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Brown Ring Patch Disease Control on Annual Bluegrass Putting Greens 2021 Report

RESEARCH REPORT BROUGHT TO YOU BY:

Brown Ring Patch Disease Control on Annual Bluegrass Putting Greens 2021 Report Pawel Petelewicz1, Pawel Orlinski2, Marta Pudzianowska2, Matteo Serena2, Christian Bowman2, and Jim Baird2 1Agronomy Department University of Florida, Gainesville, FL 2Department of Botany and Plant Sciences University of California, Riverside, CA 951-333-9052; jbaird@ucr.edu

The Bottom Line: Thirty-one combinations of experimental and commercially available fungicide treatments were tested against an untreated control for their ability to control brown ring patch (BRP) disease (Waitea circinata var. circinata) on an annual bluegrass (Poa annua) putting green in Riverside, CA. All treatments were applied curatively on January 24, 2021 and repeated either two (February 7) or three (February 16) weeks later. A combination of natural disease decline and treatment effects resulted in almost no disease symptoms present on February 16. On April 8, disease symptoms returned on select plots including the untreated control (disease severity = 2.4 on a scale of 0-5, and 3.4 nine days later). Treatments containing Premion (PCNB, tebuconazole) + Par SG (pigment), Oximus (azoxystrobin, tebuconazole), Ascernity (benzovindiflupyr, difenoconazole), or Mirage Stressgard (tebuconazole) exhibited the longest residual activity against BRP as evidenced by no disease activity at 69 days since previous treatment. Both BRP disease control and Poa seedhead control (likely from DMI fungicides) contributed to turfgrass visual quality differences among treatments. All treatments were applied again on April 19 and most were effective in controlling BRP even though disease activity in the control also subsided naturally. Overall, results of this study demonstrated several fungicides and combinations that are effective against BRP including four products that demonstrated exceptional residual control.

Acknowledgments Thanks to the Golf Course Superintendent Association Chapters of California and Southern Nevada and the California Turfgrass & Landscape Foundation (CTLF) for financial support of this research, and to companies for financial support and product donations.

Introduction Brown ring patch (BRP) caused by the fungus Waitea circinata var. circinata is a disease mostly found on annual bluegrass (Poa annua) and roughstalk bluegrass (Poa trivialis) putting greens. The causal agent is closely related to Rhizoctonia species with symptoms occurring as small yellow rings that can enlarge and turn brown and sunken. Brown ring patch usually occurs when daytime temperatures are between 6595F and under low nitrogen fertility. At the turfgrass research facility in Riverside, widespread disease occurrence has only happened in recent years and usually during the months from January thru April. In general, most fungicides that are effective against Rhizoctonia diseases are also effective against BRP. A notable exception was reported to be thiophanate-methyl. Previous studies have also demonstrated differences among fungicides in regards to both speed and longevity of BRP control.

Objectives This study was conducted to evaluate efficacy of 31 different fungicide treatments to control brown ring patch disease on annual bluegrass (Poa annua) putting greens. An unplanned, secondary objective was to evaluate residual disease control among the fungicide treatments.

Materials and Methods The study was conducted on mature annual bluegrass ‘Peterson’s Creeping’ turf established in 2007 on a Hanford fine sandy loam amended with sand. Turf was mowed 3-5 days/wk at 0.125 inches. Fungicide treatments were applied curatively on January 24, 2021 and thereafter as shown in Table 1. Treatments were applied using a CO2-powered backpack sprayer equipped with TeeJet 8003VS nozzles calibrated to deliver 2 gallons/1000 ft2 of carrier. Experimental design was a complete randomized block with 5 replications. Plot size was 4 ft × 6 ft with no alleys. Environmental data throughout the study period were collected from an on-site weather station and are presented in Appendix 1. Plots were evaluated for BRP disease severity on a 0 to 5 scale, where 0 is no disease and 5 is 100% of the plot is diseased, as well as for turfgrass visual quality (1-9; 9=best). Data were analyzed using analysis of variance for each evaluated trait and rating event separately and the means were compared using the Fisher’s protected least significant difference (LSD) test at the 0.05 probability level (P ≤ 0.05).

