Die back on Little Bluestem

Question: I have a large planting of Little Bluestem. Most are thriving but a few patches are turning reddish brown and dying back. Any thoughts on what might be causing this? Plants are in full sun.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 17, 2023, 4:24 PM EDT
response: More information can help us narrow-down a potential diagnosis but we can also consult with our plant pathologist as soon as he returns from an out-of-state horticulture conference. (It may be a few days but we'll reply as soon as we have feedback.)  You can look for indications of diseases like Southern Blight (like its characteristic spore capsules) since this fungus affects a very wide variety of plants and thrives in hot, humid weather. Is the planting being irrigated regularly or does it receive surplus water by way of a nearby roof downspout outlet?  If you tug on the foliage of some dead-looking plants, do they pull up easily or do they still feel firmly rooted? If you dig one up, are its roots mushy and dark (or do they have blackened blotchy areas) or firmer and light-colored (tan-white or light brown)? Are there a number of grubs under its root ball?  About when did the symptoms begin, in recent days/weeks or gradually a month or more ago? Was any pesticide (for insects, disease, or weeds) or fertilizer applied to that planting bed before the symptoms appeared?  Do you see any lesions on the dying (not totally dead) grass blades? If so, can you share close-up photos?  Miri

responder: The Question Asker Replied July 17, 2023, 4:47 PM EDT
response: Miri: Thank you for the prompt response. I will look into the questions you raise and get back to you. One thing I do know is that the affected area receives surplus water by way of a nearby roof downspout outlet. Could that be triggering (or permitting) to the development of southern blight spores?   Christopher

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 19, 2023, 11:43 AM EDT
response: Hello Christopher,  Our plant pathologist is concerned this might be Southern Blight or a type of root/crown rot. Yes, the added influx of water (during rainy weather at least) from a roof downspout might be contributing to the plants' vulnerability to those diseases as Little Bluestem (and most ornamental grasses) thrive in drier rather than wetter conditions. There is no treatment or cure for any of the above pathogens but if you think the issue might repeat itself (and if the drainage can't be redirected elsewhere) then it may be worth replacing the dead plants with other species more tolerant of occasionally-damp soil. Feel free to let us know what you find if removing any of the affected plants in terms of root conditions or other symptoms.  For a grass-like look, if that is your preference, options include rushes (genus Juncus) and sedges (Carex), of which there are several native species. Regarding Carex, there is a recently-published pamphlet from Mt. Cuba Center (a native plant public garden in Delaware) highlighting the results from trial plantings to see which species perform best in certain circumstances.  If replacement plants don't need to be grassy, there are a number of native perennials that will do well in semi-wet conditions, especially if the site receives full sun.  Miri