Black Spots

[eldone]

Hi,
My orchid has a fairly new leaf that is turning black and the black area seems to be progressing fairly rapidly. I grow my orchids in a case under fluorescent lights and use a fan to circulate the air. I do not mist my orchids as I learned that the hard way. I do use Physan 20 on occasion but not recently. It seems to be contained to this one leaf right now and no other orchids seem to have this problem. I am planning on taking the leaf off should I take more than just the one leaf to make sure I get it all?

Any ideas?

[tom499]

looks like you;ve got bugs, I would give it a thorough check for mites etc.

[kmarch]

It looks like the kind of fungal blackening that comes from not enough air circulation. I have to really keep the fans going on my Masdevallias or they get like this. Go ahead and just take the one leaf off for now. Watch the rest of the plant closely and increase air circulation around the plant.

[tom499]

darn, i was nearly right..sorta

I've learnt something new

I had that on one of my masd. i just used to ignore it, the leaf yellowed and died. rest of the plant seems ok. I'll open the vents more

[Cynthia, Prescott, AZ]

You may find at this point that the leaf will just pull out. If not, then cut it as low as you can to leave the other leaf in place. Rots like this will usually stop at the pseudobulb.

However, I don't like the somewhat shriveled look of the other leaves on this plant. They have sort of a rippled look. I hate to say it but it looks very much like the fungal problem I had in my greenhouse. I believe it to have been a fusarium wilt, and only Thiophanate methyl worked to cure the plants. Most old leaves never recovered, and the plants had to outgrow the damage, which they are starting to do. You may want to read my thread on fusarium wilt.
Fungal Warnings: #1-Garden Safe Fungicide and #2-fusarium in peat

[tizzycat]

Tom, as a fellow uk resident can I ask: do your grow your orchids in a greenhouse??

[tom499]

some i do, some i dont

The reason is down to what I have available. I'm 17 still living at home waiting to go to Uni (where my orchids will go then I dont know ) so I am stuck with my bedroom and my parents unheated greenhouse.

and when i say unheated, i mean 12 degrees night temp in summer

This forces me to grow paphs, phals, oncs, dens, etc indoors all the time.

My vandas go in the greenhouse during the day for the sun and watering and are brought in at night.

My masd. pleione and disa are out there 24/7during summer. but they will have to come indoors into my parents semi outer room once temp go lower.

[PhalPal]

Mike my first instinct was fungal but I have never personally dealt with it. I cut everything off that looks that suspicious and spray with PharmSolutions. Love the stuff.
Cynthia - just how does a fungal problem spread from plant to plant? Touching? Or it really doesn't, just the same conditions exist for all the plants in the same place?

[tizzycat]

The reason I was asking is that I have a greenhouse, which is usually heated (but currently having probs with the power supply) and was wondering if my small collection continues to grow whether there was a possibility of moving some outside into the GH.

Tom, when do you go to Uni (october??). I do hope you will still find time to visit the forum. What will you be studying.

I just noticed your gold star CONGRATULATIONS

[BillC]

Jumping away from the subject of the thread: Oh to be seventeen and waiting to go to University. Live every minute of it Tom, (and good luck with the black leaf to Eldone).

Bill

[Cynthia, Prescott, AZ]

Stress is what weakens plants and makes them susceptible to fungal spores. I am sure I don't have enough light, but am working on it, not to mention over crowding. Spores are normally around, but in my case the condition started to snowball, with a severe excess of spores. In addition to treating the infected plants 2 or 3 times at week on their leaves, and twice a month or so at the roots, I have been spraying the entire GH with various systemic preps to keep the spore count down. As I say, I think the real secret is to not have the plants under stress, high light plants getting lots of light (like that little Catt type plant of the original poster) and low light plants being kept out of too much light.

[eldone]

Thanks so much for the help. The black leaf is now removed and I will start treating the plants for the fungal problem and see what happens. I did notice that many of my other orchids are also showing signs of shriveling leaves. I know that it is not roots rotting off and I was a little bit stumped. I figured that I needed to water twice a week but now it sounds like it may be a fungal problem.

