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

Dollar spot (Clarireedia spp.) is a common and widespread disease on golf courses across the country. It can infect many species of turfgrass, especially creeping bentgrass and annual bluegrass greens, tees and fairways. Single-site fungicides, which bind to a specific enzyme or interfere with a single metabolic process, have been used to treat dollar spot since the late 1960s. However, annual application limits and fungicide resistance have developed since then, leading to a demand for new control methods.

There are seven classes of fungicides that are labeled for dollar spot control. The level of control will vary with rates and application intervals.

How to get extended control

Posterity^® fungicide (active ingredient pydiflumetofen) is the most active SDHI fungicide for the turf market. It features a single-site active ingredient for control of dollar spot, especially on fairways. 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 the introduction of 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.

Target multiple diseases

For the most broad-spectrum control, Posterity XT fungicide is an excellent choice to control dollar spot mid-season, as it provides additional control of over 20 other diseases, including brown patch and gray leaf spot.

Brown patch (Rhizoctonia solani) will occur when temperatures are greater than 63°F along with high humidity and/or extended leaf wetness in the summer. An application of Posterity XT for dollar spot control will prevent brown patch should weather conditions favor that disease.

Posterity XT can also be used for the control of gray leaf spot (Pyricularia oryzae, formerly called Pyricularia grisea), which often occurs in the hot, humid weather of late summer. It is primarily a disease of tall fescue and perennial ryegrass in the transition zone. When applying Posterity XT to prevent gray leaf spot, the application will also provide excellent control of dollar spot.

Posterity XT applied at 1.5 fl. oz. will provide 14 days of control of both diseases and, in most situations, 21 days of control will be realized.

Resistance Management

Building a foundation program that includes a multi-site contact fungicide in each application is recommended for a solid disease control program. Secure^® Action™ fungicide is an excellent tool for resistance management, as it has no known resistance. Secure Action is 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.

Up to 12 applications of Secure Action may be used in rotation with Daconil^® Action fungicide to protect your course all season long with multi-site contact on both greens and fairways. Secure Action should be applied at a rate of 0.5 fl. oz./1,000 ft.² (six acres per gallon) every 14-21 days.

The following practices are recommended for dollar spot control as part of your summertime agronomic program:

• Apply fungicides preventively, starting when conditions become favorable for disease: temperatures between 59° F to 86° F, continuous high humidity, cool nights and heavy dews.
• Visit GreenCastOnline.com/DollarSpot to sign up for dollar spot alerts in your area, which are based on the Smith-Kerns dollar spot prediction model.
• Avoid back-to-back applications of single-site fungicides in the same class.
• Rotating Secure Action with Daconil Action can help ensure that a multi-site contact fungicide is in every spray application. For broad-spectrum disease control that lasts 14 days, tank mix with the labeled rates of Posterity, Posterity Forte or Posterity XT.

Curative recommendations

Since curative treatments with single-site fungicides may put your turf at risk for fungicide resistance, it is best to use preventive applications. If curative applications are necessary, it's best to spray a multi-site contact like Secure Action before using a single-site fungicide 14 days later. Tank-mixing and alternating fungicides with different modes of action is recommended for dollar spot to help combat resistance.

For more information on:

• Building an agronomic program: visit GreenCastOnline.com/Programs
• SDHI resistance management: click here
• Additional articles: click here

 
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© 2023 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. Syngenta supports a FIFRA Section 2(ee) recommendation for the use of Daconil Action for control of dollar spot. Please see the Section 2(ee) recommendation to confirm that the recommendation is applicable in your state. The Section 2(ee) recommendation for Daconil Action must be in the possession of the user at the time of application. Action™, Daconil^®, GreenCast^®, 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 property of their respective third-party owners.