With the Iowa temperatures expected to continue in the upper 90’s with high humidity for the foreseeable future, it presents conditions conducive to Pythium blight activity. Pythium is known as one of the most destructive turf diseases in the Midwest and overnight it can lead to large turf death. With most turf managers fungicide programs winding down for the year; it might be the time to have a bottle of Cyazofamid (Segway®) handy for a knockdown contact application.
Pythium is a high temperature disease which presents the most damage under daytime temps in excess of 86⁰F, followed by nights in the high 60's. It usually affects close-mown turfgrass under intense management. Symptoms generally include small circular patches (1-2 inches) accompanied with a cotton-like mycelia that appears in the early morning. Pythium is often first noticed on sites with poor drainage. It is also easily spread by mechanical means and can be carried over turf by foot traffic and/or mowing equipment. Reducing your nitrogen fertility inputs, avoiding night watering, increasing air movement, and improving areas with poor drainage reduces your threat for disease incidence.
Below are some pictures of the cotton-like mycelia seen in the early morning.