You might post on the Roses Forum.
There are many helpful & knowledgeable people there.
Best luck!

sylvia

Some gardeners will disagree, but you don't necessarily have to cut them all out. There are several species of canker fungi that may behave differently, and the weather affects their behavior. But often, small cankers are self-limiting and will eventually produce only a spot of dead bark, which the rose may be able to regenerate if the cane isn't girdled. The rule of thumb in old rose books is to cut below them if they cover over half the girth of a cane-- not to cut automatically.

Although active cankers produce spores, these don't readily infect canes once the weather warms up. All are cool-weather, wet-weather critters. They aren't going to gallop through the garden all summer.

In the upper South and Mid-Atlantic, we'll have some springs when canker does a lot of damage. Ruthless pruning won't stop it, and it isn't likely to kill established plants if there is no pruning.

You might consider discarding plants which are particularly susceptible.

If you are considering dormant treatment, copper is probably effective against a wider range of cankers than is lime sulfur. Be careful with copper, however, as it is somewhat hazardous. A dormant-strength spray of Wilt Pruf or other anti-transpirant might help, but this hasn't been checked in trials.