[eldone]

Cynthia - I noticed in your thread on fusarium wilt that you preferred liquid Thiophanate methyl. I looked at Oak Hill and I only saw Thiophanate methyl in a concentrated powder form. Do you think the powder will work OK or do you use the powder to make a liquid?

[Cynthia, Prescott, AZ]

The powder is fine. I use so much of it, that the liquid is a convenience, and I get less exposure to the dust in the air. I get plenty of exposure to the mixed liquid as it is. Getting the thiophanate in a small quantity is hard enough, so be happy you can get it in powder form. One more item of importance is to mix the thiophanate in RO, distilled, rain, or DI water. I read some where that alkaline water, PH over 7, reduced the shelf life of fungicide mixtures. Since you are going to use this often, you don't want to have to make up a fresh batch every time.

[eldone]

Cynthia - I have been treating my orchids for Fusarium Wilt as suggested but recently took some of them out of the pots and checked the roots to see what is going on. I found that many of the roots are either stiff, brown, dead looking or the longer ones are mushy where they are near the bottom of the pot. I am using the S/H method and had good results originally but now they are not doing so good.

When I was using the commercially available potting mix I used to set the plants in the sink all at once and let them soak for 15 min. or so. They seemed to do fairly good except that a few of them seem to suffer from my overwatering so I switched to S/H thinking that might eliminate that problem.

I have been growing for several years and have always used softened water but I do flush each time with plenty of water and have never had this kind of trouble. I understand that softened water is not the best even though I have always used it without any major problems. However, I have switched to unsoftened water since I understand that the orchids do like it better. I have also stopped soaking them togather or reusing the water just in case that might be spreading a virus or something between the other plants.

Now to the questions:
Does the condition I have described of the roots seem to be a Fusarium Wilt issue or does it sound like something else? I am hoping that I can save them and have moved several of them to the Spag and Bag method in an effort to try to save them. Most of those seem to be improving slightly.

My other question is regarding the S/H method, has anyone else had similar kinds of troubles with this or is it just me?

[Tobi]

Eldone,
I personally don't use S/H, but I have mentioned in another post that a few
of the long time growers in the orchid society that I belong to that have been
growing this way for a few years are moving away from it because of ongoing
fungal problems. I'm not suggesting that S/H is not a good way to grow
orchids, only passing on information from some of the growers.

[pikevi]

I purchased an Oncidium lanceanum ( species?) a few months ago from a store that was closing. Since I was interested in species at that time she gave me that one with lots and lots of black spots/patches. She told me it is because of the previous winter and the black dots are due to neglect: water condensation and susequent sun burn without aeration.

I trusted her and bought it. I have had a single new growth since then and it seems to be alright devoid of black spots or any type of necrosis.

I think I posted a pix at the time of purchase. I will post a pix with the new growth later.

The markings are very similar and I may still need to treat it.

It still may be due to fungi and hence is still under isolation ( not quarantined).

Does anyone use thiophanate(s) in a closed environment?

[Cynthia, Prescott, AZ]

I too had terrible root loss at the time I recognized the fusarium problem. Don't know if the fusarium did it or another fungal infection, but I would think the Thiophanate is good for that, but if you can, find some other systemic fungicide/s that state they are good for root rot fungal infections, and rotate these with the Thiophanate at the roots. I won't know until spring, when I repot everything, how well I am doing on the root problem.

Pike, I use the Thiophanate in a greenhouse. Is that closed enough. If you are thinking a terrarium, I would think it is OK. I have not had any luck with the Thiophanate on my pleuothalids, and have lost most of them. Don't know if these guys are particularly sensitive to the fungicides or what. I used the systemics in a terrarium with them, but I had the problems in and out of the terrarium, so don't think there is any difference because of being in a terrarium.

[pikevi]

Thanks, Cynthia.

I was wondering if it would cause some mucosal irritation in a closed environment.

If the black spots appear on the new growth I may have to go for it too.

Here is the photo onf the one I have. old leaves a in bad shape. New one seems OK, so far. It is not strictly under quarantine. It sits quite far away from the others.