More  P  =  More  Poa    

 

 

Mizzou  Field  Day  next  Tuesday,  July  30th  at  8:30  am    Make  plans  to  join  us  next  Tuesday  for  the  University  of  Missouri  Turfgrass  &  Ornamental  Field  Day  held  at  South  Farms  (directions  can  be  found  here).    We  have  a  great  lineup  of  topics  and  speakers  during  our  morning  sessions,  and  have  three  informative  afternoon  tours  given  by  local  experts  that  follow  a  golf,  sports  turf,  or  landscape/horticulture  track.    In  addition,  we  have  15  vendors  lined  up  and  ready  to  show  off  equipment  and  plant  management  solutions.    It’s  a  full  day  celebration  of  learning  and  camaraderie.    Plus,  the  temperatures  couldn’t  be  better  for  a  MO  July.                Links  are  below  to  access  registration  for  both  attendees  and  vendors,  and  the  complete  field  day  agenda.  Hope  to  see  you  there.        For  the  full  agenda,  click  here.    For  attendee  registration,  click  here.  For  exhibitor/vendor  registration,  click  here.      Weather    

   

In  the  words  of  our  state  climatologist,  “What  a  difference  a  year  makes!”.    Last  year,  July  was  the  5th  hottest  on  record,  which  makes  our  current  average  July  feel  like  a  cold  blast.    The  remaining  July  forecast  also  looks  like  a  string  of  pearls,  as  the  jet  stream  will  push  a  cold  front  through  \  Missouri  and  leave  some  areas  only  having  weekend  highs  reaching  the  70’s  (can  that  be  right??).        

50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.0 90.0 95.0

100.0

7/1 7/3 7/5 7/7 7/9 7/11 7/13 7/15 7/17 7/19 7/21 7/23 7/25 7/27 7/29 7/31

Tem

pera

ture

(°F)

Columbia, MO July Daily Max/Min Temperature Normal vs 2013

Avg Max Temp Avg Min Temp 2013 Max Temp 2013 Min Temp

Jul 1-23, 2013 Avg: 76.7°F Dept. from Norm: -0.8°

2012 = 85.2℉

A

A Cool, Dry JulyA. Temperatures are just below normal average for July. Source: Pat GuinanB. Our dry July has landed us on the radar of the U.S. drought monitor. Nothing as

severe as western KS, but some areas are 1.5 - 3” below normal for the month. - Source: UNL drought monitor

B

More  P  =  More  Poa    

 

 

Precipitation  thus  far  in  July  has  been  spotty,  with  some  areas  like  Jefferson  City  right  on  the  monthly  average,  but  most  others  running  from  1.5”  to  even  3”  below  normal  for  the  month.    This  dry  July  pattern  has  put  us  on  the  radar  of  the  US  drought  monitor  (http://droughtmonitor.unl.edu),  but  as  I  noted  last  week  not  nearly  at  the  severe  level  like  last  year  or  currently  in  western  KS.      The  currently  passing  cold  front  is  giving  Kansas  a  dose  of  rain  now  and  should  impact  Missouri  this  Friday  and  early  weekend,  so  hopefully  some  tall  fescue  lawns  will  pop  out  of  dormancy.    Quick  Hits    -­‐ Heat/drought  stress  on  tall  fescue  lawns  has  been  an  issue  over  the  last  two  

weeks.    With  the  (now  previous)  heat  stress  and  lack  of  water,  these  lawns  will  not  take  traffic  very  well.    In  particular,  it  is  important  to  restrict  mowing  on  dormant  or  heat  stressed  lawns.    In  several  lawns  around  the  area,  I’ve  noticed  lines  of  discolored  mower  wheel  tracks  where  lawns  where  mowed  during  the  heat  of  the  day.    If  it’s  browned  out  or  looks  wilted,  water  it  or  let  it  be…  

 

   -­‐ Too  wet:    On  putting  greens,  physiological  root  decline  has  been  prevalent  on  

samples  as  we  enter  into  the  last  chapter  of  summer.    Our  wet  spring  has  set  up  some  greens  with  high  organic  matter  content  by  creating  a  waterlogged,  low  oxygen  condition  at  the  exact  time  bentgrass  root  growth  is  needed  most.    This  root  decline  is  observed  as  darkened  vascular  cylinders,  and  sloughed  off  epidermis  and  cortex  layers.    As  you  can  imagine,  numerous  secondary  pathogens  swarm  in  on  the  compromised  tissues,  including  take  all  patch  and  Pythium  spp.      Many  superintendents  are  using  penetrant  type  wetting  agents  to  get  this  water  through  the  profile,  past  the  organic  matter,  and  out  of  the  top  

More  P  =  More  Poa    

 

 

inch.    In  addition,  routine  venting  of  greens  with  solid,  pencil  or  bayonet  tines  should  be  done  to  promote  water  infiltration  and  get  the  bad  air  out.      

