Snow mold prevention on putting greens; reduced cool season turfgrass disease activity in fall; warm season disease prevention.
Weather
After a cool start, September turned on the burners and ended 3-5 degrees above normal in the region. Since 1943, September 1 marks on average the last 90-degree daily high temperature recorded in Indianapolis. This hasn’t held true in the last six years, however (see table below). This year, above normal temperatures occurred in Indy from 9/10 through the end of the month, with a spike of three days in the 90s from the 19th – 21st.
Rainfall was scarce throughout the region in September until the remnants of Hurricane Helene staggered through. Indianapolis, central IN, northern IN and particularly east into the Ohio Valley were in the moderate, extreme and exceptional drought categories, with much of Indiana having less than half of the normal rainfall in September. Evansville and southern IN/KY were also in a similar deficit but received much more rainfall (3+ inches) in late September from Helene. Thoughts and prayers go to the unfortunate in western NC, TN and throughout the Southeast who bore the brunt of this terrible storm.
Forecasts indicate no real chance to get back into the 90s with some cool mornings and prime cool season turfgrass growth ahead. Newly planted landscape plants and turfgrass seedlings will likely need supplemental irrigation as rainfall chances through early October remain low, despite our area being wedged between air masses of vastly different temperatures.
Snow Mold Prevention Needed?
Fall woolly bear sightings have been occurring frequently around my house the last few days which are much more welcome than fall armyworms as detailed in this recent article by Dr. Richmond. As myth and legend have it, if these caterpillars of the Isabella Tiger Moth have longer black bands and shorter middle brown bands, a long, cold and snowy winter lies ahead. The ones crawling around my abode have been mostly black, which would be foreboding and interesting fodder for conversation in the Woolly Bear Festival held in Vermilion OH, but hold little meteorological merit. To read more about woolly bears, see this NOAA article.
Their arrival does make fall snow mold prevention a timely topic. Although gray snow mold can occur closer to the Michigan border, pink snow mold caused by Microdochium nivale is the most often observed culprit. On lawns, fungicide prevention is not suggested. On higher cut turfgrasses, damage is often short-lived and is often recovered from quickly. Careful attention to the final fungicide application prior to putting the putting green to bed for the winter is much more important. To avoid removing protection from fall rains and changing weather, make the final fungicide application the last operation, as close as possible to significant snowfall and not at the first sign of a cold snap. In most cases, this means eyeing Thanksgiving or even Christmas, and not Halloween. Since pink snow mold is the major contributor south of Michigan, fungicides such as fludioxonil, iprodione, or the strobilurins should be utilized. Under heavy disease pressure, combination products or mixtures of fungicides will provide more long-lasting control. Dr. Paul Koch at U of Wisconsin runs the largest snow mold fungicide testing program in the country (perhaps the world). View these results here.
September Heat but Less Disease Activity = Functioning Fall
Despite the heat, September was fairly quiet on the disease front in the region. Dollar spot flared at the end of the month when some humidity returned but the span from 9/3 – 9/15 experienced a sharp decrease in disease severity (see Smith-Kerns model of IN here). The same holds true for brown patch on tall fescue and leaf spot/melting out on Kentucky bluegrass, which after a summer of torment, finally took a break. September marks the end of 100 days of H-E-double hockey sticks for golf superintendents and turfgrass managers, and along with October is the best time of year for cool-season turfgrass.
After suggesting an overseed instead of fungicide application early in September, a homeowner responded with the question, “Don’t my young seedlings also need fungicide protection?”. The short, political answer was maybe, but in reality the answer this September, and for most home lawn situations is no. While using the calendar month to boldly define the weather is painting with a broad brush, (especially for southern IN/KY), September holds some key weather advantages for cool-season turfgrass recovery. From start to end of month, daily high temperatures decrease by 10 degrees from 81 F to 71 F. September rainfall in Indianapolis averages sub 3 inches, and humidity drops precipitously unless the tropics flare up. Most importantly, day length decreases rapidly in September, with photoperiod decreasing by 1 h 15 minutes from month’s start to end. Ninety+ degree heat therefore doesn’t hit the same in September, with a duration several hours shorter than the height of summer. For all of these reasons, September is prime time for turfgrass growth and recovery, and the month when diagnostic calls slow to a trickle.
Warm Season Turfgrass Disease Prevention
Soil temperatures have been in the range (70-75 F) for those in the southern portion of the state or those managing bermudagrass sports fields in Indiana to turn their attention towards prevention of warm season diseases. Large patch on zoysiagrass is starting to show symptoms on our zoysiagrass at the Daniel Center, which is slowing growth and rapidly turning towards dormancy. On bermudagrass fields, spring dead spot prevention is the target, as the pathogen infects now but doesn’t show its deeds until next season’s spring greenup.
Two fall applications are usually suggested to maximize control of these two diseases. If making the first application now, I suggest watching the weather, and perhaps adapting to make the second one 21 days later instead of 28 depending on the forecast. For both diseases, applying in higher water carrier volumes (although difficult over large acreages) may maximize control. The recommendation is still to water in applications targeting spring dead spot since it’s a soilborne disease, but research varies on how much that factor contributes to overall efficacy. Unless treating for water repellancy over the winter in susceptible soils, addition of a wetting agent to the tank is not necessary and hasn’t been shown definitively to add to control of either of these diseases.
Speaking Events
It’s nearing winter conference season! A few of the events I’ll be presenting at include:
- Area IV Turf and Lawn Clinic (11/15),
- Heart of America GCS Education Conference (11/18),
- Purdue Turf & Landscape Seminar (11/20-11/21),
- Rocky Mountain Turfgrass Conference (12/3-4),
- GCSAA Conference & Trade Show (2/3-2/6),
- Indiana Green Expo (2/10 – 2/12).
For information on these and several other Indiana education events, see the MRTF events page. I’d also like to thank the MRTF, Hoosier, Indiana and Michiana chapters for operating research fundraiser tournaments this summer and fall to further all of our research efforts.
Hope to see and meet you there!
Extension Turfgrass Pathologist – Purdue University
Follow on Twitter: @purdueturfpath