Results Brown ring patch disease was noted on the research green on January 7, 2021 and severity could be considered 4 or 5 on a 0-5 scale (data not shown). By the time the study could be initiated on January 24, BRP disease activity had subsided to <1.5 and treatment applications made on January 24 and repeated on either February 7 or 16 resulted in almost no disease activity on February 16 when only one ring was observed in a plot on that day (data not shown). On April 8, disease symptoms returned on select plots including the untreated control (disease severity = 2.4 on a scale of 0-5, and 3.4 nine days later). Treatments containing Premion (PCNB, tebuconazole) + Par SG (pigment), Oximus (azoxystrobin, tebuconazole), Ascernity (benzovindiflupyr, difenoconazole), or Mirage Stressgard (tebuconazole) exhibited the longest residual activity against BRP as evidenced by no disease activity at 69 days since previous treatment (Table 2). Both BRP disease control and Poa seedhead control (likely from DMI fungicides) contributed to turfgrass visual quality differences among treatments (Table 3). All treatments were applied again on April 19 and most were effective in controlling BRP even though disease activity in the control also subsided naturally (Tables 2 and 3). Overall, results of this study demonstrated several fungicides and combinations that are effective against BRP including four products that demonstrated exceptional residual control (Fig. 1).

Tables and Figures Table 1. Fungicide treatments tested against brown ring patch disease. Riverside, CA. 2021. No. 1

Treatment

Company

Rate

Timing

Premion

PCNB, tebuconazole

AMVAC

4.0

oz/M

PAR SG

pigment

Harrell’s

0.37

oz/M

Premion

PCNB, tebuconazole

AMVAC

6.0

oz/M

PAR SG

pigment

Harrell’s

0.37

oz/M

Premion

PCNB, tebuconazole

AMVAC

8.0

oz/M

PAR SG

pigment

Harrell’s

0.37

oz/M

PCNB

AMVAC

8.0

oz/M

PAR SG

pigment

Harrell’s

0.37

oz/M

Oximus

azoxystrobin, tebuconazole

AMVAC

0.8

oz/M

ACM

Oximus

azoxystrobin, tebuconazole

AMVAC

1.0

oz/M

ACM

Oximus

azoxystrobin, tebuconazole

AMVAC

1.6

oz/M

ACM

Rayora

flutriafol

FMC

1.4

oz/M

ACM

Traction

fluazinam, tebuconazole

Nufarm

1.3

oz/M

ACM

Ascernity

benzovindiflupyr, difenoconazole

Syngenta

1.0

oz/M

ACM

Briskway

Syngenta

0.9

oz/M

ACM

Posterity Forte

Syngenta

0.84

oz/M

ACM

Posterity XT

Syngenta

1.5

oz/M

ACM

Maxtima

azoxystrobin, difenoconazole pydiflumetofen, propiconazole, azoxystrobin pydiflumetofen, propiconazole, azoxystrobin mefentrifluconazole

BASF

0.6

oz/M

ACM

Maxtima

mefentrifluconazole

BASF

0.6

oz/M

ADM

Mirage Stressgard

tebuconazole

Bayer

1.5

oz/M

ACM

Mirage Stressgard

tebuconazole

Bayer

1.5

oz/M

ADM

UCR 003

classified

ACM

UCR 003

classified

ACM

UCR 003

classified

ACM

UCR 003

classified

ADM

UCR 003

classified

ADM

UCR 003

classified

ADM

UCR 004

classified

ACM

UCR 004

classified

ACM

UCR 005

classified

Secure

fluazinam

Syngenta

2 3 4 5

Untreated Control

Active ingredient

Turfcide 400

0.5

UCR 005

classified

Medallion SC

fludioxonil

Syngenta

1.3 0.33

oz/M

ACM ACM ACM ACM

ACM

oz/M

ACM

Secure

fluazinam

Syngenta

UCR 006

classified

ACM

UCR 006

classified

ACM

UCR 007

classified

ACM

UCR 007

classified

ACM

Application codes (timing): A = 1/24/21; C = 2/7/21; D = 2/16/21; M = 4/19/21

oz/M

Table 2. Effects of fungicide treatments on brown ring patch disease severity (0-5; 5 = worst) on annual bluegrass (Poa annua) turf. Riverside, CA. 2021. All treatments were previously applied on 2/7/21, except treatments 16, 18, and 22-24, which were previously applied on 2/16/21. All treatments were then applied again on 4/19/21. No.

