguous synonym)
Tuberolachnus viminalis (Burmeister, 1835)

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Taxonomic Notes

This species is in the subfamily and tribe Lachninae: Lachnini.

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Biostatus and Distribution

This cosmopolitan adventive aphid was first found in Auckland in December 2013. It has since spread to its primary host plants, willow trees (Salix species (Salicaceae)), in other parts of the country. Its feeding produces much honeydew and accompanying sooty mould. The honeydew can be a problem for honey producers and sheep farmers. Feeding can weaken trees of some willow species.

Conservation status: Widespread, primarily living on willows and is a pest for honey producers, some sheep farmers and willows on river banks, it may also infest apple and pear trees in orchards.

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Life Stages and Annual Cycle

This aphid is believed to overwinter as winged females. Trees are colonised in late winter or early spring, as early as August or even late July in Auckland where colonies of wingless aphids were found in early September. In mid-October winged aphids were found in colonies. Winged aphids disperse to other trees. There are several overlapping generations per year with high numbers being found in late summer and early autumn. In the autumn many winged aphids are produced.

Only female aphids are known in New Zealand and many other parts the world. Female only populations are exhibit pathogeneses. The adult females are either winged and wingless. Adult giant willow aphids are one of the largest aphids in the world, their body is 5.0-5.8 mm long. Wingless adults (Apterae) are mid to dark brown and have several rows of black patches. Their body is covered with fines hairs that gives the abdomen a greyish-golden sheen. On the centre of their back is a large dark brown ‘thorn’ or tubercle. Near the back of the abdomen are a pair of large low cones (siphunculi) that excrete honeydew. The winged adults (Alates) have two pairs of clear wings that are held above their body. The forewing has a dark brown front edge. They have three pairs of legs that are partly reddish, and a pair of antennae that are less than half the length of the body. The underside of the head has a short rostrum that holds the stylets used for feeding.

Mature females give birth to live young, nymphs, that look like the wingless adults. An adult female may give birth to about 35 nymphs, but this can be up to 71 offspring. There are four nymphal instars (stages). The growing nymph goes to the next instar by moulting, changing its skin. The dorsal (top) side of the skin splits and the next stage pulls itself out. The fourth instar moults into the adult. Fourth instar nymphs that will become winged adults, have wing buds.

In one study (Collins & Leather 2001) the aphid requires about 196 degree days above 5.5°C to complete nymphal development. Winged females produced fewer nymphs than wingless females. Most young were produced at 20°C. Other research has shown that at temperatures above 25°C survival is very poor, though there is inconsistency between some of the research.

Aphid behaviour
When a colony of aphids is disturbed or they perceive danger such as waving a hand near them, the aphids lift and wave their hind legs.

While the aphids are seen in colonies of adults and nymphs, some wingless adults wander off and may found new colonies. In the warmer summer weather colonies of the aphid seem to be continually on the move.

Feeding and honeydew
Like other Hemiptera, the giant willow aphid has sucking mouth parts. The long stylets, special shaped rods, are held in the rostrum. When it wishes to feed the aphid moves the tip of the rostrum to the surface of a branch or shoot. The stylets are then gradually pushed into the plant. The inner pair of stylets, form two tubes, one through which saliva is injected into the plant and a second through which plants juices are sucked up into the insect. The giant willow aphid inserts its stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew. Black fungi (sooty moulds) grow on the honeydew.

  • Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
    Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
  • Wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Underside of a wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Underside of a wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Underside of a winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Underside of a winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of moulting winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Colony of moulting winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Colony of winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Colony of winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Honeydew on leaves of a willow tree (white arrow) secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), (black arrow). Image: Nicholas A. Martin © Nicholas A. Martin
    Honeydew on leaves of a willow tree (white arrow) secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), (black arrow). Image: Nicholas A. Martin © Nicholas A. Martin
  • Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree.  Image: Nicholas A. Martin © Nicholas A. Martin
    Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree. Image: Nicholas A. Martin © Nicholas A. Martin
  • Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
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Recognition

The Giant willow aphid primarily breeds on willow trees (Salix species), but winged adults can be found elsewhere, even on buildings. On willow trees giant willow aphid lives in colonies on stems and branches and is quite different from other aphids and other insects found on these trees. Even on other host plants it is very distinctive.

