Friday, July 29, 2016

Dr. Lee Miller July Report

     Dr. Lee Miller is the Turfgrass Pathologist from the University of Missouri.  This is part of his report for July.  This really hits home for me.  Dan and I have put in an enormous amount of time trying to care for our greens.  It has been a very frustrating July.  In the past 29 days we have recorded over 9 inches of rain.  We are reevaluate some of our cultural practices for next season.  I also believe we need  more and better fans.  I will look into this for next season.   We have a lot of Bentgrass growing around the surrounds of our greens that is burning out we need to replace this grass with a hardier variety like Turf type Fescue on the green sides and Zoysia grass in the aprons.  We are not the only course that is having issues.  That does not make Dan or I feel any better.  I hope this article helps explain what we are going through.  We are battling exactly what he is saying in this post.  You can access Dr Millers site  from my blog at the bottom right of my page.  Just hit the link University of Missouri Turf Pathology.  He puts out a new post once a month.   Below is Dr. Millers July Post.

Dr. Lee Millers Post

Bentgrass Decline – The Perils of Too Much Water

Samples of declining bentgrass putting greens have flooded into the MU Plant Diagnostic Clinic over the last two weeks.  This persistently terrible weather pattern for bentgrass health has taken an extreme toll on the health of these cool season plants that are perilously trafficked, groomed, and cut at marginally sustainable heights.  Many are also facing maintenance heavy and high expectation tournaments in late July or August, which are doing no favors.
Below are the three most often observed problems on bentgrass putting greens we’ve seen in the Clinic over the past month in order of prevalence.  Note all of the issues are root related.  Management practices should be focused on this aspect during these times of turmoil, while simultaneously not neglecting the normal stress preventers (raising mowing heights, smooth rollers, spoonfeeding, etc.).  A preventive soilborne fungicide program is warranted, but also realize the answers to these problems will not solely come out of your sprayer boom.  Lastly, the physiological decline of the plant due to inhospitable weather conditions is paramount here. So addressing this first, as I will, can reduce your management inputs substantially for the true biotic issues.

Early August Outlook
  1. Heat expected to return next week. - Source: NOAA CPS
  2. Above average rainfall pattern expected to stay in the early August. - Source: NOAA CPS
 

1. Root Physiological Decline

Physiological Root Decline
  1. Sloughing off of cortex of hot saturated root.
  2. An extremely affected root, with only a very unprotected vascular cylinder remaining.


Air vs. water - the struggle is more than real now in a bentgrass root’s existence.  Needs both, but most of the time the overabundance of water is the true enemy.  Water excludes air indiscriminately in pore spaces of saturated soils, and then holds a constant temperature for an extended amount of time.  Root growth stops at 86 degrees F (30 C), and daily 2” soil temperatures in native soils were averaging 90 degrees and above during this latest heat wave.  These water soaked soils simply don’t cool off at night, leaving roots to continually boil.  This high specific heat capacity of water keeps fish in the deep pond happy, but won’t keep shallow roots growing in the wading pool of a summer putting green rootzone. Managing greens with a soil moisture meter (TDR) is a good way to dial in the difference between underwatered, adequate, or oversaturated. 
Recently, Dr. Bill Kreuser from the University of Nebraska posted a video regarding the cooling effects, or lack thereof, of syringing greens (click here to view).  Several superintendents are stopping or considering stopping the practice of cooling off greens with water throughout the afternoon heat and focusing on utilizing morning irrigation only to provide water throughout the day.  From a root perspective, this is a wise move, since most syringing practices in my estimation provide considerably too much water into the rootzone during the heat of the day.  This water sticks in the organic matter, heats up, and commences to sous vide the short root system for an extended amount of time.  Additionally, this excess water provides a suitable environment for soilborne pathogens, particularly Pythium root rot.
The true hero of cooling is air movement.  As stated a few times in these updates, fans have been the best, most consistent fungicide and plant health tool I’ve observed.  As shown by David Han at Auburn University, fans reduce not only air and canopy temperature, but also soil temperatures by 5 – 7 degrees F.  This makes sense when thought of in the air vs. water perspective.  Humidity in the air and moisture on the leaf is reduced, allowing the plant to continually move water through its system and out to the atmosphere.  Functioning roots in turn pull water out of the soil pores and leaves air, which won’t hold on to that high temperature so stubbornly when the evening hours finally arrive.  So break out the generators and box fans on troubled greens to encourage recovery, and put in a request for 220 volts of beautiful wind.
Lastly, venting greens needs to go on your calendar just as much as when to make fertilizer and pesticide applications.  This is a crucial water and air management tool for your rootzone during the summer heat, and should be planned biweekly at a minimum.  The damage done during the venting process pales in comparison to the damage that will be done if venting doesn’t occur regularly.

2. Pythium Root Rot

Pythium Root Rot Still Widespread
Several samples of “wow” amounts of Pythium root rot have been submitted recently.


In past reports, I have beaten to death the amount of Pythium root rot observed this season.  In the last few weeks, several samples of “wow” Pythium root rot infections have continued to come in, indicating again how widespread this epidemic is in the region.  A preventive program using watered-in (approximately 1/8 inch) fungicide applications should been in place, particularly in areas heavily impacted by July rains and those that have had a history of the disease.  As detailed by Dr. Jim Kerns at NC State University, a 14 day rotational program using Segway (low rate) as a base (i.e. Segway – Signature Xtra – Segway – Banol – Segway – Subdue, etc.) is the current suggestion for controlling this difficult disease.  Dr. Kerns will be visiting the MU campus on September 21 to give a seminar to the Plant Sciences Division.  Superintendents interested in attending should send me an email for more details.

3. Summer Patch

Summer Patch on Bentgrass
  1. Stand symptoms include a mottled and wilted appearance. Fairly indiscriminate from other root issues.
  2. Roots appear with darkened vascular cylinders.
  3. Pathogen mycelium coming out of root stele.


Last, but certainly not least, we have observed a number of cases of summer patch on creeping bentgrass as the primary cause of decline, and also as an “add-on” in root physiological decline.  This pathogen begins to infect earlier in the summer (65 F soil temperature) and gradually takes out the root system with summer stress being the final deliverer of symptoms.  Stand symptoms appear as mottled, droughty areas.  Individual roots have extremely darkened vascular cylinders with symptoms that extend all the way up to the base of the plant.  On bentgrass putting greens, a preventive strategy of watered in applications of QoI fungicides (Heritage, Insignia) or mixtures with QoI fungicides (i.e. Briskway, Lexicon) are recommended.    
Lee Miller
Follow on Twitter!  @muturfpath
Like on Facebook! Mizzou Turfgrass
Extension Turfgrass Pathologist
University of Missouri 








Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)