Treatment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Untreated Control Premion** + Par SG Premion + Par SG Premion + Par SG Turfcide 400 + Par SG Oximus Oximus Oximus Rayora Traction Ascernity Briskway Posterity Forte Posterity XT Maxtima Maxtima Mirage Stressgard Mirage Stressgard UCR 003 UCR 003 UCR 003 UCR 003 UCR 003 UCR 003 UCR 004 UCR 004 UCR 005 + Secure UCR 005 + Secure + Medallion SC UCR 006 UCR 006 UCR 007 UCR 007

4/8/21 2.4 AB* 0.2 GH 0.0 H 0.0 H 0.8 E-H 0.0 H 0.0 H 0.4 F-H 0.8 E-H 0.4 F-H 0.2 GH 0.8 E-H 2.2 A-C 2.6 A 0.8 E-H 0.6 E-H 1.0 D-H 0.0 H 0.6 E-H 1.6 A-E 1.0 D-H 0.6 E-H 1.0 D-H 0.2 GH 0.6 E-H 1.4 B-F 2.4 AB 2.0 A-D 0.0 H 0.4 F-H 1.6 A-E 1.2 C-G

Disease Severity (0-5; 5 = worst) 4/17/21 4/26/21 3.4 A-C 0.2 EF 0.8 H-K 0.0 F 0.4 I-K 0.0 F 0.0 K 0.0 F 2.4 B-G 0.2 EF 1.0 G-K 0.0 F 0.4 I-K 0.0 F 0.0 K 0.0 F 2.0 C-H 0.8 C-F 0.4 I-K 0.0 F 0.0 K 0.0 F 1.2 F-K 0.4 D-F 3.0 A-E 1.6 B-D 4.2 A 1.6 B-D 1.6 E-J 1.2 C-F 0.2 JK 0.6 C-F 0.0 K 0.0 F 0.2 JK 0.0 F 1.8 D-I 0.4 D-F 3.2 A-D 1.8 BC 2.6 B-F 1.4 B-E 2.2 C-H 1.2 C-F 2.0 C-H 1.4 B-E 2.0 C-H 0.6 C-F 0.8 H-K 0.2 EF 2.6 B-F 2.6 AB 3.8 AB 2.6 AB 3.4 A-C 3.2 A 0.2 JK 0.2 EF 0.2 JK 0.0 F 2.6 B-F 1.0 C-F 3.0 A-E 1.4 B-E

Means followed by the same letter or by no letter in a column are not significantly different (P=0.05). For fungicides rates, refer to Table 1.

5/2/21 0.0 C 0.0 C 0.0 C 0.0 C 0.2 C 0.0 C 0.0 C 0.0 C 0.0 C 0.0 C 0.0 C 0.0 C 0.2 C 0.2 C 0.2 C 0.6 BC 0.0 C 0.0 C 0.0 C 0.2 C 0.2 C 0.2 C 0.2 C 0.0 C 0.2 C 1.0 AB 1.2 AB 1.6 A 0.2 C 0.2 C 0.2 C 0.2 C

Table 3. Effects of fungicide treatments on turf quality (1-9; 9 = best) in response to brown ring patch disease on annual bluegrass (Poa annua) turf. Riverside, CA. 2021. . All treatments were previously applied on 2/7/21, except treatments 16, 18, and 22-24, which were previously applied on 2/16/21. All treatments were then applied again on 4/19/21. No.

