Reddish Powder on Yellowing & Dying Leaves

[New Orchid Lover]

I have 7 dendrobiums, and they are all having a similar problem. From the bottom up, they are turning yello, the leaves get wilty looking, and then fall off, but before they do, when they 1st start to turn, if i touch them, they leave a reddish powder on my fingers. The wierd thing is, at the bottom of the plant, I am getting new "stalks" and growth, but now those even stop about midway and turn brown and dry out and die. As I'm writing this, I have one that has only one leaf at the top of the stalk, a new growth coming up from the bottom ony an inch and a half long, that is also starting to turn.

I keep them indoors near a window with morning sun. They get direct sun until about 9:30am and I only water once they turn almost completely dry.

Anybody have any thouguhts?

[janet_a]

did this happen all of a sudden? how long have you had the plants? when were theyt last repotted?

if it were me, bearing in mind i only have 2 dens and don't really know what the heck i'm doing with them, i'd yank 'em out of the pots, disinfect with a bleach spray, repot in fresh medium, and gradually put them somewhere where they'll get more light. my understanding is that dens like high light; mine didn't start blooming until i put them in a full western exposure.

there are also some types that lose all their leaves naturally. but that powder doesn't sound good; you may have to spray them down with a fungicide or something.

[E-Jag]

I have 2 very healthy dens, thanks largely to this forum, and have been advised that, when growing and/or blooming, dens like A LOT of light. Mine get at least 2 hours of direct sun a day. During this time they also like a lot of water - I soak mine (they're in clay pots) every 3 days. Fertilize "weakly weekly" during this time, bearing in mind that they don't like a lot of nitrogen. During that time of year when they aren't growing/blooming, let them dry out in between waterings - don't water as often. Can't help you with the reddish powder. This advice, of course, is worth exactly what you paid for it. Good luck. It will all work out.

________________
E-Jag

[mayres]

Are you sure you don't have a spider mite problem? Put some of the powder-like residue on some white paper and see it any of it is moving.

[Lucinda Brown]

A lot of times overwatering can cause some of this but for the powder try Ortho Insect & Disease control.Home depot & Lowe's usually carry it.It is safe for them[use it myself] and will help with any fungus or insect problems that might be going on.In other words-covers all the bases.Good luck!

[Cynthia, Prescott, AZ]

Mites might be the problem. Read this: Checking For Mites

If it is not mites, then the next posibility would be some kind of fungal, bacterial, rust problem. I would suggest you consider combing the internet for a small quantity of Phyton 27. It is a systemic fungicide and bacteriocide. Expensive, but the only really big guns I know of.

[Ellen]

What Mayres says - Sounds like spider mites. Spray the plants with an insecticide that works on mites, making sure to get it on the undersides of the leaves where the mites hang out. Then keep the plants outdoors (unless it's below freezing where you live) and spray them hard with a hose whenever you water. You will probably want to reapply the insecticide a couple of times at 1-2 week intervals to make sure you get the mites as new ones hatch out. The spider mite problems that I've had have mostly been on non-orchid plants (hibiscus, palms, etc). As soon as I've put the plants outdoors, the spider mites have disappeared as if by magic.

[turkeytaker]

It sounds like it could be 'rust.' I just had a few dends with this problem (got them from a trade), and they had a pretty heavy coat of the fungus, especially near the base of the leaves, right up against the pseudobulb.

The leaves were really mottled and floppy, and I originally blamed spider mites. After a few unsuccessful applications of miticide, someone told me that it could be fungal and one treatment eliminated most of the problem.

Like Cynthia said, a good one for that is Phyton. I, personally, just use the Bayer Rose insecticide, since it's cheaper and more available where I am.

[New Orchid Lover]

Thank you all for your great advise. I checked, and they WERE moving. They look like tiny little lice, small enough to crawl in the grooves of my finger prints!!! I'm going to buy an good insecticide as advised and let you all know what happens.

Thanks again you guys. You're GREAT!

New Orchid Lover, what you need is a MITICIDE, rather than an insecticide. Mites are not insects. Check the label to make sure the product is good against mites. Many insecticides are not. That's why someone recommended the Ortho, as it covers a multitude of problems.