The adult females are either winged and wingless. Adult giant willow aphids are one of the largest aphids in the world, their body is 5.0-5.8 mm long. Wingless adults (Apterae) are mid to dark brown and have several rows of black patches. Their body is covered with fines hairs that gives the abdomen a greyish-golden sheen. On the centre of their back is a large dark brown ‘thorn’. Near the back of the abdomen are a pair of large low cones (siphunculi) tat excrete honeydew. The winged adults (Alates) have two pairs of clear wings that are held above their body. The forewing as a dark brown front edge. They have three pairs of legs that are partly reddish, and a pair of antennae that are less than half the length of the body. There are usually many nymphs in their colonies.

Sometimes it can be hard to find giant willow aphids even when a colony is present in a willow tree. When a tree has many leaves look for the honeydew shining on the top of leaves. Then look above the leaves with honeydew for the aphid colony, which could be on the underside of a branch or stem.

  • Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and one of the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
    Adult wingless giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), note the black ‘thorn’ and one of the two black cone-shaped siphunculi. Image: Nicholas A. Martin © Plant & Food Research
  • Wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Wingless adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Winged adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs; note the dark ‘thorn’ (black arrow) and nymph being born (red arrow). Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs; note the dark ‘thorn’ (black arrow) and nymph being born (red arrow). Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in spring. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in spring. Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in early spring. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in early spring. Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Colony of winged giant willow aphids, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree. Image: Nicholas A. Martin © Nicholas A. Martin
    Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree. Image: Nicholas A. Martin © Nicholas A. Martin
  • Honeydew on leaves of a willow tree (white arrow) secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), (black arrow). Image: Nicholas A. Martin © Nicholas A. Martin
    Honeydew on leaves of a willow tree (white arrow) secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), (black arrow). Image: Nicholas A. Martin © Nicholas A. Martin
  • Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
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Natural Enemies

Four species of ladybird have been observed feeding on giant willow aphids in New Zealand. The three long established species are only occasionally found feeding on the aphid. The recent arrival, the Harlequin ladybird, has a repuation of giving good control of aphids and in Auckland I have seen popultions of giant willow aphid reduced to low levels by this ladybird.

Parasitoids are reported from some east Asian countries.

When the aphids are disturbed, they wave their legs in the air. This is presumably a defensive behaviour.

Table: Predators of Giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), from Plant-SyNZ database (21 February 2017). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific NameCommon NameClassificationEnemy TypeReliability
Index
Biostatus
Adalia bipunctata (Linnaeus, 1758)Two-spotted ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
Coccinella undecimpunctata Linnaeus, 1758Eleven-spotted ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
Harmonia axyridis (Pallas, 1773)Harlequin ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
Harmonia conformis (Boisduval, 1835)Large spotted ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
  • Adult two-spotted ladybird, Adalia bipunctata (Coleoptera: Coccinellidae), about 5 mm long.  Image: Tim Holmes © Plant & Food Research
    Adult two-spotted ladybird, Adalia bipunctata (Coleoptera: Coccinellidae), about 5 mm long. Image: Tim Holmes © Plant & Food Research
  • Larva of two-spotted ladybird, Adalia bipunctata (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
    Larva of two-spotted ladybird, Adalia bipunctata (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
  • Adult eleven-spotted ladybird, Coccinella undecimpunctata (Coleoptera: Coccinellidae) on a lettuce leaf. Image: Plant & Food Research Photographer © Plant & Food Research
    Adult eleven-spotted ladybird, Coccinella undecimpunctata (Coleoptera: Coccinellidae) on a lettuce leaf. Image: Plant & Food Research Photographer © Plant & Food Research
  • A fully grown larva of eleven-spotted ladybird, Coccinella undecimpunctata (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
    A fully grown larva of eleven-spotted ladybird, Coccinella undecimpunctata (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
  • Two adult large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae); note the variation in the size of the spots on the elytra.  Image: Tim Holmes © Plant & Food Research
    Two adult large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae); note the variation in the size of the spots on the elytra. Image: Tim Holmes © Plant & Food Research
  • Late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae).  Image: Tim Holmes © Plant & Food Research
    Late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
  • Dorsal view of a late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae).  Image: Tim Holmes © Plant & Food Research
    Dorsal view of a late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
  • Late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae).  Image: Tim Holmes © Plant & Food Research
    Late instar larva of large spotted ladybird, Harmonia conformis (Coleoptera: Coccinellidae). Image: Tim Holmes © Plant & Food Research
  • Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae), note the white on the head and pronotum and the black M-shape on the pronotum.  Image: Nicholas A. Martin © Plant & Food Research
    Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae), note the white on the head and pronotum and the black M-shape on the pronotum. Image: Nicholas A. Martin © Plant & Food Research
  • Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae).  Image: Nicholas A. Martin © Plant & Food Research
    Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
  • Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae).  Image: Nicholas A. Martin © Plant & Food Research
    Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
  • Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
    Adult Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
  • Third instar (stage) larva of Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae).  Image: Nicholas A. Martin © Plant & Food Research
    Third instar (stage) larva of Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
  • Larva of Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae).  Image: Nicholas A. Martin © Plant & Food Research
    Larva of Harlequin ladybird, Harmonia axyridis (Coleoptera: Coccinellidae). Image: Nicholas A. Martin © Plant & Food Research
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Host Plants

