First disease report of the 2023 season from the Purdue Turfgrass Pathology program. Highlights include prevention of large patch and soilborne diseases on golf putting greens and mowing tips for spring lawncare.
Hello everyone, and welcome to the first installment of the Purdue Turfgrass Pathology Disease Reports. I, and on occasion a guest author, will provide updates every few weeks during the season of disease activity. These regional observations will stem from our research plots, travels throughout the region, reports and photos from turfgrass managers, and turfgrass submissions to the Purdue Pest and Plant Diagnostic Lab. These reports will also serve as a look forward to issues on the horizon, therefore the first portion of every report focuses on the past and forecasted environmental conditions that could act as cues to potential turfgrass disease activity. While centered in Indiana, the net will be cast to other areas of the Midwest as necessary. Hopefully, these reports can broaden your scouting network, and aid in your management of turfgrass diseases and abiotic disorders. If you have any questions, comments or feel like an abiotic disorder or disease problem should be highlighted in a future report, please reach out to turfpath@purdue.edu.
Weather
Official astronomical and meteorological spring has been in effect for several weeks now, (do you feel the days getting longer?) and the temperatures are starting to follow suit. March was relatively mild and near normal for the most part, but the real story has been the persistent rainfall events throughout most of the region. A swath from Arkansas – southern MO/St. Louis – southern IL – southern IN/Cincy and another in northern IN – southern MI have been the hardest hit, with 200-300+% of the amount of normal rainfall falling in some localities in March. Cool weather + persistently wet conditions often result in intense large patch outbreaks for those managing zoysia (more on this below). In the near forecast, a cool front is set to break through today and tomorrow with a temperature drop and high potential for another round of severe storms. Unfortunately, this front seems also set to wreak some havoc at the Masters tournament later this week.
The pattern seems set to change next week for Indiana and much of the region. Higher than normal temperatures are expected, and even some 80s in Indianapolis, Cincinnati, St. Louis and Louisville could occur late next week. Fortunately, the region may also shake its soggy ears and dry out a bit next week. This sets up a spring bloom explosion and will spark the thresholds quickly for preemergent herbicide applications and soilborne disease prevention.
Large Patch of Zoysiagrass
The first few tinges of green zoysiagrass are here in West Lafayette with greenup moving along much faster south. Curt Schriever (@curtschriever), GCS at Wichita Country Club in Kansas has an awesome tradition of taking photos on April 1 of a zoysia fairway to show the progress of spring greenup. Shocking the differences over 12 years. These tinges mean large patch prevention, particularly on areas that didn’t receive fall preventive fungicide applications, may be needed now. Previous research conducted by me and others has shown that getting ahead of large patch infection, (earlier than the typical first mow or adage of 50% spring green up), may be necessary in high disease pressure. This wet weather pattern has certainly yielded that high disease pressure scenario. Wet and shaded areas that have been prone to damage in the past, (maps of previous outbreaks can be extremely beneficial) should be scouted persistently now and may need an application.
Soilborne Disease Prevention on Putting Greens
Soil temperatures in Indiana are creeping upwards quickly, and areas south such as Louisville and St. Louis are in the window to initiate preventive fairy ring and soilborne disease prevention. The cool front passing through will give some leeway and push the window past the weekend, but the next week’s return of warm temperatures and for some of you return from the Masters) will place the environment squarely back into the firing zone.
The preventive fairy ring program consists of two applications separated by a 21-28 day interval initiated when the threshold of 55-60 F two inch soil temperature over a 5 day average has been reached. The DMI fungicides (i.e. prothioconazole, tebuconazole, triadimefon, metconazole, mefentrifluconazole, etc) were first studied and have been traditionally used, but some have also used the SDHIs (i.e. benzovindiflupyr, penthiopyrad, pydiflumetofen) or mixtures of the two with some success. Wetting agents do not need to be tank-mixed with these preventive applications, although they don’t seem to affect fungicide performance. Remember, however, that for curative fairy ring applications, wetting agents must be tank-mixed with the fungicide. Make sure to water in the applications with at least 1/8” of post application irrigation and preferable closer to ¼”. Most fungicides tie up to organic matter quickly and are difficult to move through the soil profile.
These applications targeting fairy ring are broad spectrum and yield the benefit of protecting roots from take-all patch and summer patch. Also, they also can provide foliar disease control, and near future spring conditions are forecasted to turn conducive for dollar spot. In our previous studies, these preventive fungicide applications, despite being watered in, did provide some dollar spot control. Akin to the spring preemergent herbicide applications, watered-in spring fungicide applications on putting greens can serve as a solid tee-off to the disease management season.
Lawns
Forsythia is starting to bloom around town, signifying the time is nigh for spring fertilization and preemergent application. The mowers are purring as well, and as a PSA pay attention to soil conditions after these heavy events. Don’t be the guy in the above photo who has created a compacted rut that will collect water. Also remember to keep the grass the trees of the lawn by mowing higher rather than shorter and mowing frequently enough to avoid scalping. Neither rut making nor hay bailing are great ways to start off the season.
On the disease front, some Microdochium patch/pink snow mold activity occurred on lawns over the winter, particularly in the shade. Affected areas should be heavily raked to break up the mat and allow for regrowth. For more information on this, see the previous Turf Tip here.
Lee Miller
Extension Turfgrass Pathologist – Purdue University