Turfgrass Diseases Update

Dave HanAssociate Professor & Extension SpecialistAuburn University /Alabama Cooperative

Extension System

STMA Conference, January 2011

Disease DiagnosisA process of elimination

1. Start with a list of possibilities based on turf species and time of year

2. Look for clues and patterns3. Rule out diseases, narrow the list of

possibilities4. Repeat steps 2 and 3, if needed5. Send sample to a diagnostic lab

Turfgrass Diseases(Partial) List of Possibilities

Bermudagrass• Dollar Spot, Spring Dead Spot,

‘Helminthosporium’ Blight, Fairy Ring, Large Patch, Curvularia blight, Pythium Blight

Bluegrass• Brown Patch, Dollar Spot, Fairy Ring,

‘Helminthosporium’ Blight, Pythium Blight, Summer Patch, Other root diseases

Ryegrass• Brown Patch, Gray Leaf Spot, Rust,

‘Helminthosporium’ Blight, Dollar Spot, Fairy ring

Tall fescue• Large Patch, Dollar Spot, Rust,

‘Helminthosporium’ Blight

Large Patch / Brown Patch / Zoysia Patch

Causal Agent: Rhizoctonia solani

Time of year: Spring and Fall(warm season grasses) Spring, summer and fall (cool season grasses)

Hosts: All grasses

Large PatchZoysiagrass

Large patchZoysiagrass

Large PatchSt. Augustinegrass

N. Tisserat, KSU

Large patchZoysiagrass

Large / Brown Patch Conditions Favoring Disease

Wet, humid weather Turfgrass going into or coming out of

dormancy Large Nitrogen applications when

turfgrass is not actively growing (too early in spring or too late in fall, or in summer heat stress)

Excessive thatch, poor soil drainage, low air movement, over-watering

Traffic, other stress

Large Patch Control Cultural Control

Reduce thatch, dethatching and aerification may be needed annually

Mow at optimum height Irrigate during fall and spring only as

needed to prevent drought stress

Large Patch Control Chemical Control

Preventive applications work best Use minimum of 2.5 gal/1000 sq. ft.

Don’t water in. Preventative Fungicides:

• Azoxystrobin (Heritage)• Flutolanil (Prostar) • Triadimefon (Bayleton)• Pyraclostobin (Insignia)

Can use contact fungicides for curative applications• Recovery will depend on growing conditions

Fairy Ring Caused by a variety of Basidiomycetes

(mushrooms and puffballs) that degrade thatch and can result in turfgrass death• Production of waxy materials that result in

hydrophobic soils• Production of ammonia and cyanide

Appear as circles or arcs from several inches to many feet in diameter.• Spread from a few inches to 2 feet per year,

slow spread

All grasses

Fairy RingZoysiagrass

Fairy RingP. ryegrass

Fairy RingP. ryegrass

Fairy Ring Control Management to reduce thatch helps reduce

symptoms Physically breaking up hydrophobic layer,

apply surfactants may help speed recovery Deep watering with root feeder Suppression of fairy rings with fungicides often

in combination with surfactants is needed• Azoxystrobin (Heritage) • Flutolanil (Prostar) • Pyraclostrobin (Insignia) • Combination products

LEAF SPOT AND CROWN ROT

Typical symptoms (pictured is bermudagrass; can occur on any grass)

“Helminthosporium” Leaf spots Caused by several

different fungi All turfgrasses All cause generic

leaf spots, and ‘melting-out’ if bad enough

Can rot sheaths and crowns

Most prevalent in spring and fall

“Helminthosporium” Leaf spots

Maintain balanced fertility - avoid high N Irrigate deeply in the morning Raise mower height during disease

outbreaks Fungicide:

• Mancozeb (Fore, Dithane, etc) • Azoxystrobin (Heritage) • Chlorothalonil (Daconil) • Propiconazole (Banner) • Trifloxystrobin (Compass) • Thiophanate-methyl (3336)

Pythium Blight

Can advance rapidly in warm, humid weather

Grass often dies in streaks, following equipment or water trails

Wash equipment thoroughly

Improve aeration and drainage

Rusts

Puccinia and Uromyces spp. Rust is a problem on zoysiagrass*,

ryegrass*, bermudagrass, tall fescue Time of year: spring or fall - spores are

blow long distances by wind Rust infected turf may appear dull

yellow or light brown from a distance Disease favored by shade, low fertility,

drought stress and infrequent mowing

Rust Control Maintain recommended fertility levels and

soil moisture to maintain growth Increase air circulation by pruning trees

and shrubs Mow frequently, remove clippings Fungicides often not needed:

• Heritage (azoxystrobin) • Chlorothalonil • Mancozeb • Banner (propiconazole) • Bayleton (triadimefon)

Fungicides

Contact:• Require good coverage to be effective• Coat the plant surface and prevent fungi

from getting in Local penetrant

• Can get inside leaves and move a little, but not throughout plant

Acropetal penetrant• Moves upwards (upwardly systemic)

True systemic• Moves up and down

Contact fungicides

Form protective barrier on leaf

Barrier must be complete for effective protection

How to get complete barrier?

– Small droplets– High pressure– Small nozzle opening– Large spray volume

Local penetrants Can move some through leaf Helps with distribution Still not truly systemic Good spray coverage still

critical With all contacts, reapplication

intervals are relatively short: 5-14 days

Barrier breaks down due to mowing, rain, UV exposure, etc.

Systemic fungicides

Most move upwards only (acropetalpenetrant)

Move through Xylem

Longer intervals

Also have contact activity

Pythium fungicides Pythium is different Need separate set of fungicides (for the

most part) Contacts:

• Chloroneb (Teremec) Ethazol (Koban) Systemics:

• Metalaxyl (Subdue 2E), Mefanoxam (Subdue MAXX), Propamocarb (Banol), *Azoxystrobin (Heritage)

Phosphites, Organic Phosphates• Fosetyl-Al (Signature), Phosphite

salts (Alude, Vital, Magellan)

What fungicides can do

Protect turf from infection by pathogenic fungi

Kill fungi that are on or in turfgrass tissue

Stop fungi on or in turfgrass tissue from growing

Some are systemic and can get into roots

Arrest the spread of a disease

What fungicides can’t do

Grow grass! For turf to recover from disease

damage, must have good conditions for regrowth or reseeding

New Fungicides

DMI (Demethylation inhibitors)• Tebuconazole - Torque (Cleary)

Golf course only for now Limit use on bermudagrass

• Triticonazole – Trinity (BASF), Triton (Bayer) Good tolerance during summer stress for

cool season grasses

New Fungicides

Strobilurin (QoI inhibitors)• Fluoxastrobin – Disarm (Arysta)

Labeled for dollar spot control

The Label Is the Law

Reading the Label