The symptoms are most apparent when temperatures are above 32 C. Multiple pythium species have been associated with the disease including Pythium arrhenomanes and P. aristosporum(1), and P. aristosporum(2). Recently, researchers at North Carolina State University (3) have recently reported that Pythium volutum is a casual agent of Pythium root dysfunction.
It appears the P. volutum infects creeping bentgrass roots during the spring and fall when temperatures are between 12 and 24C. Symptoms do not express themselves until the warmer summer temperatures occur when the pathogens disruption of water and nutrient uptake activity of the root system becomes apparent.
Pythium root dysfunction can occur on new creeping bentgrass greens as soon as 3 months after establishment and on greens up to 8-years of age. Currently all creeping bentgrass cultivars are potentially susceptible to this disease. Fungicides for controlling Pythium root dysfunction, at least with P. volutum, are contradictory to what one might think.
The traditional pythium fungicides do not control Pythium root dysfunction, nor do the Take-all patch fungicides. If you observe disease symptoms on your creeping bentgrass greens that appear to be Take-all patch, but control measures are not effective - it might be worth having a sample checked for Pythium root dysfunction.
1. Hodges, C.F. and L.W. Coleman. 1985. Pythium-induced root dysfunction of secondary roots of Agrostis palustris. Plant Disease 69:336-340.
2. Feng, Y. and P.H. Dernoeden. Pythium species associated with root dysfunction of creeping bentgrass in Maryland. Plant Disease 83: 516-520.
3. Kerns, J.P. and L.P. Treadway. 2007. First report of pythium root dysfunction of creeping bentgrass caused by Pythium volutum in North Carolina. Plant Disease 91:632.