I am just about out of my current copper spray, and thought I would check in with folks here to see what they think works best.
I have been using copper diammonia diacetate (Southern Ag brand), it is listed for fire blight but prevention has not been stellar. It seems one can also use copper hydroxide (Kocide, etc), and that straight copper sulfate is listed and used as well.
Any advantages/disadvantages to any of these?
The copper sufate sound interesting only in that I already have a bunch and would just need to find the right dilution for the spray.
You might find this old post helpful Generic Copper Spray
Thanks @clarkinks. That was a useful link with some good prices on Kocide.
But I didn’t see much discussion of which type of Cu was best. Everyone seems to be talking as though Kocide/copper hydroxide is the way to go. Is that right? does it make that much diff? Would the copper sulfate solutions be as good?
Like you Steve I would have thought copper was copper but to many people say otherwise and say the kocide3000 is worth the money.
Copper sulfate is much more soluble than copper hydroxide which creates several problems. With copper sulfate, most of the copper ions hit the plant material quickly and may burn the tissue. Also, they are short lived and may be gone before they are needed.
A better option is a fixed copper like Kocide. The copper ions are released more slowly so they are less likely to to be phytotoxic and the biocide qualities of the copper continue for a longer time period.
The addition of lime to copper sulfate makes Bordeaux mix which is said to be safer than straight copper sulfate but I’m not sure it is safer.
The Penn State article below provides the perfect explanation: