Many years ago I saw similar sphaeroblasts of ¼ to ½ inch diameter that developed within resin pockets of the bark on balsam fir in northern Minnesota with very similar appearance to the beech bumps. Some were perfectly egg-shaped and free from attachment to the xylem, others had vascular connections.  All had beautifully swirled grain.

Dear Enrico,

I often see similar bumps on European beech and have identified them as sphaeroblasts, which are thought to develop from dormant buds. In place of a shoot, a ball of wood develops, encased in bark.  A sphaeroblast can be easily detached with a mallet etc., since its woody connection to the stem is very narrow.  The large sphaeroblast in  the attached picture shows an arrow pointing towards the woody connection on the proximal side. Some of the bark has been pared away with a knife to expose this connection. The picture also shows wood exposed on the proximal side (with partial occlusion), perhaps because of an old injury or as a result of bark dieback.  Similar canker-like areas can be seen on the bumps in John McLaughlin's photos but I doubt whether these bumps are sphaeroblasts, since their close alignment is unlikely to correspond with the positions of dormant buds.

Small bumps on American beech can also be induced by the scale insect Xylococculus betulae, which penetrates as far as the cambial zone (especially in the aftermath zones of beech bark disease [see Dave Houston's article in  J. For., 73(10), 1975].  I think that they usually look rougher and corkier than the bumps in John's photos but my experience of this insect has been limited to looking at photos and to two brief visits to the USA.

Kind regards,
David

-----Original Message-----
From: rg70200-forpath-bounces@lists.iufro.org [mailto:rg70200-forpath-bounces@lists.iufro.org]On Behalf Of Bonello, Pierluigi
Sent: 28 January 2013 18:17
To: forpath
Subject: [IUFRO RG 7.02 FORPATH] FW: Bumps on Beech


Dear colleagues,


I received these photos from one of my forest pathology students and I must admit I've never seen these things before.  Can anyone help?


Thanks!


Enrico


Pierluigi (Enrico) Bonello, Professor


Dept. of Plant Pathology
The Ohio State University
Tel: (614) 688-5401
http://plantpath.osu.edu/bonello - http://esgp.osu.edu/ - http://cmib.osu.edu - http://caps.osu.edu


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From: Diana Saintignon <saintignon.1@buckeyemail.osu.edu>
Date: Monday, January 28, 2013 12:41 PM
To: "Showalter, David N." <showalter.53@osu.edu>, Pierluigi Bonello <bonello.2@osu.edu>, Dan Herms <herms.2@osu.edu>
Subject: Bumps on Beech



While I was at Harvard I found this beech tree with some interesting wart-like mounds on its bark. Is this normal for some beeches, or could it potentially be a paper topic? Do you know what it is?

Thanks!
-Diana