In New Zealand the Giant Willow aphid has mainly been found feeding on willows, Salix species, but it has also been found breeding on apple and pear trees, especially near willow shelter belts. It has also been found on Black poplar, Populus nigra. There is one record on a native plant, Coprosma macrocarpa, but although the aphids were breeding, the population did not thrive.

Heavy infestation of giant willow aphid on very susceptible willow tree species can weaken the trees and even kill branches. Where willow trees are used by rivers to protect the banks from erosion this could also cause a problem. The susceptibility of some willow species is variable. For example, populations of aphids may be high on some weeping willow, Salix babylonica, trees but low or absent on other weeping willow trees. A long term option may be to find or breed willow trees that are resistant to giant willow aphid (Sopow and authors, 2017).

Honey bees use willow tree flowers in the spring as a source of nectar and pollen. Trees weakend by giant willow aphids produce fewer flowers. In some parts of the country this removes an important source of food for bee hives in spring.

Feeding and honeydew
Like other Hemiptera, the giant willow aphid has sucking mouth parts. The long stylets, special shaped rods, are held in the rostrum. When it wishes to feed the aphid moves the tip of the rostrum to the surface of a branch or shoot. The stylets are then gradually pushed into the plant. The inner pair of stylets, form two tubes, one through which saliva is injected into the plant and a second through which plants juices are sucked up into the insect. The giant willow aphid inserts its stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew. Black fungi (sooty moulds) grow on the honeydew.

Honeydew can be a nuisance because it coats willow tree leaves and anything under or near the trees. In addition, sooty mould fungi grow in the honeydew and surface coated with honeydew turn black.

The only sugar in willow tree sap is glucose. The honeydew secreted by giant willow aphid contains several kinds of sugar, approximately equal amounts of fructose, glucose, sucrose and a trisaccharide melezitose (Mittler, 1958 in Sopow and authors, 2017). The presence of melezitose in honey derived from giant willow aphid honeydew can cause problems for honey produces.

