Alder sucker

Alder sucker is a common on alder and part of the biodiversity these trees support

Alder sucker nymphs
Alder sucker nymphs

Quick facts

Common name: Alder sucker
Scientific name: Psylla alni
Plants affected: Alders, Alnus species
Main symptoms: White fluffy waxy covering on stems and foliage
Most active: Spring

What is alder sucker?

There are several species of sucker or psyllid that can be encountered by gardeners, they are sap sucking true bugs. Alder sucker is only found on alder. The adults are similar in appearance to aphids and up to 5mm long, green with clear wings. The nymphs are also green with some black markings and flattened in appearance however, they are usually covered in a white waxy secretion. A gallery and more information on psyllids can be found at British Bugs. With more information on alder sucker here.


The nymphs of alder sucker are covered by a ball of fluffy white waxy threads which can make it presence noticeable during the spring. They suck sap from the foliage during April-early June.

The adults, which lack the waxy secretions, are present from June-October. Overwintering eggs are laid on the shoots of alders (Alnus species) in the autumn.

Alder sucker does not usually affect the health of its host and is part of the biodiversity alder trees support.


The presence of white waxy deposits can be noticeable in the spring but this insect rarely has any effect on the health of alders. It is part of garden biodiversity and control is undesirable. 

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