The N.C. State Turfgrass Field Day is one of the best learning opportunities in the country for anyone in the turfgrass industry. This year, Dr. Jim Kerns, Lee Butler, Brandi Merrick, Dr. Joe Roberts and others talked about strategies and programs for disease management. It was great to see the results of their research and learn from their experiences.
In my travels, I frequently discuss disease management with superintendents and I often learn that they are not using the most effective fungicides or management strategies. Let’s be clear, diseases like pythium root rot can ruin your season. Disease prevention and management may be the difference between a great year and one you’d like to forget.
Overall, this has been a good bentgrass year in the Southeast. With relatively cool weather until July and multiple effective root pythium fungicides on the market – e.g., Serata, Segway and Banol – most bentgrass growers are in a decent place. If you are managing creeping bentgrass, finish the summer strong with these fundamental strategies. If you are like most golf courses in the Southeast with ultradwarf bermudagrass putting greens, start thinking – and hopefully continue to think – about upcoming winter dormancy.
Soilborne pathogens like take-all root rot (TARR), spring dead spot and pythium root rot are all concerns, especially heading into winter. The most critical time for soilborne disease management of ultradwarfs is between August 1 and November 15 in the Southeast. Mini-ring, also known as leaf and sheath blight, is a concern but can successfully be managed in the spring with rotations of DMI and QoI fungicides. If mini-ring is your primary disease, use urea-based fertilizers. Here are some useful strategies for managing critical soilborne diseases in ultradwarf bermudagrass greens:
Treatments for TARR should begin when average daily soil temperatures at the 2-inch depth drop below 86 F. Applications should be followed by 1/8 inch of post-application irrigation (PAI). Remember that with root diseases the pathogen is in the soil, so applications must be watered in to be effective. The best programs for treating TARR have included DMI fungicides and it is recommended to make applications every 21 days until soil temperatures drop below 68 F.
Treatments for spring dead spot should occur when soil temperatures drop below 70 F and should also be followed by 1/8 inch of PAI. The best programs for managing this disease include SDHI fungicides and you should make at least two applications, 28 days apart. A third application may be necessary if we have an extended fall season.
Pythium root rot can occur year round on ultradwarf bermudagrass. However, the most important time to manage this disease is between early August and early November. Alternate applications of the most effective pythium products – e.g., Serata, Segway and Banol – with phosphonate fungicides for a robust pythium program in the later summer and early fall. Serata at a rate of 0.6 ounces per 1,000 square feet and Segway at 0.45 ounces per 1,000 square feet have been effective in 14-day rotations for a total of 10 applications per season. Rotating modes of action is critical to success and resistance management. All applications should be watered in with 1/8 inch of PAI.
This is a stressful time for many but fall is in sight. Superintendents often want to do more when problems arise, but sometimes the best solution is to observe and communicate while effective fungicides do their job. Staying vigilant against soilborne diseases can truly make or break your year.
Southeast Region Agronomists:
Chris Hartwiger, director, Agronomy – chartwiger@usga.org
Jordan Booth, Ph.D., director, USGA Course Consulting Service – jbooth@usga.org
John Rowland, Ph.D., agronomist – jrowland@usga.org
Chris Neff, agronomist – cneff@usga.org