"FarmI" be given wrote
I've sprayed my peach trees with home made Burgundy mix (a variant on
Bordeaux) and was wondering how long copper sprays have to be on the plant
to be effective?

We got a very light shower within 24 hours of application but I can
still see a light blue tinge around the bud edges and it doesn't look if
much, if any, got washed off.

Given this situation I began wondering about effectiveness and not one of
my gardening books, of which I have oodles, says anything useful about how
long copper sprays need to remain on the plant to be effective as a
fungicide. Anyone got any idea?


I think they just have to be there to be effective, they don't get into the
plant, just sit on the leaves and stop the fungus from doing its stuff.
Therefore they will not cure an existing problem just stop one from
happening.

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Regards
Bob Hobden