terrycrynant's picture

Gall on oak

Observed: 3rd June 2013 By: terrycrynantterrycrynant’s reputation in Invertebratesterrycrynant’s reputation in Invertebratesterrycrynant’s reputation in Invertebrates

Firm hard fungi growing from the dead wood of an oak tree.The spherical one is just under 2" across and growing where the tree meets the ground.The irregular one is just over an inch and is growing out of the dead wood above ground level.

Species interactions

No interactions present.


terrycrynant's picture

I do not think this is a

I do not think this is a gall.The tree is still alive but has areas of exposed dead wood.This is attached to that dead wood and I think this is a fungus which has grown this spring.

GrizzledBadger's picture

Growth on Oak

Looks like a good reason then for a return visit, to see if it has grown or try to make a section of it to see whether there's a spore-mass or a gall wasp larva in the middle.


terrycrynant's picture

It is a gall

I took a slice as you suggested and it revealed not a single grub but a honeycomb of grubs.The slice shown is a small piece off the smaller gall.If the larger gall has grubs at the same density there must be hundreds in it.The grubs are 1 to 2 mm in size.The galls are growing on the new growth of bark which is growing around a damaged part of the trunk.Do the multiple grubs change your ID ?

GrizzledBadger's picture

Gall section

Hi, the term for a many celled gall I believe is plurilocular, it changes my i.d. in as much that Andricus lignicola has, as far as i'm aware, unilocular galls; single celled galls. So i.d. still stands as a gall caused by a Gall Wasp, species yet to be determined.

Oak Apple Galls are plurilocular but are soft & spongey not hard.

Save your gall remains, cover the cut surfaces with cling wrap, the undamaged cells may yet develop into wasps. Colour of larvae as well as mature size may help to i.d. the wasp.


VC55wildgarden's picture

gall on oak

Using FSC British Plant Galls keys, Redfern, Shirley & Bloxham [2nd edition], Could your gall possibly be Andricus quercusradicis (F.) agamic, Truffle Gall?
Quote "On roots close to or above the surface, irregularly shaped, soft at first, later hard and woody, contains many small chambers, each with a single larva".....
Rear them out! - great fun!
seal off the cut surface with film - or press the two surfaces together & hold with an elastic band - and hopefully, eventually, the wasps will emerge. For interest, make a note of what comes out, so that they can be identified - causer, inquiline or parasitoids.

petershirley's picture

Oak Gall

The comment above has it right, this is indeed the agamic generation gall of Andricus quercusradicis, the truffle gall. It is a very nice specimen which may well produce a number of species of chalcid parasitoids as well as adults of the gall-causer.

Peter Shirley

dejayM's picture


What an amazing post. All iSpotters should note that good pictures, keen and accurate observation, input via a comment-trail are the keys to satisfaction.
Well done all of you, specially terrycrynant.

terrycrynant's picture

No happy ending

A two days after I took the slice off the small gall both galls have been ripped apart and the grubs eaten.I think the smell resulting from me cutting one of the galls may have alerted the local mice to an easy meal.All that was left was the chewed up hard outer layers of the galls and my feeling of guilt.

GrizzledBadger's picture

May also be squirrels

Squirrels I find usually attack the Oak Apple Galls when available, so may be they took a fancy to the Truffle Gall. Birds too probably have a go at them.


VC55wildgarden's picture

Rearing out your truffle gall

Hello Terrycrynant, I usually put any gall that I wish to rear out, into a jam jar with a piece of fine mesh [old tights!] over the top, held in place with an elastic band. The jar plus gall is then kept outdoors in a sheltered place [in ambient conditions], with a label plus data [when where, who etc] placed inside the jar. If you stick the label on the outside, slugs may make a meal of the label and you lose all your data! Sooner or later after much patience, you may eventually see the gall community emerge and it then gets really interesting as you try to identify the various wasps present. Sometimes no gall causers [cynipid wasps] emerge at all and you get tiny chalcid wasp parasitoids, possibly several species. I've never reared out the occupants of a truffle gall - would love to but I have never found one! [lucky you!] It would be a fascinating exercise!