all I could find at the store today was Bonide Garden Dust that is .003% pyrethrins, 25.00% Sulfur, and 5.00% copper sulfate. I need copper sulfate for early blight control. is this the right amount of copper sulfate? or do I need a different concentration?
I don't know, since I don't use copper. Although copper and sulfur are commonly used to treat plant fungus, copper does not break down in the soil readily and is toxic to earthworms and many beneficial microorganisms. (e.g. long term use of copper based fungicides in orchards completely eradicated earthworms where copper levels in the soil were greater than 80 ppm Van Rhee 1963, 1975) As for Sulfur, it can burn foliage and make the soil too acidic-- it is used when people want to acidify their soil.