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POA ANNUA CONTROL IN WARM-SEASON GRASS SPORTSFIELDS

UPDATE

STA Victoria Wicket Seminar22 July 2015

John Neylan – Turfgrass Consulting & ResearchDavid Nickson – Grand Prix Turf

BACKGROUND

• Poa annua is an unsown component of many sportsturf areasin temperate climates.

• It is the most widespread turfgrass species occurring inintensively cultured turf and it is adapted to a broad array ofclimatic conditions from the cold Polar Regions to hot deserts.

• Poa annua is one of five of the most widely distributed plantspecies in the world and in Victoria was one of only two turftype grasses found in every horticultural region with the othergrass being couch (Cynodon sp.).

• This adaptability is due to its genetic variability that producesnumerous biotypes, even within the one location.

Poa annua on Macquarie IslandPoa annua is diverse and invasive

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• Changing conditions will stimulate the development of newbiotypes that are better adapted to those conditions.

• Even though P.annua is a difficult weed to control it also has alower tolerance than other turf species to stresses.

• With the predominance of warm-season grasses being usedon sportsfields in Victoria, P. annua is the most significantweed species.

• If it is allowed to persist it will cause significant thinning of thewarm-season species.

Figure 1: Poa annua type

% of population

0

5

10

15

2 0

2 5

3 0

3 5

4 0

T4 T3 T1 T5 T6 T2 T7

Poa annua Type

% o

f p

op

ula

tio

n

T1 T2 T3 T4

T5T6T7

Fig. 5: Poa annua characteristics

Maximum plant height

0

5

10

15

20

25

30

35

40

45

50

3 4 5 6 7 8 9 10 11

Plant height (cm)

No

. o

f p

lan

ts

• P.annua is generally treated as a weed to be eradicated.

• Most treatment methods give variable results.

• The difficulty in achieving control is due to the large seedbank.

• For any P.annua control program to be successful both preand post emergent control is required.

• Herbicide control strategies have generally concentrated onpost-emergent control with some limited use of pre-emergentherbicides. Post-emergent control can be very difficult due tothe different ecotypes of Poa annua that occur which havevarying susceptibility to the available herbicides.

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0 2000 4000 6000 8000 10000 12000 14000 16000

5 cm

4 cm

3 cm

2 cm

1cm

Thatch removed

Total

Total seedlings emerged (seedlings/m2)

Poa annua seed bank

Poa annua germination at various depths in a P. annua dominated sportsfield turf

THE PROBLEM

• Over the past 2 – 3 years it has become apparent thatcontrolling P. annua in couch and Kikuyu is becoming moredifficult.

• The inconsistent performance of any herbicide can be due tonumerous factors including;o weed biotypeo enhanced biological degradation of the herbicideo application methodo weather conditions at the time of application and temperatures

post-application.

• The most concerning problem with P. annua control is thegrowing evidence that there is increasing resistance to theavailable registered herbicides.

• Given that most sportsfields only receive 1 - 2 herbicide applications per year for the control of P. annua it is important that the most cost-effective and agronomically advantageous method is employed.

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PROJECT OBJECTIVE

• The objective of this project is to assess the efficacy of variouspre and post emergent herbicides to control herbicideresistant Poa annua in Couch and Kikuyu.

TRIAL METHODOLOGY• The trial is being undertaken on a Couch and a Kikuyu sportsfield.

• Pre-emergent herbicides: The following pre-emergent herbicideshave been used and applied according to label recommendations;

Treatment Active Product

T1 Oryzalin Embargo

T2 Pendimethalin Stomp

T3 Prodiamine Barricade

T4 Oxadiazon Ronstar

T5 Dithiopyr Dimension

T6 Untreated control

• Pre-emergent herbicide trial– Couch: Seaford Oval– Kikuyu: Frankston South

• The Pre-emergent herbicide trial was set up in late summer.

• The Post emergent herbicide trial will be set up in early spring.

Assessments are being undertaken as follows;

• % Poa annua: The % of Poa annua will be determined with the use of a 1x 1 metre grid divided into 100 squares. – Post-emergent herbicides assessed every 2 weeks for a period of 12 weeks.– Pre-emergent herbicides assessed every 4 weeks for a period of 26 weeks.

• % of squares with Couch: The % of squares with couch will be determined during the Poa annua counts.

• Turf quality: The treatments will be visually assessed for turf quality using a 0 – 9 scale where 0 = very poor and 5 = excellent.

• Turf density: The treatments will be visually assessed for turf density using a 0 – 9 scale where 0 = no turf cover and 5 = very dense.

