Green spruce aphid

What is green spruce aphid?

Green spruce aphid is a sap-sucking insect that infests spruce trees (Picea species).

Symptoms

• Green spruce aphid is up to 2mm long and is dull green with dark red eyes.
• It is most likely to be seen on spruce trees during late autumn to spring. 
• Old foliage develops a pale mottled discolouration during the winter and many of these needles will fall off in the spring. A black sooty mould may be noticeable on the stem joints.
• New growth produced in spring is unaffected, and its bright green appearance contrasts strongly with the discoloured and sparsely foliated older stems.

Control

Non-chemical control

• Natural enemies such as ladybirds, lacewings, hoverfly larvae and parasitic wasps may help to limit infestations during the summer.
• Damaged trees can be helped to recover by keeping them watered during dry spells and feeding with a general fertiliser in spring. It will take several years for a badly damaged tree to regain an attractive appearance.

Chemical control

• Small trees can be sprayed with thiacloprid (Bayer Provado Ultimate Bug Killer Concentrate), acetamiprid (Scotts Bug Clear Ultra Concentrate) or deltamethrin (Bayer Sprayday Greenfly Killer) in late August or September, and again during winter if the foliage is becoming discoloured and aphids are present.
• Little can be done to protect tall trees, other than spraying the lower branches.

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Biology

• This aphid differs from most other aphids by being active from autumn to spring, instead of in the spring and summer.
• The summer is spent as non-feeding immature nymphs.
• This pest is particularly damaging in mild winters, which enable it to breed more rapidly.
• Do not confuse aphids with other insects known as barklice or psocids. They feed on algae and fungal spores and may be numerous on trees affected by sooty mould.
• Psocids are aphid-sized, winged or wingless, and brownish-white in colour. They run rapidly over foliage, unlike the slow-moving aphids.