A Season in Extra Innings
Warm, Dry October = Indian Summer
- October 2016 was warmest since 1971. - Source: Pat Guinan
- Along with the heat, most of the region also experienced below normal rainfall. - Source: Pat Guinan
Not a single hint of winter chill has threatened to put any frost on fall pumpkins this year. October 2016 was the 10th warmest on record, and the warmest since 1971. Air temperatures across the region are 6 – 8 degrees above normal, and average 2-inch soil temperatures are still in the mid to upper 60s for most of the state. Only the far northern counties in Missouri (Atchison, Gentry, Knox, and Putnam counties) have approached freezing low temperatures (< 32 F), with most areas not getting below 35 degrees. With the exception of SW Missouri, most of the region also experienced a particularly dry October. Most regions received at least one inch less rainfall than normal for the month, with many areas of the state with a two inch or more deficit.
Forecasts indicate the warm and dry pattern to continue well into mid-November. Short-term and longer term forecasts do not indicate a temperature dip or any type of killing frost in the next 8-14 days, meaning this greatly extended window of the current growing season should persist. The recently published MU IPM Frost Freeze Probabilities Guide (click here to view) puts the extraordinary nature of these unseasonably warm fall temperatures into greater perspective. The median date for a minimum air temperature below 32 F is October 20 for much of middle Missouri, and there is a 90% probability based on historical data that most of the region will go below freezing by November 4-8. In Columbia, MO the overall season length based on the 32 F air temperature threshold is currently 206 days from April 12, (an average season length is 195 days). Since there is no suggestion of a temperature dip through early November at least, the season, and some very confused turfgrasses, will continue to grow.
8-14 Day Outlook: Doggedly Persistent Fall Pattern
- Warm temperatures expected well into mid November - Source: NOAA CPS
- Dry forecast should hold off irrigation system blowouts. - Source: NOAA CPS
- Rust: Several more emails and phone calls have been received concerning rust outbreaks in tall fescue/Kentucky bluegrass home lawns and golf course roughs. The current weather pattern has been very conducive to this disease, particularly in the last few weeks. Rust diseases are more severe on younger turfgrass stands, and seedlings from September seeding efforts may be more heavily afflicted. The current dry spell is conducive for rust outbreaks, and the extended growing season may be resulting in turfgrass stands that are running out of nitrogen. Irrigation and perhaps a small shot of soluble nitrogen (0.5 lb N/1000 sq ft) may be unusually warranted to reduce the effects of serious outbreaks. At this late stage of the season, fungicide intervention is discouraged except on extremely high amenity areas with severe symptoms.
Large Patch Still Raging
An extended season of fall zoysiagrass growth has resulted in more severe large patch outbreaks.
- Large Patch Breakthroughs: Warm season turfgrasses seem to be very confused with the unusually warm fall, and although they may be growing slowly, are not going into dormancy. This has opened the door for an extended period of large patch outbreaks, that are in some cases breaking through from earlier September fungicide applications aimed at control. On golf course fairways, an additional curative fungicide application may be necessary considering the warm forecast still ahead. In this case, spot applications on existing symptoms may be the best bet to limit spread of existing symptoms and reduce the financial burden of a late wall to wall spray. Granular applications of a strobilurin (i.e. Heritage G) may be a good solution (or non-solution, ha ha) since a calibrated spreader is all that’s necessary to head out and hit symptomatic areas. On zoysia lawns, a fungicide application this late is not recommended. Instead, make note of symptom location and target early spring prior to symptom development.
Extra Inning Implications
Similar to a very recent World Series Game 7 in early November, this fall season has gone into extra innings. The pitchers, aka turfgrass managers, have weary arms and just want to close this thing out, but Mother Nature is swinging an exceptionally hot bat. To go along with the not so subtle running theme in this update, below are a few more implications for this particularly long fall season.
- The leaves may be changing color, but warm season turfgrasses sure aren’t. Since my arrival in Missouri at 2010, nothing close to this type of fall heat spell has occurred. Zoysiagrasses and in particular bermudagrasses are still extremely green, and the evidence in the table demonstrates why. Average soil temperature and average low air temperatures are approximately 2-8 and 5-9 degrees higher than the previous 6 years, respectively. The lowest air temperature in October 2016 is similar to last year (although 2015 had a much lower average), and strikingly lower than 2010-2014. Zoysiagrass and bermudagrass have kept chugging along, and in the case of bermudagrass, some cultivars are still seeding! Many new bermudagrass cultivars in our current NTEP test are keeping mid-summer color very well now. Light fertilizer applications to bermudagrass sports fields into September and even October should work out very well this year, and even zoysiagrass fairways may have benefited from a little extra fall spoonfeed.
Bermudagrass NTEP Trial in Late October?
Very few of the NTEP bermudagrass varieties show signs of October this year.
- Keep those irrigation systems charged. Unless a sharp, and unexpected, dip in the jet stream occurs soon, irrigation systems will need to stay charged well into November and perhaps even December. To lessen the chances for winter crown dessication, turfgrasses should have adequate available water going into winter. While not as important for higher cut lawns, lower cut, sand-based putting greens and young turfgrass stands require fall irrigation prior to sustained winter temperatures to limit winter injury.
- The grass keeps growing so keep on mowing. Long, shaggy turfgrass going into winter can be prone to snow mold and other issues. Mow turfgrasses to their appropriate height (i.e. cool season lawns + 3.5 inches) until they stop growing. As a side benefit, managers of lawns and golf course roughs can mulch in falling leaves to add nutrients without fear of adding to the thatch layer. The key is to keep up the frequency of mowing. See this article for more information.
- Late seeding efforts in early to mid-October should have worked out well if provided with enough supplemental irrigation. The window for herbicide applications targeting broadleaf weed control should also remain open longer than in most seasons, meaning a one-two seeding, weed control punch should set up for a nice lawn come next spring. Remember that fall is the best time for weed control with herbicides so take advantage of it if necessary.
- Some pesky diseases such as the aforementioned large patch may recur later this fall than usual, and require one more clean up fungicide application prior to winter on golf courses and sports fields. A final application in early to mid-October will normally keep creeping bentgrass putting greens clean of dollar spot heading into winter. If this was the plan, pay attention this November as this could be a very rare year when the disease my break through and require another treatment.
Follow on Twitter! @muturfpath
Like on Facebook! Mizzou Turfgrass
Extension Turfgrass Pathologist
University of Missouri