Echeveria disorder

[Matt Maggio]

Ok,

I'm becoming a magnet for physiological disorders... mostly plant ones anyway. I suppose when plants are pushed to grow in a commercial setting, more chemical imbalances will be highlighted.

This is a problem that I've noticed among crassulaceae, particularly on Echeveria. Leaves become extremely brittle and crack at the slightest touch, like the epidermis looses elasticity and starts degrading. Sometimes the leaf will resemble alligator skin. This is accompanied by flecking (necrotic spots), and is followed by rapid death of the leaf. It starts on the eldest leaves, and progresses upward. Seemingly healthy plants can become riddled with symptoms in a matter of a week.
Prolonged cool weather (above freezing), and cold damp soil seem to predispose the plants. It has occurred every winter ( the southern California kind) on these types of plants. I've noticed the problem elsewhere during the cool season... it seems quite common and is sometimes fatal. Only once have I seen the problem on cold hardy types (agavoides, colorata, etc.), but mostly on gibbiflora hybrids and others from more southernly latitudes.
I had sent leaf samples to a lab for comparative nutrient analysis, but the results were murky. The occurrences don't seem consistent with a virus, and I've tried "infecting" healthy plants time and again with no success. In "Echeveria Cultivars", by Lorraine Schulz and Attila Kapitany, Dick Wright believes that a mycoplasma is responsible for similar symptoms. I think the problem is nutritional, and mostly likely involves nitrogen. Nitrification in soil, along with nitrogen transport and assimilation in the plant can be strongly hindered by cool damp soil and cool weather, respectively.

Has anyone else noticed this?
Any thoughts?
...I know there's at least 2% on this forum who care about crassulaceae

Matt

[Walker]

I don't have nearly as much experience with the phenomenon, but I do have an E. "Tippy" with symptoms almost identical to those in your picture. I first noticed it in early January after a particularly saturating storm system, and just wrote it off as something akin to leaf-split. Despite losing a couple mid-level leaves, new growth seems generally unaffected, and I'm tentatively optimistic the little guy will survive. For curiosity's sake, in your experience, how long does the problem persist?

[Matt Maggio]

It's strange. The disorder can persist for a few months, then the plants usually 'snap out of it' with arrival of Spring. Just the other day, however, I noticed it starting on plants even in my relatively warm greenhouse where I maintain daytime temps in the 70's and 80's. The disorder may be less associated with temperature than with winter light quality and day length. Sometimes, the plant never pulls through and most of the leaves turn necrotic.

Matt

[thistlesifter]

Hi Matt,

I've seen this. It seems more prevalent on wide fleshy light colored leaves.

I've seen similar on Aloes...I attributed it too much acid.

Spring makes everything better.

Bob
Weeks

[agavegreg]

You have to be careful with that acid, especially the ones that make you see cartoons!

[thistlesifter]

That's it..He He !