Turfgrass Pathology

Is Spring Dead Spot Dazed by the Fraze?

Lee Miller, PhDAssistant Professor & Extension Turfgrass Pathologist

University of Missouri

Spring Dead Spot

• Most severe disease of hybrid bermudagrasses in the transition zone

• Pathogen infects root tissue in the fall and limits the plants ability to overwinter

• Infected plants remain dormant and never “green up” in the spring. Plants eventually collapse to the ground and die.

• Patches can grow up to 3 feet in diameter, and if left untreated can recur in following years.

Spring Dead Spot Control

• As with most soilborne diseases, spring dead spot is difficult to control.

• Fungicides must be applied preventively in the fall, and can be quite costly. They also often require more than one year of application to achieve satisfactory control.

• Fenarimol (Rubigan), which was the most effective fungicide control, was removed from the market. Replaced by tebuconazole (Torque, Mirage) which is labeled for golf course use only.

• The effects of soil properties and fertilization are not well understood.

May 12, 2014

Velista

• Penthiopyrad: a SDHI (carboxamide), same class as active ingredients in ProStar Emerald, and Xzemplar (Lexicon Intrinsic)

• Excellent/Good control of brown patch, dollar spot, and anthracnose.

• Released in 2015. No site restrictions.

Velista for SDS Control

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Untreated No PAI 0.08" PAI 0.16" PAI 0.31" PAIUntreated No PAI 0.08" PAI 0.16" PAI 0.31" PAI

* Bars with the same letters are not significantly different (LSD, α = 0.05).Velista applied at 0.7 oz/1000 sq ft on 2 Oct and 30 Oct.

Walker, OSU 2013

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Velista for SDS Control

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* Bars with the same letters are not significantly different (Waller-Duncan, k=100).Fungicides applied twice on Sept 22 and Oct 21, 2011

MU Turf Farm, 5/24/12

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Velista for SDS Control: 2015

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Untreated Velista (0.5 oz/M) Velista (0.7 oz/M)Headway (3 fl oz/M)

* Bars with the same letters are not significantly different (Fisher’s Protected LSD).Fungicides applied twice on Sept 22 and Oct 21, 2011

MU Turf Farm, 6/9/15

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• Calcium nitrate increases pH, whereas ammonium sulfate reduces it

• When the root absorbs a nitrate ion (NO3-), a hydroxyl ion (OH-) is released, therefore increasing rhizosphere pH

• When the root absorbs an ammonium ion (NH4+), a hydrogen ion (H+) is released, therefore reducing rhizosphere pH

• Sulfate (SO4-) and calcium (Ca+) have little to no effect on soil pH

RootSoil

NO3-

OH-

NH4+

H+

NitrogenSourceIn.luenceonRhizospherepH

Alkaline

Acidic

Possible Nitrogen and pH Impact

•Dernoedon et. al. (1991) observed ammonium sulfate applications to lower soil pH and reduce spring dead spot symptoms.

•Vincelli (2005) reported a decrease in symptoms when soil pH levels were reduced below pH 5.5.

•Tredway (2010) ▪ Calcium nitrate applications suppressed field

symptoms caused by O. korrae ▪ Conversely, ammonium sulfate applications

suppressed symptoms caused by O. herpotricha

Dernoedon et al 1991., CropSci. 31:1674-1680 Vincelli 2005., University of Kentucky Extension:ID-130 Tredway 2010, APS Annual Meetings:S129

Heckman

SDS Species Differences

- Tredway, 2010

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2007 2008 2009Sulfur Coated Urea Calcium Nitrate Urea Ammonium Sulfate

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Bars with the same letters are not significantly different according to the Waller-Duncan t-test (k=100)

O. korrae O. herpotricha

- Tredway

O. korraeO. herpotricha

O. namari

SDS Pathogen in Missouri?

O

Research Objectives

1. Survey the distribution of Ophiosphaerella species responsible for spring dead spot damage in Missouri and the surrounding region.

2. Determine the impact of pH and nitrogen source on the growth of Ophiosphaerella herpotricha and O. korrae in vitro.

3. Assess the impact of nitrogen source, nitrification inhibitors, sulfur, and fungicide applications on spring dead spot severity.

Identification Procedure

• 213 isolates were obtained from 16 sites in MO, KS, AK. Reference isolates obtained from NCSU.

• DNA extracted & analyzed from 174 isolates. The ITS region was amplified using ITS1 and ITS4 primers, sequenced and compared to the Genbank database using BLAST.

N. Walker

Geographic Distribution

93%

6%

O. herpotricha O. korraeO. narmari

Field Trial - N Source, Sulfur, Fungicide

Rep 1 Rep 2 Rep 3 Rep 4 Rep 5Main Plot (NS)

Urea (46-0-0)

(NH4)2SO4 (21-0-0)

CaNO3 (15.5-0-0)

UFLEXXtm (46-0-0)

UMAXXtm (47-0-0)Applied thrice at 49 kg N ha-1 In June, July and August of 2011 and 2012

Sub-plots (F,S)1 - Fungicide, - Sulfur

2 - Fungicide, + Sulfur

3 Tebuconazole - 1 app., -Sulfur

4 Tebuconazole - 1 app., +Sulfur

5 Tebuconazole - 2 app., -Sulfur

6 Tebuconazole - 2 app., +Sulfur- Sulfur (98 kg S ha-1) applied the same time as nitrogen. - Tebuconazole (0.82 kg a.i. ha-1) applied once (mid Sept) or

twice (mid Sept + mid Oct) in the fall.

