Black Spots & Yellow New Growth on Catt
 

About a year ago I got my first orchid and immediately became wildly smitten. I now have 24 in my window sill(s) collection! All have been healthy – even the tiny ones purchased at the hardware store have thrived and produced new roots and growth. The problem: This beautiful BLC Greenwich ‘Elmurst’ has developed small black spots on one of the leaves (first pic), and most disturbing, the newest small leaf is yellow (second pic). Also, two old psuedobulbs are shriveled. What is wrong with him? When I saw the spots, I immediately drenched with Physan 20. (He had very robust growth until the latest small yellow one.) I am ready to panic. All advice is appreciated!:bua:

:bump:
I'm bumping this thread so that hopefully someone can help you.

I don't grow many Catts (and only recently started!) so can't help you much. The black spots aren't too worrying I think, Catts tend to be a bit prone to spotting.

Thanks Camille1585. Spots on Catts - Newbie Needs Help
 

Thanks for responding, Camille 1585. As I posted, I am totally new to Orchids (one year) and as bad as I hate to admit it, I am almost obsessed. I have read everything I can find on Catt diseases and looked at probably a hundred pics of Catt fungus / bacteria / sun spots, etc, but cannot be sure what this one has. I have not lost an orchid yet and I don't want to. Have a blessed day.

The spotting on the leaf tip doesn't really bother me that much. The wrinkling of the pseudobulbs does, as it suggests the plant isn't getting enough water. That happens most often from either underwatering or a bad root system.

One of the basic orchid-growing tenets that most beginners don't quite grasp is that orchids do much of their respiratory gas exchange through their roots, rather than through leaves, as is the case for terrestrial plants. That means that we must find a balance between providing sufficient water and sufficient air to the roots.

Using a coarse, open potting medium helps the air, but requires a great deal more watering to keep the plant happy. A dense medium provides plenty of water, but risks suffocating the roots when it's saturated.

From the photos, I was unsure if that yellowing growth is a smaller, old growth that is fading away, which can be perfectly normal, or if it is, as you stated, a new growth, in which case it's decidedly not, making me suggest you unpot the plant and inspect that root system.

Thanks so very much for the info Ray. I am just now beginning to grasp the balancing act between air and water. The yellow leaf that has not fallen off is NEW growth. I watched it develop from a little shoot! I fear now that he has bad roots or bacteria/fungus. He is on a screened porch with great air circulation and is in Repotme catt bark and I have been faithful at watering with weak worm tea. So, now I will unpot him, cut dead roots and repot in new medium. Should I add a little spag moss? Should I treat him with a anti-fung/bact, and should I continue to feed him with weak worm tea? Sorry for all the questions. Very appreciative of your advice.

No moss... medium bark (since it is a small plant, when bigger go to large) Catts need to dry out between waterings. Perhaps Ray can advise on fungicide, I lean toward "tincture of fresh air". Fungi don't like "dry" and so letting the plant get nearly dry before watering again will do a lot to keep roots healthy and encourage new ones. (Mine grow best after they escape the pot and send roots all over the outside.) It helps to visualize the environment in which the Cattleya group evolved - branches and trunks of trees, where they get rained on and then quickly dry out. (To quote Fred Clarke of Sunset Valley Orchids, "How well drained is the side of a tree??")

Thanks, Roberta! I will stay away from spag moss when I repot. One more question please: What do you think about weak worm tea for orchids?

This one is for Ray. He knows a lot more than I do about plant nutrition. My hesitation on that is you really don't know what (too much? too little?) you are providing in the way of nutrients. One can be much more precise with fertilizers of known Nitrogen content. Orchids don't need much at all, since they grow slowly.

Worm tea is a weak, monospecific, but natural plant probiotic, but does little to actually provide nutrition to the plant.

Is it possible that water stood in the leaf axil of the new growth after watering?

It is slightly possible that water stood in the axil. I am careful when I water, but rain does come onto the screened porch and could have pooled in the axil. Side bar: About worm tea -- probiotic is good, right? (I thought it was the all-in-all for plants. Shows how much I know!). Along with the worm tea probiotic, what should I use for nutrition? [I do not have a gh. All are on window sills in winter and screened porch in summer in North Alabama.] I am learning so much from Orchid Board. So glad I found it. Thank you so much.

One can refine fertilization, but in general, here's a very simple approach. Use any balanced orchid fertilizer (like 20-20-20)... doesn't matter the exact number, but rather that all are the same. Use 1/4 to 1/2 whatever it says on the bottle. (if it says 1 teaspoon per gallon, use 1/4 to 1/2 teaspoon) Then perhaps once every week or two weeks ("Once weekly weakly") If you want to mimic what orchids get in nature, cut the concentration even more and fertilize with every watering, flushing with clear water at least every 4th watering. Personally, I use the "every week or two" regimen, really easy to keep track of and to accomplish. When in doubt, use less... if a plant gets less than the optimum amount of fertilizer, it may grow more slowly and/or produce fewer flowers. Too much, on the other hand, can kill it. Think of fertilizer as "vitamins" rather than "food".