Jim Kerns, Ph.D., turfgrass pathologist in the Department of Plant Pathology at North Carolina State University, discussed the current state of Pythium research.
What have you seen with Pythium in the field?
Pythium is a generic term for many different diseases. The three types of Pythium diseases that are commonly observed are Pythium blight, Pythium root rot and Pythium root dysfunction. Although all of these are caused by a Pythium species, they are three distinct diseases and should be treated as such.
What are you seeing in the lab?
Right now we have not seen much in the lab. We saw Pythium blight on the ultradwarf bermudagrasses such as Champion and Mini-Verde earlier this spring. As for creeping bentgrass, we have seen very little Pythium activity in the foliage or roots. We have had plenty of moisture in the southeast, but it has not been stressful yet. I suspect that many parts of the country have had little Pythium problems. We most certainly have not seen tremendous Pythium activity yet.
How can a superintendent diagnose the problem?
I always suggest sending a sample to a lab for diagnosis of Pythium diseases. These organisms can cause issues rapidly and without appropriate diagnosis all of these diseases can be challenging to manage.
What actions should they take to begin the fight against Pythium once it arrives?
For Pythium blight: Limit N applications.
For preventive management: Segway, Subdue MAXX, Stellar, Banol, Signature, Appear and Daconil Action can be effective against this disease. Pythium blight is typically more prevalent on areas with native soil. On sand-based putting greens this disease is fairly uncommon.
To deal with Pythium root rot: Increase mowing height, alternate mowing and rolling and stay on top of spoon-feeding programs. Preventive applications of Signature, Subdue MAXX or Segway have proven effective for preventative management of PRR. However, it is important to note that almost no efficacy data exists for this disease. This is a troubling disease because our diagnostic lab has received 1,260 creeping bentgrass samples since 2008 and 17 percent of those were diagnosed with PRR. This is a common disease during stressful conditions with very little research backing up management recommendations. Another suggestion that has shown effectiveness at various golf courses is a tank mixture of Segway with Insignia.
As for curative applications for PRR: High rates of Segway or Terrazole. To our knowledge, nothing else has proven effective.
To fight Pythium root dysfunction: Initiate applications of either Insignia, Segway Heritage or a tank mixture of Signature/Banol when soil temperatures reach 55 to 65 F in the spring or fall. For minor cases, two or three applications one month after the initial application in the spring should suffice. For severe cases, another two or three applications may be warranted in the fall.
How long should it take to see some results?
For fungicides, typically it takes three to four days for a visible effect to be realized. Since these can be damaging diseases, I would closely evaluate the affected areas each day. This will let you know if you are seeing any effects from your management strategies.
Are there preventive steps that can be taken to avoid future bouts with Pythium?
Make sure you have the disease formally diagnosed at your location. Nothing can be done if you do not know what disease you are dealing with. Pythium species love water, so anything that addresses drainage will help. Even if major renovations are not affordable, things like venting or topdressing will help with all three of these diseases. Of course, after knowing what disease you are dealing with, contact your local turfgrass pathologist or extension specialist to help develop a preventative fungicide program.
Any other advice you can provide?
The only advice I can provide is if you suspect a Pythium issue have it diagnosed! We see many confused cases, especially concerning Pythium root rot and Pythium root dysfunction. They are not the same disease and the fungicides that control these diseases are widely different. Let us help you fight these organisms more effectively.