Poa trivialis:Poa trivialis: Where Does It Come From 

d H t C t l Itand How to Control It

Zac Reicher, Ph.D.

http://turf.unl.edu/p // f /

http://turf.unl.edu/

Poa trivialisPoa trivialis

• Weak perennial• Weak perennial• Outgrows other cool‐season grasses in spring and fall 

• Extremely sensitive to heat drought dollar spot• Extremely sensitive to heat, drought, dollar spot, (and who knows what else) in mid‐ to late‐summer

• Goes dormant in Augustb f d l• Re‐grows in September from crowns and stolons

Where does it come from?Where does it come from?

• Overseeded in Southern greens• Has gained popularity in last 15 years• Contaminant in seed fields• Major contaminant in northern golf course fairways• Major contaminant in northern golf course fairways, athletic fields, lawns seeded or overseeded in last 10 years

• Grows “wild” in pastures fence rows etc as a very• Grows  wild  in pastures, fence rows, etc. as a very early contaminant

• Once established, spread through aerification

Seed contamination 1998Seed  contamination‐ 19981/3 of CBG seed lots contained Poa trivialis1/3 of CBG seed lots contained Poa trivialis

Seed contamination 1998Seed  contamination‐ 1998Test sample size

2.5 gram 10 gram 50 gram

Bentgrass samples  90 90 90t t dtested

% containing  3 6 30trivialis

Matt Levy, 1998 Green Section Record

Purdue seed contamination survey- 2008y

Seed contamination 2008Seed contamination ‐ 2008

8 of 72 (11%) seed lots contained Poa trivialis8 of 72 (11%) seed lots contained Poa trivialis

• 3 seedlots = 9 Poa triv seeds/lb

• 3 seedlots = 18 Poa triv seeds/lb

• 1 seedlot = 27 Poa triv seeds/lb

• 1 seedlot = >45 Poa triv seeds/lb

7/8 seedlots were certified blue tag7/8 seedlots were certified blue tag

Keeping it outKeeping it out

Control in seedbed• Velocity 17.6WSP can be applied at 1 WAE with good safety on bent and good control on P t iPoa triv

• Certainty safety is highest at 4WAE depending on rateon rate

• Multiple apps will improve control• Both will control seedling Poa annua• Both will control seedling Poa annua

Rutledge, et al. 2010. Golf Course Management. April: 98‐ 103

Safety of Velocity 17.6SG when applied over newly‐seeded L93 creeping bentgrass. Regardless of rate or timing, Velocity had no effect on cover by 8 weeks after emergence (WAE) (Purdue 2007)emergence (WAE) (Purdue 2007).

Control of Poa trivialis by  Velocity 17.6SG when applied over newly‐seeded Poa trivialisand rated 8WAE. Though multiple applications are always more effective on Poa trivialis, single applications at 1‐2 WAE were effective (Purdue 2007)single applications at 1‐2 WAE were effective (Purdue 2007).

Effect of two applications of Velocity 17.6 SG or Certainty applied to separate stands of seedling Poa trivialis or creeping bentgrass in fall 2008 at various weeks after emergence (WAE) Data presented were collected eight weeks after emergence

90

100

Bentgrass

Poa trivialis

emergence (WAE). Data presented were collected eight weeks after emergence.

A A A A A Aa a

60

70

80

r 8 WAE

B

30

40

50

% cover

Cb b

0

10

20

c c c c0

1.5 oz/A

 WAE

1.5 oz/A

 WAE

3.0 oz/A

 WAE

3.0 oz/A

 WAE

ty 0.125

 +4

 WAE

nty 0.25

 +4

 WAE

ntreated

 control

S control

c

Velocity 1

1+2 W

Velocity 1

1+3 W

Velocity 3

1+2 W

Velocity 3

1+3 W

Certaint

oz/A

 2+

Certain

oz/A

 2 Un c

NIS

Controlling established Poa trivialisControlling established Poa trivialis

• Certainty, Velocityy y

• Start apps at temps>70F• Most aggressive:

– Certainty 0.5 oz/A * 3 apps– Velocity 17.6WSP  4.5 or 6.0 oz/A * 4 appsL i• Less aggressive– Certainty 0.25 oz/A * 2 or 3 apps

• Variability from location to location• Variability from location to location• Temps>85F improves control• Some phyto expected, low N, Fe will helpp y p , , p

Effect of Certainty or Velocity applied every two weeks on Poa trivialis controlon Poa trivialis control

Treatment Rate Apps IL IN SD SunTreatment Rate Apps IL IN SD Sunoz/A ‐‐‐‐‐‐‐% Control‐‐‐‐‐‐‐‐‐

