dr. lee miller extension turfgrass pathologist university of missouriextension.missouri.edu ›...

Lawn Management in Missouri: A Pathologist’s Perspective

Dr. Lee Miller Extension Turfgrass Pathologist

University of Missouri

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HOST

ENVIRONMENT PATHOGEN

Amount of Disease

Disease Triangle 2

According to satellite imagery estimates, turfgrass has 3 times the acreage of corn: the most planted agronomic crop.

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Grazing Point

Meristem

(Growing Point)

Stolon

Rhizome

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Transition Zone 5

Bermudagrass, Zoysiagrass, St. Augustinegrass, Buffalograss

Bentgrass, Bluegrass, Fescue, Ryegrass

2 Choices 6

So What to Choose?

• Tall Fescue - Is the most popular for a reason. Good varieties for Missouri w/some brown patch resistance: (think art) Rembrandt, Picasso, Winning Colors (blend), Revolution (blend), RTF.

!

• LOTS of shade - Fine fescue (normally in mixtures of fine, red, chewings, etc.)

!

• Most costly establishment option - Zoysiagrass

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“The picture is a sample of dead, moldy grass from a lawn!in Kirksville. The grass is a mix of bluegrass, bentgrass, &!perennial ryegrass. It was planted in May/June of this year.!It didn’t show any signs of distress until the 6” of rain we !received 10 days ago.

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- Tredway

Tall Fescue/KBG MixturesTall Fescue/KBG MixturesTall Fescue

500 seeds/gramKentucky Bluegrass

4,800 seeds/gram

- Tredway

This means a 90:10 volume mixture is really

50:50 in # of seeds!!!

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- Tredway, NCSU

Kentucky Bluegrass Can Take Over11

Disease Susceptibility

Tall Fescue Kentucky BluegrassBrown Patch Pythium

Pythium Summer Patch

Gray Leaf Spot Dollar Spot

Rust Leaf Spots/Melting Out

Red Thread

Pink Snow Mold

Powdery Mildew

Rust

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HOST ENVIRONMENT

PATHOGEN

Amount of Disease

Disease Triangle 13

Disease Terms

Disease Definition: an abnormality in

structure or function caused by a

continuous association with an infectious

agent; injures the plant or reduces its

aesthetic value

Pathogen

Most turfgrass pathogens (> 90%) are fungi.

Chemicals that control diseases are called fungicides.

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What Fungicides are NOT

• Herbicides - KILL PLANTS

• Insecticides - KILL INSECTS

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What Fungicides Are...

• A chemical that destroys or inhibits fungal

growth.

• In fact, most do not kill the pathogen at all. They

merely arrest fungal growth.

• Many “fungi - stats”, not many “fungi - cides”.

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Implications

• Fungicides are a temporary fix. The pathogen

and disease will be back.

• Fungicides need to be reapplied on regular

intervals (i.e. 21-28 d).

• Coverage is critical

• Fungicide resistance

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Diseases on Cool Season Lawns

• Brown Patch - Particularly important to manage in fescue & fescue/KBG mixture lawns - EVERY YEAR !

• Pythium blight - In some years, this disease will “grab the baton” from brown patch and cause widespread damage. !

• Melting Out - Only seen on Kentucky bluegrass, particularly when stressed or mowed too low. !

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Disease Susceptibility

Tall Fescue Kentucky BluegrassBrown Patch Pythium

Pythium Dollar Spot

Gray Leaf Spot Summer Patch

Rust Leaf Spots/Melting Out

Fairy Ring Red Thread

Pink Snow Mold

Powdery Mildew

Rust

Fairy Ring

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3

4

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• Appears in hot, moist overcast weather.

• Tall Fescue, Kentucky bluegrass

• High-cut grasses: patches are light brown and range from 2 feet to 5 feet in diameter. Grass is severely thinned.

• Distinct lesions on outer margins of patches. Tan with dark brown margins.

• Severe on highly fertilized lush grasses

Brown Patch 20

Brown Patch Diagnosis 21

Brown Patch Control

1. Reduce the duration of leaf wetness (Rhizoctonia requires ~ 9

hours of sustained moisture on the leaf).

2. Increase drainage.

3. Aerify to improve water infiltration, remove thatch.

4. Do not fertilize cool-season turfgrass too late in the spring.

5. Fungicides are best applied preventively if there is a history of

disease. QoIs/SDHIs longest residual, followed by DMIs.

6. New granular formulations.

!

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Granular Formulations

• New influx of granular formulations hitting the market. !

• Aimed at the lawn market: considerable application advantages. !

