It's hard to predict the risk of infection any given year, since a lot of the virulence depends on weather patterns. Several rust diseases, including the one that affects Ironweed and other Aster-family plants, use another unrelated host plant for part of their life cycle. Therefore, the rust fungus needs to move between them at different times of year to survive. The alternate host for the Ironweed-infecting type of rust is either pine trees or grasses, neither of which it would be practical to try to remove from the area so they don't harbor the disease.

Fortunately, Ironweeds tend to tolerate mild rust infections well, and some species or cultivars may be more resistant than others. For example, Mt. Cuba Center (a native plant public garden in Delaware) found that some Ironweeds in a recent multi-year variety trial were more vulnerable to contracting rust when they were drought-stressed in the trial garden compared to those of the same species in a natural site with more soil moisture, where the plants weren't as stressed.

If the plants aren't too much of an eyesore or aren't dying back or weakening too much due to recurring rust infections, there is no need to replace them. They can still serve pollinators if they bloom (and birds if they produce seeds). Otherwise, a different Ironweed species or variety might perform better if it has less susceptibility to rust.

Miri