Dr. Lee Miller, Extension Turfgrass Pathologist, University of Missouri
As other blogs have posted, fairy rings are currently exploding on putting greens throughout the Midwest, and Missouri is no exception. We have had plenty of rain in central MO, and most rings have stayed in the type II or green ring stage. However, some infested soils have turned hydrophobic, and even with our recent flooding rains some turf loss around ring margins has been observed. Another real problem associated with our fairy ring outbreaks and the rains has been basidiocarp or puffball production. Many are reporting having to pick over a hundred puffballs per day on their most affected greens!!!
At this point in the season, curative applications should consist of ProStar, Heritage, or Insignia applied at high rates and tank-mixed with a wetting agent. If the soil has turned hydrophobic, it is also a good idea to do some venting (not just to your spouse) by punching some holes (not just in the wall). This will hopefully allow some water through, and start to restore the balance of soil physical and chemical properties that the fairy ring pathogen has disrupted.
If you are experiencing difficulty this year, you may consider a preventive approach next spring. Recent research has shown two low rate spring applications of the DMI fungicides Bayleton, Triton, Trinity, or Tourney has resulted in good control of fairy ring in the summer. Fungicides were watered in with a ¼’ of irrigation, and best control was afforded when a wetting agent was not tank-mixed but was applied on a regular monthly schedule 2 weeks away from the fungicide application. The best timing of initial application was at 5-day average soil temperatures of 55-60°F, which should occur sometime in mid or late April in the upper Midwest. A follow-up application made 28 days later is necessary to afford the longest residual control.
The picture below shows a bit later DMI application than is recommended, but is still affording good control. DMI applications in high heat periods can cause phytotoxicity due to the growth regulating effects of these fungicides, however, with the amount of rain we have been experiencing this summer these low rate applications have not been an issue on our plots.