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Treatment14/4/15(48 DAT)

15/5/15(78 DAT)

17/6/15(111 DAT)

14/7/15(168 DAT)

Oryzalin 0 0 0** 0Pendimethalin 0 20.3* 33.7 41.7Prodamine 0 0.3 10.3** 16.3Oxadiazon 0 28.7* 39.0 100.3Dithiopyr 0 18.0 39.0** 67.3UTC 0 99.3 163.0 194.3

LSD (P<0.05) NS 36 29 75

Table 1: Seaford Oval – Average No. of squares with Poa annua

Note: *oxadiazon and pendimethalin are effective up to 70 days after application.**Other herbicides provide about 100 – 120 days control

Table 2: Frankston South – Average No. of squares with Poa annua

Treatment14/4/15(48 DAT)

15/5/15(78 DAT)

17/6/15(111 DAT)

14/7/15(168 DAT)

Oryzalin 0 22.0 49.0 50Pendimethalin 0 44.7* 71.3 133Prodamine 0 17.0 48.0 116Oxadiazon 0 68.3* 117.7 164Dithiopyr 0 21.0 62.3 134UTC 0 55.0 107.3 179LSD (P<0.05) NS NS 54 37

Note: *oxadiazon and pendimethalin are effective up to 70 days after application.**Other herbicides provide about 100 – 120 days control

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Notes on results;• Following the application of the herbicides there was low rainfall

and little or no Poa annua germination until 78 days after treatment.

• This timeframe affects the efficacy of some herbicides. • Seaford site:

– Sandy soils– Good drainage– Open position– Pre-emergent herbicides have performed well.

• Frankston South site:– Clay soils– Poor drainage– Shaded position– Conditions appear to reduce the efficacy of the Pre-emergent

herbicides.

Conclusions to date;• Site conditions affect the efficacy of the pre-emergent herbicide.

• Repeat applications for some pre-emergent herbicides is required.

• Timing of applications in relation to the peak germination of Poa annua is critical to control.

• In this case prolonged dry conditions meant that the peak Poa annua germination period was late into the period after the herbicides were applied.

• Monitoring conditions is critical in understanding how to get the best out of the pre-emergent herbicide program.

Oryzalin

Dithiopyr

Control

Seaford Site – Couch 111 DAT

OryzalinControl

Seaford Site – Couch 111 DAT

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Oryzalin Pendimethalin

Seaford Site – Couch 111 DAT

Oryzalin

Control

Dithiopyr

Seaford Site – Couch 111 DAT

Do we need Poa annua?

Frankston South Site – Kikuyu 111 DAT

Do we need Poa annua?

Frankston South Site – Kikuyu 111 DAT

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• Post-emergent herbicides: The post-emergent herbicides will be selected from the following;

HERBICIDEST1 Monument (TRIFLOXYSULFURON SODIUM )T2 Destiny(IODOSULFURON-METHYL-SODIUM)T3 Endothal (E)T4 Glyphosate (G)T5 Tribute (FORAMSULFURON)T6 Propyzamide (Kerb)T7 Mix 1 – Tribute + DensityT8 Untreated control – used to assess the natural transition of Poa

annua.T9 Mix 2 - Propyzamide (P) will be applied to half of each of the

treatments to assess the effects of using herbicides from different groups.

• GENERAL DISCLAIMER• IMPORTANT NOTICE

• Accuracy and Reliability of Information• While the Consultants have taken all care and responsibility in producing the information in this

document, the Consultants makes no representations in respect of, and, to the extent permitted by law, excludes all warranties in relation to, the accuracy or completeness of the information. The consultants, its officers, employees, directors and contractors exclude all liability whatsoever for any loss or damage, howsoever, arising out of reliance, in whole or in part, on the information.

• Exclusion of Liability • To the maximum extent permitted by law, the Consultant, nor any of its agents or sub-contractors,

directors, officers or employees shall be liable for any direct, indirect, special, incidental, consequential, punitive, or exemplary damages, including lost profits (even if the Consultant is advised of the possibility thereof) arising in any way from, including but not limited to:

• The information contained in this document (or due to any inaccuracy or omission in such information); or any other written or oral communication in respect of the historical or intended business dealings between the Consultant and the Client.

• Notwithstanding the above, the Consultant’s maximum liability to the Client is limited to the aggregate amount of fees payable for services under the Terms and Conditions between the Consultants and the Client.

• The Poa annua control strategies stated in this presentation are specific to the particular circumstances of the trial and are not meant to be implemented without careful thought and planning and taking into account local conditions. Any reference to chemicals not registered in Australia is mentioned for education purposes only.

ACKNOWLEDGEMENTS

We wish to acknowledge;

• The financial support of the Sports Turf Association, Victoria.

• Garry Woolard - Coordinator Parkland Services, Frankston City Council.

• Gavin Bock - Team Leader Active Reserves , Frankston City Council.