GOLF: Have you hollow tined aerified bentgrass greens this season?

Yes - late March/early April
Yes - mid April
Yes - within last 10 days
No - plan on May
No - don't aerify in the spring

Update (4/30/2020)

Rorschach Grass

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April - Temperature Streak Breaker

  1. As forecasted, a huge dip in temperatures should lead to a cool April. – MU Climate Center
  2. Cooler temperatures expected to stick around for the first week of May – NOAA

April will go down as a record breaker in more ways than one. As mentioned in the last update, many Missouri locations logged temperatures in the high 80s, breaking record highs for many cities. Not but 24 hours later, the bottom dropped out with freezing temperatures off and on over the following 9 days, with lows in the mid to upper 20s on April 18th. All told, the month will end below average, which breaks the streak (or record) of four consecutive months of well above average temperatures (Dec – March was 7th warmest in the past 126 years). This spring temperature roller coaster has resulted in several reports of very confused plants (see story below).

Much of the month of April was fairly dry until last week when the spigot got turned on full blast. A swath along the I-44 and I-70 corridor got a blast of 3-4" of rainfall in the last week, turning dry and near droughty conditions into wet, saturated soils in the blink of an eye. From these past nine days, April rainfall totals will end 1 or 2" above normal, meaning 12 of the last 15 months will have had above normal rainfall in MO.

Cooler than normal temperatures are expected to persist through the first week of May. May is historically Missouri's wettest month, and in true May form 0.5 – 1" of precipitation is also expected next week. Plant growth should remain slow and steady, with warm season grasses still recovering and getting back out of dormancy, while cool season species thrive in the slow steady climb of this spring.

Wet Pattern Continues

  1. A fairly dry early-mid April changed quickly to wet conditions. – MRCC
  2. May, the wettest month in MO, looks to start that way over the next 7 days. – NOAA

Quick Hits

  • COVID-19 Safety Resources for the Turfgrass Industry – Several MU Extension faculty collaborated to produce a guide sheet to aid agricultural employers, (including our industry), in taking precautions to prevent business disruption and worker exposure to COVID. The signs are in both English and Spanish, and would be suitable to print and post in communal areas and other places of work. The direct link to the two signs are:

    Poa trivialis Infesting Lawns
    After a mow, roughstalk bluegrass demonstrates its namesake.

  • Poa trivialis – Numerous observations of Poa trivialis infesting older and newly seeded lawns have been reported over the last week. This common and very difficult weed to control in home lawns, is stoloniferous expanding into larger patches with thin and stringy stolons and stems. Patches are a conspicuous lighter green color and stand out in a darker tall fescue sward in the spring. Patches are prone to get puffy and, true to its name, the thicker leaf sheaths shear and appear torn when scalped. Due to its similar size and shape to other cool-season turfgrass seeds, P. trivialis is considered one of the most common contaminants of turfgrass seed. Poa trivialis is also sold as an alternative to perennial ryegrass for overseeding warm-season grasses, which can increase the possibility of seed contamination. The photos of P. trivialis above are from several plots within the tall fescue NTEP trial planted in September 2018. We haven't observed the weed in any other tall fescue sward on the farm.

    Getting patches of this weed out once they establish is a difficult proposition. On sod farms and golf courses, Velocity (bispyribac-sodium) can be used for roughstalk bluegrass but can cause significant injury to some Kentucky bluegrass cultivars and is not labeled for other sites. Despite popular opinion, Xonerate (amicarbazone) and Tenacity (mesotrione) have been found ineffective in research studies for roughstalk bluegrass control and are not labeled for the purpose, leaving no selective control options in home lawns. Spring applied spot applications of glyphosate are most effective for control, but results in a bare spot that will need to be seeded in a tight window prior to summer stresses. Therefore, late summer applications followed by seeding may in fact be better for rebuilding lawn density. Last but not least, P. trivialis is fairly shallow rooted so areas may be dug out and seeded or resodded. Since stolons can extend beyond the patch, dig out an area approximately 6" beyond the edge of the patch to remove it completely.

  • Net blotch on Young Tall Fescue
    Not often a devastating disease, but net blotch is an early invader of young tall fescue swards.

  • Net Blotch – Also while rating the tall fescue NTEP trials, I observed a fair amount of net blotch, a disease caused by Drechslera dichtyoides, one of the leaf spot or "Helminthosporium" diseases. Net blotch is normally more prevalent on younger tall fescue stands, and is therefore most often observed on sod farms. The disease can be obvious on leaf blades and result in minor turf decline in these cool and wet spring conditions. The disease will normally phase out in the summer, however, and yield to its much nastier brethren, brown patch. Reducing leaf wetness and maintaining adequate fertility with proper mowing height is normally enough to stave off this disease without the need for fungicides. Strobilurin (or QoI) fungicides targeting brown patch later in May will also control this disease.

