Jared Hoyle mentioned that he has been getting some questions on Pythium root rot, and last week, our neighbor to the east Dr. Lee Miller at University of Missouri wrote in a great post (click HERE) that he has already seen some Pythium root rot samples from putting greens with all the wet conditions. Even in the absence of Pythium in the roots, heavy rains in spring = poor root growth = turf more likely to crash and burn when summer conditions kick in. Add Pythium and that can make it even worse. In his article, Dr. Miller also provided a caution that some of the materials superintendents apply in spring such as pre-emergent herbicides, DMI fungicides, and PGRs could be limiting root growth in spring and setting up the grass for more problems. His comment is observational from comments from superintendents but is definitely interesting and as he states, probably some research is needed.
In another excellent recent post from NCSU, Lee Butler provided some specific tips about management:
“We currently recommend that everyone start their Pythium root rot prevention program off with Segway due to it being very good in our trials over the past couple of years, even at the 0.45 oz/M rate. At the 0.45 oz/M rate, you can apply Segway 6 times instead of 3 according to the label, so you will want to rotate that in with other products like Subdue, Banol, Stellar, Appear, or Signature (in no particular order). For more information about Pythium root rot, click here. Any decent Pythium fungicide such as Subdue, Segway, Banol, Stellar, Appear, or Signature (in no particular order) should do a nice job of preventing this disease. You will likely have to make repeat applications every couple of weeks until the weather changes. Rotate through the different chemistries to help with resistance management.”
Finally, don’t forget that Pythium root rot is distinct from Pythium foliar blight. The foliar (cottony) blight is actually quite rare on putting greens. Foliar Pythium is definitely linked to warmer conditions, with nighttime lows > 68. For fungicide information on foliar Pythium, you can view the table HERE from U of Kentucky (scroll to p 17).
