Is either your irrigation incredibly hard, or do you fertilize it without allowing a good soil flush now and then? Possible build up of salts, though I've never seen it so bad before if the case.

I did fertilize it a couple times several years ago, using a small bag of citrus and avocado fertilized. I suppose it could be buildup from that. I generally water it about once every three weeks, thoroughly soaking the soil until it runs freely out the bottom. But what I notice now is that this hard soil isn't absorbing anything so it's probably not penetrating and retaining much. I don't think our San Diego municipal water is particularly hard. Thanks for the response.

Your original description sounded to me more like mycorrhizal or other type of fungus rather than salt that would normally appear as a veneer on the pot interior.

Thanks Larry, I'll read up on fungus and try to take steps to kill it when I re-pot.

Looks like all the soil particles are coated with a fungus but not necessarily rotten.

The fungal coating is preventing water absorption by the mix. Thus, the roots are also dry.

Doubt that you'll be able to "kill" the fungus. Suggest you pot into fresh potting mix, then add a wetting agent to your water before you water the tree.

Thanks Jean, I'll add a wetting agent.

I'm hopeful it'll bounce back... it's seen worse. It was attacked by a cat and left next to an open window in sub-zero temps when it was just a few feet high. Died back completely, but then sent out a new stalk from the pit!