Brown and black leaf margins

[DebsC]

Hi There, glad you worked up the 'guts' to post! No need to worry, everyone here is really nice and understanding. We're all just trying to grow our orchids as best we can.

In my area of the US it's been extremely humid this year. I have so many fans running it feels like walking into a tornado in my greenhouse!

Your pictures look familiar, as I have some orchids doing the same thing.

It is my opinion that the cause is a combination of environmental problems. In my case, the humidity is way too high, like 87% at times.

I'm not a heavy or often fertilizer, but flushing the pots with clear water couldn't hurt and might help.

I have trimmed off the damaged tissue and sprayed the entire plant with a systemic fungicide following the instructions on the bottle.

On most of my plants, it takes follow up care. One treatment is rarely enough. If the bottle says spray every two weeks, that's what I do.

Look closely and seriously at the culture you give your orchids. Improve air circulation, if you can. Fertilise weakly, weekly and flush the pots with clean water once a month or so.

Take care of everything you can in a timely manner whether it be bacterial rot or insects or whatever.

Good luck! I know how bothersome it is to have something going on with your orchids.

[auhurta]

Thank you Debs!

Well, I have been trying to figure out which fungicide I should use. I have Captan 50%. The manufacturer recommends a dosage of 2.5 g/L but it doesn't say how frequently.

Is Captan O.K.? If so, how frequently? If not, What do you use?

Thanks again!

Aura

[DebsC]

Right now, I'm using Immunox multi-purpose fungicide for roses. I've read that usually if you can use it on roses, it's okay for orchids. But do your homework or just use a couple times on a very few orchids, just to be sure there's no damage.

I'm using this because it's readily available for me at Lowe's or Wal*Mart. I have a hard time finding what I need. Small town, USA.

The main ingredient is; Myclobutanil 1.55% and it lasts on roses for 2 weeks.

Here's a link I found for Captan 50 and it tells about using it on many different plants and safety issues.

http://strawberry.ifas.ufl.edu/plant...tan%2050WP.pdf

I've never used it so can't tell you how efficient it is.

[auhurta]

Thank you Debs, I read it and decided the dose kind of arbitrarily. How do you decide the dose of something that's not specific for orchids, do you use the one for strawberries, peaches, almonds...?

Well I had a massive repotting workday. I found out that there was a very ugly fungus in the bark of the Zygopetalum, the one that had me worried crazy. I hope that's it.

Once I pulled it out of the bark, cleaned the roots with clear water, took away the remaining pieces of bark, soaked the whole plant in physan, I repotted in fresh bark and coal and used 2.5 g/l of Captan. I'll repeat the same concentration in a week and once again a week later. Hope that's enough. Also, I cut the ugly brown leaf parts and covered the wounds with the powder (Captan comes in powder).

The other 3 were fine at the root level, as far as I could see. But they recieved the same treatment and will continue to recieve the doses mentioned above.

Sorry there are no photos of the fungus, I was really overwhelmed by the amount of work with the other 14 waiting to be repotted.

I'll post the photos later to document the follow up.

Thanks again,

Aura

[Louder Than Hell]

I've been taught to use bayern previcur(cloridrate-propamocarb 66%), to cure and prevent and bayern aliete (alluminium fosetil) to cure.
Just in case others cant help you with european products

[Ray]

I'm sure it was just a typographical error, but 160 mg/liter is more in the range of nitrogen concentration, not 160g! Even so, you are definitely over-fertilizing.

I typically shoot for 125 ppm (mg/L) N, and the simple way to determine the amount to use to get that is:

10 / %N on label = teaspoons per gallon
or
13 / %N on label = milliliters per liter

With a 16% N fertilizer, therefore, your 3ml/L is more like 300 ppm N. If you are applying that to dry roots and medium, it could be quite damaging.

Personally, I would use that fertilizer at 1 ml/L, three out of four waterings, flushing with plan water on the 4th.

[auhurta]

Thank you Ray and Louder Than Hell.

I'll get my hands on some Aliette, I found the provider here.

Ray, actually I was wrong on the concentration of my fertilizer, you are right, it's 160 mg of N. I have a question though, how is the fertilizer calculation affected if I water some of my plants every week, some others 2 times a week, and the ones hanging on a piece of wood I do so everyday? Do I take your advice on fertilization (1ml/L) 3 out of 4 waterings and turn it into fertilization (1ml/L) 3 out of 4 weeks?

I don't know whether I'm making myself clear. Hope I am.

Thank you