Kitchen Garden Forum

Hi,
I recently bought slaked lime and copper sulphate (I think it was) to make my own Bordeaux mixture as it's a fraction of the price of buying it ready made.

However, I found that it was not effective (tomatoes have had it ), probably because the copper sulphate had not dissolved properly. Can anyone advise me on the correct way to mix your own?
thanks

Hello Brenda
Copper sulphate is very soluble in water but hydrated lime is not so soluble. So this mixture will stay cloudy on mixing and you are really spraying a suspension. You will need to keep shaking your container as you spray to keep the mixture stirred up. I would suggest adding a wetting agent - washing-up liquid or shampoo will do but there are some liquids sold specially for this purpose. This will help the spray mixture to adhere to the foliage. Also make sure that the leaves are covered to run-off point - don't forget the underside.
This stuff and fungicides like Dithane are effective only while they are on the leaf surface where they prevent blight spores from forming. They will not control a blight infection that has already started. You need to spray when a blight problem is likely to occur but of course its pointless spraying in wet showery weather as everything just gets washed straight off the leaves. This can be a problem as blight is most likely during warm showery weather!

Hope this helps.

John