If the spray your using is a protectant like Captan ,Mancozeb, Sulfur
or bordeaux mixture the stuff needs to be there BEFORE it rains. It
prevents the fungus from starting. Mancozeb, for example, will not
kill an infection it only stops new ones so it needs to be on the leaf
prior to infection. It also spreads on the plant with rain. If your
using a systemic ( Nova) or Stroby ( Abound) there is "kick back"
depending on the stuff being used. BUT, It's ALWAYS better to have the
spray on the leaves before it rains no matter what.

Bob

or"Weez" > wrote in message >. ..
> I was just spraying all the fruit trees and vines in my yard this morning
> and was wondering if anyone knows why the instructions and orchard owners
> say it's best to spray before rain. Doesn't that defeat the purpose by
> washing it all away?
> Louise)
> Otterburn Park, Quebec,
> Canada