Re: Bordeaux mixture
Doxiadis/Malefakis wrote:
>
> Does everyone agree with Moira that Bordeaux mixture is obsolete? It's
> quite a security blanket for us Mediterraenean primitive types....
Cali
What has mainly rendered it no-go in NZ is that we can no longer get the
cheap bluestone (copper sulphate) which is of course one of the main
ingredients. All one can buy nowadays is a very expensive chemically
pure form.
In fact I can't say I miss it. It was a bore to make and I reckon the
easily-obtained and sprayed copper hydroxide is just as effective. Its
only disadvantage is that it forms a fine suspension in water rather
than dissolving, so one needs to shake the sprayer occasionally when
applying it to keep it evenly mixed.
I read many years ago that bordeaux mix was a chance discovery, or
rather the combination of chemicals was. It seems grape growers in
France were much troubled by little boys pinching the berries from the
outer rows in the vinyard. To make the fruit unattractive the growers
tried applying various things among them limewash and copper sulphate.
Then they noticed to their supprise this mixture not only deterred the
boys it actually kept off the dreaded downy mildew. It must have taken a
fair bit of experimenting though to get from this rough type of
application to the final mixture.
One should in any case be sparing with any type of copper spray, as
where it falls on the ground it can become sufficiently concentrated to
poison worms. I don't think most of us realise how much of any spray we
apply to plants does get on to the ground. I never thought of it myself
until one occasion when we were spraying an apple tree with lime sulphur
and I had a some delicate plants around the tree I wanted to protect.
Anyway we put down a big sheet of plastic before spraying and when we
had finished it was awash. I am sure much more spray had gone on the
ground than ever had hit the plant.
Actually, we ourselves use very few even of the safer chemical sprays
nowadays, depending as far as possible on the protective action of
compost tea and similar natural remedies, though we still have no
effective organic answer to downy mildew and rusts..
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand. (on the "Ring of Fire" in the SW Pacific).
Lat. 41:16S Long. 174:58E. Climate: Mediterranean/Temperate