Table: Host plants of the Giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae) from Plant-SyNZ database (21 February 2017). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)Scientific NameFamilyReliability IndexBiostatus
Large seeded coprosma, Kākaramū, Kākarangū, Karamū, Kāramuramu, KarangūCoprosma macrocarpa CheesemanRubiaceae5endemic
Apple, Crab-appleMalus ×domestica Borkh.Rosaceae8naturalised
Black poplar, Lombardy poplarPopulus nigra L.Salicaceae10naturalised
European pear, PearPyrus communis L.Rosaceae7naturalised
 Salix ×calodendron Wimm.Salicaceae10naturalised
 Salix ×dichroa DollSalicaceae10cultivated
fine basket osier, fine osierSalix ×forbyana Sm.Salicaceae10cultivated
Brittle willow, Crack willowSalix ×fragilis L.Salicaceae10naturalised
niobe willow, weeping crack willow, Wisconsin weeping willowSalix ×pendulina Wender.Salicaceae10cultivated
 Salix ×pontederana Willd.Salicaceae10naturalised
Pussy willowSalix ×reichardtii A.Kern.Salicaceae10naturalised
Kemp willowSalix ×sepulcralis Simonk.Salicaceae10naturalised
broadleaf osier, silky-leaf osierSalix ×smithiana Willd.Salicaceae10cultivated
 Salix aegyptiaca LSalicaceae10cultivated
Egg yolk willow, Golden willowSalix alba L. var. vitellina (L.) StokesSalicaceae10naturalised
Golden willow, Silver willow, White willowSalix alba L.Salicaceae10naturalised
 Salix apennina A. K. SkvortsovSalicaceae10cultivated
 Salix auritoides Kern.Salicaceae9cultivated
Babylon weeping willow, Napoleon's willow, Weeping willowSalix babylonica L.Salicaceae10naturalised
hoary willow, sage willowSalix candida Flugge ex Willd.Salicaceae10cultivated
 Salix cantabrica Rech. f.Salicaceae10cultivated
Grey sallow, Grey willowSalix cinerea L.Salicaceae10naturalised
grey willow, sallowSalix cinerea subsp. oleifolia (Sm.) MacreightSalicaceae10naturalised
Violet willowSalix daphnoides Vill.Salicaceae10naturalised
 Salix dasyclados Wimm.Salicaceae10cultivated
 Salix disperma Roxb. ex D. DonSalicaceae10cultivated
Bitter willow, Hoary willow, Rosemary willowSalix elaeagnos Scop.Salicaceae10naturalised
heart-leaf willowSalix eriocephala Michx.Salicaceae10cultivated
rose-gold pussy willowSalix gracilistyla Miq.Salicaceae10naturalised
 Salix holosericea Ser.Salicaceae9cultivated
coastal willow, dune willow, Hooker's willowSalix hookeriana Barratt ex Hook.Salicaceae10cultivated
Pencil willowSalix humboldtiana Wild. cv PyramidalisSalicaceae9cultivated
arroyo willowSalix lasiolepis Benth.Salicaceae10cultivated
Pacific willowSalix lucida Muhl. subsp. lasiandra (Benth.) A. E. MurraySalicaceae10cultivated
Corkscrew willow, Dragon claw willow, Matsudana willow, Peking willow, Tortured willowSalix matsudana Koidz.Salicaceae10naturalised
 Salix miyabeana SeemenSalicaceae10naturalised
Broadleaf willowSalix myricoides Muhl.Salicaceae10naturalised
dark-leaf willow, whortle willowSalix myrsinifolia Salisb.Salicaceae10cultivated
Black willowSalix nigra MarshallSalicaceae10cultivated
 Salix opaca Andersson ex HerderSalicaceae10cultivated
Bay willow, Laurel willowSalix pentandra L.Salicaceae10naturalised
slender willowSalix petiolaris Sm.Salicaceae10cultivated
Purple osierSalix purpurea L.Salicaceae10naturalised
 Salix reinii Fr. & Sav.Salicaceae10cultivated
 Salix repens L. subsp. arenaria (L.) HiitonenSalicaceae10cultivated
creeping willowSalix repens L.Salicaceae10cultivated
 Salix schwerinii E. L. WolfSalicaceae10cultivated
 Salix seringeana Lecoq & LamotteSalicaceae9cultivated
Almond willow, Almond-leaved willow, French willowSalix triandra L.Salicaceae10cultivated
Osier, Hemp willowSalix viminalis L.Salicaceae10naturalised
  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree shoot in summer. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree shoot in summer. Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree shoot in summer. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree shoot in summer. Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in spring. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in spring. Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
  • Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in early spring. Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), with wingless adult females and nymphs on willow tree branch in early spring. Image: Nicholas A. Martin © Nicholas A. Martin
  • Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree.  Image: Nicholas A. Martin © Nicholas A. Martin
    Honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), on leaves of a willow tree. Image: Nicholas A. Martin © Nicholas A. Martin
  • Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
    Willow leaves covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Tim Holmes © Plant & Food Research
  • Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Willow branches covered by black sooty mould fungi growing on honeydew secreted by giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
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Honeydew Feeding

Bees, wasps, flies and ants have been seen feeding on honeydew secreted by giant willow aphids. Adults of several ladybird may also feed on giant willow aphid honeydew on willow leaves. Two species of native bird that feed on flower nectar, have also been seen feeding on giant willow aphid honeydew.

