06/01/2026
Summer is upon us, and with it is a good time to talk about typical summer root dysfunction diseases. Unlike the foliar diseases covered in Parts 1 and 2, Pythium Blight and Summer Patch attack below the surface. There are no distinct blade-level symptoms to identify — damaged roots simply cause the above-ground tissue to yellow and decline.
Summer Patch
Summer patch creates the classic "frog eye" pattern — circular rings of dead or declining turf that become visible during summer heat. The root damage, however, occurs in early spring while soil temperatures are still cool. Treatment must happen in early April before that damage is done. By May it's too late — the heat simply exposes what already happened underground. Azoxystrobin and propiconazole applied together in early spring are effective.
Pythium Blight
Pythium presents in low-lying areas, ditches, ravines, and anywhere water naturally travels or pools. While the roots are what is primarily damaged, there are surface-level visual cues — a gray smoke ring around the affected area indicates active fungal spread, and white cottony mycelium accumulates along that border overnight, most visible in the early morning. Azoxystrobin or mefenoxam are effective, though residual is shorter than most fungicide applications — overwatering accelerates leaching.
Cultural Prevention
Both diseases can be alleviated by annual aeration and improving drainage in low spots to reduce the conditions both diseases depend on. Water in the morning and avoid overwatering, particularly in areas that already struggle with drainage.
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