SURVEY QUESTION

LAWN: What percentage of home lawns do you apply a preventive grub insecticide to?

None
Less than 10%
10 - 33%
About 50%
About 75%
All - standard practice

Update (6/25/2020)

Be Like Water

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Diagnostic Lab Update

At this time, turfgrass diagnostic services at MU remain suspended due to the COVID-19 pandemic. An anticipated opening date of July 15 is planned to complete an online submission system and catch the dog days of summer. When we do open, anticipate limited hours, strict sample submission guidelines and no sample drop offs. Some of the diagnostic labs open at this time include University of Wisconsin, North Carolina State University, and Kansas State University. We appreciate your patience.

Weather

A Little Above Average, But Not Bad

  1. Temperatures running a bit above normal, but not terrible. – MU Climate Center
  2. Warmer temperatures set to return after mid-June break. – NOAA

While most things have gone poorly in 2020, the weather thus far has not been terrible in Missouri (knock on wood). June temperatures are running above normal in the state, particularly the Kansas City region, which is running 4-5 degrees above normal. The air has been dry though, and several breaks of nighttime lows in the low 60s and high 50s have minimized the impact of our usual sustained disease and heat stress periods. Not much has gone right in the first half of the year, but the growing weather has been fairly accommodating. The solstice is also behind us, meaning daylength and potential periods of heat stress for cool-season turfgrass is getting shorter. It's no late September out-of-the-woods celebration, but considering everything going on… it's something.

Problems this year have mostly revolved around water, either too much rainfall at one time or not enough of it. June rainfall centered itself right down the middle of the state as the remnants of Cristobal meandered through. Some areas in the center of the state have received 7-10 inches of rainfall in June. Last week, St Louis also received their monthly allotment in a few days, as some areas received 4-5 inches last week. The western part of the state, however, has been very dry, with some areas receiving very little June rainfall.

Forecasts indicate a departure from the cool nights and the return of humid, summer-like weather. Rain chances through Monday indicate 0.25 – 0.5 inches expected for much of Missouri, with hopefully a bigger pocket over the Kansas City area. Take this forecast with a grain of salt, however, since as our state climatologist says it is Missouri, after all.

Rain in the Middle, Dry on the Sides

  1. June saw renewed rains in mid MO, but STL and KC are getting dry. – NOAA
  2. Above average precipitation chances next week into the first of July. – NOAA


Quick Hits

    Putting Green Roots - Check 'em
    In historically weak and strong areas check root depth, moisture and consistency.


  • Root sampling on putting greens – Last week we conducted some soil sampling on one of our experimental nematode trials, and along with pulling samples for nematode counts (sent off since our lab is still closed) we also examined root quality. In the photo above, you might clearly think that treatment 4 (an experimental) was the best. However, this is why we replicate, and in reality over four replications none of the treatments stood out above the rest. The exercise did, however, emphasize that routinely checking root and soil conditions with a standard 0.5 – 0.75 inch soil probe is a vital practice for monitoring the health of golf putting greens. While TDR probes are valuable monitoring tools for setting irrigation targets, they are still a complement to routinely pulling a core and looking for 1) powder dry sand pouring out of the hole, 2) a distinct mushroom smell to the core, and/or 3) using an eye dropper to place a few water droplets to observe water infiltration. On the flip side, pushing deep in the profile may elucidate problems deep below such as black layer caused by trapped moisture and improper drainage. One can't assess this from a 4-inch cup cutter plug. In problematic vs. good areas of greens perhaps imitate what we did last week on a smaller level, and take stock of root depth and quality by placing the core over a sieve and rinsing with water. Now is a good time to see what pitching arms are on the bench to get through August.

  • Brown Patch Rampant – Brown patch exploded on tall fescue through mid-June on our research plots, and my lawn. We are also seeing it ramp up on our creeping bentgrass putting greens.

  • Dollar spot, on the other hand, has remained eerily silent. The Smith-Kerns model has modeled several dips in disease pressure this spring/early summer, which we haven't observed in previous years

  • With the impending forecast, this is probably a good time to shut down verticutting on putting greens until fall, and to take off the grooved rollers if you haven't already. A small increase in greens height, and a few days of rolling only may also be a good idea.


