Spots and more spots

[gngrhill]

Boy, sometimes I just wish an experience orchid grower could just enter my grow space and tell me where I'm going wrong. I have spots. All my dens are affected in some way (except my nobiles ) Very small , pitted, black spots. some have lots of spots, some have just a few. some are on the old leaves, some are on the new leaves. Some are even affecting the tiniest new growths coming up. For reference, my temps now are averaging 65F days and 55F nights. Humidity is ranging from 55 to 80 depending on how cold it is outside to keep the heater running. Some are under the t-5s, but I have moved most of them out from under the lights because I thought it might be the lights or heat from the lights causing the spots. I do not mist, so no water on the leaves. I have tested for virus, negative. I just don't know what I need to change to make them stop. Leaves all looked ok when I got them, so it has to be me

[tucker85]

Without seeing your orchids it's hard to say what the problem is and even if I saw them I might not know for sure. I think it's possibly a leaf spotting fungus but I'm going to suggest one thing that you might want to try. Buy a product called MagiCal by Technaflora. Every time you fertilize add 1 teaspoon of MagiCal to each gallon of fertilizer water if your fertilizer does not contain calcium or 1/2 teaspoon of MagiCal per gallon if your fertilizer already has calcium in it. This will only help new growth so the old growth will still be susceptible to fungus spots. If it doesn't help, it won't hurt either but do it for at least one year. If you want more explanation I'll be glad to expound on my suggestion.

[fishmom]

The suggestion of calcium is a good one. Another product is Cal-Mag, by Dynagrow. It is commonly found in the hydroponic shops around here.

You might also think about air flow. Are you running a fan? Stale air can promote fungal leaf spots, and improved air movement might be helpful.

[gngrhill]

Thank you both for your replies. I do run a fan 24/7. I water with half rainwater and half tap water and my tap water is well water and has a high amount of calcium in it. Do you still think calcium could be an answer ?

[estación seca]

Which Dendrobiums? There are a lot for which 55 F / 13C at night would be too cold. There are a lot for which that would be just fine.

[tucker85]

Originally Posted by gngrhill

Thank you both for your replies. I do run a fan 24/7. I water with half rainwater and half tap water and my tap water is well water and has a high amount of calcium in it. Do you still think calcium could be an answer ?

It's hard to know for sure. I'm just going by my experience. I grow outdoors in Florida and I had major fungus problems for several years. We have a lot of calcium in our water here but I read an article in the St. Augustine Orchid Society newsletter about calcium and I decided to give it a try. The improvement wasn't instantaneous but over time my fungus problems were cut by 90%. If nothing else, I think it might be worth a try. I heard a talk by Jack Peters who makes Jack's fertilizers and he said manufacturers can't put a lot of calcium and magnesium in their dry fertilizer products because it will form hard clumps in storage. In any case a liquid cal/mag product like MagiCal has worked wonders for my plants. I do agree that air movement is also very important.

[Ray]

Leaf spotting is almost always a fungus. The spores are easily distributed by air movement, not just by water.

CaliMagic is a good product - I have sold tons of it over the last while - and can help "toughen up" the plants, but is not a cure. Give the Inocucor product a try, as it will introduce beneficial bacteria and fungi that can prey on the bad ones.

[No-Pro-mwa]

Sounds like what I had last summer. It killed my project plant then spread to a few others. I sprayed them with a copper fungus spray a few times and I am trying to put more calcium/mag and I am also using Rays inocucor. I do think it's helping as the new growth on the 2 Onc. don't have spots on them. Also my Aeridovanda which had caught it from the plant that started it, I had to cut off one whole leaf and the tip of another. It seemed to stop it and it had bloomed in Oct. and the other day I see a spike starting on it again so it must be happy again. Unfortunately they all still have black spots and those are not going to go away.

[Leafmite]

I have read that you should not use copper on Dendrobiums. I haven't tried to kill orchids this way, yet, so I cannot give an opinion on whether it is true or not. You could consider what Ray suggests.
I just bought the Calimagic. Under the lights, my orchids are growing like it is summertime and I cannot use powdered milk as I would when the orchids are outside.
If you can find a way to heat the space where your orchids are, that may help. While the cooler temperatures may not kill the orchids, these consistently lower temperatures could be causing them stress which lowers their immunity to disease.
When you water with cooler temperatures, it is best to keep the water off of the leaves. Be careful to make sure that the water you use isn't too cold, either. That can also stress a plant.
Good luck!

[No-Pro-mwa]

Leafmite I will try and remember that. I didn't have any Dens at the time.