➡ No specialized equipment - can use spreader !

➡ Spread in wider array of conditions (wind)!

➡ No need to lug around water tank door to door. !

!

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0

5

10

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25

% B

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atch

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ntre

ated

Insi

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Her

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Her

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7/31/12

Applications made on a 28 d interval starting May 22 . Columns with the same letter do not significantly differ according to the Waller Duncan k-ratio test (p=0.05, k=100).

(4 lb)

a

(4 lb)(3 lb)

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Untreated Control Armada

Pillar G Headway G

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Pythium

• Extremely hot & wet weather >90’s, heavy rains

• Primarily Kentucky bluegrass, but last year tall fescue

• Greasy matted appearance, dark brown

• Prevalent in shaded areas, and overwatered areas.


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Pythium disease control

1. Reduce the duration of leaf wetness (Pythium requires ~ 13

hours of sustained moisture on the leaf).


3. Aerify to improve water infiltration.


5. Phosphites/azoxystrobin can be used preventively.

6. Fungicides, if necessary, are in different classes than normal

fungicides. (ex. Subdue or Segway)

!

!

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Brown Patch or Pythium? 30

Melting Out/Leaf Spot• Appears in hot, wet weather. Noticed

in late August/early Sept 2013.

• Kentucky bluegrass, perennial ryegrass (primarily on seedlings)

• Spotty at first, grass dies out in irregular areas in heavy outbreaks

• Pale white lesions with some dark black spots.


• Most prevalent on low mow KBG

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Melting Out Control

1. Reduce the duration of leaf wetness.




5. RAISE mowing heights.

6. Fungicides are best applied at the first sign of disease.

Preventive applications on seedlings may be necessary if

seeding in spring.

(Headway, Heritage, Curalan, 26/36)

!

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• All like it hot.

• All are most damaging on seedlings and younger turf.

- Reason it’s best to seed in September instead of April.

• All are foliar, so reducing leaf wetness duration will limit the

disease epidemic.

• All three diseases greatly enhanced by lush, high nitrogen

turfgrass.

!

!

Pythium blight, Brown Patch, Melting Out

Common Threads 34

Dollar Spot

• Appears in mild - warm weather.

• Kentucky bluegrass, perennial ryegrass etc. etc.

• Most ubiquitous disease, infects a large number of hosts.

• Leaves are bleached white and straw color. Patches 1-6 inches or more across. Lesions are hour glass shaped.

• Severe on under fertilized grasses.

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Dollar Spot Control




4. Fertilize in the fall, spring be careful.

5. Fungicides are best applied preventively or at the first sign of

disease. DMIs (Banner, Bayleton, Triton, Trinity, etc.),

Dicarboximides (Curalan), Benzimidazoles (3336)

6. Fungicide resistance is a concern.

!

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Common Thread 38

Warm Season Turfgrass Diseases

Bermudagrass Zoysiagrass

Spring Dead Spot Large Patch

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Large Patch

• Brown patch kissing cousin

• Infects zoysiagrass during fall and spring when growth is slowed down by cooler temperatures

• As name implies, large patches that may “fire” to orange margins when disease is active.

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Large Patch Control




4. Be careful with fertilization too early in the spring or too late in the

fall.

5. Fungicides are best applied preventively in the fall or early

spring. DMIs (Torque, Triton etc.), QoIs (Heritage, Headway).

!

!

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Chinch Bugs

Biology:

➡ Sucking mouth parts

➡ Gradual metamorphosis

➡ All nymphs suck plant juices

➡ White wings with triangular black markings

➡ Females lay 20 eggs per day for 2-3 weeks

➡ 1-2 generations per year

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Damage: 20-25 nymphs/sq ft Monitoring: Sidewalks/Driveways, Coffee Can/Float, Hot day/Plastic Bag !

Damage is usually worse: ➡ Along sidewalks ➡ Curbs ➡ Driveways ➡ Cart paths ➡ Sunny locations

!Control:Curative - Pyrethroids

!!

Chinch Bugs 46

Hunting Billbugs

• Turfgrass species: Mainly Zoysiagrass (cv. “Meyer)

• Damage is often mistaken as:

➡ drought dormancy

➡ chinch bug or white grub damage

➡ dollar spot or large patch symptoms

!

