Copper sulphate, bordeaux mixture and the curse of the mildew

mildew blighted grape vines

My mildew blighted grape vines

I’ve got mildew. Not me personally of course, but my grape vines. It was shaping up to be a bumper year for grapes with all the rain that we have had. However that has turned out to be the problem.

The moisture in the air has resulted in mildew on the vines. Initially I thought I might be able to avoid spraying it but the rain has persisted and the mildew is getting worse. Unfortunately it has damaged the early grapes on one vine and I will have to take some action to prevent the other vine going the same way.

But what to do? I know about Bordeaux mixture to treat fungal infections on grape vines but I have been unable to find the copper sulphate needed to make the mix. All the gardening books say it should be available in garden centres. But here in Victoria it isn’t. All I could find was other commercial copper fungicides and if you are an organic gardener you can understand my reluctance to use them.

However it turns out that is readily available in stock/horse feed stores to treat copper deficiency. So tomorrow I will be heading down to buy some. Otherwise I’ll have no grapes left to eat.

2 Responses to “Copper sulphate, bordeaux mixture and the curse of the mildew”

  1. Keith Lofthouse says:

    I had no trouble at all getting Copper Sulphate in a 25kg bag from Farm Supplies, Stawell, so it is available even if, surprisingly, it did come from Taiwan! I too plan to use it to spray on my grapes this year after my bumper crop was ruined last year. A local wine-grower advised me to use the CS but did not mention the bordeaux mixutre. It may not be necessary, but I am checking with him.

  2. Matt says:

    Hi Keith,

    Thanks for your reply. I eventually found the copper sulphate from a stock feed supplier also.

    I think the addition of the lime in the Bordeaux mixture helps it adhere to the leaves.


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