Damaged black eyed Susan’s, and what to do about it - Ask Extension
It’s been a banner year with tons of plants and they’re starting to bloom. But one plant, away from most of the other black eyed Susan’s, but in...
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Damaged black eyed Susan’s, and what to do about it #662121
Asked July 09, 2020, 5:44 PM EDT
It’s been a banner year with tons of plants and they’re starting to bloom. But one plant, away from most of the other black eyed Susan’s, but in a tight clump of three other plants. The other plants are fine. But this one died looking pretty ugly. It went fast, maybe two days. The two photos that aren’t just the leaf show what it looked like. The white powdery stuff was only at the very bottom of the stem, near the roots. But it drooped yesterday, we watered it (though I’m pretty sure That wasn’t the problem. We pulled it up by the roots and stuck it in the trash.
The one picture attached that’s just of the leaf, shows the other plants that other than that slight discoloring of the leaves seem to be doing great.
What do you think the problem is? And is there anything I should do with the remaining plants ( that are about 2 feet away.)
Thanks
Montgomery County Maryland
Expert Response
The plant with the wilting symptom and white mycelial growth appears to have Southern blight. This is caused by a fungus, Sclerotium rolfsii. This fungus can attack probably all herbaceous perennials and is favored by hot weather. It generally causes the top of the plant to collapse with quite visible fine white mycelia and mustard seed-like fruiting bodies on the stem and at the base of the plants. Oxalic acid is released and girdles the tissue (causing wilting) but it does not kill the roots.
You took the correct action by removing the plant material and placing it in the trash (rather than compost). Minimize the use of deep mulch and keep mulch away from the stems of the plants. Here is more about Southern blight prevention: https://extension.umd.edu/hgic/topics/southern-blight
There are two primary diseases that cause black-eyed Susan leaves to get black
You took the correct action by removing the plant material and placing it in the trash (rather than compost). Minimize the use of deep mulch and keep mulch away from the stems of the plants. Here is more about Southern blight prevention: https://extension.umd.edu/hgic/topics/southern-blight
There are two primary diseases that cause black-eyed Susan leaves to get black
spots that progress to black blotches and sometimes totally blackened leaves: Septoria leaf spot and angular leaf spot. Plants are not usually killed, but can die back to the base. To manage these diseases, do not water overhead. Keep plants thinned so they have good air circulation and dry quickly after rains. At the end of the season (or earlier is the plants look dead), remove all infected plant material and discard in the trash so that infected material will not reinfect plants next year.
Some types of Rudbeckia (R. fulgida 'Goldsturm' especially) are more susceptible to leaf spot diseases than others.
Christa
Christa
Thanks, this seems to be what the problem is.
We've had issues with that small spot for a number of years. We even managed to kill mint, which I didn't think was possible. I'm guessing that might have been the issue.
As I said, it's only a small spot (1&1/2 square?) in an otherwise fine garden bed. I didn't originally make the bed, it was done by the builder ages ago though we've amended it with mulch and stuff over the years.
Should I pull out that soil around there to prevent it going forward? If yes, how deep should I go and is there anything else I should be aware of for that? If not, how do I get rid of it going forward?
Thanks.
Michaela
PS I thought I posted this reply already, but I don't see it. If this is redundant, please excuse the operator error
We've had issues with that small spot for a number of years. We even managed to kill mint, which I didn't think was possible. I'm guessing that might have been the issue.
As I said, it's only a small spot (1&1/2 square?) in an otherwise fine garden bed. I didn't originally make the bed, it was done by the builder ages ago though we've amended it with mulch and stuff over the years.
Should I pull out that soil around there to prevent it going forward? If yes, how deep should I go and is there anything else I should be aware of for that? If not, how do I get rid of it going forward?
Thanks.
Michaela
PS I thought I posted this reply already, but I don't see it. If this is redundant, please excuse the operator error
For the southern blight, removal of the top few inches of soil should eliminate most of or enough of the inoculating spores. You can replace it with topsoil or compost and mix that into the remaining soil in that location. The only other approach going forward is to monitor for the renewed appearance of plant symptoms or signs of fungus. As mentioned earlier, minimally persistent soil-surface moisture and good air circulation are general preventative conditions for fungus control.
Miri
Miri
