Phostrol fungicide for downy mildew nightmare

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wood1954

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So i followed the manufacters label and used 5 oz of product per gallon erring on the safe side as the label says the high level is 8 oz per gallon. The Texas A&M site says .64 oz per gallon is safe, as does Penn State, sure wish i had done more research before i sprayed. I will probably lose 50% of my foliage. Maybe the label is a typo? Almost all plants on their label are recommended to mix 2.5-5 pints per 100 gallons, grapes and a couple other fruits were 2.5-5 pints per 10 gallons. Well nothing to do about it but go have dinner and a glass of wine. Penn state did see leaf burn on Chardonnay, my Itascas didn't burn as much as my Marquette. Just wanted to let others know about this.
 
Sorry to hear about the damage to the foilage. I use a similar phosphorus acid mix also. I like to use it during the summer tank mixed with captan to both lower the pH and provide some downey mildew protection.

Maybe the label is a typo?

Not likely. The label is heavily scrutinized and also a legal statement that they would be sued for damages over if there were a typo.

2.5-5 pints per 10 gallons

I pulled up the label. It is 2.5-5 pints and "Apply in a minimum of 10 gallons of water per acre."

Grapes are sensitive at over 0.5% mixture of phosphorus acid. This is why the 0.64oz per gallon rate is there. Damage is seen at a 1% rate.

You've already found some resources out there. Here is a free and nice guide offered by Purdue that is quite comprehensive.
https://ag.purdue.edu/hla/Hort/Documents/ID-465.pdf
 

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