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Biology:

Dormant adults over-winter !Egg laying spring to early summer

Eggs deposited in leaf sheaths or in feeding punctures in stems

Eggs hatch in 3 to 5 days

Grubs eat there way down through stem and pop out rhizome. One to two generations per year

Hunting Billbugs 48

Hunting Billbug Control!• Damage may be masked by maintaining adequate fertility and

irrigation !Insecticides: ➡ Preventive - Site w/History

Pyrethroids for adult control in spring: Talstar - bifenthrin DeltaGard - deltamethrin Scimitar - lambda-cyhalothrin Merit - imidacloprid ➡ Curative

Combination Products: Allectus – bifenthrin + imidacloprid Aloft – bifenthrin + clothlanidin

Biological control: ➡ Steinernema carpocapsae nematodes

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AprilMay

June July AugSept

Oct

Large Patch

Chinch Bugs

Hunting Billbugs

Recovery

Symptoms

Symptoms

The Zoysia Pest Timeline 50

HOST

ENVIRONMENT

PESTS

Amount of Disease

Disease Triangle 51

Integrated Disease Management

• Numerous factors can be manipulated to increase turfgrass health & reduce disease severity

- Moisture (Drainage & Leaf Wetness) - Temperature - Fertility - Shade - Organic Matter

• Fungicides should be last resort. Environmentally are much better than they used to be, but the bottom line is they cost $$$.

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What do pathogens need to survive & cause disease?

• Water

• Temperature

• Host - preferably stressed out.

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Columbia)Regional)Airport)(189072012) Top)3)Driest)May)1)–)Aug)19)periods 2012)))))))4.71” 1911)))))))5.12” 1936)))))))5.39”

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1890 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

May

-Aug

Pre

cip.

(in.

)

May-Aug Precipitation Columbia, Missouri (1890-2012)

1993 1943

1995 1981

1901 1976 1936 2012

1990

1911

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Drought

July 30, 2013

US Drought Monitor - droughtmonitor.unl.edu

August 14, 2012

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8/4/12 10/30/12

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8/4/12 10/30/12 58

9/22/12 59

Drought Resistance Mechanisms

Escape ! Rapid development where plants complete their life cycle (go to

seed) before or during a water deficit. Poa annua

Avoidance !  Plants maintain high water potential by maintaining water

uptake or reducing water loss. Large root systems or adapted leaves with less stomata or stomata that close rapidly

Tolerance ! Low tissue water potential achieved by maintenance (or

suspension) of regular physiological processes. Dormancy in perennial grasses: 4-6 week grace period

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Most Impacted Lawns

Cool season turfgrass lawns – particularly fine fescue shade mixtures and Kentucky bluegrass !Lawns that were watered inefficiently

Particularly early in the summer if irrigation was applied too frequently = short roots

!Lawns that were mowed during dormancy or too short

Not necessary !

Lawns with too much organic matter/thatch Holds water too high in the soil profile !

Lawns that were fertilized too late in spring/early summer More disease susceptible & favored shoot instead of root growth

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Footprinting Due to Drought Stress 62

Thatch

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2012 Calculations• Span 7/8 - 7/22: No rain - estimated 3.467” of water

lost to atmosphere (short crop evapotranspiration)

• Average lawn ~ 0.2 acres

• 1 acre inch = 27,154 gallons water; 3.467” lost = 94,143 gallons

• Need 13,180 gallons water for 70% ET replacement over average lawn.

• Golf course in STL: 300,000 gallons/day. Over average 100 managed turf acres, only 44% ET replacement.

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Deep & Infrequent?

• In ground sprinkler systems: 39-51% adjusted sprinkler time seasonally, 16-24% never or rarely do.

• 65-83% of homeowners (in ground and non-) responded they didn’t know how much water they were applying to lawns.

• Water when lawn looks dry: Non-in ground: 52-60% In ground: 19-26%

Bremer et al, Kansas State Univ., 2012

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- Tredway, NCSU

Kentucky Bluegrass Can Take Over66

Bermudagrass Zoysiagrass Tall Fescue

Kentucky bluegrass Perennial ryegrass

Fine fescues Low!

High!

Drought Resistance67

Bottom Line

• Consumers need to be better educated on drought impact on lawns and how to utilize irrigation.

• In extreme drought conditions, it’s often best to leave lawns dormant and not water. This is better than bringing it back and weakening it with inconsistent irrigation.

• Kentucky bluegrass is more drought susceptible than tall fescue. Lawns planted in mixtures of these 2 species may be more KBG, so identifying the host is important.

