Cattleya leaf problem: bacteria? fungus? cold damage?

[Orchidreamer]

I got some new catts, and the leaves arrived with some worrying symptoms, namely, black patches and spots on both old and new leaves. Well the vendor said it's just cold damage, but I'm worried it may be something more serious like fungus or bacteria that would spread. To me, the 1st and 2nd pics remind me of anthracnose, and the last pic reminds me of black rot. I've never seen anything like pic #3. I don't know if I'm simply "overreacting" so please let me know what you think!

[Leafmite]

It looks like cold damage to me. I always disinfect to prevent a secondary infection.

[tucker85]

Although the first two photos do look like cold damage to me, the third photo looks different from any cold damage I've seen. It could be an opportunistic fungus or bacteria that is secondary to the cold damage or it may just be a symptom of cold damage that I haven't seen before. You should know pretty quickly. If it's cold damage it won't spread. I would keep the plant isolated from your collection and maybe give a couple of doses of a systemic fungicide if you have any. That's just my opinion.

[Orchidreamer]

Hmm I noticed some new brown/black patches today on both old and new leaves. I'm pretty sure they weren't there last night. Fortunately, no more growths rotted away like the 4th picture.

I've been spraying with physan. The only systemic fungicide I have is thiomyl, which is generally used to treat root rot and certain types of leaf spots. I guess I could try it...

[james mickelso]

Try St. Augustine Orchid Society - North Florida Orchid Growing. There is a good disease section with pictures.

[Gage]

Pics 1 and 2 are localized fungus, just cut off the damaged bits at a clean green place, and better air circulation will help prevent this. Pic 3 looks like old insect damage, nothing to worry about if it is indeed only underneath. Pic 4 is black rot, again cut off the damaged portions at a clean point, and disinfect the rhizome with peroxide. Always disinfect your cutting tool between cuts. Hope this helps.

[tucker85]

Originally Posted by Orchidreamer

Hmm I noticed some new brown/black patches today on both old and new leaves. I'm pretty sure they weren't there last night. Fortunately, no more growths rotted away like the 4th picture.

I've been spraying with physan. The only systemic fungicide I have is thiomyl, which is generally used to treat root rot and certain types of leaf spots. I guess I could try it...

Thiomyl is an excellent systemic fungicide. I would use it on that orchid every 3 weeks for a couple of months. Physan is good also but it's only topical. Once the fungus is in the plant tissue Physan can't reach it.

[Gage]

Originally Posted by tucker85

Thiomyl is an excellent systemic fungicide. I would use it on that orchid every 3 weeks for a couple of months. Physan is good also but it's only topical. Once the fungus is in the plant tissue Physan can't reach it.

I second that.

[Orchidreamer]

Ok thank you, I will do some plant surgery and treat with thioyml. I don't hear thiomyl discussed much (usually people mention phyton 27). I bought it mostly because it was cheaper than phyton 27 and is easier to mix. Good to hear it's a good choice.