Fungal Infection?

[DesignerofBeauty]

I purchased a stereochilus brevirachis a few months ago. I've been watering the orchid using my facet sprayer, being as careful as possible not to get the leaves wet. I will also get a small squirt bottle to water the orchid as well. The shape of the wooden mount doesn't allow for soaking, without leaves being directly submerged in water. That being said, I try to avoid getting the leaves wet, but it's inevitable.

Today I noticed black spots on the underside of one leaf, and one black spot on a neighboring leaf. No other leaves seem to be affected. Upon closer examination, the leaf just fell off. Should I remove the other leaf that has one black spot? If this is a fungal infection, how should I proceed caring for the orchid? I have Physan 20 and hydrogen peroxide. Thanks!

---------- Post added at 01:50 PM ---------- Previous post was at 01:48 PM ----------

Here's a link to pictures. For some reason, I wasn't able to attach images directly to my post. The leaf was located to the left of the bottommost leaf.

Fungal Infection? - Album on Imgur

[estación seca]

Are you growing it in the open, or in a terrarium?

I don't grow this plant. However, what you show suggests to me the plant is unhappy, the leaf began dying, and the fungus moved into a dying leaf. The problem is not caused by fungus. It's caused by incorrect growing conditions. Your task is to find out why the plant is unhappy and fix the growing conditions. I would suspect it isn't getting enough water and/or the humidity is too low.

A tiny plant like that is going to get completely wet whenever it rains in habitat, and every time there is dew at night. It is covered in water in habitat for hours at a time after each rain, and each night there is dew. The idea of not getting water on the leaves makes no sense.

According to IOSPE it comes from Yunnan province in China, but IOSPE gives no elevation nor temperature information. There is a huge range of temperatures in that region, depending on how high in the mountains it grows. It would be very important to find out this plant's temperature requirements.

Something small is not likely to tolerate being dry for very long. An occasional spritzing with water in a typical low-humidity home will not be enough water. If it is a cool-growing plant, it will also become very unhappy with warm nights. The behavior you describe is typical for miniature monopodial plants that aren't getting enough water, or are experiencing too low relative humidity.

[jkofferdahl]

I agree that ES is right on the money here. In looking up this plant, several pictures I found show the plant being wet, which flies in the face of not getting it wet. It appears that the leaf pinched off. I agree that the cause of this may well be fungal, though not necessarily. Again agreeing with ES, there are a lot of factors which could potentially cause this. On other miniature epiphytic orchids I've seen leaves pinch off when the plant was kept too wet and allowed to get too cold - I'm not saying that is the cause here but it can happen.

I don't know under what conditions this species likes to grow. In fact, this isn't a genus I'm familiar with, other than by name. Were this my plant, I would first take the step of treating it with a copper-based fungicide. It may not be necessary but it's a good preventative move anyway. But the important thing you need to do is to make sure that your growing conditions are appropriate for the plant. I've not been able, on a quick search, to locate such information. You may have to contact the original seller for it.

[estación seca]

If the original seller told you not to get the leaves wet, I would not believe much else from them.

[jkofferdahl]

Originally Posted by estación seca

If the original seller told you not to get the leaves wet, I would not believe much else from them.

Funny, yes, but also frightfully true.

[DesignerofBeauty]

I was under the assumption not to get the leaves wet as this is the advice I've been reading regarding watering larger orchids. I purchased the orchid from Andy's. The tag mentions "M" for water, which means 3-5 waterings per week. I've been watering every other day. Usually, the next day the mount is dry, unless it's very cloudy out (in this case it's only very slightly damp). Light says "BR", which means Bright Indirect Sunlight. Temperature states I/W, which means "intermediate/warm". Per my temperature monitoring device, the temperature is between 68-81 degrees. The only thing I can see wrong here is the light might not be sufficient. I keep my orchid in a low-tech open terrarium that houses other tiny plants. Lately, in New England we haven't been getting much sun. Weather conditions have been mostly rainy. I just purchased a T5 bulb I'm going to use to supplement lighting. I've been monitoring the humidity nearby the orchids with the temperature monitoring device. I did purchase a humidifier, and if the humidity is below 50%, I turn on the humidifier. However, we haven't had much need for heat or A/C yet in New England, so I haven't had to turn it on for quite a while. 90% of the time I have a ceiling fan on and sometimes a box fan is positioned nearby the orchids, not pointing directly on them.

[estación seca]

You should wet the leaves and everything when you water orchids, unless perhaps your relative humidity is always over 80%, and leaf rot is a significant issue. This isn't the case anywhere in a house in the US. Wetting the leaves rinses off dust and spider mites.

Andy's M means Moist, not to dry out. 3-5 waterings per week might be average in a greenhouse. In a home or in a drier greenhouse people might need to water every day, or more, to keep a tiny plant constantly moist. Letting it dry between waterings will not be good for it.

I doubt this plant will be happy in relative humidity of 50% or less.

[DesignerofBeauty]

So it's perfectly fine to water the leaves, and potentially have that water get into the crown of the plant?

I'll water the orchid daily, and maintain a humidity of 60-70% and increase lighting to make more favorable conditions. Please forgive my lack of experience with this.

[estación seca]

Nothing to forgive! You couldn't have known.

If the plant is happy the water in the crown won't hurt. If it's unhappy a dry crown won't help.

The relative humidity you mention is what I might aim for in the absence of information from somebody who knows the plant. In that kind of humidity you may not need to water every day. Pay attention to the plant. It needs to stay moist, not dripping wet.

You can also call Andy and ask him detailed information on growing it. That would probably be better information than what I can give. Remember when Andy says "slight drying between waterings" that means just a little less wet, not completely dry between waterings.

[jkofferdahl]

I wondered if this plant came from Andy's. I even checked his site but apparently he no longer has it. When he talks about watering, he is referring to watering in the conditions of his greenhouse. There, the plant has just about ideal humidity and temperature.

I have a lot of Andy's mounted plants. It's essentially impossible to over-water a mounted orchid, and especially the way Andy mounts. Additionally, you can water them in the morning and even in my house, at 70 percent RH, they're dry by mid-afternoon, if not earlier. Most of my mounted orchids get watered at least twice a day (when growing), and if I'm home it's three times a day; all of my mounted Phals are watered twice daily. Knowing what Andy's label says, I'm just about certain that your plant needs more frequent watering.

When I water my mounted orchids I use a sprayer and blast away. The leaves get wet, water gets in the crowns, and life goes on. I've used this method for years now and can honestly say that I've never lost an orchid to crown rot due to this.

Regarding ES's suggestion about calling Andy, it's brilliant in its simplicity. Andy knows all, and is happy to share his knowledge.