Pseudomonas?

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Mathias

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Hi all,

I would appreciate some input on what might have affected some of my Cattleya plants. I have something that attacks the new growths, starting with a small black sunken spot or brownish tinge on the new growth. This spreads until the whole leaf tip is black and then the whole leaf might die if severe enough. Sometimes it stops when half of the leaf is black. I have difficulties deciding on what it can be. I am considering Pseudomonas (Bacterial Brown Spot - Acidovorax), but then the older leaves should be affected as well. The other thing I am thinking of is false spider mites. However, I do not see any mites even with a x15 lens. Can they be too small to detect even with this magnification?


 

Stone

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Could be. But I've only seen it on my plants starting as a perfectly round water-soaked spot which spreads quite slowly (for me) and not very far. In paphs at least, you can see the infection spreading from the spot on the inside of the leaf when you hold it up to the light. So, it starts round then gradually becomes irregular.
This looks a bit like Black Rot (Pythium) a fungus which you can control with Banrot.
 

Ozpaph

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The bottom appearance is unusual with a multifocal pattern of disease. A bit unusual for bacterial or fungal infection.
 

Mathias

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Could be. But I've only seen it on my plants starting as a perfectly round water-soaked spot which spreads quite slowly (for me) and not very far. In paphs at least, you can see the infection spreading from the spot on the inside of the leaf when you hold it up to the light. So, it starts round then gradually becomes irregular.
This looks a bit like Black Rot (Pythium) a fungus which you can control with Banrot.
Thanks for the tip. But I thought Black rot was fatal. I have had this in my collection for a few months now and it only affects the new growths.

The bottom appearance is unusual with a multifocal pattern of disease. A bit unusual for bacterial or fungal infection.
Yes, I agree. That is why I am so confused. Can anythin viral give this pattern of disease?
 

Rick

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Have you tried any treatments so far?

I had similar looking issues with new growths on some new Catts in my collection. Since all the Catts in my collection come from auctions and gifts within our local society members, this condition looks very common based on the leaf quality of these plants I received.

I added some "Cichlid Sand" (equivalent to fine ground oyster shell) as a top dress, and fed a reduced potassium feed. (you might look up some of the threads on K-lite). I dumped some cinnamon on the affected growths/spots.

It didn't "cure" the older infected growths, but most of the rot was halted, and all new growths came up bigger, tougher, and shinier, and apparently resistant to what ever disease agent this might be.

So I rarely see this black spotting in plants grown in my collection, although it seems to be a common problem among the local growers in their collections.
 

Mathias

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Have you tried any treatments so far?

I had similar looking issues with new growths on some new Catts in my collection. Since all the Catts in my collection come from auctions and gifts within our local society members, this condition looks very common based on the leaf quality of these plants I received.

I added some "Cichlid Sand" (equivalent to fine ground oyster shell) as a top dress, and fed a reduced potassium feed. (you might look up some of the threads on K-lite). I dumped some cinnamon on the affected growths/spots.

It didn't "cure" the older infected growths, but most of the rot was halted, and all new growths came up bigger, tougher, and shinier, and apparently resistant to what ever disease agent this might be.

So I rarely see this black spotting in plants grown in my collection, although it seems to be a common problem among the local growers in their collections.
I have started a floramite/avid combined spray in order to halt/remove any false spider mites that might be behind it. However, I do not really think it is behind these disease patterns. I have also started to give some epsom salts to the plants. Other than that, nothing.

I have followed the K-lite threads with great interest and I am considering trying it on part of my collection. Right now I am using an organic fertilizer weakly at every watering. I add mussel shells to my paphs but maybe I should also add it to my Cattleyas?
 

Rick

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I have also started to give some epsom salts to the plants. Other than that, nothing.

I have followed the K-lite threads with great interest and I am considering trying it on part of my collection. Right now I am using an organic fertilizer weakly at every watering. I add mussel shells to my paphs but maybe I should also add it to my Cattleyas?
If you look at the last two tables I posted, you will see that pretty much all plants have a calcium requirement. And generally they need a lot more Ca than Mg. Whether or not they can tolerate high K varies under certain circumstances.

If you have really soft water, or use rain or RO water then you need to be careful of Mg overdose. Mg (and K for that matter) should only be supplied with an excess of calcium. Depending on how finely ground your mussel shells are, you may not be supplying enough easily available calcium.
 

Mathias

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If you look at the last two tables I posted, you will see that pretty much all plants have a calcium requirement. And generally they need a lot more Ca than Mg. Whether or not they can tolerate high K varies under certain circumstances.

If you have really soft water, or use rain or RO water then you need to be careful of Mg overdose. Mg (and K for that matter) should only be supplied with an excess of calcium. Depending on how finely ground your mussel shells are, you may not be supplying enough easily available calcium.
I only add a slight amount of epsom salts. I use rain water with approx. 10% added well water. My well water is rich in calsium (dH =17, Alkalinity = 420 mg HCO3/l), and the proportions of Mg and Ca is 19 mg/L Mg and 94 mg/L Ca according to a recent analysis.
 

Rick

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I only add a slight amount of epsom salts. I use rain water with approx. 10% added well water. My well water is rich in calsium (dH =17, Alkalinity = 420 mg HCO3/l), and the proportions of Mg and Ca is 19 mg/L Mg and 94 mg/L Ca according to a recent analysis.
Your well water is a pretty good base. I would consider going to a 20% well water with the rain water. The alkalinity is surprisingly higher than the hardness. Your collection may also benefit from a nitrogen source with a bit more ammonia if you are presently lopsided to nitrate.
 

Mathias

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I think I have found what caused the blackened new growths on my cattleyas. It was a calcium deficiency, which is sometimes called "blossom end rot" when dealing with vegetables (tomatoes etc.). Some pictures I have seen matches my plants perfectly. And my symtomes have almost dissapeared since I added well water to my rain- or osmosis water as well as adding a Cal-Mag supplemented fertilizer to my fertilizer regime.

One of the reasons for the deficiency was that I used an organic fertilizer which apparently was low in avaliable calcium.
 

eggshells

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I am not sure but as Rick has been preaching to us. That when K exceeds calcium concentrations in the leaves. It is more prone to erwinia attack.
 

Mathias

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Rick

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You can have leaf tissue damage from defficiencies and overdose without having invading disease.

The hard part about nutrition problems is to figure out if you have a deficiency or an excess, since the symptoms of K overdose are the same as Ca deficiency. (This is because excess K blocks the uptake of Ca, causing "deficiency" even when Ca is present).

What I've been seeing over the years, is that you can get a year or two of relief from K overdose, by increasing Ca as if it was deficient, but over time if the K is not reduced, the plant will keep sucking it up and you can never keep up with the apparent "Ca deficiency". Or you end up building up too much total salt in the potting mix and burn off all the roots.


So now is a good time to get that TDS meter, and start flushing those pots to keep total EC levels down.
 

Rick

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Does potatoe react like orchids??
Plants is plants, but potatoes have the highest K uptake requirements of all crop plants. They are a domesticated high turnover plant selected to make a ton of starchy tuber and then die back.

But their general metabolic requirements are really not that far off an orchid for just the foliage part.
 

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