  • Forceful Fairy Ring

    1. Prominent fairy ring in commercial lawn setting this week.
    2. Fairy ring on putting greens with a side of brown patch. Basidio bros…

  • Fairy Ring Everywhere – Alternating wet and dry spells have driven some impressive fairy ring occurrence over the past three weeks. Our former NTEP variety trial, not treated with spring preventive treatments, is currently getting hammered by the disease with both Type II green rings morphing into necrotic Type I rings along patch margins. Curative applications of flutolanil or the strobilurins (i.e. azoxy-, pyraclo-, fluoxa-) should at this point be tank-mixed with a wetting agent with at least 0.2 inches of post-application irrigation. Remember this disease kills mostly by hydrophobicity, so getting the water along with the fungicide down into the soil profile is key. On lawns where fungicides may not be allowed, aerifying or spiking just along the patch margin and watering the area heavily may aide in reducing symptoms.

Be Like Water

Be Like Water

  1. Sod laid on May 7 in KC stuck in between the road and sidewalk. Needs roots & water.
  2. Tall fescue at the end of two slip and slide runs. Needs roots, but no more water.

Just a few weeks ago, I, like many, watched the Bruce Lee 30 for 30 documentary, and his famous quote has been ringing through my ears while attempting to help managers remotely through photos and descriptions. The quote relays the power of being freely adaptable to any situation and changing practices with the circumstance. The one weather curveball we have had this season, as with most seasons, just happens to be water - lack or abundance of rainfall.

Too much water early may inhibit root systems, and if dry conditions follow a "flash drought" situation can occur. In KC, STL and southern MO, which in some areas had double the normal amount of rainfall in May, several turfgrass stands are going into a quick dormancy state which is being mistaken for widespread disease occurrence. This is especially true for newly sodded lawns as pictured above. New sod and their compromised root systems aren't able to adapt to the quick changes of heavy rainfall to no rainfall. In these situations, it's critical to monitor the rooting or "take" of the sod by gently pulling on a few areas, and delivering smaller, more frequent pulses of irrigation to the depth of the roots and not too the point of runoff. A recipe for brown patch on tall fescue… yep. However, in this case, the disease is better than losing the new sod to permanent wilting of the stand… and that's a turfgrass pathologist stating that.

These yin and yang of periods of heavy rainfall followed by dry conditions can also spur, and make quickly apparent, preferential water flow in soil caused by localized dry spot (LDS). It's probably no coincidence that we are seeing early, damaging fairy ring occurrence this year and reports of problematic LDS on putting greens. Low humidity, yet still suitable growing conditions for cool-season turfgrass is also increasing the load and importance of water transport, making these LDS stand out.

Natural soils are not immune, but sand-based putting greens are much more prone to LDS due to particle size and structure. Dr. Stan Kostka on June 8 pointed out a study done by Tim Bauters at Cornell that found only 3% of hydrophobic sand added to a wettable sand was enough to render the whole mix non-wettable. That's not a lot considering the ample amount of organic matter that can transition to hydrophobic organic coatings upon microbial breakdown. Conduct a simple water droplet test. Consider wetting agent options (there are a ton of them) and consult with others on their experience with them.

Bruce Lee didn't incorporate this into the analogy, but perhaps should have. Adapting practices to the water needs of turfgrass is an ever flowing, changing dynamic in summer. Irrigation systems, whether they are on a sports facility, golf course or home lawn are not set it and forget it devices and require constant adjustment during the season to follow plant water needs. Decisions should be made on areas that absolutely require water to maintain a stand, versus turfgrass species such as tall fescue that have robust drought dormancy mechanisms. Although going brown, established turfgrass stands on lawns or lower amenity areas rarely perish completely and are simply biding time until rainfall occurs again. They move with the water. A movement away from the necessity of a perfectly green lawn (or out-of-play area) every day of the year in fluctuating environmental conditions is perhaps another of the flowing, water-like changes necessary in the collective public psyche.



Lee Miller

Extension Turfgrass Pathologist
University of Missouri
turfpath@missouri.edu
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