I have never seen this before. A month ago I bought this as a stunning, very healthy looking plant. Now it is getting these gray spots. Is it a fungus? Can I do anything about it?
This is Agave 'Joe Hoak' and dear to my heart.

I'm not experienced with these plants, Hetty, but my guess would be a blight or other fungal disease. I noticed that there are water droplets on the leaves...is there any way to help the leaves stay drier to retard the spread?

I don't use fungicides, so I can't help with types or applications to use, sorry.

If it were my plant, I'd probably quarantine it, if possible, and then cut away the infected leaves, dipping shears or knife in a disinfecting (10% bleach and water) solution after each cut and discard in the household trash. Then attempt to keep the leaves as dry as possible, while allowing the plant to have as much direct sun as can be had.

Hopefully, someone with more experience will chime in soon, but I wouldn't wait too long to contain it, especially if you have others of this type of plant.

Have you noticed any bugs present?

Thanks. No bugs, no.

My guess is either sun burn or over-watering. I had an Americana that got sunburnt like that,

See the gray/black spots forming on this sunburnt agave. And yours being variegated like it is, is probably going to be much more susceptible to full sun.

http://www.thegardenforums.org...

Over-watering will do that as well. I was told the cells cannot uptake the water fast enough and it causes the cells to burst and make those spots. I have an agave that looks similar but when I put it where it doesn't get as much water, the new growth is all fine.

I'm not saying that's what's wrong with your plant, Hetty. It could be a fungal disease or ? ... many things look similar. Just reporting on the situation with my agave and what "cured" it.

I will stop watering it. I checked with the grower and they told me it had been in full sun, so I know it is not sunburn.

Frost damage is another possibility, maybe.

We have not had any.

That probably rules that out then. Looking more and more like the too wet thing. Or?

Hetty,
I'm with Al on this one. Looks like a burn. To be safe, keep it away from all the other collection. See what develops. I would not cut out the damage, you may make more in the process. Also I would maybe keep a tent or umbrella over it during the hottest parts of the day. Water plus heat is ok. It's those cold spells with water that rot sets in. Also remember a little cinnamon sprinkled over it to keep the rot/fungus in hand. I am no expert, it is only my best guess. Keep us informed on this. I would like to know what comes of this. I too love this agave. Good luck.
Stush