March 12, 2024: Early Spring Arrival – Turfgrass Science at Purdue University

March 12, 2024: Early Spring Arrival

Highlights: Spring 2024 is weeks ahead of schedule; lawn preparation; soil temperature status; fungicide timing for dollar spot and soilborne diseases; yellow patch observations; short survey request.                                                                                                                                                                                                                                                    

Turfgrass Pathology Program Impact Survey

Scan QR code for brief survey.
Follow this link or scan QR code above to access the survey.

Welcome to a very early spring 2024. Before the season and slate of reports comes out this year, I’d like to ask the favor of filling out a very short survey. The goal is to find out how the Purdue turfgrass pathology program is impacting your turfgrass management operation and how we might do better. Please let us know if there are any disease issues or research areas that need attention.

If you have any questions now or have a disease diagnosis or management issue during the season, please reach out to We are happy to help. – Lee Miller



Maps and Signs of Early Spring
A. National Phenology Network describes Indy’s spring as 14 days early.
B. Forsythia already blooming near Lilly Hall on campus.

Along with the clocks last weekend, spring has been in fast forward since mid-February. Over the last 30 days, temperatures are 8-9 degrees above normal in the region, and the first ten days of March (see below) are 10 – 12 degrees above average. The National Phenology Network ( states Indianapolis is two weeks ahead of the normal spring schedule (1991-2020). If warm weather continues this week as forecasted, Michigan State’s fantastic growing degree day tracker web application ( would have Indianapolis at 127 GDD32 and 45 GDD50 ahead of 2023 by next Monday, March 18. For context, the current 56 GDD50 tally wasn’t reached in 2023 until April 4. By all measures, spring is springing well ahead of schedule with budding, blooming and emerging plants (and morels in southern IN) following suit. Tomorrow (March 13th) is our first mow of the season at the Daniel Turfgrass Research Center and last year it was on April 3rd. For our region at least, the groundhog was right.

Blazing Spring Temps March into March
Temperatures are considerably above normal throughout the region. — MRCC
A good dose of rainfall for most in early March. — MRCC

Snowfall for the season was 25-50% of average for much of Indiana with 8-12 inches common for much of the state and 12-24 inches closer to the Michigan border ( Snow blowers were mostly in the garage as the few multi-inch snow events were often followed quickly by snow melting temperatures. Rainfall has been the main precipitation over the last month, with most of the region below average over the period. A strong system in early March of last week, particularly in southeast Indiana into Ohio, yielded 0.75 – 2+ inches that has recharged soil moisture.   

The forecast indicates a dip in the jet stream next week and a return to cooler than average temperatures for the region. Although slightly above average chances for precipitation are also forecasted, seriously accumulating snow doesn’t seem to be in the cards for most in Indiana. Tender flower buds and sensitive plants may need to be covered, since after all it is still March in Indiana.   

Warm spring temps forecasted to tame
A. Cooler temps next week may slow down spring a bit. - NOAA
B. A hearty spring rainfall trend seems to stay on track next week. - NOAA


First garden to prepare is the lawn
Make sure no leaves are left smothering the lawn.

The forsythia is in bloom, but I suspect next week’s cooler temperatures will extend the window a bit for getting applications out earlier than a normal spring. This being said, for many of us the lawn is presumably days and not weeks away from requiring care. If not done already, it’s time to tune the mower, sharpen the blades and plan on mowing the winter fuzz off very soon. I’ve heard mowers purring around town already. Make sure to pay attention to conditions before the first (and all) mow as soils tend to stay wet longer in the spring due to reduced evapotranspiration. Ruts and compaction produced now won’t help in the long run.  

The first garden a property owner should prepare in the fall is the lawn. Recent research indicates no detriment to mulching tree leaves in, which integrates nutrients and builds rich organic matter in often times very poor home lawn soils. If leaves were not removed or completely mowed in last fall and are on the surface, spring removal is absolutely necessary, so they don’t smother the lawn and cause disease. Similarly, if the first spring mow is a little too late make sure to not leave heaps of clippings on top of the lawn.  


Soil Temperature Status & Soilborne Putting Green Disease Prevention

Soil temperature threshold for fairy ring prevention not reached yet.
A. At our most southern IN location, 5 d average 2” soil temperatures not quite into range.
B. Soil temperatures also not quite there in St. Louis yet.

Spring soil temperatures are creeping up quickly, but in most of the region are not quite there yet to initiate fairy ring and soilborne disease prevention on creeping bentgrass putting greens. The five-day average 2” soil temperature (shown above for southern IN and St. Louis, MO) should be sustained in the 55 – 60°F range to initiate the first watered in application. We haven’t reached this threshold level in Indiana and perhaps only Springfield, MO stayed in this range long enough last week to consider making the first application. With the current forecast set for cooler temperatures, the environment will presumably give a reprieve until the next wave of heat rolls in.

Soil temperature can be monitored on several websites. On a national basis, first search for your state’s Mesonet website which is often maintained by your land-grant university. In Indiana, the Turf Disease Prediction Tool housed on the Purdue Turfgrass website was built last year in collaboration with the Midwest Regional Climate Center. This web application houses 2” soil temperature information from 14 sites throughout Indiana and plots the daily and 5-day average. In Missouri, threshold charts have been sustained by my friends at Mizzou for five cities here –


Dollar Spot – Pay Attention & Scout

Along with the soil temperature information, a decision support tool for dollar spot based on the Smith Kerns model can also be found at the Turf Disease Prediction Tool (also maintained at MO site above). The dollar spot probability threshold is set at 20% for preventive action. Since March 6, the model has started to go off, particularly in southwest IN, reaching levels above this 20% threshold on March 9th. For reference, this threshold wasn’t reached in the Evansville area until May 10, 2023. I suspect that for much of Indiana the model will remain below threshold over the next cooler spell and as with the soilborne disease prevention will need to be closely monitored earlier this spring than last year.


A Little Yellow Patch (aka Cool-Season Brown Patch)

Yellow patch in late February
A. Yellow patch in some instances can be mistaken for pink snow mold. 
B. After incubation, hyphal strands of the pathogen are a characteristic sign of the disease.

Yellow patch, or cool-season brown patch, was observed during some of my scouting runs in the late February. This disease is caused by one of the weaker, opportunistic Rhizoctonia pathogens (R. cerealis), yielding symptoms in cloudy late winter/early spring temperatures (50 – 65°F) which were in abundance during our 4th cloudiest January on record.

Field symptoms of this disease can be easily confused with Microdochium patch (aka pink snow mold). Microdochium patch will cause more extensive blighting and may produce a more pink or red, brick-colored ring pattern that can spread more quickly due to spore release. On the other hand, yellow patch moves slowly via mycelium and doesn’t often lead to severe damage. Therefore, these two “aka’s” are quite different in that yellow patch symptoms will dissipate quickly when higher temperatures and conducive growth conditions arrive later in the spring. On the other hand, symptoms caused by Microdochium patch on greens may require fungicide intervention to facilitate recovery. Curative fungicide applications for yellow patch do not result in quicker recovery than untreated areas, and are not recommended. With the mild winter and low snow cover, I do not expect to see much pink snow mold/Microdochium patch activity unless this spring turns much cooler.  


Lee Miller
Extension Turfgrass Pathologist – Purdue University 
Follow on Twitter:  @purdueturfpath


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