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Old 01-09-2016, 03:44 PM
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Black Spots on Phal

Hi All,

I've recently moved back to Trinidad and Tobago and am helping my mother with the orchids she inherited from my grandfather (more on that in another post)

One of the Phals that I have has lots of leaf damage (and also needs repotting I know, but given I have 40 orchids to care for, I'm only doing what's urgent at the moment).

Some is mechanical and I think some (the perfectly round holes) are due to insects. But there are lots of black spots both on the top and underside of the leaves that I'm not sure what they are - sun damage? fungus? Some of the other orchids have it as well.







This plant (and all the others) have been growing out in the yard under a mango tree for the past year, so basically anything could have happened to them.

Would love your thoughts on what the problem is/what I can do to help this plant's health.
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Old 01-09-2016, 07:03 PM
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Looks like fungal damage, mostly on aging leaves. The old leaves will continue to age and eventually drop. To minimize fungal infection and spotting on new leaves, provide the plant with calcium. This can come from several possible sources:

Readily soluble sources:

Cal-Mag (calcium-magnesium) supplement (works, but can be expensive)

Gypsum, dissolved about 2 or 3 cc per 4 liters water, or 1 tsp/gallon (builder or hobby store Plaster of Paris is gypsum with the water driven off, and can also be used; gypsum and plaster are cheap)

Calcium nitrate (sometime you can find this in garden centers)

Less soluble sources (provide calcium steadily over long periods of time, mix in with potting medium):

Limestone chips

Eggshell

Broken sea shell chips (clam and snail shells are better because they are made of aragonite, a more soluble form of calcium carbonate. Oyster shells are OK too, but are made of calcite which is more slowly soluble)

If you can get a garden fungicide, you can treat this plant and the others you mentioned in your other recent post.

The mechanical damage is most likely due to insects such as grasshoppers, or possibly snails.
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Old 01-09-2016, 07:45 PM
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Do these plants reside outdoors year round? If so......are there significant periods of wet? How about temperature? Are there periods of cool(er) as well? Those spots appear to me to be highly weather related if they are basically outdoor plants? Can we see a shot of the plants in their normal location(s)? Ok.....I just peeked at your other post and see that they are primarily outdoor plants - possibly we could discuss each one and help you out plant by plant (?) - can you post a picture of where this phal was hanging, tell us what the weather is like there typically in terms of temperature, air movement, rain, etc. I would expect orchids that are too cool and/or too wet to show signs like this one........as you noted - lots of good roots and highly salvageable yet......

Last edited by mayres; 01-09-2016 at 07:50 PM.
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Old 01-09-2016, 09:11 PM
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My understanding is that the OP is in Trinidad and Tobago - probably not cold there, but could be periodically very wet?
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Old 01-09-2016, 10:19 PM
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Thanks for the advice Catt - I had a feeling that it might be a fungal problem. Will get a fungacide and then sort out something for the long term later on.

Mayres - these plants have been grown outdoors under a mango tree for the past year (prior to that they were grown outdoors but under a semi-transparent covering). In Trinidad we have temperature highs of 30-35 deg Celsius year round, with lows of mid/high 20s. So it doesn't ever really get cold here. There is high humidity and at the moment we're in rainy season so it rains once or twice a day heavily with bright sunshine in between showers; however I think the canopy of the mango tree blocks a lot of the rain. Good breeze/airflow. The plants are potted in gravel/charcoal mix to deal with the frequent rain.

I think damp probably was an issue, because the plants were covered with a thick layer of dead leaves from the trees above, which kept everyone just way more damp and prevented airflow around the leaves. I have already tidied up the area and gotten rid of the dead leaves that were everywhere.
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Old 01-11-2016, 01:13 PM
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Sounds wonderful - how about sharing a picture of the growing area with some of the orchids one of these days! Not many of us are blessed to be able to have our plants out year round as you do.........enjoy!
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Old 01-11-2016, 06:35 PM
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Leaf spots

symptoms could be caused by either fungal or bacterial pathogens. The sunken tissue and yellow area, with no fungal fruiting bodies, suggest bacterial - likely Acidovorax.

Copper products will protect new tissue from either.
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