Coelogyne cristata with fast growing black splotches on leaf tip

[KleioP]

Hi all,

I first noticed these black spots on the tip of one of the leaves of my Coelogyne cristata one week ago (although it could be they were there longer). I cut the leaf well under the damaged area, into the green part, but yesterday I noticed the spots being back (and looking slightly different, now more watery almost). This morning, not even 24 hours later, the splotches are increasing. Any idea what might be happening? Is this what leaf tip die back looks like or could this be bacterial?

One note, because I had spider mite problems I did 3 treatments with paraffin oil (more for prevention, I do not think this plant was infected). The last treatment was a couple of days after I cut the leaf, so could this be a problem of oil entering the leaf at the point of cutting?

Otherwise the plant looks very green and healthy, with the exception of one more leaf that has a black tip (also in pictures).

Thank you very much for your help!

[rbarata]

Coelogynes, in my experience, are prone to get spots on the leaves...if I show you my tomentosa you would tell me to toss it.
Anyway, from your description it might be bacterial. See this page.
Another word about mites... if you had a mite problem the chances are that it caught all your plants.

[KleioP]

Thank you very much for the response!

Looking at the diseases page you sent me suddenly I started worrying that what I thought was mite damage may have actually been something more sinister all the while and that I may have completely misdiagnosed... Attached are pictures of the first plant, which I suspected had damage from invisible red spider mites. When I noticed this damage about a month ago I wiped the leaf and noticed red streaks. However could this be me wiping off damaged tissue due to a bacteria/fungus, and not insects? As shown in the pictures, today the leaves of that plant are yellowing one by one.

I also attach current pictures of my odontobrassia, which since a while (a month or more) has these circular leaf discolorations. I do believe they are getting worse... I had attributed it to spider mite damage plus oil entering the grazed leaf, but maybe not?

Taken together with the coelogyne, any idea if this could be caused by a pathogen that is making its way through my plants?

I will try treating the coelogyne with hydrogen peroxide for now and see if this helps...

Thank you again very much!

[rbarata]

Originally Posted by KleioP

I will try treating the coelogyne with hydrogen peroxide for now and see if this helps...

URGENT!!! Don't use peroxide. It is usable only in certain location of the plant and under very specific conditions. Otherwise, you will risk killing the plant.
I don't know if this was caused by mites and there are multiple possible causes as some genera are prone to issues like these.
Let's see what others say.

[estación seca]

What are your growing conditions? Temperatures, relative humidity? I ask because mites tend to be active during times of low relative humidity and warm temperature.

I think the photos in the second post show potential mite damage. I prefer 70% alcohol, or insecticidal soap, over oil sprays for thin-leafed plants. Mites are outdoors in the environment, so you cannot eradicate them. I spray the entire surface of all my plants once every week or two with plain water. This kills mite eggs and controls populations.

[KleioP]

Originally Posted by rbarata

URGENT!!! Don't use peroxide. It is usable only in certain location of the plant and under very specific conditions. Otherwise, you will risk killing the plant.
I don't know if this was caused by mites and there are multiple possible causes as some genera are prone to issues like these.
Let's see what others say.

Thank you for the advice, just out of curiosity, since physan etc are not available in Europe, are you perhaps aware of any other orchid-specific fungicide alternatives that we have access to here? It is good to know what the options are if need be.

---------- Post added at 08:22 PM ---------- Previous post was at 08:09 PM ----------

Originally Posted by estación seca

What are your growing conditions? Temperatures, relative humidity? I ask because mites tend to be active during times of low relative humidity and warm temperature.

I think the photos in the second post show potential mite damage. I prefer 70% alcohol, or insecticidal soap, over oil sprays for thin-leafed plants. Mites are outdoors in the environment, so you cannot eradicate them. I spray the entire surface of all my plants once every week or two with plain water. This kills mite eggs and controls populations.

Thank you for the response! I live in a pretty humid area (rains all the time, and the temperature rarely ever goes above 25oC (about 80F). So the temp in the house is 60-80F and the humidity 40-60%. Minimum it ever goes to is 30%, but usually for very short periods, and can reach over 80%.