     -­‐ Too  dry:  On  the  flip  side  of  this,  there  are  also  several  superintendents  dealing  

with  localized  dry  spot  (LDS)  and  some  fairy  ring  activity  as  we  go  through  this  brief  period  of  drought.    In  one  case  earlier  in  the  month,  the  LDS  had  set  in  an  inch  below  the  surface  below  the  organic  matter  layer.    At  this  point,  a  wetting  agent  should  be  used  to  combat  LDS,  and  if  fairy  ring  is  the  problem,  a  fungicide  (ProStar,  Heritage,  or  Insignia)  should  be  tank-­‐mixed  with  a  wetting  agent.    Again,  venting  is  also  suggested  in  these  areas.          

 -­‐ So  how  to  get  it  not  too  wet  and  not  too  dry?    I  would  be  remiss  not  to  mention  

the  utility  of  TDRs  or  time  domain  reflectometer  sensors.    These  devices  are  gaining  popularity  among  many  superintendents  for  measuring  volumetric  water  content  and  dialing  in  soil  moisture  on  putting  greens.    If  you  are  using  one,  what’s  your  desired  range?    (See  survey  above).          

   

-­‐ I  am  also  noticing  considerable  amounts  of  surface  and  foliar  algae  on  recent  putting  green  samples,  particularly  from  those  that  also  have  wet  soil  profiles  due  to  over-­‐irrigation  or  high  organic  matter.      Many  pathologists  may  not  consider  algae  a  true  pathogen,  but  where  there  is  a  canopy  opening  it  is  obvious  that  algae  competition  considerably  reduces  the  ability  of  the  bentgrass  plant  to  regrow.    Some  of  these  algae  (aka  cyanobacteria)  have  been  shown  to  produce  a  phytotoxic  secondary  metabolite  to  gain  this  competitive  advantage,  and  can  cause  a  disease  termed  yellow  spot  in  otherwise  healthy  bentgrass.    Daconil  Ultrex,  mancozeb,  and  the  phosphite  fungicides  have  been  shown  to  restrict  algae  growth  and  allow  for  bentgrass  regrowth.    In  addition,  switching  to  an  

Algae invasion on putting greensA. Closeup of algae infesting the crown and leaf sheath of a bentgrass plant. B. Algae accumulation around the leaf tip.

A B

More  P  =  More  Poa    

 

 

ammonium  sulfate  nitrogen  source  and  using  a  wetting  agent  may  also  help  reduce  algae  infestation.    For  more  information  from  some  of  my  colleagues  on  this  subject,  several  links  are  provided  below.  

 o Algae,  yellow  spot  and  cyanobacteria:  PACE  laboratories  o Yellow  spot  and  the  potential  role  of  cyanobacteria  as  turfgrass  

pathogens:    Tredway  et  al.  2006          o Algae  management  for  golf  course  putting  greens:  Kaminski  &  Inguagiato  

 Don’t  put  P  on  the  Poa    

   As  some  of  you  know,  I  left  the  country  last  week  for  the  International  Turfgrass  Research  Conference  (ITRC)  in  Beijing,  China.    I  call  the  ITRC  the  Olympics  of  turfgrass  because  it  occurs  every  4  years  and  brings  together  a  diverse  variety  of  turf  researchers  that  may  not  interact  on  a  regular  basis.    Despite  its  tough  time  on  the  schedule  for  an  extension  turfgrass  pathologist,  discussions  of  water  and  pest  management  issues  with  colleagues  from  Australia,  China,  Great  Britain,  etc,  are  invaluable  benefits  to  attending  this  conference.  It  also  was  my  first  time  in  Asia,  (for  all  72  hours  of  it).  The  cultural  experience  was  extraordinary,  and  I  learned  quite  a  bit  about  life  on  the  other  side  of  the  world.        A  piece  of  research  that  caught  my  attention  at  the  conference  was  authored  by  Raley,  Landschoot,  and  Brosnan  (from  Penn  State  and  UT)  and  investigated  fertility  practices  and  their  impact  on  Poa  annua  infestation  of  a  2-­‐year  old  bentgrass  putting  green.  In  this  2-­‐year  study,  nitrogen  rate  had  no  impact  on  the  amount  of  Poa  annua  infestation.    The  rate  of  phosphorous,  however,  did  have  a  pronounced  impact  on  Poa.    P  treatments  included  ~  1,  2,  or  3  lbs  P/1000  ft2  per  year  in  5  equal  applications,  or  no  P  treatment.    All  treatments  that  included  phosphorous  had  increases  of  3-­‐7%  Poa  cover  (no  difference  among  the  three  rates)  whereas  Poa  

2013 ITRC - Beijing, ChinaA. The temple at Jingshan Park. B. Like pools, it may be a good idea to restrict the use

of P on bentgrass putting greens.

A B

More  P  =  More  Poa    

 

 

cover  actually  decreased  (2%)  in  plots  that  were  not  treated  with  phosphorous.    In  addition,  turfgrass  color  ratings  were  higher  in  plots  that  didn’t  receive  P,  because  there  was  less  Poa  infestation.    This  correlation  isn’t  the  first  time  higher  Poa  infestation  was  linked  to  exogenous  P  application,  but  it  definitely  drove  the  point  home.                                  Hope  to  see  you  next  week  at  Field  Day!    Lee  Miller  Follow  on  Twitter!    @muturfpath  Like  on  Facebook!  Mizzou  Turfgrass  Extension  Turfgrass  Pathologist  University  of  Missouri