Cattleya walkeriana with black spots on leaves

[estación seca]

I have used craft knives to remove spots with about a cm of healthy tissue around them, leaving round holes. Then I treated the cut surface with powered cinnamon. Systemic fungicides take a while to be transported through the plant. I would treat with a systemic fungicide and with a contact fungicide.

[Leafmite]

You will need to remove the infected part of the leaf. I usually disinfect the other leaves and stems with Isopropyl alcohol to disinfect (It isn't good for the roots, though). If you do have a systemic fungicide, you could then use it as a precaution.

The calcium is utilized when the plant is building new cells so you won't see the preventative effects until there is new growth. I usually add extra calcium when my Cattleyas are sending out new growth but have eggshells mixed in with the medium to provide a steady supply. Eggshells must begin decomposing before they release Calcium so it takes some time before they prove their worth. If the old growths have had adequate calcium, they will be more resistant but, once an infection gets into a plant, the plant becomes stressed and usually it will spread into the older growths, too, if the infected part isn't removed.

Good luck!

[isurus79]

Or you could simply point the fan closer to the plant to increase air movement and help eliminate an environment which fungus thrives. You'll need to add artificial lighting as well. This species thrives in a hot, bright, arid part of Brazil which receives very little rain during winter. If its not actively growing, don't water it.

[Orchid Whisperer]

I've never heard of chlorine (such as from tap water) causing any damage similar to this.

Calcium deficiency, and susceptibility to infection, is consistent with observations from other plants.

If you can't find a calmag supplement locally, you can provide calcium with calcium nitrate, or with gypsum (plaster of Paris) dissolved at one teaspoon per gallon.

[katrina]

What Isurus said. C walkeriana hates cool and dark. Hates it. Add in dampness during cool and dark and you soon won't have the plant.

I grow mine very bright and rather dry during the winter.

This past summer we had a lot of rain for an extended period and w/it came cooler than normal temps and I lost a couple of my walkerianas to something that looked very similar to your black spots. [also lost a violacea and a handful of other catts] I would cut and treat w/fungicide/disease combo product but I never did stop it and I ended up throwing the plants out because every time I turned around another one was showing the same issue. I'm not saying that what you have there is exactly what I had...so many different issues can look similar...but you might want to make sure you keep it separated from others. Be especially careful of water splashing from that one onto other plants.

The problem w/some of these "rots" is that they are in the plant tissues so cutting what appears to be the infection doesn't always stop it because it's in the vascular system and continues to spread.

Keep it on the dry side and as bright as you can get it. Good luck!

[Leafmite]

Good luck!

[Jasonmc89]

Thanks for the great response everyone!

Here's what I've done..

-Treated with a systematic fungicide.
-Removed the worst of the black spots and dusted the cut area with cinnamon.
-Ordered a full spectrum fluorescent light bulb which I'll put in an old desk lamp to help increase light during our dull winter days.
-Water less frequently.

Does this sound like a good plan?

Thanks again.

[wintergirl]

Good plan but still add calcium...It will prevent further problems.

[isurus79]

Originally Posted by Jasonmc89

Thanks for the great response everyone!

Here's what I've done..

-Treated with a systematic fungicide.
-Removed the worst of the black spots and dusted the cut area with cinnamon.
-Ordered a full spectrum fluorescent light bulb which I'll put in an old desk lamp to help increase light during our dull winter days.
-Water less frequently.

Does this sound like a good plan?

Thanks again.

Sounds good! As said previously, adding calcium (which means you have to add magnesium, both of which are typically sold together in the same bottle) will probably help too.

[Jasonmc89]

Just thought I'd give everyone an update!

I stuck to my plan and used a fungicide, applied a cinnamon and water paste to the black spots, used a Cal/Mag supplant and now place the plant under artificial light on particularly dull days.

The black spots have completely stopped showing up and the existing ones have sunken, dried out and don't seem to be doing anything now. I've had more root and leaf growth and I now have two flower spikes coming up!

Thanks for your help everyone.