Oncidium Twinkle....or is it a leopard? Spotted leaves and burnt tips

[Ray]

There are any number of things that can cause such leaf damage. Deficiencies in calcium or magnesium are not among them. The former results in death of newly-growing tissue - you said it grows great, so that’s not it. Magnesium deficiencies show up as chlorosis - yellowing leaves...nope. Your water supply probably has plenty of both.

Yes, it could be due to residues in the potting medium, but you stated it continues with divisions that have apparently been repotted, so that doesn’t sound like the problem.

I think you’re dealing with a bacterial or fungal infection, either of which can be very easily spread via splashing water.

There are several directions you can take, but I’d start with a copper treatment - Southern Ag’s Liquid Copper Fungicide or Phyton 27 come to mind. Copper compounds kill both fungi and bacteria. If you suspect your growing area is contaminated, Physan at a teaspoon/gallon can be sprayed on the plants and benches.

A couple of weeks after you treat the symptoms, you might consider a periodic treatment with a plant probiotic to keep such things at bay. I sell Quantum-Total, which I am getting to really like for orchids, vegetables and my landscaping, but there’s also Quantum Orchid (same thing at a higher price) or formulations like EM-1 available. I have found that with regular use, I just don’t see such issues any longer.

[WaterWitchin]

Originally Posted by MJG

...

About calcium and magnesium....I have been blindly using the same orchid food for years. Recently I began reading about orchid fertilizer and nutrition and I actually read ALL of the ingredients in my orchid food. It contains no calcium or magnesium. I started supplementing just a couple of weeks ago. It's too soon to see if that's been part of the problem. If it is, I'm already heading in the right direction.

I did -- finally -- just repot. I also am careful to keep water off the leaves.

Thanks for all of the advice!

Are you using tap water or RO, rainwater? If you're doing tap water, find out how much calcium and magnesium are in your water. If using RO, rainwater, etc. and haven't been using anything with cal/mag in it, it's likely a start of the source of your problems. Especially looking at the tip of the leaves.

[Ray]

I looked up the water report and ended up going to Syracuse, as his town said they get their water from wells in Syracuse.

Both levels are low, but reasonable, and if used to water regularly, it's no issue.

[MJG]

Rbarata, I read your resource link. My twinkle's malady looks very much like some of the fungal ailments. The pictures look similar and descriptions match. I will treat it with some of the recommended fungicides. I'm not seeing any kind of rot. None of the spots are soft. The orchid has lived with this degree of spottedness for several years. It doesn't behave like an orchid that's succumbing to something, so I'm going to attack this with the fungal presumption first.

I did recently repot it from fir bark into a fresh fir bark mix. I trimmed away some bad roots but overall its root system looked good. Is there any reason to avoid fir bark mix for this type of orchid? It's what I've always used.

Regarding fertilizer I have been using Jack's 30-10-10 on all of my orchids. I use fertilizer sparingly most of the year, but weekly-weakly through the summer. I've been reevaluating fertilizers recently. I live next to one of the cleanest lakes in the U.S. Our tap water is lake water, filtered, with chlorine and fluoride added. Nothing else. I water the orchids with tap water. I decided to switch to MSU for rain water as a fertilizer. The MSU has the added calcium and magnesium that I think I need. I also want to get a water analysis as Ray suggested to someone in another post.

So that's been my thought process on the fertilizer. Then last night I was reading that the higher nitrogen in the 30-10-10 formulations is needed for orchids potted in fir bark. Most of my orchids are potted in a fir-bark based mix. I feel like I'm running in circles. Go with MSU or stay with Jack's 30-10-10?

And yes, the bottom line is using fertilizer sparingly, which I've been careful about for the last couple of years.

---------- Post added at 02:57 PM ---------- Previous post was at 02:48 PM ----------

Ok, SORRY for the confusion. I made this last post above without seeing the two posts from Ray and the one from Waterwitchin above! I'll reread.

Fyi, as I said I use tap water. Ray, you're correct about Syracuse's water supply (and wrong about my gender. I'm a "she") I live in the Village of Skaneateles. Our water source is different from Syracuse -- right out of Skaneateles lake with the chlorine and fluoride added.

---------- Post added at 03:16 PM ---------- Previous post was at 02:57 PM ----------

That is, the Village of Skaneateles' municipal water supply is our lake water, with chlorine and fluoride added. That's what our tap water is. We're not drawing our water directly from the lake like some do. But also we and Syracuse do not have the same water source.

The reason I am going on and on about the water source is because of the fertilizer question. I assumed our lake water is more similar to rain water than to well water. So MSU for rain water is more appropriate than MSU for well water? Versus Jack's 30-10-10???

Thank you so much for your advice and patience!!! I'd love to figure out the appropriate fertilizer for this guy.