  • Red Thread Just Starting on Perennial Ryegrass

    1. Perennial ryegrass starting to show symptoms of red thread.
    2. Pink mycelium and red sclerotia (black arrows) are tell-tale signs of red thread infection.

  • Red Thread – The first small symptoms and signs of red thread caused by Laetisaria fuciformis were observed on perennial ryegrass earlier this week. The disease can impact a number of turfgrass species in spring and early summer, but is much more prevalent in this region on fine fescues and perennial ryegrass. The characteristic "red threads" are fungal sclerotia that serve as the primary mechanism for overwintering. Maintaining proper fertility, avoiding overwatering (impossible this past week), and reducing leaf wetness usually are enough for control. Even in severe cases, a single fungicide application may be all that is necessary, with several fungicide classes offering good control.

  • Zoysia Steps Back, Large Patch Leaps Forward

    1. The environment for severe large patch outbreaks is ripe in late April.
    2. Zoysia is not growing at full strength, making large patch symptoms begin to stand out.

  • Large Patch – With freezing temperatures sending zoysia back in the house and a healthy dose of rainfall to greet it back out the door, large patch symptoms were bound to make a spectacular debut this past week. The turf farm had its first real set of symptoms this week, and several reports also came in from STL and Springfield. Hop on it early with a spring fungicide application in areas with a known history, because the forecast through early May looks extremely favorable for continued symptom development.

  • Bentgrass Greens Disease Prevention – On bentgrass greens, the environment for dollar spot pressure is upon us according to the Smith- Kerns model. Check it here, along with soil temperature which is cruising along in the range for soilborne disease control. With the current rain events and forecasted rains for next week, spring preventive Pythium root rot control should also be considered. Segway at the 0.45 fl oz rate should be considered a part of that program as a tank-mix with other fungicides aimed at controlling the ETRI patch diseases.

Cold Snap = Rorschach in the Grass

Speckled Turfgrass for Different, Yet Related Reasons

  1. Bentgrass hit with granular fertilizer can show uneven greening patterns.
  2. Our young bermuda NTEP plot showing some "tiger printing" from mid-April frosts.

As if something else needs to test our mind's flexibility in projecting meaning on the world, several turfgrass species have become living Rorschach inkblots after wild April temperature swings. Spotty creeping bentgrass, helped along by a granular fertilizer application, and bermudagrass with patchy tiger striping were evident this past week.

In the past week, several calls have come in with concern of off color, poorly performing bentgrass greens with shallower than normal roots. Almost all of them hollow-tine aerified in early April, right before the bottom dropped out with almost a sustained week of freezing temperatures from April 9 – 18. Slow recovery left some aerification holes to fill, and these holes may be the key to the mediocre growth. The air in those open, or even sand-filled holes dropped dramatically from 80+ degree temperatures quickly down to sub-freezing. Bentgrass plants were presumably cold-shocked, while at the same time being in recovery mode from the aerification process. Mid-April was also extremely dry, and crowns were exposed by aerification to a cold, low humidity wind that swept across the greens surface… a scenario we often associate with winter dessication.

Granular fertilizer applications normally applied in larger N doses to encourage recovery, may release with plants in such a state of shock that they were not active enough to take it up. As with the speckled greens above, we often see this response on our research greens with aerification and granular fertilizer applications made a little too late in the season. The green, speckled pattern is presumably from either or a combination of two factors along with granular N release – 1) increased or decreased penetration of the fertilizer granule through preferential flow through the open turf canopy of the aerification hole, and/or 2) more active, less affected plants taking the fertilizer up preferentially. These spots normally even out over a few weeks, particularly when light spoon fed sprayable summer N is applied and bentgrass growth resumes with optimal temperatures.

Bermudagrass "tiger striping" is a bit more complex, and it's apparent in the above photo of our NTEP plots that the phenomenon related to chilling injury is cultivar dependent presumably based on the greenup stage that occurred during the temperature drop. We also can see this pattern in the fall as our neighbor, Dr. Megan Kennelly from Kansas State, wrote about in this previous blog post. As with fall occurrences, bermudagrass pops right out of this condition when optimal temperatures arrive.

Lee Miller

Extension Turfgrass Pathologist
University of Missouri
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