Adelgids
Adelgids are aphid like insects that suck the sap from conifers. Often covered in a white waxy material some also induce galls.
Quick facts
Scientific name Adelgidae
Plants affected Conifers
Main symptoms Fluffy white wax, some species cause galls
Most active Year round
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What are adelgids?
Adelgids are true bugs (Hemiptera) closely related to aphids, and like aphids they also feed on plant sap. They are found on conifers and can have complex lifecycles including more than one host. Several species can be found in gardens, any plant damage is often superficial and in most cases these insects can usually be considered part of the
Spruce pineapple gall adelges, Adelges abietis. Found on spruce (Picea) this species causes green pineapple shaped galls up to 20 mm long, usually on young shoots. The galling can cause distortion of shoots, affecting the appearance of trees. Yellow, winged adults (gallicolae) leave the galls in late summer and lay eggs, the nymphs soon hatch and overwinter close to buds. In spring the nymphs feed on plant
Douglas fir adelges, Adelges cooleyi. A
Larch adelges, Adelges laricis. This species is only found on larch (Larix) and spruce (Picea). On larch it covers itself in a white waxy material and it can cause the foliage to become discoloured and distorted and a premature loss of needles. On spruce it forms pineapple galls that are up to 15 mm long. The blackish nymphs of this adelgid overwinter on young larch shoots, maturing in early spring and laying eggs at the base of leaves. Nymphs from these eggs develop into wingless or winged 1.5 mm long dark green adults. The winged individuals migrate to spruce. Wingless individuals continue to breed on larch and extensive populations can develop, characterised by large quantities of white wax threads and honeydew. Those that migrate to spruce give rise to a wingless generation that produces gall forming individuals in the following spring. Winged individuals mature in these galls in summer and migrate to larches where they lay eggs.
Scots pine adelges, Pineus pini. This adegid produces a white wax which can disfigure Scots pine (Pinus sylvestris) but damage is usually minor. This adelgid overwinters as nymphs that mature into 2 mm long dark brown to red adults in early spring. These adults lay eggs which develop into winged or wingless adults by early summer. The winged forms migrate to other Scots pine, whilst the wingless forms produce further generation on the original tree. There can be several generations in a year.
Weymouth pine adelges, Pineus strobi. Very similar in appearance and lifecycle to Scots pine adelges but only affects Weymouth pine, Pinus strobus. Native to North America and now widespread in Europe.
Balsam woolly adelgid, Adelges piceae. This adelgid is found on firs, Abies species. Found on the woody parts of the plant, the white waxy ‘woolly’ areas can become extensive. Large populations can cause
Management
The damage adelgids cause is often minor and can usually be tolerated and treated as part of the biodiversity the host trees can support.
- Where possible tolerate or accept populations of adelgids as part of the biodiversity in a garden
- Encourage predators in the garden, such as ladybirds, ground beetles, birds, hoverflies, parasitoid wasps and earwigs
- Use finger and thumb to squash adelgid colonies where practical
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