Dendrob. leaves suddenly losing color and mottling
Hi!
I have had this dendrobium chrysanthum for about 4 months, and until yesterday it had been thriving (new roots, cane growth, new leaves). I was away from home for 1 day, and I was dismayed to find that in the 24 hours of my absence, something terrible appears to have afflicted my plant. New mottling, yellowing, and multiple leaf tips where the color looks like it was literally drained away, leaving the leaf tips to be nearly translucent.
Its not possible that this is due to sunburn, this plant is grown only under a horticultural LED light. My temp/humidity gauge shows the high/low history and there was no heat surge while i was gone. No sign of pests (that i could see). Fungus seems out of the question because there is excellent air movement and the orchid is mounted on cork bark, the leaves just dont have the prolonged moisture on their surface required to support rapid fungal growth.
I only use rainwater (which i filter with a Berkey) to water my orchids. MSU fertilizer + Quantum Orchid once every ~10 days. Kelpmax once per month (started 2 months ago).
I only got into the orchid care hobby about a year ago, so im rather new to all this. It is the first time I am encountering an issue with one of my plants, which happens to be one of my favorites so I am very concerned.
The change in the leaves happened over the course of just 1 day, and did not effect any of the new leaves that have grown in while the plant has been in my care. The plant had a few little black spots that looked to me like sunburn when I got it (theres a picture of the plant I took on June 10th, which shows the black spots), they have not changed at all in the time that i have had this orchid. No new black spots have appeared. The change in the plant is all color loss, mottling, yellowing and withering leaf tips.
Could it be calcium/magnesium or some other nutrient deficiency? If so, what is the best way to ensure my plants are getting enough cal/mag?
What do I do with these damaged leaf tips? Cut them off?
Sorry this post is long, im just very worried and want to provide enough info about the plant's care to help facilitate a diagnosis of the issue.
Any ideas/suggestions/advice would be greatly appreciated! Thanks!
When something like this happens to a thin-leafed orchid I always look for spider mites.
Mounts indoors truly do need watering every day during the growing season, especially Dendrobiums in active growth. This seems to be an mature growth? When water-stressed, those are the first leaves to go. I found it very difficult to keep up with watering mounted Dendrobiums and I no longer grow them like that.
__________________ May the bridges I've burned light my way.
Great comment about spider mites. Spider mites are definitely nasty. While they're just trying to survive themselves ------ their effect on orchids can be real nasty. They can really take down orchids.
In the pics ----- I can see that the leaves are wet - which also brings up the question of - are they often wetted like that? Spider mites get drowned by water. Usually, the spider mites won't take down a plan in 24 hours. But they can certainly build up their numbers real quick.
By the way, no need to filter rain. And your New York tap water is probably fine for most Dendrobiums. They are mostly not delicate plants. MSU has some calcium and magnesium I think. What you show is neither calcium nor magnesium deficiency. I'm betting on a day without water.
__________________ May the bridges I've burned light my way.
Thank you guys so much for your replies! I dont think it can be spider mites because when I am home I drench my chrysanthum with a spray bottle 1-3x per day, roots leaves and all. However I do have a ceiling fan and several small oscillating fans in the room where I keep most of my orchids, so things dry out quickly, so maybe youre right. Would I be able to see spider mites with the naked eye? I very thoroughly inspected this plant and I didnt see anything pest-wise. But ofcourse, i am all too aware that external parasites can hide themselves very well so I wont discount the possibility. What do you recommend in terms of pesticides? I am hesitant to use anything that is too toxic or has a noticeable odor. I always have a foster cat in residence in my plant room, and I once used a "natural" horticultural insect repellent on my plants that had a very strong unpleasant smell and my foster cat was not pleased lol. But ill use whatever is necessary to protect my plants from bugs. 😹
Good to see another chysanthum grower join. Mine is the same age and size as yours !
I can't help on why the leaves don't all look perfect - mine don't either so maybe I am doing the same thing wrong as you but so far mine has grown 16 leaves this year - yep some look like yours too but at this growth rate I think mine is performing spectacularly well so I'm not bothered about a few yellowing tips which I honestly did put down to sunburn on mine and haven't been fussed about it much since.
I don't know if that helps or not but like said I think yours looks fine - they lose all their leaves in winter anyway don't forget.
Edit: to check for spider mites get a white piece of toilet paper, spray a bit of water on it, then wipe over the underside of a couple of leaves - check the color of the tissue. If there are brown or red specks on the tissue, chances are you have mites.
Last edited by Shadeflower; 07-25-2021 at 05:13 AM..
Maybe it's not spider mites for your case. But ----- good question about whether you can see spider mites with your eyes.
The answer is ----- generally you can ----- but not clearly, as they're relatively small. So seeing them can mean just seeing tiny dots (eg. black or red, or some other colour - depending on the sort of spider mite and their age etc).
Eg. red spider mites attack my cymbidiums. And spider mites attack my catasetum type orchids, as well as other orchids --- such as the Jackfowlieara types. On cymbidium leaves ----- I'm definitely able to see them with just own eyes ------ the red spider mites - as red dots, that are either stationary ----- or some may move around a bit ----- ie. can actually see them travel slowly from one point to another.
Spider mites can generate spider webs on the plant too. They can do that. So sometimes ----- seeing fine webs in addition to little dots is more information.
Also - notice in pic #2 of the opening post ...... the tips of leaves are brown/dead. This doesn't necessarily mean anything bad ------ but just mostly means either not enough water getting to there ---- either by not enough watering, or roots not getting the water to there, or sometimes too much fertiliser.
Update: im fairly sure the issue is anthracnose. The biggest tip off is the fact that the leaves were wasting away always starting from the tips and then making their way down the leaf. Ive started treating all my plants with thiomyl. Im repotting, disinfecting, etc. So far my chrysanthem seems to be responding positively to the thiomyl treatments.
Im surprised because I have a ton of air movement in the room with my plants (large ceiling fan always running medium-high speed, plus smaller oscillating fans), the chrys. is mounted so its not like it didnt dry out quickly every day. However I think the issue was due to a lot of high temp and high humidity days/weeks in july and august. Thats my best guess. Hoping the multiple rounds of thiomyl treatment wont somehow disrupt the flowering that im expecting from the affected cane in the fall 😬
Dendrob. leaves suddenly losing color and mottling
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