The following question was sent to the P&PDL diagnosticians here at Purdue University:
Question: Could you please discuss stripe smut and red thread and how to get rid of it?
Answer: Stripe smut infected plants become pale green or yellow during the spring and fall. Closer inspection reveals narrow yellow-green streaks running parallel to the veination and these streaks quickly turn silver to grey. These streaks are the fruiting bodies of the fungus just under the surface of the leaf. As these fruiting structure expand the leaf surface ruptures releasing black dusty spores. The leaves quickly turn brown, split and shred and looks fairly similar to grass mowed by an extremely dull mower.
Stripe smut is far less common than red thread primarily because improved cultivars are generally resistant to this disease. Thus the best control for a serious stripe smut problem is renovation with resistant cultivars. Check with your local county extension agent or Michigan State University for cultivars recommended in your area.
If a fungicide application is warranted, a single application of a sterol inhibiting fungicide in spring or early fall should help control smut. Stripe smut tends to be a high nitrogen disease whereas red thread is a low N disease and so it is rare that both of these diseases will be seen on the same lawn, thus have the presence of these diseases confirmed prior to initiating any control measures.