Possible disease on cattleyas

[SouthPark]

True. 4.6 mg per litre at first glance looks like a lot. It's all relative I guess! Will be interesting to see how much an orchid needs to get into it to stay healthy in general.

[rbarata]

Don't want to be wrong but I think I used a concentration of 5 ml MgSO4/l which is 5000 ppm (MgSO4). If my thoughts are correct, that's roughy 2.155 ppm Mg.

[Orchid Whisperer]

Epsom salts are much more cost-effective than commercial Cal-Mag products. The $30 cost for a single bottle of Cal-Mag supplent will get you a lifetime supply of Epsom salts at your local Pharmacy, plus either gypsum (CaSO4•2H2O) or calcium nitrate.

[ArronOB]

Ok, I’ve decided to concentrate on mineral deficiency as the issue, most probably magnesium.

I couldn’t find any Epson salts. We don’t live near shops and I am trying to get out of the habit of jumping in the car and driving for 30 minutes every time I need something. Thus I looked around to see what I already have and came up with this - Yates Trace Element Chelates.

The analysis is given as:

% w/v
Sulphur 0.53
Iron. 0.34
Magnesium 0.34
Zinc 0.34
Manganese 0.26
Boron 0.13
Copper 0.043
Molybdenum 0.005

The manganese is listed as being ‘as lignosulphate chelate’

Does this sound useful, or more importantly can it do any harm?

I intend to test it on the three affected plants if it’s harmless.

Cheers
Arron

[Roberta]

I don't know the toxicity of some of those components, but the fact that magnesium is in there at similar levels of sulfur, iron, and especially zinc and manganese, and not that much more than boron, would lead me to suspect that this brew could be very damaging. To get enough magnesium, the amount of some of those others that you would get seems to me to be potentially very toxic to orchids.

The potential magnesium deficiency in the plants is not an emergency... the Epsom salts can wait until the next time you go to the grocery store or pharmacy.

[Dollythehun]

Can you order online? Does Amazon ship to your area? I agree w Roberta, that sounds like quite a witches brew of chemicals.

[Orchid Whisperer]

Re: Yates supplement, all of the elements are essential plant nutrients, but I'm not sure whether the concentrations are OK, too high, or in a form that is available (Though the fact that they are chelated suggests the elements are plant available). Boron is problematic, it is an essential nutrient, but providing it can be tricky, providing too much can be harmful.

How were you planning to mix this up? What concentration of Mg were you planning to deliver in the solution of dissolved supplement?

The magnesium issue is not urgent, surely you will be going to a grocery store or pharmacy sometime in the next month or so and can pick up some plain Epsom salts?

[rbarata]

I would wait instead of risking killing the plants.

[ArronOB]

Yeah, ok, it can wait.

Cheeers
Arron

[ArronOB]

Originally Posted by rbarata

My Laelia tenebrosa also had this issue (same symptoms) and I assumed it was Mg deficiency.
Watered it with Epson salts and, while the leaves never recovered from those "stains", the new ones grow without it.
I was advised to never water with fertilizer and Epson salts together. I used them for a month, then one week without fert or salts, then resumed fertilization.

Some info here.

Did it have the same black spots on the underside of the leaf?