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1

Understanding Plant Health & Products

Bill Kreuser

http://turf.unl.edu/

Characteristics of a Healthy Turf

• Superintendents Perspective?

• My View…

1. Efficient Energy Capture/Conversion/Utilization

2. Perceive and Adapt to Abiotic or Biotic Stress

Normal “Healthy” Plant Metabolism

H2O + CO2 Sugar + Water

Other Nutrients (N,P,K)

CO2 + H2O  Sugar + O2

Plant GrowthSugar StorageSeed ProductionSecondary Metabolites

Light Energy

Controlled Flow of Energy

Normal/Healthy Energy Release

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Potential for Problems

• Systems substrate limited

– Not enough CO2, O2, N, or light energy

– Stomata close, roots saturated, shaded environment

• Systems hindered by environmental conditions

– Pathways not working to potential

– Nutrient deficiency, temperature, water status

Consequences of Substrate Limitation

• Light Limited

– No energy to drive photosynthesis

– Photosynthesis < Respiration = Slow Death

• CO2 Limited

– Stomata closed 

– High temperature in cool‐season turf

• O2 Limitation

– Anaerobic respiration is inefficient

– Burns more stored sugars and produces toxic products

Inefficiencies Increase Oxidative Stress

Absorbed electrons have to go somewhere

Free electrons forms damaging reactive oxygen species (ROS)

Different sources of stress generate damaging reactive oxygen species

Drought

Salinity

Pathogen

Stomata Close 

Heavy Metals in 

Soil

Production of ROS

Sub‐optimal Temps

UV & High Light

Too Much Light Energy

Plants Evolved Mechanisms to Control Reactive Oxygen Species

Production of ROS always occurs

Antioxidants

Vitamins

Pigments

Proteins

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Antioxidant Proteins Quench ROS

• Superoxide Dismutase

• Ascorbate Peroxidase

• Catalase

Plants Respond to ROS Concentrations

• ROS serve as signal molecules

– Plants adjust antioxidant concentrations

– Altered gene expression

– Hormone Levels change

– Change in physiology and morphology

• Helps the plant adapt to stress

– Abiotic and Biotic

Many stress response genes are relatedPlant Stress Preconditioning

1. Maximize growing environment to resist stress

2. Minor, non‐lethal, stress induces expression of genes to avoid or tolerate future stress

3. Exposure to one stress conditions plants to cope with a different stressful condition

Promote Healthy Growing Environment

• Fertilization

• Mowing

• Soil Management

• Proper Irrigation

• Anaerobic rootzone

• Denitrification & Leaching

• Shallow rooting

• Thatch accumulation

• Algae

• Moss

• Black layer

• Poor stress tolerance

• Poor quality playing surface (rutting, divoting)

• Poor shear strength

• Disease (pythium blight, brown patch, etc…)

• Waste of water ($$$$$)

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Deficit Irrigation Preconditions Plants to Stress

• Theory:

Water Stress → Oxida ve Stress → Plant Preps

• Common Adaptations

– Deeper Rooting

– Increased Antioxidant Production

– Reduced Respiration/Increased Carb. Storage

• Result:

– Increased Stress Tolerance

Irrigation Frequency AffectsTurfgrass Roots

0

10

20

30

40

50

60

70

80

June July August September

TNC in turfgrass roots

(mg g

‐1)

Light & frequent

Deep & infrequent

Fu, J., and P. H. Dernoeden. 2008. Carbohydrate metabolism in creeping bentgrass as influenced by two summer irrigation practices. J. Am. Soc. Hortic. Sci. 133(5):p. 678-683.

