Temperature Finally Flips to Fall
September was one for the record books as several cities including Springfield, St. Louis, West Plains, and Columbia experienced their warmest September. The unofficial statewide temperature of 74.7 F ends up 6.4 degrees above average (largest departure from average for the year) and will presumably end up as the 2nd warmest September on record (since the warmest in 1931). September also had the highest dew point on record, and September had the highest departure from average for the year. All of this resulted in a September that felt much like the meat of July, and considerable physiological stress on cool season turfgrasses. This effect was particularly severe on bentgrass putting greens in the region, which did not appreciate a jolt of summer occurring after August. The first few days of October didn't offer much relief, but we've now settled into a fall pattern that may…
Turn quickly to winter. Forecasts into this weekend and into mid-October indicate a turn towards cold, perhaps even freezing weather as the jet stream plummets south. Northern parts of the region should experience their first frost of the season that may dip down even into St Louis and southwards. Hard to imagine snow, but our northern neighbors should be getting a good dose of it through the weekend.
Rainfall over the last two weeks has followed the same broken record, with significant rains occurring in the west and north, with the east receiving much less. Not coincidentally, putting green samples are still coming in from these regions where the spigot simply won't turn off. Forecasts do indicate a dry down into next week, which will undoubtedly be welcome in those regions.
October Dry Down?
Frost/Freeze Guide: If you're curious about when the first fall frost traditionally occurs in Missouri visit The Missouri Frost/Freeze Guide here. This informative web application uses historical information to show the dates and probabilities for when a first freeze event should occur in your Missouri location. For example, using the "weather station map" tab, St. Charles should have a 10% probability of having a 32 F temperature before Oct. 7 and a 30% probability before Oct. 17. Another neat feature is the extreme date maps, which shows the earliest dates of temperatures at or above 32 F (or various other temps) in mid to late September for most of Missouri (none in the last 20+ years). The median date for the first fall frost at or below 32 F in Missouri is mid-October for middle portion of the state, so if it does occur later this week it'll be approximately 10 days early for most Missouri residents. This would indeed be right out of the fryer (90s on October 1-2) to the freezer in just over a week's span.
Late September Fairy Ring Outbreak on Putting Greens
Bermuda vs. Zoysia NTEP Trial - Sept 27
1-2-3 of Late September Pythium
South Farm Showcase - Sept 28
The turfgrass demo area included many kids activities, including planting seed.
Large Patch & Spring Dead Spot Prevention Time
With the quick advent of fall, a late shift towards warm-season disease prevention also ensues. The first fall preventive fungicide application for both spring dead spot and large patch on areas with a history of the disease should be timed around the 70 degree 2-inch soil temperature threshold (5-day average). Except for Kansas City, this just occurred in the past five days for most of the region.
An often-asked question is if an earlier application in late August or early September was "wasted". In mid-September, some reports were received and observations of active large patch were made at the research farm in some of our typical areas. Many of these areas recovered along with the summer-like temperatures that persisted through the month. Another fall application on a 21 to 28-day interval should suffice for large patch prevention on high amenity zoysia, but remember this fall when next May and June come around. Scout intensely and be quick to make a curative application if necessary. If this cold weather sticks around and zoysia goes quickly into the winter good night, consider an early spring preventive rather than relying solely on fall applications, a strategy that has worked well in our previous studies.
Spring dead spot prevention, however, may be a tougher nut. Applications made earlier this September may indeed not do a good job at preventing the disease come next spring. Two applications on a 21 – 28 day interval will most likely be necessary this fall, but in reality might it need to be three? The table below shows the dates over the last nine years that the 70-degree soil temperature threshold has been reached. Obviously apparent are the last four years in which the threshold has been later than the previous six. Particularly in 2017, sub-par control from preventive spring dead spot applications was reported in several instances, and we also noticed this effect on our own plots. The ineffective applications in most cases were applied in mid-September and mid-October as per tradition. In reality, the 70 degree threshold occurred much later, which should've pushed the second application 21 – 28 days later into late October or even November. Serendipitously that year we did make later applications that ended up working much better than the earlier applied treatments.
Long story short, once again the summer ghoul has worked the graveyard shift well into our fall. This weather shift has already had ramifications on cool season turfgrass health. It also may translate into a required shift of our preventive strategies for warm season turfgrass disease management later towards Halloween then we've previously considered, or in the case of large patch, a slide towards next spring.