First, I'd want to confirm exactly what the problem is. Rudbekia can be prone to fungal problems, especially if planted in crowded conditions or in areas of high humidity and with the occurrence of overhead watering. But it is certainly not a given. The cultivar 'Goldsturm' is also very prone to a bacterial leaf spot that may be prevalent regardless of cultural conditions. In this case, I'd consider removal and selection of less susceptible cultivar.

Both situations can be addressed with a copper based fungicide beginning in late spring before obvious symptoms occur but if truly a fungal issue, improving cultural conditions should eliminate any need for treatment.

Here is a link that might be useful: Rudbeckia leaf spot

Thanks, Gardengal. I don't know what cultivar I've got. Maybe I can research that but the leaves look exactly like the ones pictured in the link you sent me.
Jennie

I've been having the same problems on my BES plants for a few years now. The nice thing is it doesn't affect the flowering at all, just the leaves. I read that if you're dealing with this disease, unlike you would normally do, you should cut the plants back entirely to the ground in the fall. Clean up the area around the plants also to reduce the chance of this fungus carrying over to the following year. I think I'll try that this year and see what happens.

Mine self-sow, and in areas where they are too crowded the foliage can turn grey and the plants die. It's not a fungus that appears in spots, though, in my case it's powdery mildew that effects the plants/leaves more as a whole.

Keeping them well spaced seems to be the key, and contrary to what we normally assume, keeping them well-watered really seems to help prevent mildew.

Some years back I had a large & expanding clump (6 ft long by 4 ft wide) of BES (pass me down plants - no cultivar name) that started getting black leaves. Plants had been in the same spot for 4-5 years. The black mold didn't seem to bother the blooms, wintering over, or the spreading tendancy of the BES, just very unsightly. After 3 or 4 years of this I finally had enough and dug everything out. This was a big job & I remember the plants laying around on the nearby grass as I dug & dug.

The next year I had BES everywhere - in every bed, next to every shrub, grass, & tree, mixed into my Pink Turtlehead -but no mold/mildew/fungus anywhere! Prior to this I had never had a single seedling anywhere.

Since then the BES have spread & grown. I pull them out where & whenever I find them, let them grow any place I like, & yank them in full bloom if the color seems to glaringly wrong. I have a full garden, mulch heavily and seldom have much seeding of anything, but I must have spread the BES seed into every nook and cranny.

I will never be rid of them, not that I completely want to be, & I haven't actually tried hard to get rid of them, just control them somewhat. Once in awhile they even arrange themselves quite nicely all by themselves.

So beware - if you dig them up, be careful, and don't do it on a windy day, with seed already set & raring to go .....everywhere.

BES wasn't part of the plan. If you look hard you can still see the Turtleheads behind them. Picture is from 9/3/04 in the back yard the season after I removed ALL the BES (they were in the side yard). Since then I have removed the sedums behind the bench (too many bees) and let the BES have that space back as far as they want to go toward the tree, but have to shovel prune then to give the turtles and daylilies & little shrubs their space.

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Beautiful, leslie!

My original BES looks like this:

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But many of the seedlings look like this:

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Hard to believe they are such close relatives.

Diggingthedirt,

All my BES seedlings have been exactly the same, & as far as I can tell, exactly the same as the original no-name plants. Too bad! I really like that orange flower and I am one of the few gardeners, it sometimes seems on the forums here, who uses a lot of orange in my gardens.

Funny thing is I don't really like orange with reds & yellows in the hot combos you see in books. And although I like orange fine with just yellow, I really prefer it with deep blue-purple, dark foliages, dark russets (a sort of dark red orange I guess), & bronzy-green foliages. My favorite combos though are oranges with blue-greens & silvers. I think I'll go out and buy some orange annuals for the fall! Thanks for posting the pictures.

I finally know why my BES get black leaves -its just been the past 3 years and I have had them for 20 years- I will try cutting them down to the bone this fall if that doesnt help I will try the fugicide-thanks

I have black spots all over one BES. This article came up that was written in 2011 which states it is not a fungus but a beetle. I included the link. I am going to do what she says and use an insecticide for beetles and cut off the black spotted leaves.

Here is a link that might be useful: Beetle