Mexico silt loam, pH = 5.5

10 samples : all O. herpotricha

Digital Imaging Analysis

Area under the disease progress curve (AUDPC)

• Summary of Disease Severity over time

DIA* AUDPCEffect p-value p-value

NS 0.2327 0.4667F <.0001 <.0001

NS*F 0.3927 0.1370S 0.0018 0.0003

NS*S 0.2848 0.1787F*S 0.9635 0.0146

NS*F*S 0.1794 0.6177Year <.0001 <.0001

ANOVA – Combined Data

* Disease severity as measured by digital image analysis. Data was subjected to analysis of variance using PROC Mixed in SAS with repeated measures.

Type III test of fixed effects

Columns with the same letter are not statistically different according to Tukey’s test (P< 0.05). Means were averaged across all isolates. Error bars represent the standard error of the mean.

A

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AMS +

Untreated

AMS +

2 fung apps

AMS +

1 fung app

Columns with the same letter are not statistically different according to Tukey’s test (P< 0.05). Means were averaged across all isolates. Error bars represent the standard error of the mean.

AMS-S

AMS+S

2013

1 - Fung, - Sulfur

2 -Fung., +Sulfur

3 Teb.-1 app., -Sulfur

4 Teb.-1 app., +Sulfur

5 Teb.-2 app., -Sulfur

6 Teb.-2 app., +Sulfur

Trt. 5 Trt. 6

6/10/13

Trt. 6 Trt. 1

Trt. 2 Trt. 3

Columns with the same letter are not statistically different according to Tukey’s test (P< 0.05). Means were averaged across nitrogen and sulfur treatments. Error bars represent the standard error of the mean.

May 23, 2013

AMS +

Untreated

AMS +

1 app.

AMS +

2 app.

Columns with the same letter are not statistically different according to Tukey’s test (P< 0.05). Means were averaged across fungicide treatments. Error bars represent the standard error of the mean.

April 2013

+ S + S+ S - S - S

September 2013

-S -S-S +S+S

Columns with the same letter are not statistically different according to Tukey’s test (P< 0.05). Means were averaged across nitrogen treatments. Error bars represent the standard error of the mean.

Project Conclusions

•Ophiosphaerella herpotricha is the predominant spring dead spot pathogen in Missouri (92% of isolates sampled), however, some overlapping distribution does exist.

•The results of the in vitro nitrogen source assay do not directly correlate with previous response to nitrogen source observations in field research.

• Sulfur applications may be as effective at reducing spring dead spot severity as a single fungicide applications.

•Two years of management practices may be needed before acceptable control is achieved.

The Story Continues• Beck et al. (2013) demonstrated oxadiazon (Ronstar) could be used as

a pre-emergent when bermudagrass is recovering from SDS.

Prodiamine, oryzalin, dithiopyr, dimethenamid, pendimethalin, and

indaziflam all limited recovery.

• Manganese impact? Needs more research, but some field trials show

an effect. (Tredway, Perry thesis)

• In numerous trials, hollow-tine aerification has been shown to reduce

disease severity and increase fungicide efficacy.

Turfgrass Pathology

Does SDS feel the fraze?

June 23, 2014

Turfgrass Pathology

Darian Daily, Cincinnati Bengals KORO Field Topmaker

Mike Munie, Perfect Play Fields & Links GKB Combinator

Redexim Turf Stripper

Turfgrass Pathology

Fraze Mowing Benefits

• Remove thatch and accumulated organic matter

• Promote new growth, particularly effective for grasses with rhizomatous growth - Kentucky bluegrass, bermudagrass, zoysiagrass.

• Removal of weeds

• Improved seed germination: seedbed preparation.

• Improved field safety and play- level & firmness.

• Transition of cool-season to warm season.

} 6X weekly post-fraze

July 22, 2014

Does SDS feel the fraze?

July 25, 2014

4 weeks post fraze mowing

Year 1 - Disease Progress

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Research at MU

• Inoculated 11,000 sq ft ‘Patriot’ research area - nitrogen

source, fungicide, manganese + fraze mowing

• 35 new NTEP varieties slated to be inoculated and

screened for spring dead spot resistance.

Turfgrass Pathology

2015

Fraze Mowing - June 30, 2015

0 mm

4 mm

8 mm

Nitrogen SourceCalcium Nitrate (0.5 lbs N/M - 6 weeks)

Ammonium Sulfate (0.5 lbs N/M - 6 weeks)

Fungicide

Velista (0.7 oz/M) after fraze & on 10/14

None

Manganese6 lb MnSO4 - 3 apps: 2 weeks apart

None

The Manganese Falcon?• Structural, redox, and electron transport

roles in photosynthesis. Activator of enzymes in plant.

• More available in lower pH soils.

• Disease often alters the accumulation and oxidation state of manganese within the infected tissue.

• Take all patch and summer patch converts Mn+2 to Mn+4 at the root surface, rendering it unavailable to the plant.

• Use of manganese sulfate (2 lbs/1000 ft2) may reduce TAP and SP in low manganese soils.

Schulze et al. 1995

Turfgrass Pathology

Fraze: 6/30Pic: 7/30

Even Frazing Zoysia

8 mm 4 mm 0

Turfgrass Pathology

Conclusions• New fungicide chemistries hold more promise for spring dead

spot.

• Curative control is still a multi-year process that will require an

integrated approach.

• Lowering soil pH may reduce spring dead spot in the Missouri,

which is mainly caused by O. herpotricha.

• Fraze mowing is probably not a one bullet cure, but may speed

recovery when integrated with other practices.

Thank you for your attention &

any questions?

Contact Information

Lee Miller, Ph.D.

University of Missouri

turfpath@missouri.edu

www.turfpath.missouri.edu

Twitter:@muturfpath

(573) 882-5623