Recurring bacterial? issue with Cattleya leaves
 

My two Hazel Boyds came from a group of 20 or more at the greenhouse. All of them had/still have this issue. Any ideas for treatment or prevention?

* black areas affect only new growth and usually appear once leaf is open.

* sometimes spreads and requires removal of part of leaf. other times doesn't spread & leaf matures normally, but marred by black areas.

* not a result of water sitting on leaves--I'm diligent with these plants.

* air flow is constant and sufficient in the growing area. I experimented with an additional small fan close to these two catts for a while. Had to water more often, but no effect on appearance of black spots.

* I've had these guys for a year or so-- none of my other plants have been affected.

Fungus spots on new growth is a classic sign of calcium deficiency. You can increase calcium several ways. You can use a fertilizer that has more calcium, like the MSU pure water formulas. You can use a calcium/magnesium supplement like the one I use called MagiCal by Technaflora. You can top dress the media with dolomite lime or oyster shell. A couple of my friends have good results with dolomite lime. You really don't need to worry about giving too much calcium. Calcium is not mobile within the plant so needs to be available whenever the plant is putting on new growth. It's used by the orchid to build strong cell walls that resist insects and fungus. Here's a link to some further information on calcium.
http://staugorchidsociety.org/PDF/20...ps-Calcium.pdf

That was my first thought as well, but I don't think that's what she's dealing with, Tucker.

1) She is seeing that in this particular hybrid only, not everything.

2) Necrosis due to calcium deficiency occurs at the tip of new growth, as that's the apical meristem that's being calcium-starved, not elsewhere in the leaf.

Do you add extra calcium? I add eggshells to my Cattleyas and whatever else I have had trouble with in the past and that seems to eventually take care of the problem. You might want to add another source of Calcium in the meantime.
Calcium helps to strengthen the cell walls of plants.

---------- Post added at 10:43 AM ---------- Previous post was at 10:42 AM ----------

Looks like the question was already answered. :)

Calcium deficiency was my thought too. I have a number of Catts and some show no signs at all but others seem to be prone to it. I have been adding a supplement for about 6 months and new growth seems to be looking better, so that's why I do think some Catts need more than others. My pseudobulbs were also spotted with black on the affected ones.

Thanks, Tucker, Leafmite, and Silken. I have a calcium supplement, so easy enough to give it a try.

Ray, any thoughts on what it might be if it's not calcium deficiency?

I'm with Ray.
It does not look like Calcium deficiency to me either given the location.

Maybe this particular one is prone to fungal attack or has some other underlying issue like virus which also makes a plant vulnerable to diseases.

Leafmite- If you add egg shells to potting mix, you won't see effect very soon at all as it takes quite a bit of time for the shells to break down, especially in such dry mix like bark chips.

Any thoughts, assuming it's not viral, on what I might do to reduce/eliminate the fungal issue?

Like I said, it only happens on newly opened leaves. Wonder if there's a booster I could give the plant when new growths are forming.

Only on newly opened leaf...then it could be the deficiency.
What fertilizer are you using?
If what you use has Ca in it, then I don't think it can be deficiency.

So this particular Cattleya (what is the name by the way?) always develop this black necrotic spots on the new leaves and then they do not progress any further?

Slc. Hazel Boyd 'Debbie'. I use Klite, Kelp and have infrequently supplemented with calcium. Sometimes the spots progress and the affected portion has to be cut off. Sometimes it doesn't progress much further, the leaf matures and no more problem with that leaf. At the time I bought them, my plants were 2 of about 20 fairly recently divided and potted parts of one formerly huge Hazel Boyd. All the divisions were showing this issue.

the attached pics show 1. development of the spots in plant #1 since my first post. 2. A matured leaf on which the spots stayed contained 3. A recently opened leaf with the issue on plant # 2 4. whole plant shot of #2. 5. a new growth on plant #2 which is currently perfect, but not likely to remain that way after it opens.