yellow spots on leaves
 

i have a dendrobium that for some reason is getting many many little yellow spots on some of its leaves. the leaves will get enough spots to turn completly yellow then they will fall off. this only happens on the newer growths. i have checked for pests but i cant find any and all my other plants are doing fine. does anyone have a diagnosis?

Hi
do you happen to have a picture of an affected growth before all yellow / dropping?

That would help if you are able.

Wrong temperatures while misting might lead to such, but I am guessing since I grow in a greenhouse, and don't recall much an ailment like this except water in the growths.......yellow spots first???? Hmmmmm.

Pictures, please.......
Take care
Rex

Here is it on one of the older growths [IMG]http://i931.photobucket.com/albums/a...psd2e88555.jpg[/IMG]

---------- Post added at 06:24 PM ---------- Previous post was at 06:23 PM ----------

And here is another picture [IMG]http://i931.photobucket.com/albums/a...ps65d7074e.jpg[/IMG]

---------- Post added at 06:26 PM ---------- Previous post was at 06:24 PM ----------

http://i931.photobucket.com/albums/a...psc57f5cf4.jpg

Some orchids naturally get some yellow or brown spots, but these seem somewhat excessive. I'd be worried about some type of viral or bacterial infection.

You may need to discard the plant or at least keep it quarantined from your other orchids.

Ok thanks

Look here....www.staugorchids.com. You'll find what you are looking for there. Get rid of the plant.

James M
the link is broken:(

801 -- some of the leaves look like maybe cold damage to me. Grocery store dendrobiums prefer temps in the middle 50s F or higher at night. Colder interferes with their metabolism and absorption of minerals.

I've also seen insect damage causing this discoloration (a possible second problem). Are their scale insects on the backside of those yellow spots? The dry brown are old fungus spots with nothing to worry about. Fungus spots and bacterial spots only dangerous when dark and moist.

It could also be virus, as folks are wont to mention.

Isolate, identify, and then treat/dispose according to discovery.

that worst leaf -- is the leaf surface smooth, or uneven? Virus lesions interfere with the tissue causing thicker/thinner/bumpy/pitted/colored/discolored/etc. It is obviously a virus with these symptoms in the newest growth, esp while the newest growth is taking place. It is harder to tell when the symptoms appear after it is a year old (which is common). It might still be virus.

Critter creek offers (offered??) a testing service for a nominal fee.

Is it important to keep?:(

Rex

Nevermind about the 'only appearing on new leaves' part some of my plants did get scale/ mealybug but most have been treated and are in a separate room. The plants left in the room the dendrobiums are in are all still infected.

Brevipalpus spidermites with associated fungus… my guess.

Spidermites and fungus, yes. But the first picture looks like virus, which makes sense that it would be an older leaf showing the most symptoms.