Certainty 75WDG 0.25 2 ‐9 e 3 c 18 b

Certainty 75WDG 0.50 2 26 d 8 c 64 ab

Certainty 75WDG 0.25 3 32 cd 12 c 41 b

Certainty 75WDG 0.50 3 90 a 42 bc 86 a

Velocity 80SP 0.65 4 52 bc 63 ab 23 b

Velocity 80SP 0 98 4 77 ab 88 a 18 bVelocity 80SP  0.98 4 77 ab 88 a 18 b

Velocity 80SP  1.3 4 62 abc 96 a 23 b

No differences in South Dakota (shade) and in Wisconsin

Golf Course Management, October 2007

Long‐term conversion studyLong term conversion study

• Stand: 90% triv/10% CBG fairway

• 7 herbicide treatments:– Certainty 

• 0 25 oz/A * 2 apps• 0.25 oz/A   2 apps

• 0.50 oz/A * 2 apps

• 0.25 oz/A * 3 apps

• 0 50 oz/A * 3 apps• 0.50 oz/A * 3 apps

– Velocity 17WSP• 3.0 oz/A * 4 apps

4 5 /A * 4• 4.5 oz/A * 4 apps

• 6.0 oz/A * 4 apps

• ½ of plots were seeded w/L93 after last application

• Repeated for 3 years on separate areas

Long‐term conversion studyLong term conversion study

• Applications started in Junepp

• Last application on Aug 1

• Aerified/seeded on Aug 15/ g

• Recorded data through 46 weeks (until start of next year’s apps)y pp )

• Long‐term control was largely affected by short‐term herbicide efficacy

• Short‐term control was largely affected by weather

Maximum and minimum air t t itemperatures in West Lafayette, IN, in 2006 –2008.

Poa trivialis and creeping bentgrass cover after Certainty or Velocity applications rated at 46 WAT (weeks after final treatment) in 2006.  Means are averaged over two seed treatments and three replications.  Lower case letters are used to compare creeping bentgrass cover while upper case letter are used to compare roughstalk bluegrass cover.  Bars with the same letter and case within the same rating date are not significantly different (P <0.05). Between 1 June and 1 Sep, there were a total of 21 days with max temps > 85F and max temps remained > 85F for 3 consecutive days on 4 occasions.

Poa trivialis and creeping bentgrass cover after Certainty or Velocity applications rated at 46 WAT (weeks after final treatment) in 2007.  Means are averaged over two seed treatments and three replications.  Lower case letters are used to compare creeping bentgrass cover while upper case letter are used to compare roughstalkbluegrass cover Bars with the same letter and case within the same rating date are not significantly different (Pbluegrass cover.  Bars with the same letter and case within the same rating date are not significantly different (P <0.05). Between 1 June and 1 Sep, there were a total of 28 days with max temps > 85F and max temps remained > 85F for 3 consecutive days on 5 occasions.

Poa trivialis and creeping bentgrass cover after Certainty or Velocity applications rated 46 WAT (weeks after final treatment) in 2008.  Means are back‐transformed and averaged over two seed treatments and three replications.  Lower case letters are used to compare creeping bentgrass cover while upper case letter are used to compare roughstalk bluegrass cover.  Bars with the same letter and case within the same rating date are not significantly different (P <0 05) Between 1 June and 1 Sep there were a total of 7 days with max temps > 85Fsignificantly different (P <0.05). Between 1 June and 1 Sep, there were a total of 7 days with max temps > 85F and max temps remained > 85F for 3 consecutive days on 1 occasion. 

Control recommendationsControl recommendations• Buy good seed, test 50 grams if possible• Early applications over new seedlings to minimize future 

contamination (some seed contamination still exists)• Avoid further contamination through sanitation when 

aerifyingaerifying• Apply starting in late May/June >75F• Most aggressive:

C i 0 5 /A * 3– Certainty 0.5 oz/A * 3 apps– Velocity 17.6 SP 4.5 or 6.0 oz/A * 4 apps

• Temps >85F improves control• Reseeding after application improves competition  and long‐

term control• Reseeding interval after applicationg pp

• Certainty 2‐3 weeks• Velocity 10 days

Keeping Poa trivialis aliveKeeping Poa trivialis alive

E i i l h d d• Easier in cool, shaded areas

• Avoid drought stressg– Difficult because extremely shallow rooted

• Preventative disease control – dollar• Preventative disease control – dollar spot, others?

Effect of season‐long fungicide applications made every two weeks from May through September cover of fairway height Poa trivialis (exceeds label recommendations in most cases) (Purdue 2006).

100

E ld

70

80

90 EmeraldProstarSubdueEmerald+ProstarEmerald+Subdue

50

60

70

vialis cover

Emerald+SubdueProstar+SubdueEmerald+Prostar+SubdueEmerald+Prostar+Subdue+HeritageControl

20

30

40

% Poa

 triv

0

10

20

Poa triv physiologyPoa triv physiology

Can we take advantage of its natural growthCan we take advantage of its natural growth patterns to get better control?

Mean %Cover Ratings 110

105

00)

95

100

r (1-

10

90

95

%C

ove

L93

80

85

% LaserPulsar

80

4/215/5 5/196/2 6/166/307/147/288/118/259/8 9/2210/6

Date

Mean dry weight (mg)/cm stolon 6n

5

6st

olon L93

Laser

3

4

g)/c

m s

Pulsar

2

3

wt (

mg

0

1

dry

w

6/106/247/87/228/58/199/29/169/3010/144

Date