Brown Spots on Tips of Dendrobium Nobile Leaves

[Leafmite]

Here are some helpful sites:

Orchid Pests, Orchid Diseases

http://www.houstonorchidsociety.org/...ySueBottom.pdf

I usually consult these when I am worried about my orchids. Here is some information on plant nutrition, some more helpful than others:

Diagnosing Nutritional Deficiencies
BIL 226 - Lecture 12
http://landresources.montana.edu/NM/Modules/Module9.pdf
Ikisan - Boron in citrus

I hope this information helps you pinpoint the problem.

[KristenJ]

Thanks Leafmite

I'm not sure what's wrong with the hybrid, but I'm pretty sure I have Anthracnose on the other Nobile. I have read that you should not use copper based fungicides on dendrobiums. Any recommendations? On the St. Aug site they recommend a systemic containing thiophanate methyl like Cleary's 3336, but I am having trouble finding that here (I just moved). I read about ones that have thiomyl instead. Can I substitute that if I can find it? They also recommend a protectant (Mancozeb), which I found online but it contains zinc. Will this be safe for use on dendrobiums?

[NYCorchidman]

I think I see severely shriveled canes in your first picture. Maybe the plant is very dehydrated and the leaf tip is dying. Then, fungal attack found its way.
How's your watering?
I water my nobiles everyday. They need lots of water during growing season.

Is spotting present only on that leaf? If so, I would just cut that leaf off and keep an eye one the plant for further spread.

Cleary is available on the internet. I hear mancozeb is fine on dendrobium, but I haven't used any chemicals on my nobiles as mine never had any issues other than VERY occasional little sunburn spots (like one or two per season on one particular plant) so far.
Lots of water, sun and air keep them happy and strong usually.