Water Stress Increases Temperature Tolerance

• Drought Preconditioned Turf Increased Heat Tolerance– Wehner and Watschke, 

1981; Jiang and Huang, 2000

Jiang, Y., and B. Huang. 2001

Trinexapac‐ethyl and Stress Tolerance• Increased Water Use Efficiency

– Slightly Lower ET (King et al., 1997: Marcum and Jiang, 1998; Ervin and Koski, 2001)

– Increase Salinity Tolerance and Improved Dry Down

• (Jiang and Fry, 1998; Pessarakli et al., 2006)

• Improved Heat Stress Tolerance

– More Stress Hormones and Antioxidants (Ervin and Zhang, 2003)

– Increase Sod Storage Life in Heat (Heckman et al., 2001 & 2002)

• Increased Non‐structural Carbohydrates 

– During Suppression Phase Only (Han et al., 1998 & 2004; Richie 2001; and Ervin and Zhang, 2007)

Trinexapac‐ethyl Increases Cytokinins

Species TE App 2 WAIT 4 WAIT 6 WAIT 8 WAIT

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ng g‐1 fwt ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐

Bentgrass + 35.1a 50.2a 42.8a 47.0a

‐ 34.7a 43.5b 36.4b 32.6b

Kentucky bluegrass + 43.0a 44.2a 32.3a 58.3a

‐ 48.0a 32.0b 29.9a 54.1b

Bermudagrass + 86.4a 85.3a 81.6a 88.9a

‐ 89.9a 72.1b 70.5b 74.0b

Ervin and Zhang, 2008

PGR Metabolism

• Decreased Efficacy During Summer– Lickfelt el al. (2005)

– Beasley and Branham (2007)

– Kreuser and Soldat (2011)

• TE Metabolism Directly Related to Air Temperature (Beasley and Branham, 2005)

– 6.4 Day Half Life at 64°F (18°C)

– 3.1 Day Half Life at 86°F (30°C)

Doubling Temperature (°C) Doubles TE Breakdown

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GDD Can Predict These TE Growing Degree Days System• Air Temperature Predicts TE Re‐application Intervals

• Calculating GDD 

– By Hand: • Get Yesterday’s Average Temperature 

• Convert to Celsius

• Add Temperatures 

– Use Weather.com

– Excel Spreadsheet– http://www.hort.cornell.edu/turf/

Poa annua Response

Four Week TE Applications

200 GDD TE Applications

Primo Maxx Re‐Applied Once GDD = 200 GDDModel Then Reset to Zero

Verified for Five Years In WI & NY

1x Primo (0.125 oz/M)

2x Primo (0.250 oz/M)

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What About Application Rate?

Primo Maxx Re‐applied Every Four Weeks

1x Primo (0.125 oz/M)

2x Primo (0.250 oz/M)

200 GDD TE At 1x and 2x Rates

1x Primo (0.125 oz/M)

2x Primo (0.250 oz/M)

Why Doesn’t App Rate Matter?

Loss of Efficacy

GA Synthesis PathwayInactiveGA19

↓Inactive GA20

↓Plant Active GA1 

↓Inactive GA8

Causes fluctuations in suppression

TE Blocks

Plant Makes More

Plant Makes Less

Proteins

Prohexadione Ca (Anuew) lasts longer than trinexapac‐ethyl

40%

70%

100%

130%

160%

0 200 400 600 800 1000

Relative Clip

ping Yield (% Control)

Trimmit (11 oz/A)

Anuew

Primo Maxx

The Mowing Height Effect

Actual Clipping Yield Relative Clipping Yield

Primo Maxx Application Rate Primo Maxx Application Rate

Collar Height Grass Grows 50% Slower Than Greens Height Grass

More Relative Yield Suppression on Collar Height

Grass Than Greens

Collar Height 0.250” Greens Height 0.125”

Seasonal Variation in Cold Hardiness

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Cold Hardiness Inversely Related to Crown Moisture Content

Cold Temperature Stress Management

• Fall Fertilization

• Raise Mowing Heights

• Soil Management

• Irrigation?

CarbohydratesProline & Soluble 

Protein

Avoiding Light Stress

• Healthy Growing Conditions

– Sufficient Nitrogen

– Air flow and irrigation

– Pigments

Pigments Increase Visual Quality & Alleviate Light Stress

Non‐Treated Turf Pigment

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Evaluation of Plant Colorants

Turfgrass Colorants:

– Dyes, pigments, paints 

– Alter light quality

– Pigments aggressively marketed during the past 5 years

• Claims:– Cool turf, oxidative stress prevention, kill pathogens, early spring green‐up, less N

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

200 300 400 500 600 700 800 900 1000

Norm

alized

 Absorban

ce

Wavelength (nm)

