Alder sucker

Alder sucker is a common on alder but the damage caused is seldom serious.

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.

Symptoms

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 and these feeding activities may reduce the vigour of new shoots.

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.

Control

Apart from the presence of noticeable white waxy deposits in the spring this insect rarely causes any damage to alders and there is no need to control it. Indeed alders being large trees would be hard to difficult in any case.


Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.