How long does it have to be dry for dormant spray to be effective? This is standard lime sulfur and/or spray oil.
Those of you local will understand the reason for the question; its amazing how creative the weather forecasters are getting in coming up with graphics to indicate the different amounts of rain per day - can't have a seven day forecast looking all the same.
Thanks much
I usualy wait to put my dormant spray on until the trees are beginning to break dormancy. The lime sulfur has more effect that way, and the oil is still effective against overwintering pests. For apples and pears, for example, we put our first delayed dormant spray on between bud stage 4-5. The down side is that you may be out there more days as the trees break dormancy at different times. Our pears are often sprayed 2 weeks earlier than our apples. But we have very few mildew problems this way.
tlb:
"How long does it have to be dry for dormant spray to be effective?" - "Those of you local will understand the reason for the question"
You've got me smiling here... With "lime sulfur and/or spray oil" (the same combination I use) - my 'guess' is the-longer-the-better! I assume the sulfur 'burns' the offending lichens / mosses, and the oil smothers the hibernating crawlers? I figure - the dryer it stays - the more gets adsorbed...
Maybe we'll get a dry stretch pretty soon..? We're sure owed one! 'My question' has always been: the instructions tell you to spray with "dry and increasingly warm temperatures"... That isn't how it happens - the dryer - the colder! Maybe that's their way of dodging responsibility if it 'doesn't work?' "Well, it got colder, not warmer..." I've read that extreme cold might 'drive it' into the plant. --- I don't know that I've ever witnessed such extreme cold around here (Willamette / Tualatin Valley), and know I've never detected any damage from this combination of spray - though I've also read 'we' shouldn't 'mix it' like that 
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I'd watch for some dry stuff - they seem to be able to predict dry and cold real well - then hit 'em good!
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