Quince Rust Remediation on Hawthorn Tree near Pond
I am in need a a treatment regimen for an washington hawthorn tree in our front flower bed that sits about 12 feet from a 300 gallon pond containing Koi and Shibunkin. I first noticed the rust this afternoon, in full display with 3 to 6 mm spores, when trimming the tree along our walkway. I realize that any treatment will have to wait until next spring and I am looking for something that will carry the least risk for the fish and frogs in the pond. In the meantime I am pruning away the worst of the fungal infection. Thank You for any assistance you can offer.
Rust (Cedar/quince, Cedar/apple, Cedar/hawthorn) is a common problem in our area, and one that we generally don't recommend treating.
It does not kill the tree, and you have probably had it for a while but only noticed because you were pruning.
If you feel you need to treat, and the tree is small enough, you could use a copper fungicide in early spring as the leaves are expanding, according to label instructions.
It should be o.k for the pond, put try to avoid the spray drifting there.