Dendro with spots

[SundayGardener]

Hello,
This dendro is finishing its blooming cycle. It was looking good then the leaves started developing spots, turning yellow and dropping. It is not in a high humidity area. I do have it isolated from other orchids.

Thinking at first that this was some sort of bacterial brown spot, I treated the spotty leaves with Physan. I know the pictures don't necessarily look like brown spot, but what I initially saw was just dark spots on leaves with the spots getting larger. Physan on the leaves that looked diseased didn't help and it spread further on the plant, which I have now sprayed in its entirety with Physan.

Should I be using a different product? So far, my biggest issue has been root rot, but now I seem to be branching out and exploring all the other ways that an orchid can be taken down. Speaking of which, is Physan appropriate for Anthracnose? Several oncidiums have browning leaf tips...but it certainly hasn't been warm here.

That link at the top of the page to different diseases is very helpful but I might be projecting hypochondriac tendencies on my plants. Except the dendro, something is definitely off there.

Thanks!

[WhiteRabbit]

[SaraJean]

I’ll give this a shot. What type of Dendrobium is this and how long have you had it?
I’ve had this exact thing happen on a few of my Latouria and Spatulata type Dens. Occasionally an older leaf, here and there, will look like this before it falls off but that is more age related. If you have had many leaves fall off on most or all of your growth that’s an issue. When I had this happen on mine, it was usually caused by one of two things
1. Damage to the leaf that introduced a small localized infection. I.e mechanical damage or sunburn, leaf got cold and wet... resolved itself, didn’t spread to other leaves, didn’t bother treating because the leaf falls off anyways.
2. Wasn’t getting enough water. That resulted in them dropping leaves like hot cakes
Because- A: wasn’t watering orchid enough, or, B: orchid had a poor root system and the couldn’t take up water.

I would check your roots, honestly. And the physan is probably doing more harm than good depending on how you are using it (personally, I use it to disinfect my tools, inorganic media, and surfaces only; not actually on my orchids).

For the oncodium, could you post pics? Im not nearly as comfortable with those as I am with Dens but pics always help. I like to use Thiomyl (Clearys) for a fungicide if necessary. But I rarely tend to treat my orchids and I never treat something unless I know for sure what I’m spraying for (like bacteria vs fungus, scale vs thrips vs sunburn, snails vs root rot) . The best advice I have ever been given was from someone who has been growing orchids for over 40 years: Find out what’s causing issues and fix that. That little nugget of wisdom made me want to smack my head and say “DUH!”. It completely changed how I looked at growing my orchids for the better with being proactive rather than reactive. Btw, How’s the air movement around this one?

[Dollythehun]

"2. Wasn’t getting enough water. That resulted in them dropping leaves like hot cakes
Because- A: wasn’t watering orchid enough, or, B: orchid had a poor root system and the couldn’t take up water. "
Exactly, just happened to me. Oncidiums also are thirsty plants. I wonder if it's your watering habits not disease?

[SaraJean]

Originally Posted by Dollythehun

"2. Wasn’t getting enough water. That resulted in them dropping leaves like hot cakes
Because- A: wasn’t watering orchid enough, or, B: orchid had a poor root system and the couldn’t take up water. "
Exactly, just happened to me. Oncidiums also are thirsty plants. I wonder if it's your watering habits not disease?

Yep, that was my most common culprit for leaf loss in my Dens. My pots looked like a I was trying to grow a bunch of bare twigs for a year or two. Great look for Halloween decor, not so great for a formerly healthy orchid. They’re better now, thankfully, and have forgiven me for my poor care

[King_of_orchid_growing:)]

I don't recommend using Physan on the plant. I don't consider this a safe usage of the product. I am on the camp that it is better used for disinfecting inanimate objects like benches, tabletops, pots, mounts, or gardening tools. It could end up being more trouble than good if used on the plant itself, in my opinion.

I'd look more towards your cultural conditions and see if it is correct for the type of Dendrobium you have. I've generally never really had to use fungicides or pesticides with orchids in the genus Dendrobium. If something goes wrong with the Dendrobium, I usually look at any cultural issues first and correct that instead. Remember, generally speaking, if the cultural aspect of growng the orchid correctly is not addressed first, it doesn't matter how much fungicide you use, the problem will either recur or outright kill the plant.

Please keep in mind that the genus Dendrobium is one of the largest genera in the orchid family. It is not useful to overgeneralize "Dendrobium culture". It is much more useful to narrow down the cultural requirements to either the section level, (if growing hybrids or species), or the species level, (if growing species).

[SundayGardener]

It's a Latouria type dendro. I haven't even had it a month It is in its bloom cycle.

I have been watering 2x week, always until water runs out (distilled water only). To be honest, I'm not in a big hurry to look at roots because that always ends with me repotting which then seems to make things worse. The best repotting experiences I've had have been using lava rock. So maybe I'll peek on the weekend, when I have more time and I can get some potting stuff together.

So physan isn't meant to apply to plants? I did look at the St. Augustine reference and the Physan is more affordable than Banrot. I wasn't expecting to see dark spots from insufficient watering, so this is a new one on me! I thought for sure this would be some kind of infection.

My other dendros (same type) are doing fine which also threw me off. I got a Little Atro months ago, and I have to say, I don't know what to look for at the roots. For this L.A., the roots are always a pale color, there are no aerial roots (weren't at time of purchase). I kind of have to soak it because it is so tippy, but the roots don't change color or seem to be rotting. Or doing much of anything. Honestly, they kind of look like straw which doesn't seem right, but the plant seems healthy enough. With catts, phals and anything with new root growth, it's much easier for me to say healthy, or boo.

For the oncidiums, I think I'll just leave them alone, I don't want to make things worse. I'll take pictures later when the light is better.

Thanks for the help! I never would have put this together with needing more water. Getting the water right is where it all falls apart.

[King_of_orchid_growing:)]

By the way, what I mean by identifying the Dendrobium by section is, for example, like so...

Dendrobium Section Latouria

Dendrobium Section Spatulata

Dendrobium Section Stachyobium

Dendrobium Section Dendrobium

Dendrobium Section Calcarifera

Dendrobium Section Callista

Dendrobium Section Formosae

Dendrobium Section Dendrocoryne

---------- Post added at 07:47 PM ---------- Previous post was at 07:45 PM ----------

Lava rock is fine as a potting media.

Watering can be an issue.

Temperature can too.

What are the temperatures?

I would recommend checking the roots to see if they are dying back. Better to check sooner than later. Roots can die rather quickly.

[SaraJean]

Originally Posted by SundayGardener

Thanks for the help! I never would have put this together with needing more water. Getting the water right is where it all falls apart.

I just want to make sure you understand what I meant when I wrote this:

Originally Posted by SaraJean

2. Wasn’t getting enough water. That resulted in them dropping leaves like hot cakes
Because- A: wasn’t watering orchid enough, or, B: orchid had a poor root system and the couldn’t take up water.

There is a difference between A and B. The first can be fixed by increasing the frequency of your watering. But if it’s the second one (poor root system/few roots/weak roots/root rot) that situation may not be improved by increased watering and can actually make things worse.
You mention in your original post that root rot has been your biggest problem with orchids. That could be what’s going on here. Good news is- I have found these types of hybrids sturdy and they can recover fairly easily and quickly. If you can correct what’s going on now, it may not miss a single blooming cycle


EDIT: you mention it being tippy. Make sure it’s roots arent being banged around and damaged as the orchid wiggles in its pot or gets tipped over. Keep it secure and stable

Is there a reason you are using distilled water? Tap water should be fine for these unless you have extremely hard water or you home uses a water softener. Just flush once a month to remove any sort of salt build up

[SundayGardener]

We do have really hard water with a high concentration of lime and other minerals. We do have a water softener (with the resulting water still being extremely hard, it leaves deposits on everything). Stores sometimes sell out of distilled water here, especially in the winter, because we all use it for appliances, humidifiers etc.

I checked some more and this is a semi-Latouria, also Phalaenthe (25% I think). I watered it yesterday and the media in the pot is still moist. It drains freely and appears to be in a fine gritty mix. I do have small (really small, like 2-4 mm) lava rock which would be less of a change from what it is in now, but I don't know if that would provide enough space for air pockets? I also have orchiata in different sizes and perlite in small and large chunk.

It was looking pretty good but as of today I saw more spotting on leaves.

Are you all using Physan to disinfect pots, surfaces and tools? So far I've been using bleach with detergent and water for pots and plastic tubs and so on, and either a flame or rubbing alcohol for metal snippers.