Bulbous growths on Horse Chestnut

[Boo Who?]

Any ideas what is causing these bulbous growths?

Connectivity doesn’t appear to be lost in the tips until they become quite substantial in size. They are relatively heavy in comparison to their size. Middle of live ones is dark brown and larger growth rings, dead ones appear to have radial cracks within but not in the bark.

The tree has them throughout the crown in varying sizes.

Anyone know what it is and recommendations to prolong the life of the tree?

Pruning them all out would leave the canopy very sparse, but as I said not all are causing dieback.

[timbernut]

Think it’s called fasciation there’s an old thread somewhere on AT about it (where I learned about it after posting similar pics of willow or ash with ‘flat’ twigs), think it’s bacterial

[Boo Who?]

Im aware of fascination in the form of twig flattening and proliferation of buds in ash... I’ll look into that, but not convinced it’s the same. I was thinking gaul of some sort perhaps?