Treatment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Turf Quality (1-9; 9 = best) 4/17/21 4/26/21 3.6 J-M 5.8 D-G 6.0 AE 6.8 A-C 6.2 A-D 7.0 AB 6.8 A 7.2 A 4.0 H-L 6.6 A-D 5.4 B-G 6.2 B-F 5.6 A-F 5.6 E-H 6.6 AB 6.2 B-F 5.0 D-I 5.6 E-H 5.6 A-F 5.8 D-G 6.0 A-E 6.2 B-F 5.2 C-H 5.6 E-H 3.6 J-M 5.4 F-H 2.4 M 6.4 A-E 5.0 D-I 5.4 F-H 6.2 ABCD 5.6 E-H 6.2 A-D 6.4 A-E 6.2 A-D 6.4 A-E 4.8 E-J 5.6 E-H 3.4 K-M 5.8 D-G 4.0 H-L 5.2 GH 4.4 F-L 5.4 FGH 4.8 E-J 6.0 C-G 4.6 F-K 6.0 C-G 5.2 C-H 5.6 E-H 3.8 I-L 4.8 H 3.2 LM 5.2 GH 3.2 LM 4.8 H 6.4 A-C 6.2 B-F 6.0 A-E 5.8 D-G 4.2 G-L 5.6 E-H 4.0 H-L 5.8 D-G

4/8/21 5.0 E-G* 6.4 A-C 6.6 AB 6.8 A 6.4 A-C 6.6 AB 6.8 A 5.8 A-F 5.6 B-G 6.0 A-E 6.2 A-D 6.0 A-E 5.4 C-G 4.6 G 6.2 A-D 6.2 A-D 5.6 B-G 6.6 AB 5.8 A-F 5.4 C-G 5.2 D-G 6.0 A-E 5.8 A-F 6.6 AB 5.8 A-F 5.8 A-F 5.0 EFG 5.0 EFG 6.8 A 5.8 A-F 4.8 FG 6.2 A-D

Means followed by the same letter or by no letter in a column are not significantly different (P=0.05). For fungicides rates, refer to Table 1.

5/2/21 5.8 B-E 6.2 A-C 6.6 A 6.6 A 6.4 AB 6.0 A-D 6.0 A-D 5.8 B-E 6.0 A-D 6.0 A-D 5.8 B-E 5.8 B-E 5.8 B-E 6.0 A-D 5.4 DE 5.6 C-E 6.4 AB 6.2 A-C 6.0 A-D 5.8 B-E 5.8 B-E 6.0 A-D 5.8 B-E 6.0 A-D 5.6 C-E 5.2 E 5.6 C-E 5.4 DE 6.2 A-C 5.8 B-E 5.8 B-E 6.2 A-C

Figure 1. Brown ring patch disease pressure in plot of one of the fungicide treatments (left) compared to treatment 4 (Premion + Par SG; right), 59 days after previous application. Photos taken on April 17, 2021. Riverside, CA.

Appendix 1. Environmental data for the study period (January 2021 to April 2021) for the Los Angeles Basin derived from California Irrigation Management Information System (CIMIS) Station #44 (U.C. Riverside).

Month Year

Total ETo (inA)

Avg Avg Min Avg Avg Min Avg Total Avg Sol Avg Vap Avg Air Avg Rel Max Air Air Max Rel Rel Dew Precip Rad Pres Temp Hum Temp Temp Hum Hum Point (in) (Ly/dayB) (mBarsC) (°FD) (°F) (°F) (%) (%) (%) (°F)

Jan 2021

2.98F

1.63

304F

6.3

Feb 2021

3.51F

0.01

409F

6.9F

67.5F

43.4F

68.0

44.2

55.5

Mar 2021

4.66

1.14

503F

7.6F

67.6

43.4F

54.8F

Apr 2021

5.87

0.00

583F

9.7F

75.5

50.6F

Tots/Avgs

17.00

2.80

450

7.6

69.7

45.4

A 25.4 mm = inch B W/m2 = 2.065 Ly/day C kPa = 10 mBars D °C = 5/9 × (°F -32) E m/s = 2.24 mph F One or more daily values flagged

55.1F

70F

Avg Avg Soil Wind Temp Speed (mphE) (°F)

28F

47F

31.7F

4.0

50.9

47F

33.0F

4.1F

53.3

54F

36.1F

4.0F

55.5

61.9

54F

43.1F

4.4F

62.3

56.8

36.0

4.1

55.5