By Lane Tredway, Ph.D., technical services manager for Syngenta

Don’t wait until July or August to begin planning for Pythium. While that is the key time to prevent Pythium blight on cool-season grasses, other Pythium diseases can attack throughout the growing season. Many people think of Pythium as a single pathogen, but it is actually a group of diseases with unique symptoms and management strategies. Understanding the differences among Pythium diseases is essential to their diagnosis and effective management.

Three Pythium diseases are common in golf course turf:

• Pythium blight
• Pythium root rot
• Pythium root dysfunction

Their importance varies regionally and by grass species. Determining which Pythium diseases have the potential to develop in your turf is a critical first step in developing an effective disease management plan.

• Pythium blight is a foliar disease, most often caused by Pythium aphanidermatum in cool-season grasses. Bluegrasses and ryegrasses are most susceptible to Pythium blight, but bentgrasses and fescues can also be affected when conditions are highly favorable. The disease is stimulated by hot and humid weather, particularly when night temperatures are consistently above 68 F.
  On warm-season grasses, Pythium blight usually attacks in the fall, winter and spring when these grasses are stressed and growing slowly. The ultradwarf bermudagrasses are particularly susceptible to Pythium blight, and frequent outbreaks occur during periods of cool, cloudy and wet weather. Symptoms of Pythium blight on bermudagrass putting greens are often mistaken for leaf spot and, in fact, it is common for both diseases to develop at the same time. It is always best to submit a sample to a diagnostic lab before making a curative fungicide application.
• Pythium root rot has been one of the most frequent disease problems on putting greens over the last few years. This disease attacks the roots, crowns and other below-ground tissues and can result in rapid thinning or death of affected turf. All turf species can succumb to Pythium root rot, but it is most destructive to putting green turf. Pythium root rot can be caused by more than 20 Pythium species that collectively grow under a broad range of soil temperatures. As a result, Pythium root rot can occur virtually any time of year and a program approach is essential for effective management. Syngenta agronomic programs incorporate five unique chemistries to effectively prevent Pythium root rot and other diseases.

Pythium root rot symptoms on a creeping bentgrass putting green, Greensboro, N.C., 2010

• Pythium root dysfunction is a disease of creeping bentgrass putting greens that is mostly limited to Transition Zone climates. Newly constructed putting greens are most susceptible, with the disease becoming less severe as the greens mature over eight to 10 years. Three species of Pythium (aristosporum, arrhenomenes, volutum) have been shown to cause this disease. Infection of bentgrass roots occurs primarily in the fall and spring, causing the turf to be more prone to heat and drought stress during the summer.

Syngenta solutions for Pythium diseases

Syngenta offers an industry-leading portfolio of products for Pythium management:

• Appear^® II fungicide is a liquid formulation of a phosphonate fungicide that includes a turf-enhancing pigment and improved tank-mix compatibility. Appear II provides excellent prevention of Pythium blight and anthracnose, and can help to prevent Pythium root rot when tank mixed with Daconil^® Action™ fungicide as part of a comprehensive program.
• Daconil Action contains the plant activator Acibenzolar-S-methyl, which triggers natural defense responses in the turfgrass plant. Daconil Action has shown excellent activity against Pythium blight* when applied on a preventive basis, and provides suppression of Pythium root rot when tank mixed with Appear as part of an overall program.
  • The Daconil Action + Appear II Multipak, with 1.19 gal. of Daconil Action and 2 gal. of Appear II, offers 10% savings.
• Subdue Maxx^® fungicide can be used for management of Pythium diseases in turfgrasses. With preventive and curative activity against a broad range of root- and foliar-infecting Pythium species, Subdue Maxx is an effective foundation for any Pythium fungicide program.
• In addition to its excellent activity against brown patch, summer patch and other summer diseases, Heritage^® Action fungicide offers preventive activity against Pythium blight and Pythium root rot. Tank mixtures of Heritage Action and Segway^® fungicide SC have provided more effective and long-lasting control of Pythium root rot, compared to either product applied alone. Heritage Action is also an effective option for prevention of Pythium root dysfunction in creeping bentgrass putting greens.
  • The Daconil Action + Heritage Action Multipak, with 2.5 gal. of Daconil Action and two 1 lb. bottles of Heritage Action, offers 14% savings.

For more details on the diagnosis and management of Pythium diseases, as well as fungicide efficacy rankings, visit the Turfgrass Disease Identification Guide for Golf available at GreenCastOnline.com.

Pythium root rot control using a Syngenta agronomic program for agronomic program for Northern Transition Zone creeping bentgrass putting greens, NC State University, 2017

GCSAA Webinar Series - Myths and Misconceptions of Pythium Diseases in Turfgrass

Lane Tredway, Ph.D., Syngenta technical manager, debunks several misconceptions about Pythium diseases, such as the myth that Pythium is only a problem in cool-season turf. He also explores the differences between various Pythium diseases — such as root rot and root dysfunction — and the various fungicide and cultural practices superintendents can employ for effective Pythium management. Additionally, he focuses on disease diagnosis and fungicide resistance management. Watch the Myths and Misconceptions of Pythium Diseases in Turfgrass webinar (below) by Dr. Lane Tredway, and earn 0.1 GCSAA Education Points.

Note: After viewing the webinar, you must go to the GCSAA website and fill out the GCSAA external education affidavit to receive GCSAA Education Points.

Syngenta hereby disclaims any liability for Third Party websites referenced herein.

All photos are either the property of Syngenta or are used with permission.

© 2024 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. Action™, Appear^®, Daconil^®, GreenCast^®, Heritage^®, Subdue Maxx^® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are property of their respective third-party owners.