Turfscreen

Harmonizer

UVB

UVA

UVC

Pigment Absorption Spectra

UV Damage Region

VA Tech researchers found Green Lawngercolorant increased UVB tolerance

Higher Quality Too

Avoid High Rates of Colorants in Shade

Pigments Field Evaluations

Harmonizer ControlCivitas

Harmonizerw/ Civitas

Pigments Improved Turf Quality

Visual Turfgrass Quality (1‐9 Scale; >6 Acceptable)

Treatment CI

Civ+2xHarmonizer

8.2a

Civ+Harmonizer 7.7b

Harmonizer 7.5c

Turf Screen 7.4c

Control 7.1d

Civitas Alone 5.0e

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Surface Temperature Increased 1‐6°F

Treatment °C

Civ+Harmonizer

30.3a

Civ+2xHarmonizer

30.3a

Civitas Alone 30.1b

Harmonizer 29.8c

Control 29.4d

Largest Temperature Increase Immediately After App

Pigment Field Conclusions

• Pigments Mask Turfgrass Decline 

• Alleviates UV and High Light Stress

• Temperatures Increased with all Treatments

–Green Color

–Potential to Reduced Transpiration (Implications???)

The Role of Fungicides and Plant Health

Primary Role of Fungicides is Biotic Stress Avoidance

Secondary Benefits of Strobilurins• Growth Chamber Wheat:

– Increased Roots

– Increased Antioxidants

– Increased Cytokinins(Grossman and Retzlaff, 1999)

• Growth Chamber Creeping Bentgrass:

– No Differences in Visual Quality

– Occasionally Increased Root Architecture with Pyraclostrobin

Brosnan et al. (2010)

Field Evaluations of Strobilurins

University of Tennessee Research

Quality: Strobilurin > Other Fungicides Only During Disease Breakthrough 

Rooting: No Difference Between Products

Strobilurins are Very Effective Fungicides 

Plants Can Sense Pathogens

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Adapted from Cortes‐Barco, 2010

Civitas Primes Plant Defense (JA) Pathway

DefenseProteins

Building Blocks

AlmostJA

ActiveJA

How Does Civitas Work?

Two Potential Mechanism

1. Directly Elicits a Response (PAMP)

2. Preconditions Plants

• Civitas is Slightly Inhibiting Gas Exchange

• Mild Photoinhibition 

• Oxidative Stress

• Triggers Plant Defense

Harmonizer™ Pigment Important Component of Civitas 

• Limits Absorbed Light and Oxidative Stress

Civitas Reduces CO2 ExchangeRate Amax

0 A

1.3 A

2.5 B

5.1 B

10.2 C

Respiration & QuantumYield Not Affected By Civitas

Light x TMT: p<0.001

Reduced Transpiration Rate

TMT: p<0.001

15.25

15.50

15.75

16.00

16.25

0 1.3 2.5 5.1 10.2

Tran

spir

atio

n (

mo

l H

2O m

-2s-1

)

Civitas Application Rate (ml m-2)

0

1.3

2.5

5.1

10.2

A

A

C

AB

BC

Another Sign of Decreased Gas Exchange

Civitas Alters Cuticle Structure

Control 48 Hrs.

48 Hrs. 2nd App

Sign of Oil Persistence

Strive to Promote Good Agronomics First

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How to Increase Plant Health

• Reduce Environmental Stress ‐Avoidance

–Abiotic Stress

–Biotic Stress

• Increase Plant Stress Tolerance

–Precondition Plants For Stress

–Alter Plant Physiology

The Big Three!

CULTIVATION AND MOWING

Sharpness is a Good Thing!

Sharp Dull

Effect of reel/bedknife contact and sharpness on mm of shredded leaf tips

*

**

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Frequency of Clip

FOC Formula

Ground speed(inches per minute)Reel RPM

number of Reel Blades.

