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The large willow bark aphid a very large aphid and can cause alarm when dense colonies form on the bark of willow trees. It causes little damage to the trees.
Large willow aphid (Tuberolachnus salignus) on Willow (Salix caprea)
Aphids, also known as greenfly and blackfly, are sap-sucking insects. At 5mm in length the large willow bark aphid is one of the largest aphids in the UK. It is greyish black and has a characteristic sharks fin shaped tubercle on its abdomen.
Large willow bark aphid can form dense colonies on willow bark during the summer months. They suck sap from the bark and excrete a sugary liquid called honeydew. This can make the plant and the ground below sticky which often attracts wasps and flies. A black sooty mould may develop on the honeydew and, although harmless to plants, can spoil their appearance.
Despite their numbers, the aphids seem to have no significant effect on the tree's health or vigour.
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 can be tolerated.
Aphids have many natural enemies, including ladybirds, hoverfly larvae, lacewing larvae and parasitic wasps. Pest control products based on natural compounds or with a physical mode of action are less likely to have serious effect on natural predators.
If they are a nuisance because of the honeydew production, the aphids can be controlled on small trees by spraying insecticides.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
The biology of willow bark aphid is not well known and the purpose of the characteristic sharks fin tubercle is unknown. The aphid spends most of its time on willow and dense colonies can form on willow trees during the summer. Reproduction is parthenogenetic and colonies reach their maximum size in autumn.
Colonies can persist throughout much of the winter but generally disappear in February to reappear again in late spring, it is not known where the aphid goes during this time.
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Chemicals: using a sprayer
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