Copper Sulphate (CuSO4) Solution as a Fungiside ?

[SouthPark]

I haven't used phyton 27 before, but let me get this 'straight' heheh.

Do we first establish how many grams per litre of the substance is in the phyton 27? - such as 260 gram per litre - assuming 260 gram per litre of 'liquid' (in the phyton 27 bottle).

So if the mass per volume of this substance is Y = 260 g/L, and we need to get a 'concentration' down to say D = 0.8 gram per litre, and if we happen to have say 'W' litres of water that we're going to be using, such as 500 mL of fresh water (ie. W = 0.5 Litre), then the amount 'x' of Phyton 27 liquid that we should add to our fresh water could be calculated using:

x = (D.W)/(Y-D) ?

eg. x = (0.8 * 0.5)/(260 - 0.8) = 0.00154 litre (or 1.54 mL) ?

So adding approximately 1.5 mL of phyton 27 to 0.5 litre of water is ok, right?

UPDATE: ok - instead of gram per litre, we can go with the stated 21.36 percent active substance. So in 1 litre of phyton 27 liquid, we could say there's 213.6 mL of active substance. So will make Y = 213.6 mL/L. Then keep W = 0.5 L of the chosen amount of freshwater we're going to use. The desired or target concentration "D" for orchids could be say 0.3 percent of the phyton 27 concentration, ie. D = (0.3/100) * 213.6 = 0.6408 mL per litre. That is, D = 0.6408.

So x = (D.W)/(Y-D) = (0.6408 * 0.5)/(213.6 - 0.6408) = 0.001505 litre, or approx 1.5 mL.

Adding 1.5 mL of phyton 27 to 0.5 litre of freshwater should be workable.

[estación seca]

I have read in books by and been told by southern Florida Vanda growers that they must use preventive fungicides during their hot, humid summers. Fungicide availability varies from country to country. I might suggest talking to other orchid growers in your region to find out which fungi tend to give problems and which fungicides are useful. Not all fungicides kill all fungi, and not all fungi are susceptible to all fungicides.

[KennyS]

Since the copper sulfate pentahydrate is in powder form, calculating in grams is the easiest for me. Otherwise, you must first convert the mililiters to grams to know how much copper sulfate you need to add to get your stock solution.

The Phyton 27 label contains the following information:

Content Phyton 27 bottle (stock solution): 2.16 lb of copper sulfate per gallon.
Dosage: 15-40 fl.oz per 100 gallons.

This is equivalent to:
Content Phyton 27 bottle (stock solution): 258.5 grams of copper sulfate per 1 Liter.
Dosage: 1.17-3.12 milliliters per 1 Liter.

This results in a dilution of 0.12-0.31% and 0.30-0.81 grams of copper sulfate per 1 Liter.

The result is ultimately the same as your conclusion SouthPark.

[SouthPark]

Thanks for that cross-check KS! And thanks Ray! I found this thread very helpful!

[SouthPark]

One thing I noticed or thinking about is the active ingredient being copper sulphate pentahydrate. If assuming we have 1 L of phyton 27, then some online sources have gone through the workings to find that the copper sulphate content in copper sulphate pentahydrate is approximately 64 percent copper sulphate.

At the moment, I just assume the 213.6 gram per litre is that active ingredient (copper sulphate pentahydrate) listed in the specifications.

[Ray]

I think the important part is the elemental copper, which in copper sulfate pentahydrate, is 25.975%, making Physan 25.975% of 213.6 or 5.54%.

Whether copper sulfate, copper acetate, copper hydroxide, or whatever other copper compound is used, it's the copper concentration that's important.

[SouthPark]

Originally Posted by Ray

I think the important part is the elemental copper, which in copper sulfate pentahydrate, is 25.975%, making Physan 25.975% of 213.6 or 5.54%.

Whether copper sulfate, copper acetate, copper hydroxide, or whatever other copper compound is used, it's the copper concentration that's important.

Thanks Ray! That helps a lot. I'll keep that in mind about the copper content being most important here.

Some online work was done to find the copper content being that value you got ---- which was approx 25.45% copper in copper sulphate pentahydrate. That's very close to your value (as is the resulting 5.44 percent copper in phyton 27 liquid).

Based on percentage copper in phyton 27, the same formula can be used to get the amount of phyton 27 to add to 'W' litres of freshwater to make up an orchid-safe solution containing 0.3 percent of the 5.44 percent copper (ie. a final copper concentration of 0.01632 percent copper in orchid safe solution).

W = 0.5 litre of freshwater to be used for making orchid-safe copper solution (changeable value)
Y = copper concentration in phyton 27 = 5.44 % (fixed value)
D = desired orchid-safe copper concentration = 0.01632 % (normally fixed value)

x = (D.W)/(Y-D) = (0.01632 * 0.5) / (5.44 - 0.01632)

x = 0.0015 litre or 1.5 mL (of phyton 27 liquid to be added to 0.5 L of freshwater).

To make things really easy, the calculation just boils down to:

x = W * 0.003

With 'W' being the amount of freshwater we'll be using.

So if W = 2 litre of freshwater, then we have to add x = 0.006 L or 6 mL of phyton 27 to 2 litres of freshwater.