Preliminary Data 2005

* *

Bedknife position at various aggressiveness settings relative to center line of reel

Effect of bedknife position on basal rot anthracnose

% p

lot i

nfec

ted

NonAg

Neutral

VeryAg

NonAg

Neutral

VeryAg

NonAg

Neutral

VeryAg

0.105 0.115 0.135

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Mowing Summary

• Mower Setup Crucial to Plant Health– Mower Sharpness

– Frequency of Clip

– Aggressiveness of Cut

– Design of Mower

• Aggressive Mowing Practices Promote Disease and Annual Weeds

Irrigation Basics

• Irrigation is a primary cultural practice– Required to maintain high quality turf

• Replace rootzone water lost through evaporation and transpiration– Affected by temperature, solar radiation,

humidity, wind speed, and rooting depth

Irrigation Basics

• Amount and frequency change throughout the growing season

Under-Irrigation

Wilt

Insufficient Rootzone Moisture(under-watering)

• Slow growth (recuperative potential)

• Wilt

• Hard surface

• Susceptible to insect pests

Brown patch

Thatch accumulation

Excessive Irrigation

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Excessive Irrigation

Algae / moss

Poa annua

Excessive Irrigation

Frequent irrigation maintains soil water content at levels most prone to compaction!

• Leaching

• Anerobic rootzone

• Shallow rooting

• Denitrification

• Thatch accumulation

• Algae

• Moss

• Black layer

• Poor stress tolerance

• Poor quality playing surface (rutting, divoting)

• Poor shear strength

• Disease (pythium blight, brown patch, etc…)

• Waste of water ($$$$$)

Deficit Irrigation Preconditions Plants to Stress

• Theory:

Water Stress → Oxidative Stress → Plant Preps

• Common Adaptations– Deeper Rooting

– Increased Antioxidant Production

– Reduced Respiration/Increased Carb. Storage

• Result:

– Increased Stress Tolerance (Healthier?)

Irrigation Frequency AffectsTurfgrass Roots

0

10

20

30

40

50

60

70

80

June July August September

TNC in

 turfgrass roots

(mg g‐

1)

Light & frequent

Deep & infrequent

Fu, J., and P. H. Dernoeden. 2008. Carbohydrate metabolism in creeping bentgrass as influenced by two summer irrigation practices. J. Am. Soc. Hortic. Sci. 133(5):p. 678-683.

Water Stress Increases Temperature Tolerance

• Drought Preconditioned Turf Increased Heat Tolerance

– Wehner and Watschke, 1981; Jiang and Huang, 2000

• Increased Low Temperature Tolerance

– Lindsey Hoffman, Michelle DaCosta, Jeffrey Ebdon, and Jiuzhou Zhao, 2009

Jiang, Y., and B. Huang. 2001

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Irrigation Summary

• Improper Irrigation is a Leading Cause of Turfgrass Failure

• Slightly Drier is Often Better Than Wet

– Enhanced Rooting

– Mild Water Stress Preconditions Plants

• Use Latest Technology to Improve Irrigation Efficiency

Its All About Nitrogen (Usually)

• Law of the Minimum

• Small Nitrogen Applications ↑ Quality & Health

• How Much Nitrogen Is Required?

Nitro

gen

Po

tassium

Ph

osp

ho

rus

Iron

FertilizerAtmospheric Deposition

Clipping Returned

Denitrification,Volatilization

Runoff

Leaching

Plant Available N

Soil Organic N Pool

Clippings Removed

Soil Nitrogen Pool Too Often Neglected

Frank et al., 2006

MSU Monmouth Lysimeters

Soil Nitrogen Pool Too Often Neglected

Qian et al., 2003

Soil Nitrogen Pool Too Often Neglected

Qian et al., 2003

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Checkbook Method of N Management

Nitrogen Additions = Nitrogen Removal/Loss

Annual Nitrogen Surplus• Increasing Soil N• Excessive Growth/Thatch• Nitrogen Leaching

Annual Nitrogen Deficit• Slow Depletion of Soil N• Steady Decline in Quality• Eventual Stand Collapse

Checkbook Method of N ManagementEasier Said Than Done!

DON’T COMMIT TO AN ANNUAL NITROGEN RATE!

Goldilocks Method

Strategies to Increase Efficiency1. Light Frequent Soluble N2. Flexibility in Application Rate3. Return Clippings & Use PGRs 

to reduce N Removal 4. Monitor Changes Over Years

Real Nitrogen Fertility Example

• ‘Memorial’ Bentgrass Putting Green

• 3 Biweekly N Rates– 0.1, 0.2, 0.4 lbs N/M

• +/‐ Trinexapac‐ethyl

• Measured Quality, Clipping Yield, Color Biweekly

• Other Nutrients Sufficient 

Clipping Yield Response to Nitrogen Rate

0.1 lb N/M0.2 lb N/M0.4 lb N/M

Doubling N Rate Increased Clipping Yield 0‐40%

What About Clipping Yield and Ball Roll?