I do hope that this is "just" mites and not something else! So the yellowing of the Beallara leaves could be because of mites even so long after treatment? And those transparent spots that keep appearing on the Odontobrassia leaves (even after 3x treatment one week apart)? Or are they in fact likely to be oil damage?

I do see your point about using a different oil for thin-leaved plants- I think that's what I will do next time.

I have to say I am very worried about rotting new growths etc when I spray with water-based substances. Is this really a concern or just my imagination? It feels like the water has no escape until the pseudobulb forms! Any way to shower/spray them and avoid rot?

Many thanks!

[Blueszz]

Originally Posted by KleioP

! Any way to shower/spray them and avoid rot?

I try to avoid spraying them or showering them, so far so good, no mites causing a problem, that I'm aware of.

If unintentionally one of my plants gets rained on, like my big Vanda suavis, I bring it inside and use a fan for instance during the night.

With windy weather plants might dry faster too but with the climate I live in, I'd rather keep my plants dry than that they get rained on, or sprayed etc. I have some exceptions, like my Coelogyne cristata and the Maxillaria I own. They get showered by the rain every now and then intentionally, preferably when it pours.
So far without ill effects.

Münster DE vs Limburg NL: our climate probably doesn't differ that much from each other.

[estación seca]

Various Oncidium hybrids frequently have spots. I think even a single insect bite will cause spots like those. Apids or other insects might bite and move on. Your humidity isn't extremely high, so I think you will always need to watch for mites.

I don't think preventive treatment with fungicide is a good idea. Fungus attack is rare unless the relative humidity is high, routinely over 60%, or the plant is stressed from too high or too low temperatures. Healthy plants are rarely attacked by fungi otherwise, so paying attention to good cultural practices is important. In addition, fungicides may kill beneficial organisms that keep fungi at bay. I think it's a better idea to use probiotic preparations rather than fungicides.

[KleioP]

Originally Posted by Blueszz

I try to avoid spraying them or showering them, so far so good, no mites causing a problem, that I'm aware of.

If unintentionally one of my plants gets rained on, like my big Vanda suavis, I bring it inside and use a fan for instance during the night.

With windy weather plants might dry faster too but with the climate I live in, I'd rather keep my plants dry than that they get rained on, or sprayed etc. I have some exceptions, like my Coelogyne cristata and the Maxillaria I own. They get showered by the rain every now and then intentionally, preferably when it pours.
So far without ill effects.

Münster DE vs Limburg NL: our climate probably doesn't differ that much from each other.

Thanks Nicole!

Indeed our climate must be quite similar. I tend to do it the same, if they all have to get wet I will use the fan. I have been a bit worried about the coelogyne with those tube-like new growths, but maybe I should not be so concerned Glad to hear you don't get mites, I am now completely paranoid at every little discoloration I see

---------- Post added at 09:59 PM ---------- Previous post was at 09:51 PM ----------

Originally Posted by estación seca

Various Oncidium hybrids frequently have spots. I think even a single insect bite will cause spots like those. Apids or other insects might bite and move on. Your humidity isn't extremely high, so I think you will always need to watch for mites.

I don't think preventive treatment with fungicide is a good idea. Fungus attack is rare unless the relative humidity is high, routinely over 60%, or the plant is stressed from too high or too low temperatures. Healthy plants are rarely attacked by fungi otherwise, so paying attention to good cultural practices is important. In addition, fungicides may kill beneficial organisms that keep fungi at bay. I think it's a better idea to use probiotic preparations rather than fungicides.

Yes, I tend to be very against using such products. But I guess it is good to at least know what is out there if ever there is a need. But I would definitely not use them preventatively. Good to know that such infections are rare!

Do you think I should do any additional treatments with all the plants or at least the seemingly affected ones? Or just wait and see at this point?

[Blueszz]

I do get why you are worried about the new growths. I lost one because it got wet watering the plant. But it must have got wet multiple times plus it was touching wet sphagnum.
This didn’t keep me from watering overhead though. Together with a big Maxillaria variabilis I shower them with a 5 liter watering can at least every 2 weeks. That is, if the weather allows though. Not too cold, some sun and some wind.