Large willow bark aphid

The large willow bark aphid is a very large aphid that can form dense colonies form on the bark of willow trees. It is part of the biodiversity supported by healthy willows in gardens.

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Large willow aphid (<EM>Tuberolachnus salignus</EM>) on Willow (<Em>Salix caprea</EM>)
Large willow aphid (Tuberolachnus salignus) on Willow (Salix caprea)

Quick facts

Common name Large willow bark aphid
Latin name Tuberolachnus salignus
Plants affected Willows (Salix)
Main symptoms Large grey aphids in dense colonies on stems
Caused by Sap-sucking aphids
Timing Summer to late winter

What is large willow bark aphid?

Aphids are sap-sucking true bugs. They range in size from 1 to 7mm (¼in or less) long. Some aphids are known as greenfly or blackfly, but there are species that are yellow, pink, white or mottled. There are more than 500 aphid species in Britain. 

Some feed on only one or two plant species, but others can be found on a wide range of plant hosts. Many have lifecycles that involve more than one host plant. Almost any plant can be a host to aphids, including ornamentals, vegetables, fruit, greenhouse plants and houseplants. 
  At 5mm in length, the large willow bark aphid is one of the largest aphids in Britain. It is greyish black and has a characteristic shark's-fin-shaped tubercle on its abdomen, the function of which remains unknown.


Large willow bark aphid can form dense colonies on willow bark during the summer and autumn. Very occasionally, it has been found on apple. The aphid is rarely found in early spring, and where it goes during this time is not certain. 

The aphids suck sap from the bark and excrete a sugary liquid called honeydew. This can make the plant and the ground below it sticky, and is often fed on by wasps and flies. A black sooty mould may develop on the honeydew which, though harmless to plants, can marr their appearance.

These aphids are part of the biodiversity that healthy willow trees can support, and are the basis for many food chains. Even high densities of aphids seem to have no significant effect on the tree's health or vigour.

Can you help solve the mystery of where this aphid goes in early spring?

The giant willow aphid is rarely seen in early March, April and May, and is usually only found on willows. Despite it being a well-studied aphid, where it goes in early spring remains uncertain.

In 2022, however, colonies were found in May on a quince (Cydonia oblonga) in Hertfordshire. An unusual time of year and host!
  • Download the paper detailing this sighting here (PDF, 497KB)
We are therefore asking gardeners, if they see this insect in early spring or on a plant other than willow, to submit sightings here to help us understand more about this insect's intriguing biology. Please include an image, date and location of the sighting.

Large willow aphid (Tuberolachnus salignus) on willow (Salix daphnoides)


This aphid is part of the biodiversity that healthy willows can support in gardens and does not unusually need to be managed. Despite the large colonies of large willow bark aphid that can develop, they seem to have no significant effect on the tree's health or vigour, and the presence of this insect supports many aphid predators.  

This aphid can produce large amounts of sticky honeydew, which can be inconvenient and provide a food source for wasps. It may be simpler to avoid the area for few weeks rather than attempt control.

  • Where possible, tolerate aphids – they form an important part of many food chains and can be part of a healthy garden ecosystem
  • Use finger and thumb to squash aphids if necessary
  • Encourage aphid predators in the garden, such as ladybirds, ground beetles, hoverflies, parasitoid wasps and earwigs. Be aware that in late spring and summer, aphid populations often build up before natural enemies are active in sufficient numbers, and populations may then decline
  • Further management information for aphids can be found on the general aphids page here


The willow bark aphid has been extensively studied. Although on wild willows and those in gardens it has no noticeable effect on host plant health, in commercial willow plantations, it may reduce tree growth.

The aphid spends most of its time on willow, and dense colonies can form on willow trees during the summer. Reproduction is parthenogenetic (doesn't require fertilisation) and colonies reach their maximum size in autumn.

However, many questions about the aphid's biology remain. The purpose of the characteristic shark's fin tubercle is unknown. Colonies can persist throughout much of the winter but generally disappear in February to reappear again in late spring, and it remains a mystery where the aphid goes during this time.

See also...

Influential points information on large willow bark aphid*

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