No Correlation of Yield and Ball Roll

Fertilize to Maintain Acceptable Quality, Not to Increase Green Speed

Average Turfgrass Quality and Color Index

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0.2 lbs N/M With Primo

0.4 lbs N/m No Primo

The Proof is in the Pictures

TE Reduces N Requirements

0.1 0.2 0.3 0.4 0.50.0

(lbs N/M)

No TETE (0.25 oz/M, 200 GDD)

Nitrogen Requirements for THIS PUTTING GREEN

Desired QualityRating

Nitrogen Needed to Achieve Desired Quality Nitrogen Reductions with

Primo MaxxWithout TE With TE

1-9 Scale lbs N/M/month % lbs N/M/Season

7.0 0.3 0.4 25% -0.6

7.5 0.4 0.6 33% -1.2

8.0 0.5 1.0 50% -3.0

•TE applied every 200 GDD at 0.25 oz/M

•Assuming 6 Month Growing Season •May to October

Sometimes N Isn’t the Problem

Other Nutrient Deficiencies 

Phosphorus Deficient Turfgrass

• Resembles LDS• Non‐responsive to N Fertilization

• High pH Root Zones at Risk

• Reliable Soil Test Interpretations Available

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Befo

re P Fe

rtilization

Week A

fter P

 Fertilizatio

n

Make Small Test Applications to Verify Soil Tests 

K, Ca, Mg, S, & Micronutrient Soil Test Results are Particularly Problematic 

Pop Quiz: Why is this plot greener than the 

control?

K Fertilization of Turf

-Can range from 0-800 kg ha-1 year -1

(mean ~ 200 kg ha-1 year -1 ).

-Why so high?-Taken from corn?-Early on, N rates of ~400 kg ha-1 year -1

-Helps drought, traffic, heat tolerance?-Prevents snow mold damage?

Microdochium nivalePink Snow Mold (PSM)

Typhula incarnataGrey Snow Mold (GSM)

Potassium affects snow mold susceptibility?

0 kg ha-1 year -1

200 kg ha-1 year -1

800 kg ha-1 year -1

Dr. Micah Woods

0 kg ha-1 year -1

200 kg ha-1 year -1

800 kg ha-1 year -1

Why would K affect snowmold susceptibility?

-An osmotic affect?

-Gene expression, plant defense?-JA Pathway or others?

-By modifying carbon metabolism?- Non-structural carbohydrates- Carbon skeletons from the TCA cycle

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Pink Snow Mold Pink Snow Mold

Kaplan- Meier Survival Analysis of LI50

Pr > χ2 = 0.2777

Day

s to

50%

Nec

rosi

s (L

I 50)

Grey Snow Mold Grey Snow Mold Kaplan- Meier Survival Analysis of Day50

Pr > χ2 = 0.0071

Day

s to

50%

Nec

rosi

s (L

I 50)

Grey Snow Mold Regression of Day50 by Tissue K Content

Day

s to

50%

Nec

rosi

s (L

I 50)

Grey Snow Mold Regression of Day50 by Tissue K Content

Day

s to

50%

Nec

rosi

s (L

I 50)

Ca ?Mg ?Metabolites ?Others ?

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Calcium

-Correlated with both diseases on multiple sample dates.

-Cell wall composition?

-Cellular messaging?

Disease Summary

-K Fertilization affects snow mold severity.-Particularly for GSM.

-Differences between pathogens? -A function of pathogen aggressiveness?

-Subtle effects of K?

-What about Ca?

Metabolites?

Sure Fire Ways to Boost Plant Health

1. Maintain a Healthy Growing Environment

2. Be More Flexible with N Applications

3. Setup Mowing Equipment to Minimize Plant Stress

4. Maintain Growth Suppression with PGRs to Realize Secondary Benefits

5. Experiment with New Products Slowly– Great Potential Requiring More Research