Table: Feeders on honeydew of Giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), from Plant-SyNZ database (21 February 2017). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific NameCommon NameClassificationHoneydew feedingReliability
Index
Biostatus
Adalia bipunctata (Linnaeus, 1758)Two-spotted ladybird (Beetle)Coleoptera: Coccinellidaeadults feeding on honeydew 10adventive
Anthornis melanura (Sparrman, 1786)Bellbird (Bird)Passeriformes: Meliphagidaebirds feeding on honeydew 10endemic
Apis mellifera (Linnaeus, 1758)Honey bee (Wasp)Hymenoptera: Apidaefeeding on honeydew on leaves 10adventive
Bombus terrestris (Linnaeus, 1758)Two-banded bumble bee (Wasp)Hymenoptera: Apidaeadults feeding on honeydew on leaves 10adventive
Coccinella undecimpunctata Linnaeus, 1758Eleven-spotted ladybird (Beetle)Coleoptera: Coccinellidaeadults feed on honeydew 10adventive
Halmus chalybeus (Boisduval, 1835)Steelblue ladybird (Beetle)Coleoptera: Coccinellidaeadults on leaves with honeydew 9adventive
Harmonia antipodum (Mulsant, 1848)Antipodean ladybird (Beetle)Coleoptera: Coccinellidaeadult feeding on honeydew 10endemic
Harmonia conformis (Boisduval, 1835)Large spotted ladybird (Beetle)Coleoptera: Coccinellidaeadults feeding on honeydew 10adventive
Huberia brounii Forel, 1895 (Wasp)Hymenoptera: Formicidaeworkers feeding on honeydew on leaves 10endemic
Ochetellus glaber (Mayr, 1862) (Wasp)Hymenoptera: Formicidaeworkers feeding on honeydew on leaves 10adventive
Polistes chinensis (Fabricius, 1793)Chinese paper wasp (Wasp)Hymenoptera: Vespidaeadult feeding on honeydew on leaves 10adventive
Prosthemadera novaeseelandiae (Gmelin, 1789)Tui (Bird)Passeriformes: Meliphagidaebirds feeding on honeydew 10endemic
Vespula sp.Wasp (Wasp)Hymenoptera: Vespidaefeeding on honeydew on leaves 7adventive
  • Adult honey bee,  Apis mellifera (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
    Adult honey bee, Apis mellifera (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
  • Adult Two-banded bumble bee, Bombus terrestris (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
    Adult Two-banded bumble bee, Bombus terrestris (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
  • Adult Two-banded bumble bee, Bombus terrestris (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
    Adult Two-banded bumble bee, Bombus terrestris (Hymenoptera: Apidae) feeding on giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae), honeydew on willow, Salix sp., leaves. Image: Nicholas A. Martin © Nicholas A. Martin
  • Adult steelblue ladybird, Halmus chalybeus (Coleoptera: Coccinellidae), about 4 mm long. Image: Tim Holmes © Plant & Food Research
    Adult steelblue ladybird, Halmus chalybeus (Coleoptera: Coccinellidae), about 4 mm long. Image: Tim Holmes © Plant & Food Research
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Control

Giant willow aphid can reach high numbers on many kinds of willow trees. It is regarded as a pest, because it may weaken or even kill trees and because of its copious production of honeydew. The honeydew and associated sooty mould fungi cause problems for honey producers, wool producers and fruit orchardists. Also the sooty mould is unsightly and the honeydew attracts wasps in the autumn that may be hazardous.

Insecticides
It is not practical to use insecticides to control giant willow aphid on large trees. However, they may be the best current solution for coppiced willows used for basketry. The plants will be vulnerable to colonisation after winged aphids start being produced, from mid-October onwards in Auckland. It is best to regularly monitor plants for aphids and apply insecticides in response to finding colonies of aphids. It may be easier to look for honeydew on leaves and then check if there is an aphid colony on a stem above the honeydew. Thoroughly treat the affected trees and in periods of high risk, e.g. in summer, treat all trees.

Biological Control
The only predators found in New Zealand are ladybirds. Up until April 2016, ladybirds only occasionally fed on giant willow aphids and provided no control. In April 2016, the harlequin ladybird, Harmonia axyridis, was discovered in Auckland and both adults and larvae readily feed on giant willow aphids. It will take several years to see what level of control the harlequin ladybird will provide, but in the first summer (2016-17) where the ladybird was present in early spring, it prevented high populations of aphids developing and then reduced the population to a very low level.

