cooper's picture

Galls on Willow trees

Observed: 6th February 2011 By: cooper
Gall close up
Branches closer to show gall locations
The Willow (probably Crack) galls were on
Description:

These Galls are on the top Willow trees (Probably Crack Willow) The close up shows one of the branches/ galls which fell to ground. The gall was 9 cm end to end and is probably one of the smaller ones as those still on the trees look rather larger - a bit like small birds at a casual glance !
This is the first year we have noticed them having lived here 15 years, so fairly sure this is the first year they have been present.

Identifications

No identification made yet.

Species interactions

No interactions present.

Comments

DavidHowdon's picture

Viral

I seem to recall some suggestion that these may be viral in origin, although I have also seen an insect suggested as the cause. Cannot recall any more details at the moment.

petershirley's picture

Galls on willows

The causer of these galls is unknown. They have previously been attributed to a mite (Stenacis triradiatus (= Eriophyes triradiatus)), then an unknown virus, and now are thought to be caused by a phytoplasma. They are common and widespread, being particularly prominent, as these are, in the winter.

Peter Shirley