Roses
Q.

Black spot on roses

Zone Zone 5 | Jsutherland added on June 12, 2016 | Answered

Can roses become resistant to fungicide macozeb?

A.
A.Answers to this queston: Add Answer
roseman
Answered on June 19, 2016

I suppose it is possible that the black spot fungus could become resistant after years and years of heavy use. I have not seen that yet though. One thing to keep in mind here. Even after the black spot fungus has been killed, the marks it leaves on the foliage will not disappear. Those marks are there for the life of each leaf. However the new foliage coming forth should be free of the black spot if the fungus has been killed. The mancozeb leaves a yellowish powdery residue on the foliage and that is part of how it works. Trying to wash that off or lessening it can effect how well it works. In some cases folks will mix the mancozeb and some Immunox together in the same spray tank for spraying on the roses as this does lessen the yellowish powdery residue it leaves. This can work well but may hinder how well the mancozeb will work in severe cases.

00
Was this answer useful?

Log in or sign up to help answer this question.
Did you find this helpful? Share it with your friends!

You must be logged into your account to answer a question.

If you don't have an account sign up for an account now.

Looking for more?
here are more questions about...
Roses
Join Us - Sign up to get all the latest gardening tips!

Do you know a lot about gardening?
Become a GKH Gardening Expert

Learn More