Wasp parasitoids of giant willow aphid are known in East Asia and one has been identified as a candidate for release into New Zealand (Sopow and authors, 2017).

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Additional Information

Wasp danger
Wasps, Vespula species and paper wasps, Polistes species, feed on honeydew. In late summer, when wasp populations are high and there is much honeydew on willow trees, many wasps may be in trees where people are present. As a result, there is an increased danger of people being stung.

Effect of giant willow aphid honeydew on fruit orchards
Although giant willow aphids do not feed on fruit, the present of aphids on willow tree growing close to fruit trees means that the fruit can be contaminated with aphid honeydew and that sooty mould fungi may grow on the fruit. This means that the fruit must be cleaned before sale, especially fruit for export (Sopow and authors, 2017).

Effect of giant willow aphid honeydew on sheep wool
Sheep will sit in the shade of trees. If these are willow trees infested with giant willow aphid, the wool will become contaminated with honeydew. Soil and dirt may adhere to the sticky wool and sooty moulds may grow on it. This lowers the quality of the wool (Sopow and authors, 2017) that needs to be cleaned before sale. The willow trees may be important for erosion control and cannot be easily removed and replaced.

Effect of giant willow aphids on flood control
Heavy infestation of giant willow aphid on very susceptible willow tree species can weaken the trees and can kill branches . Where willow trees are used along rivers to protect the banks from erosion, loss of trees could cause problems in floods.

Effect of giant willow aphid honeydew on bee honey
The only sugar in willow tree sap is glucose. The honeydew secreted by giant willow aphid contains several kinds of sugar, approximately equal amounts of fructose, glucose, sucrose and a trisaccharide melezitose (Mittler, 1958 in Sopow and authors, 2017). Melezitose has low solubility and crystalizes out as the moisture content of the honey drops, creating granulated honey.

Honey affected by the presence of melezitose is often called ‘cement honey’, because it makes the extraction of commercial honey difficult. Much of the crystalline honey remains in the comb, which reduces yield.

However, there are reports in New Zealand that honey from willow honeydew is good for overwintering bees. In other counties there are reports that melezitose causes dysentery in honey bees, but observation in New Zealand indicate that the bees do not consume the melezitose crystals.

Honeydew from willow trees contains salicylic acid and may contribute to a sour taste in the honey.

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Information Sources

Catalogue of Life: 28th September 2016: Species details: Tuberolachnus (Tuberolachnus) salignus (Gmelin, 1790). http://www.catalogueoflife.org/col/details/species/id/65cf373411fee6d07843f2ca67315db3/synonym/76ced9e44e676333ee670830abf0bcd7 (Accessed November 2016, source of synonyms).

Collins, C.M.; Leather, S.R. 2001: Effect of temperature on fecundity and development of the giant willow aphid, Tuberolachnus salignus (Sternorrhyncha: Aphididae). European journal of entomology, 98(2): 177-182.

Gunawardana D, Flynn A, Pearson H, Sopow S. 2014. Giant willow aphid: a new aphid on willows in New Zealand. Surveillance, 41: 29-30.

Oezder N, Saglam O 2008. Effect of temperature on the biology of Tuberolachnus salignus (Gmelin)
(Sternorrhyncha: Aphididae) on Salix alba.J. Central European Agric. 9, 155-159.

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Sopow SL, Jones T, McIvor I, McLean JA, Pawson SM. 2017. Potential impacts of Tuberolachnus salignus (giant willow aphid) in New Zealand and options for control. Agriculture and Forest Entomology. (on line)

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Acknowledgements

Ian McIvor (Plant & Food Research), for information about host plants of the aphid.

John McLean, Gisborne, for information about the aphid and honeybees.

Stephanie Sopow (New Zealand Forest Research Institute) for information about the aphid and making available a newly published paper.

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

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Other Images

  • Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
    Colony of adult giant willow aphid, Tuberolachnus salignus (Hemiptera: Aphididae). Image: Nicholas A. Martin © Nicholas A. Martin
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Suggested Citation

Martin NA. 2017. Giant willow aphid - Tuberolachnus salignus. Interesting Insects and other Invertebrates. New Zealand Arthropod Factsheet Series Number 74. http://nzacfactsheets.landcareresearch.co.nz/Index.html. Date Accessed. ISSN 1179-643X.

Landcare Research       Plant and Food