Cattleya with white on leaves
 

I've got this white pattern on the leaves of a cattleya mounted on a shingle. Is it powdery mildew? Something else?

What should I do to treat it?

http://www.orchidboard.com/community.../IMG_0153a.jpg

can't view the picture, sorry

Whoops. Don't know what happened there. I'm still trying to figure out how to upload images here.

Minerals in your water. Just like on your windshield and beverage glasses if allowed to drip dry. If you're using tap water, it means your dissolved solids are way too high for orchids. But it could also be from your fertilizer solution.

Most often the minerals in "hard" water that cause that residue are calcium, magnesium, iron, lime and some other minerals that I don't now remember. They aren't salts so not as much of a problem for the orchids.

FWIW - Andy of Andy's Orchids once told me that the calcium in hard water is in a form that is virtually useless to plants and even though I have a lot of Ca in my water supply...I still have to supplement w/it. I get a white residue on all of my pots in the winter months when I'm watering w/only tap but I have a friend who waters w/rain water only and she gets that same white residue on her pots but not as heavily as mine. Either way...it's how I've been watering for all my plants and the only ones I've had trouble with are those that require extremely "pure" water...like phrags, masdies and some of the other cloud forest plants.

I do clean the leaves though because the residue can reduce the ability of the plant to perform photosynthesis. Like a shade cloth on the leaves. There are a lot of home remedies for the film...diluted lemon juice in water, milk, diluted vinegar and water...they all seem to work. I clean and then rinse the leaves well. In the summer, w/the summer rains hitting the plants I don't see much of that residue. I would avoid those leaf shine type products as they have been reputed to clog the pores. I don't know if that's true but it's what I've heard. Plus, for orchid shows...I understand those leaf shine products can get a plant disqualified. If you don't want to mess w/mixing something up on your own...there are a number of citrus based leaf cleaners on the market. Repotme has one...as does Ray, I believe.

Side note - if you just got the plant and the grower was using fungicide as part of his/her protocol...that can also cause a white residue. If there was a fungus problem I would leave the residue until the problem appears to be resolved.

Cattleya with white on leaves
 

I think Andy should have payed more attention in chemistry class... The calcium in the water, whether it be from the local geology or from the fertilizer or additives we use, is the ion Ca++, and that's what the plant absorbs.

All epiphytes benefit from pure water, as that's what they have evolved with, since the nutrition is pretty much limited to whatever washes out of the forest canopy during frequent rainstorms. Even then, as little nutrition as that may be, it still is only present in that water for the first instant of the storm, and after that it's pretty much pure water.

Many orchids are tolerant of high mineral content, and calcium is an essential mineral that should be supplied regularly, but that doesn't mean they like it at high levels, and an excess can actually lead to deficiencies in P & Mg, with regular levels of 100 ppm or more, according to a Penn State publication I saw.

Hmmm given my other thread about water quality I'm perplexed. I'm pretty sure that I have very soft water. None of my other plants have this. This is the only one I have mounted so I do mist it more than the others. It is next to a napenthes carnivorous plant that also gets misted often and that doesn't have a single bit of it -- and my understanding is those are even more sensitive to water quality.

The main difference is fertilizer. The orchid had recently started putting out some roots so I had started fertilizing a bit stronger.

I'll give the leaves a good rinse and dial back the fertilizer regimen.

Good to know! And, this (Mg deficiency) could explain a couple of catts that I feel are deficient in some nutrient but I couldn't pin-point what it was. Again, good to know...guess I'll be pulling out the epsom salts.

We have been wondering what this was too, a similar problem. We have had this cattleya for 10 years and it has never bloomed. Each year we hope this will be the year. It looks like this could be the year. But back to the problem. Our plant has a similar white waxy substance on the leaves. We use RO water, but we do use peter's professional water soluble fertilizers, at 1/4 strength every other watering. So I can't see it being a water/mineral/salt issue. We just thought it was a different type of cattleya, because it is different than any others we have. Is this the same or something different?

Looks like that has a lot of Rhyncholaelia digbyana in it. That plant has very waxy leaves. As the leaves shrink and expand with drying/wetting, the wax sometimes flakes off. The solution would be to keep it more evenly moist, but that is risky in a pot.

Thanks for the information estacion seca. Not the same thing. This a NOID that we have been waiting for it to bloom in hopes that we can ID it. It is one strange character. Photo show this years hope.

Those are really tiny roots. I bet somebody here could guess what it is. I would guess it's something that grows in a lot of sun, maybe a lithophyte.

I second that digbyana is in there somewhere. It has very distinctive leaves.

A relative - Rl glauca also has a waxy coating on the leaves but they are greener than digbyana's. If it's a cross you likely will never know the exact name.

FWIW - digbyana's roots a very much like that.

Thanks for the info, both of you. Estacion seca and Katrina not only does it resemble Rhyncholaelia digbyana, it is Rhyncholealia digbyana, I believe. It started to open its bloom, yesterday. I will post photos on the cattleya board, because we are high jacking rothrock42's thread here. Sorry about that, rothrock42 what kind of cattleya is yours, could it be Rl. glauca. And that is just the natural waxy build up on the leaf. As others have said start with good quality water, RO ,rainwater ,or distilled. Use you fertilizer weakly - weekly and flush you plant with straight or clear water every month or so should resolve any water issues. If this is a water/ mineral/salt issue.

No problem Selmo -- I've learned a lot.

It is a Laeliocattleya Loog Tone 'SD'. Which evidently is known for its waxy leaves. It is mounted It had some of that on the leaves when I bought it and at the time I just figured it was minerals from foliar feeding or what not. I just panicked a bit since I had expected it to lesson in my care.

It is mounted so I had been misting it more than my other Cattleya alliance plants. I've misted it with distilled water a couple of times and that seems to have knocked back the white.

It was blooming when I bought it and it is wonderfully fragrant so I want to be sure to give it the best treatment I can and get it to bloom again.