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0.00#

5.00#

10.00#

15.00#

20.00#

25.00#

30.00#

35.00#

40.00#

45.00#

1/1#

2/1#

3/1#

4/1#

5/1#

6/1#

7/1#

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9/1#

10/1#

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Precipita

6on#(in

.)#

Date#

Columbia,#Missouri*#Annual#Accumulated#Precipita6on##Normal#vs.#2013#

30Iyear#normal#

2013#Accumulated#

*Columbia#Regional#Airport#

10.07"#surplus##thru#May#31#

26.71#inches#thru##May#31#

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Too Much Water = Disease Cause #1

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What do these have in common?

Reducing Leaf Wetness Duration for Foliar Disease Suppression

• Mowing

• Poling, whipping, dragging

• Tree pruning/removal

• Fans (also lowers air and soil temperatures)

• Irrigation timing

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Early morning: 4 AM to 8 AM

• Evaporative losses minimized (Cooler temperatures)

• Better distribution of water (Calm winds)

• Knocks dew & guttation fluids off leaf blades and decreases leaf wetness period discouraging fungal growth and infection)

Irrigation - What Time of Day?73

Fertilization

Feed turfgrasses when they are actively growing!

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Environmental Responsibility 75

Clean up after your fertilizer application by blowing/sweeping particles off of driveways or street gutters and back onto turf areas.

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Nitrogen• Nitrogen (N)

–An adequate supply of N is associated with vigorous growth and deep green color.

–Turf that is deficient in N will result in: • Lack of turf density

• Stunted, pale green plants

• Reduced recuperative potential from pests and environmental stresses

–Turf has the ability to remobilize N from older tissue to provide N to younger tissue.

–Therefore, N deficiency symptoms will show up at the tips of older leaves first.

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Nitrogen Deficiency Symptoms 78

Low nitrogen High nitrogen

Brown patch Pythium blight

Leaf Spot/Melting Out Spring dead spot

Large patch Gray leaf spot

Snow molds

Dollar spot Anthracnose basal rot Red thread Rust Pythium root dysfunction

!Key is don’t fertilize at the wrong time!!! !

Cool season - Nothing after May 1, fall fertilize in mid September!Warm Season - Only fertilize from May - August!

N Fertilization & Turf Disease 79

Nitrogen Timing

• Use the Oyster Rule

★ No fertilizing cool season

turf (longer cut) unless the

month has an “R” in it. !

★ Conversely, don’t fertilize

warm season turf in months

with “R”s.

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Cool-Season Lawn Fertilization

• Common lawn care practice: Every 4-6 weeks. - Weed & Feed

• Heavy spring applications, and any summer applications lead to severe outbreaks of brown patch and Pythium

• Three applications a year max:

๏ Spring “Awakening”: 0.5 lb N (preferably with slow release forms: i.e. SCU) before May 1

๏ Fall “Recovery”: 1 lb N early - mid September

๏ Fall “Winterizer”: 1 lb N early - mid October

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Cool-Season Maintenance Calendar82

Conclusions

• Use all of your resources to determine the cause of the problem -

including a diagnostic lab if necessary.

• Drought dormancy is not necessarily a bad thing. Consumers

should be made aware of irrigation practices that can enable the

plant to enter dormancy properly (i.e. Deep and Infrequent)

• Fertilizer application or overwatering during the summer may do

more harm than good.

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http://extension.missouri.edu/main/

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Email List Serve Website

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When Things Go Wrong

1. Identify the problem!

2. Describe the problem - PICTURES!

3. Take precautionary measures!

4. Develop a list of possible causes!

5. Gather evidence!6. Eliminate possible causes!7. Select and implement a course

of action!

8. Evaluate effectiveness of selected action!

9. Repeat Steps 5 to 8 if necessary

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Sample Submission

• Take pictures of symptoms and email to [email protected].!

• 1-2 Plugs per sample: square 2-4” on each side (each suspected problem)!

• Depth - only down to root zone, shake off excess soil!

• Wrap bottom in aluminum foil to stabilize; pack rest of box with newspaper or packing material; NO PLASTIC BAGS!!

• Ship overnight for best results.

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No Need to Overdo It!! 91

Where to Take the Sample?

• For larger, patchy or ring symptoms that are larger than the cup

cutter, this is a critical aspect to obtaining a good diagnosis

• Too far in the middle of the patch has the least amount activity

of the true pathogen, and much more from opportunistic

pathogens

• Like mowing, use the 1/3rd rule: 1/3rd healthy turf, and 2/3rd

symptomatic turf

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Email: [email protected] Website: www.turfpath.missouri.edu

Phone: (573) 882-5623

Mizzou Plant Diagnostic Clinic95

dr. lee miller extension turfgrass pathologist university of missouriextension.missouri.edu ›...

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