Manage anthracnose and rapid blight on Poa annua greens

By Dean Mosdell, Ph.D., technical services manager for Syngenta

Rapid blight (Labyrinthula terestris) is a turfgrass disease that can affect Poa annua, Poa trivialis and perennial ryegrass species. Although its origin is unknown, it most closely resembles a pathogen of marine grasses. This explains why disease severity is correlated with saline irrigation water and soil salinity. Cultural practices, such as salinity management and using tolerant species in winter overseeding, are important for rapid blight management.

Rapid blight

A limited number of fungicides effectively suppress rapid blight’s severity. Fungicides in the QoI class and mancozeb were once the only options for superintendents. Although resistance has not been detected, continuous applications of a single mode of action fungicide can cause a shift in pathogen sensitivity, not only in Labyrinthula, but in other pathogens like anthracnose present in the thatch/soil during application. Managers of Poa annua greens in California need to implement a preventive fungicide program to not only control rapid blight, but other key diseases such as anthracnose and summer patch.

Anthracnose (Colletotrichum cereale)

  • One of the most destructive diseases of Poa annua putting greens across the country.
  • Most severe on stressed turf, but can be found on greens from the spring through the fall.

A preventive fungicide program, combined with cultural practices, can help manage severity of anthracnose.

Treating rapid blight and anthracnose

Ascernity® fungicide is a systemic fungicide that contains SOLATENOL® technology, a SDHI (FRAC code 7) and difenoconazole, a DMI (FRAC code 3), for broad-spectrum disease control including anthracnose and rapid blight on Poa annua putting greens (2ee label). The Syngenta disease management program for Poa annua greens in California includes Ascernity, Velista® and Heritage® Action™ fungicides in combinations or rotations with Secure® Action™ or Daconil® Action™ multi-site contact fungicides. This strategy controls all the key Poa annua diseases for a robust greens fungicide program.

In a University of California Riverside trial Ascernity, Velista and Secure Action fungicides were applied to a Poa annua putting green with a history of rapid blight and anthracnose incidence. Applications were made on a 14-day interval from June-September and ratings for presence of disease and turf quality were recorded. Ascernity, Secure Action and a tank mixture of Velista and Secure Action showed outstanding rapid blight and anthracnose control at the end of the trial. Ascernity applied alone effectively suppressed these diseases (see image below).

Control of Rapid blight/Anthracnose on Poa annua with New fungicides UCR 2015.
% disease rated 14 days after last application

University of California, 2015. Fungicides applied on 14-day intervals starting in early summer. 

A greenhouse trial at Clemson University in 2015 shows the benefits of tank-mixing Secure Action with Velista or Heritage fungicide (or with Heritage Action) for control of rapid blight on perennial ryegrass. For added convenience, Multipaks containing combinations of different Syngenta products can be viewed at

To learn how to prevent rapid blight and other key turf diseases as part of an agronomic program, visit

Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations. Trials reflect treatment rates and mixing partners commonly recommended in the marketplace.

© 2022 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 Ascernity to suppress rapid blight on Poa annua greens. Please see the Section 2(ee) recommendation to confirm that the recommendation is applicable in your state. The section 2(ee) recommendation for Ascernity must be in the possession of the user at the time of application. Action™, Ascernity®, Daconil®, GreenCast®, Heritage®, SOLATENOL®, Velista® and the Syngenta logo are trademarks of a Syngenta Group Company. Secure® is a trademark of Ishihara Sangyo Kaisha, LTD. All other trademarks are the property of their respective owners.

Want to receive articles like this in your inbox each month?

Sign-up now to get tips and new product information to stay ahead of the game with Syngenta.

* Indicates required field

Email Subscriptions