Start with the why does that plant get that disease? What is the soil the plant is growing in like? Is it a good, healthy soil that will grow strong and healthy plants that are better able to ward off disease pahtogens? Is the soil well endowed with organic matter and is it evenly moist but well drained? Prevention of any plant disease starts with the soil the plant is growing in.

perennialfan, one of the most overlooked step in IPM is to identify which plants are inherently susceptible to specific disease and/or insect problems and to avoid bringing them into the garden.

Unfortunately, your Rudbeckia is especially prone to septoria, and other leaf diseases, as well. This is your reality, no matter what the condition of the soil is. It's especially true now that this location has seen a bad outbreak.

However, there are some things you can do that might make a difference. Doing all you can to foster a healthy soil system IS important, of course. And hopefully, you did a good housekeeping job in the rubbeckia bed last year by removing all of the old mulch and fallen debris from the plants. Avoid over crowding and over-head watering, too.

You might want to research the possibility of 'disease resistant' hybrids, I don't if anything like that exists for Rudbeckia.

Good luck! Maybe last year was a fluke and with some good management practices you can have a nice display this year. It's one plant that is missing from my gardens (by choice), however.