By Lisa Beirn, Ph.D., technical services manager for Syngenta

As spring temperatures rise and turfgrass begins to flourish, so does the fungus that causes dollar spot (Clarireedia spp.). Warm days and cool nights that result in heavy dews create ideal conditions for disease development. While most turfgrass species are susceptible to dollar spot, the disease is often most severe on closely mown turf.  

How do I control dollar spot?

Minimize symptoms with cultural practices like:

• Dew removal
• Thatch management
• Proper fertility maintenance

When dollar spot pressure is elevated, preventive fungicide applications are very effective for control and should be initiated in the spring before symptoms appear. If curative applications are necessary, employing a multi-site contact fungicide like Secure^® Action™ fungicide is optimal.

Posterity^® fungicide (active ingredient pydiflumetofen) is the most active SDHI fungicide for the turf market. Spring applications of Posterity provide up to 28 days of dollar spot control. Use Posterity as a preventive fungicide treatment at 0.16 fl. oz. per 1,000 ft.² in an agronomic spray program. 

With Posterity Forte fungicide, a combination of pydiflumetofen, azoxystrobin and propiconazole, the level of disease control has gotten even better. The low label rate of 0.42 fl. oz. per 1,000 ft.² will provide up to 28 days of dollar spot control when applied in the spring. Posterity Forte will also provide control of leaf spot and brown patch. 

For broader spectrum control, Posterity XT fungicide is also an excellent choice, as it provides up to 28 days of control of 20+ diseases including dollar spot, brown patch and gray leaf spot.

How do I manage resistance?

The fungus that causes dollar spot can rapidly develop resistance to fungicides. Certain chemical classes are more prone to resistance, so be careful when building an agronomic program. For chemistries that are high-risk for resistance development such as the SDHIs, it's crucial to rotate to a different chemical class after each application. Medium-risk chemistries, such as DMIs, can be applied twice before rotating to a different chemical class. In all situations, tank mixing with a low-risk fungicide like Daconil^® Action^™ fungicide or Secure Action can help delay or prevent resistance.  

Secure Action is an excellent tool for resistance management, as it has no known resistance. It’s a multi-site contact fungicide containing the active ingredient fluazinam, which disrupts the production of energy at multiple metabolic sites within the fungal cell. Additionally, Secure Action contains the active ingredient acibenzolar-S-methyl (ASM), which boosts turf’s natural defenses against dollar spot and increases the dollar spot control interval for up to 21 days.

Resistance management is an important consideration used in the development of Syngenta agronomic programs. For more information, see the Turf Agronomic Programs from Syngenta for your area. 

Optimize your program with agronomic alerts

The Smith-Kerns dollar spot model, developed by Dr. Damon Smith and Dr. Jim Kerns, can help predict when outbreaks of dollar spot may occur. The model uses relative humidity and air temperatures to generate a dollar spot risk index based on location. Research has shown that the Smith-Kerns model can help optimize fungicide application timings based on when dollar spot is likely to develop in your area. 

To help you maximize dollar spot control, Syngenta has incorporated the Smith-Kerns model into a user-friendly format that sends customized dollar spot alerts for your area. 

Sign up to receive automatic notifications when conditions are prime for dollar spot in your area.

© 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™, Daconil^®, Posterity^® and the Syngenta logo are trademarks of a Syngenta Group Company. Secure^® is a registered trademark of Ishihara Sangyo Kaisha, LTD. All other trademarks are the property of their respective third-party owners.